0025674: Debug dev guide: misprint in Saving and dumping shapes and geometric objects...
[occt.git] / dox / user_guides / ocaf / ocaf.md
ba06f8bb 1OCAF {#occt_user_guides__ocaf}
72b7576f 2========================
e5bd0d98 4@tableofcontents
72b7576f 6@section occt_ocaf_1 Introduction
8This manual explains how to use the Open CASCADE Application Framework (OCAF).
9It provides basic documentation on using OCAF. For advanced information on OCAF
10and its applications, see our offerings on our web site at
11<a href="http://www.opencascade.org/support/training/">www.opencascade.org/support/training/</a>
13OCAF (the Open CASCADE Application Framework) is a RAD (Rapid Application Development) framework used for
14specifying and organizing application data. To do this, OCAF provides:
16 * Ready-to-use data common to most CAD/CAM applications,
17 * A scalable extension protocol for implementing new application specific data,
18 * An infrastructure
19 * To attach any data to any topological element
20 * To link data produced by different applications (*associativity of data*)
21 * To register the modeling process - the creation history, or parametrics, used to carry out the modifications.
23Using OCAF, the application designer concentrates on the functionality and its specific algorithms. In this way, he avoids architectural problems notably implementing Undo-redo and saving application data.
25In OCAF, all of the above are already handled for the application designer, allowing him to reach a significant increase in productivity.
27In this respect, OCAF is much more than just one toolkit among many in the CAS.CADE Object Libraries. Since it can handle any data and algorithms in these libraries - be it modeling algorithms, topology or geometry - OCAF is a logical supplement to these libraries.
29The table below contrasts the design of a modeling application using object libraries alone and using OCAF.
31**Table 1: Services provided by OCAF**
33|Development tasks |Comments | Without OCAF | With OCAF |
35|Creation of geometry| Algorithm Calling the modeling libraries | To be created by the user | To be created by the user|
36| Data organization | Including specific attributes and modeling process | To be created by the user | Simplified|
37| Saving data in a file | Notion of document | To be created by the user | Provided |
38| Document-view management | | To be created by the user | Provided |
39| Application infrastructure | New, Open, Close, Save and Save As File menus | To be created by the user | Provided |
40| Undo-Redo | Robust, multi-level | To be created by the user | Provided |
41| Application-specific dialog boxes | | To be created by the user | To be created by the user |
45The relationship between OCAF and the Open CASCADE Technology (**OCCT**) Object Libraries can be seen in the image below.
3d68eaf5 47@figure{/user_guides/ocaf/images/ocaf_image003.svg, "OCAF Architecture"}
72b7576f 48
49In the image, the OCAF (Open CASCADE Application Framework) is shown with black rectangles and OCCT Object Libraries required by OCAF are shown with white rectangles.
51The subsequent chapters of this document explain the concepts and show how to use the services of OCAF.
53@section occt_ocaf_2 Basic Concepts
55@subsection occt_ocaf_2_1 Overview
57In most existing geometric modeling systems, the data structure is shape driven. They usually use a brep model, where solids and surfaces are defined by a collection of entities such as faces, edges etc., and by attributes such as application data. These attributes are attached to the entities. Examples of application data include:
59 * color,
60 * material,
61 * information that a particular edge is blended.
63A shape, however, is inevitably tied to its underlying geometry. And geometry is highly subject to change in applications such as parametric modeling or product development. In this sort of application, using a brep (boundary representation) data structure proves to be a not very effective solution. A solution other than the shape must be found, i.e. a solution where attributes are attached to a deeper invariant structure of the model. Here, the topology itself will be one attribute among many.
65In OCAF, data structure is reference key-driven. The reference key is implemented in the form of labels. Application data is attached to these labels as attributes. By means of these labels and a tree structure they are organized in, the reference key aggregates all user data, not just shapes and their geometry. These attributes have similar importance; no attribute is master in respect of the others.
67The reference keys of a model - in the form of labels - have to be kept together in a single container. This container is called a document.
dba69de2 69@image html /user_guides/ocaf/images/ocaf_image004.png "Topology-driven vs. reference key-driven approaches"
70@image latex /user_guides/ocaf/images/ocaf_image004.png "Topology-driven vs. reference key-driven approaches"
72b7576f 71
72@subsection occt_ocaf_2_2 Applications and documents
74OCAF documents are in turn managed by an OCAF application, which is in charge of:
76 * Creating new documents
77 * Saving documents and opening them
78 * Initializing document views.
80Apart from their role as a container of application data, documents can refer to each other; Document A, for example, can refer to a specific label in Document B. This functionality is made possible by means of the reference key.
3d68eaf5 82@subsection occt_ocaf_2_3 The document and the data framework
72b7576f 83
84Inside a document, there is a data framework, a model, for example. This is a set of labels organized in a tree structure characterized by the following features:
85 * The first label in a framework is the root of the tree;
86 * Each label has a tag expressed as an integer value;
87 * Sub-labels of a label are called its children;
88 * Each label which is not the root has one father – label from an upper level of the framework;
89 * Labels which have the same father are called brothers;
90 * Brothers cannot share the same tag;
91 * A label is uniquely defined by an entry expressed as a list of tags (entry) of fathers from the root: this list of tags is written from right to left: tag of label, tag of its father, tag of father of its father,..., 0 (tag of the root label).
dba69de2 93@image html /user_guides/ocaf/images/ocaf_image005.png "A simple framework model"
94@image latex /user_guides/ocaf/images/ocaf_image005.png "A simple framework model"
72b7576f 95
96In the above figure inside the circles are the tags of corresponding labels. Under the circles are the lists of tags. The root label always has a zero tag.
98The children of a root label are middle-level labels with tags 1 and 3. These labels are brothers.
dba69de2 100List of tags of the right-bottom label is "0:3:4": this label has tag 4, its father (with entry "0:3") has tag 3, father of father has tag 0 (the root label always has "0" entry).
72b7576f 101
102For example, an application for designing table lamps will first allocate a label for the lamp unit (the lamp is illustrated below). The root label never has brother labels, so, for a lot of lamps in the framework allocation, one of the root label sub-labels for the lamp unit is used. By doing so, you would avoid any confusion between table lamps in the data framework. Parts of the lamp have different material, color and other attributes, so, for each sub-unit of the lamp a child label of the lamp label with specified tags is allocated:
104 * a lamp-shade label with tag 1
105 * a bulb label with tag 2
106 * a stem label with tag 3
108Label tags are chosen at will. They are just identifiers of the lamp parts. Now you can refine all units: set to the specified label geometry, color, material and other information about the lamp or it’s parts. This information is placed into special attributes of the label: the pure label contains no data – it is only a key to access data.
110The thing to remember is that tags are private addresses without any meaning outside the data framework. It would, for instance, be an error to use part names as tags. These might change or be removed from production in next versions of the application, whereas the exact form of that part might be what you wanted to use in your design, the part name could be integrated into the framework as an attribute.
dba69de2 112@image html /user_guides/ocaf/images/ocaf_image006.png
113@image latex /user_guides/ocaf/images/ocaf_image006.png
72b7576f 114
115So, after the user changes the lamp design, only corresponding attributes are changed, but the label structure is maintained. The lamp shape must be recreated by new attribute values and attributes of the lamp shape must refer to a new shape.
dba69de2 117@image html /user_guides/ocaf/images/ocaf_image007.png
118@image latex /user_guides/ocaf/images/ocaf_image007.png
72b7576f 119
121The previous figure shows the table-lamps document structure: each child of the root label contains a lamp shape attribute and refers to the sub-labels, which contain some design information about corresponding sub-units.
123The data framework structure allows to create more complex structures: each lamp label sub-label may have children labels with more detailed information about parts of the table lamp and its components.
125Note that the root label can have attributes too, usually global attributes: the name of the document, for example.
dba69de2 127As in the case of the table lamp example above, OCAF documents aggregate a battery of ready-to-use attributes, which represent typical data used in CAD. This data includes not only the Shape attribute, but a wide range of Standard attributes corresponding to the following types:
72b7576f 128
129 * Geometric attributes
130 * General attributes
131 * Relationship attributes
132 * Auxiliary attributes
134@subsubsection occt_ocaf_2_3_1 Documents
136Documents offer access to the data framework and manage the following items:
138 * Manage the notification of changes
139 * Update external links
140 * Manage the saving and restoring of data
141 * Store the names of software extensions.
142 * Manage command transactions
143 * Manage Undo and Redo options.
145@subsubsection occt_ocaf_2_3_2 Shape attribute
147The shape attribute implements the functionality of the OCCT topology manipulation:
72b7576f 148 * reference to the shapes
149 * tracking of shape evolution
151@subsubsection occt_ocaf_2_3_3 Standard attributes
153Several ready-to-use base attributes already exist. These allow operating with simple common data in the data framework (for example: integer, real, string, array kinds of data), realize auxiliary functions (for example: tag sources attribute for the children of the label counter), create dependencies (for example: reference, tree node)....
155@subsubsection occt_ocaf_2_3_4 Visualization attributes
157These attributes allow placing viewer information to the data framework, visual representation of objects and other auxiliary visual information, which is needed for graphical data representation.
159@subsubsection occt_ocaf_2_3_5 Function services
161Where the document manages the notification of changes, a function manages propagation of these changes. The function mechanism provides links between functions and calls to various algorithms.
dba69de2 163@image html /user_guides/ocaf/images/ocaf_image008.png "Document structure"
164@image latex /user_guides/ocaf/images/ocaf_image008.png "Document structure"
72b7576f 165
e2b55410 166
dba69de2 167@section occt_ocaf_3 Data Framework Services
72b7576f 168
169@subsection occt_ocaf_3_1 Overview
171The data framework offers a single environment in which data from different application components can be handled.
173This allows you to exchange and modify data simply, consistently, with a maximum level of information, and with stable semantics.
175The building blocks of this approach are:
177 * The tag
178 * The label
179 * The attribute
181As it has been mentioned earlier, the first label in a framework is the root label of the tree. Each label has a tag expressed as an integer value, and a label is uniquely defined by an entry expressed as a list of tags from the root, 0:1:2:1, for example.
183Each label can have a list of attributes, which contain data, and several attributes can be attached to a label. Each attribute is identified by a GUID, and although a label may have several attributes attached to it, it must not have more than one attribute of a single GUID.
185The sub-labels of a label are called its children. Conversely, each label, which is not the root, has a father. Brother labels cannot share the same tag.
187The most important property is that a label’s entry is its persistent address in the data framework.
dba69de2 189@image html /user_guides/ocaf/images/ocaf_image009.png "Contents of a document"
190@image latex /user_guides/ocaf/images/ocaf_image009.png "Contents of a document"
72b7576f 191
192@subsection occt_ocaf_3_2 The Tag
194A tag is an integer, which identifies a label in two ways:
196 * Relative identification
197 * Absolute identification.
199In relative identification, a label’s tag has a meaning relative to the father label only. For a specific label, you might, for example, have four child labels identified by the tags 2, 7, 18, 100. In using relative identification, you ensure that you have a safe scope for setting attributes.
dba69de2 201In absolute identification, a label’s place in the data framework is specified unambiguously by a colon-separated list of tags of all the labels from the one in question to the root of the data framework. This list is called an entry. *TDF_Tool::TagList* allows retrieving the entry for a specific label.
72b7576f 202
203In both relative and absolute identification, it is important to remember that the value of an integer has no intrinsic semantics whatsoever. In other words, the natural sequence that integers suggest, i.e. 0, 1, 2, 3, 4 ... - has no importance here. The integer value of a tag is simply a key.
205The tag can be created in two ways:
207 * Random delivery
208 * User-defined delivery
210As the names suggest, in random delivery, the tag value is generated by the system in a random manner. In user-defined delivery, you assign it by passing the tag as an argument to a method.
212@subsubsection occt_ocaf_3_2_1 Creating child labels using random delivery of tags
dba69de2 214To append and return a new child label, you use *TDF_TagSource::NewChild*. In the example below, the argument *level2*, which is passed to *NewChild,* is a *TDF_Label*.
72b7576f 216
72b7576f 217~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
218TDF_Label child1 = TDF_TagSource::NewChild (level2);
219TDF_Label child2 = TDF_TagSource::NewChild (level2);
222@subsubsection occt_ocaf_3_2_2 Creation of a child label by user delivery from a tag
224The other way to create a child label from a tag is by user delivery. In other words, you specify the tag, which you want your child label to have.
dba69de2 226To retrieve a child label from a tag which you have specified yourself, you need to use *TDF_Label::FindChild* and *TDF_Label::Tag* as in the example below. Here, the integer 3 designates the tag of the label you are interested in, and the Boolean false is the value for the argument *create*. When this argument is set to *false*, no new child label is created.
72b7576f 228
72b7576f 229~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
230TDF_Label achild = root.FindChild(3,Standard_False);
231if (!achild.IsNull()) {
232Standard_Integer tag = achild.Tag();
236@subsection occt_ocaf_3_3 The Label
238The tag gives a persistent address to a label. The label – the semantics of the tag – is a place in the data framework where attributes, which contain data, are attached. The data framework is, in fact, a tree of labels with a root as the ultimate father label (refer to the following figure):
dba69de2 240@image html /user_guides/ocaf/images/ocaf_image007.png
241@image latex /user_guides/ocaf/images/ocaf_image007.png
72b7576f 242
244Label can not be deleted from the data framework, so, the structure of the data framework that has been created can not be removed while the document is opened. Hence any kind of reference to an existing label will be actual while an application is working with the document.
246@subsubsection occt_ocaf_3_3_1 Label creation
dba69de2 248Labels can be created on any labels, compared with brother labels and retrieved. You can also find their depth in the data framework (depth of the root label is 0, depth of child labels of the root is 1 and so on), whether they have children or not, relative placement of labels, data framework of this label. The class *TDF_Label* offers the above services.
72b7576f 249
250@subsubsection occt_ocaf_3_3_2 Creating child labels
dba69de2 252To create a new child label in the data framework using explicit delivery of tags, use *TDF_Label::FindChild*.
72b7576f 254
72b7576f 255~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
256//creating a label with tag 10 at Root
257TDF_Label lab1 = aDF->Root().FindChild(10);
259//creating labels 7 and 2 on label 10
260TDF_Label lab2 = lab1.FindChild(7);
262TDF_Label lab3 = lab1.FindChild(2);
dba69de2 264You could also use the same syntax but add the Boolean *true* as a value of the argument **create**. This ensures that a new child label will be created if none is found. Note that in the previous syntax, this was also the case since **create** is *true* by default.
72b7576f 266
72b7576f 267~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
268TDF_Label level1 = root.FindChild(3,Standard_True);
269TDF_Label level2 = level1.FindChild(1,Standard_True);
271@subsubsection occt_ocaf_3_3_3 Retrieving child labels
273You can retrieve child labels of your current label by iteration on the first level in the scope of this label.
dba69de2 275
72b7576f 276~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
277TDF_Label current;
279for (TDF_ChildIterator it1 (current,Standard_False); it1.More(); it1.Next()) {
280achild = it1.Value();
282// do something on a child (level 1)
286You can also retrieve all child labels in every descendant generation of your current label by iteration on all levels in the scope of this label.
288for (TDF_ChildIterator itall (current,Standard_True); itall.More(); itall.Next()) {
289achild = itall.Value();
291// do something on a child (all levels)
dba69de2 295Using *TDF_Tool::Entry* with *TDF_ChildIterator* you can retrieve the entries of your current label’s child labels as well.
72b7576f 296
dba69de2 297
72b7576f 298~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
299void DumpChildren(const TDF_Label& aLabel)
301 TDF_ChildIterator it;
302 TCollection_AsciiString es;
303 for (it.Initialize(aLabel,Standard_True); it.More(); it.Next()){
304 TDF_Tool::Entry(it.Value(),es);
4ee1bdf4 305 cout << as.ToCString() << endl;
72b7576f 306 }
309@subsubsection occt_ocaf_3_3_4 Retrieving the father label
311Retrieving the father label of a current label.
dba69de2 313
72b7576f 314~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
315TDF_Label father = achild.Father();
316isroot = father.IsRoot();
318@subsection occt_ocaf_3_4 The Attribute
320The label itself contains no data. All data of any type whatsoever - application or non-application - is contained in attributes. These are attached to labels, and there are different types for different types of data. OCAF provides many ready-to-use standard attributes such as integer, real, constraint, axis and plane. There are also attributes for topological naming, functions and visualization. Each type of attribute is identified by a GUID.
dba69de2 322The advantage of OCAF is that all of the above attribute types are handled in the same way. Whatever the attribute type is, you can create new instances of them, retrieve them, attach them to and remove them from labels, "forget" and "remember" the attributes of a particular label.
72b7576f 323
324@subsubsection occt_ocaf_3_4_1 Retrieving an attribute from a label
dba69de2 326To retrieve an attribute from a label, you use *TDF_Label::FindAttribute*. In the example below, the GUID for integer attributes, and *INT*, a handle to an attribute are passed as arguments to *FindAttribute* for the current label.
72b7576f 328
72b7576f 329~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
332 // the attribute is found
336 // the attribute is not found
339@subsubsection occt_ocaf_3_4_2 Identifying an attribute using a GUID
dba69de2 341You can create a new instance of an attribute and retrieve its GUID. In the example below, a new integer attribute is created, and its GUID is passed to the variable *guid* by the method ID inherited from *TDF_Attribute*.
72b7576f 343
72b7576f 344~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
345Handle(TDataStd_Integer) INT = new TDataStd_Integer();
346Standard_GUID guid = INT->ID();
dba69de2 348
72b7576f 349@subsubsection occt_ocaf_3_4_3 Attaching an attribute to a label
dba69de2 351To attach an attribute to a label, you use *TDF_Label::Add*. Repetition of this syntax raises an error message because there is already an attribute with the same GUID attached to the current label.
353*TDF_Attribute::Label* for *INT* then returns the label *attach* to which *INT* is attached.
72b7576f 354
72b7576f 355
72b7576f 356~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
357current.Add (INT); // INT is now attached to current
358current.Add (INT); // causes failure
359TDF_Label attach = INT->Label();
361@subsubsection occt_ocaf_3_4_4 Testing the attachment to a label
dba69de2 363You can test whether an attribute is attached to a label or not by using *TDF_Attribute::IsA* with the GUID of the attribute as an argument. In the example below, you test whether the current label has an integer attribute, and then, if that is so, how many attributes are attached to it. *TDataStd_Integer::GetID* provides the GUID argument needed by the method IsAttribute.
365*TDF_Attribute::HasAttribute* tests whether there is an attached attribute, and *TDF_Tool::NbAttributes* returns the number of attributes attached to the label in question, e.g. *current*.
72b7576f 366
72b7576f 367
72b7576f 368~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
369// Testing of attribute attachment
371if (current.IsA(TDataStd_Integer::GetID())) {
372// the label has an Integer attribute attached
374if (current.HasAttribute()) {
375// the label has at least one attribute attached
376Standard_Integer nbatt = current.NbAttributes();
377// the label has nbatt attributes attached
380@subsubsection occt_ocaf_3_4_5 Removing an attribute from a label
dba69de2 382To remove an attribute from a label, you use *TDF_Label::Forget* with the GUID of the deleted attribute. To remove all attributes of a label, *TDF_Label::ForgetAll*.
72b7576f 384
72b7576f 385~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
387// integer attribute is now not attached to current label
389// current has now 0 attributes attached
391@subsubsection occt_ocaf_3_4_6 Specific attribute creation
dba69de2 393If the set of existing and ready to use attributes implementing standard data types does not cover the needs of a specific data presentation task, the user can build his own data type and the corresponding new specific attribute implementing this new data type.
72b7576f 394
dba69de2 395There are two ways to implement a new data type: create a new attribute (standard approach), or use the notion of User Attribute by means of a combination of standard attributes (alternative way)
72b7576f 396
397In order to create a new attribute in the standard way do the following:
dba69de2 398* Create a class inherited from *TDF_Attribute* and implement all purely virtual and necessary virtual methods:
399 + **ID()** – returns a unique GUID of a given attribute
400 + **Restore(attribute)** – sets fields of this attribute equal to the fields of a given attribute of the same type
401 + **Paste(attribute, relocation_table)** – sets fields of a given attribute equal to the field values of this attribute ; if the attribute has references to some objects of the data framework and relocation_table has this element, then the given attribute must also refer to this object .
402 + **NewEmpty()** - returns a new attribute of this class with empty fields
403 + **Dump(stream)** - outputs information about a given attribute to a given stream debug (usually outputs an attribute of type string only)
72b7576f 404* Create the persistence classes for this attribute according to the file format chosen for the document (see below).
dba69de2 406Methods *NewEmpty, Restore* and *Paste* are used for the common transactions mechanism (Undo/Redo commands). If you don’t need this attribute to react to undo/redo commands, you can write only stubs of these methods, else you must call the Backup method of the *TDF_Attribute* class every time attribute fields are changed.
72b7576f 407
408If you use a standard file format and you want your new attributes to be stored during document saving and retrieved to the data framework whenever a document is opened, you must do the following:
dba69de2 410 1. If you place an attribute to a new package, it is desirable (although not mandatory) if your package name starts with letter "T" (transient), for example: attribute *TMyAttributePackage_MyAttribute* in the package *TMyAttributePackage*.
411 2. Create a new package with name "P[package name]" (for example *PMyAttributePackage*) with class *PMyAttributePackage_MyAttribute* inside. The new class inherits the *PDF_Attribute* class and contains fields of attributes, which must be saved or retrieved ("P" - persistent).
412 3. Create a new package with name "M[package name]" (for example *MMyAttributePackage*) with classes *MMyAttributePackage_MyAttributeRetrievalDriver* and *MMyAttributePackage_MyAttributeStorageDriver* inside. The new classes inherit *MDF_ARDriver* and *MDF_ASDriver* classes respectively and contain the translation functionality: from T... attribute to P... and vice versa (M - middle) (see the realization of the standard attributes).
4ee1bdf4 413 4. M... package must contain *AddStorageDrivers(aDriverSeq : ASDriverHSequence* from MDF) and *AddRetrievalDrivers(aDriverSeq : ASDriverHSequence* from MDF) methods, which append to the given sequence of drivers *aDriverSeq*, which is a sequence of all new attribute drivers (see the previous point) used for the storage/retrieval of attributes.
dba69de2 414 5 Use the standard schema (*StdSchema* unit) or create a new one to add your P-package and compile it.
72b7576f 415
416If you use the XML format, do the following:
dba69de2 417 1. Create a new package with the name Xml[package name] (for example *XmlMyAttributePackage*) containing class *XmlMyAttributePackage_MyAttributeDriver*. The new class inherits *XmlMDF_ADriver* class and contains the translation functionality: from transient to persistent and vice versa (see the realization of the standard attributes in the packages *XmlMDataStd*, for example). Add package method AddDrivers which adds your class to a driver table (see below).
418 2. Create a new package (or do it in the current one) with two package methods:
e2b55410 419 * *Factory*, which loads the document storage and retrieval drivers; and
420 * *AttributeDrivers*, which calls the methods AddDrivers for all packages responsible for persistence of the document.
dba69de2 421 3. Create a plug-in implemented as an executable (see example *XmlPlugin*). It calls a macro PLUGIN with the package name where you implemented the method Factory.
72b7576f 422If you use the binary format, do the following:
e2b55410 423 1. Create a new package with name <i> Bin[package name] </i> (for example *BinMyAttributePackage*) containing a class *BinMyAttributePackage_MyAttributeDriver*. The new class inherits *BinMDF_ADriver* class and contains the translation functionality: from transient to persistent and vice versa (see the realization of the standard attributes in the packages *BinMDataStd*, for example). Add package method *AddDrivers*, which adds your class to a driver table.
dba69de2 424 2. Create a new package (or do it in the current one) with two package methods:
425 * Factory, which loads the document storage and retrieval drivers; and
426 * AttributeDrivers, which calls the methods AddDrivers for all packages responsible for persistence of the document.
427 3. Create a plug-in implemented as an executable (see example *BinPlugin*). It calls a macro PLUGIN with the package name where you implemented the method Factory.
428See <a href="#occt_ocaf_4_3_3">Saving the document</a> and <a href="#occt_ocaf_4_3_4">Opening the document from a file</a> for the description of document save/open mechanisms.
72b7576f 429
dba69de2 430If you decided to use the alternative way (create a new attribute by means of *UAttribute* and a combination of other standard attributes), do the following:
431 1. Set a *TDataStd_UAttribute* with a unique GUID attached to a label. This attribute defines the semantics of the data type (identifies the data type).
432 2. Create child labels and allocate all necessary data through standard attributes at the child labels.
433 3. Define an interface class for access to the data of the child labels.
72b7576f 434
dba69de2 435Choosing the alternative way of implementation of new data types allows to forget about creating persistence classes for your new data type. Standard persistence classes will be used instead. Besides, this way allows separating the data and the methods for access to the data (interfaces). It can be used for rapid development in all cases when requirements to application performance are not very high.
72b7576f 436
dba69de2 437Let’s study the implementation of the same data type in both ways by the example of transformation represented by *gp_Trsf* class. The class *gp_Trsf* defines the transformation according to the type (*gp_TrsfForm*) and a set of parameters of the particular type of transformation (two points or a vector for translation, an axis and an angle for rotation, and so on).
72b7576f 438
dba69de2 4391. The first way: creation of a new attribute. The implementation of the transformation by creation of a new attribute is represented in the <a href="#occt_ocaf_11">Samples</a>.
72b7576f 440
4412. The second way: creation of a new data type by means of combination of standard attributes. Depending on the type of transformation it may be kept in data framework by different standard attributes. For example, a translation is defined by two points. Therefore the data tree for translation looks like this:
e2b55410 442 * Type of transformation <i>(gp_Translation)</i> as *TDataStd_Integer*;
443 * First point as *TDataStd_RealArray* (three values: X1, Y1 and Z1);
444 * Second point as *TDataStd_RealArray* (three values: X2, Y2 and Z2).
72b7576f 445
dba69de2 446@image html /user_guides/ocaf/images/ocaf_image010.png "Data tree for translation"
447@image latex /user_guides/ocaf/images/ocaf_image010.png "Data tree for translation"
72b7576f 448
449If the type of transformation is changed to rotation, the data tree looks like this:
e2b55410 450 * Type of transformation <i>(gp_Rotation)</i> as *TDataStd_Integer*;
451 * Point of axis of rotation as *TDataStd_RealArray* (three values: X, Y and Z);
452 * Axis of rotation as *TDataStd_RealArray* (three values: DX, DY and DZ);
453 * Angle of rotation as *TDataStd_Real*.
72b7576f 454
dba69de2 455@image html /user_guides/ocaf/images/ocaf_image011.png "Data tree for rotation"
456@image latex /user_guides/ocaf/images/ocaf_image011.png "Data tree for rotation"
72b7576f 457
e2b55410 458The attribute *TDataStd_UAttribute* with the chosen unique GUID identifies the data type. The interface class initialized by the label of this attribute allows access to the data container (type of transformation and the data of transformation according to the type).
72b7576f 459
461@section occt_ocaf_4_ Standard Document Services
463@subsection occt_ocaf_4_1 Overview
465Standard documents offer ready-to-use documents containing a TDF-based data framework. Each document can contain only one framework.
e2b55410 467The documents themselves are contained in the instantiation of a class inheriting from *TDocStd_Application*. This application manages the creation, storage and retrieval of documents.
72b7576f 468
469You can implement undo and redo in your document, and refer from the data framework of one document to that of another one. This is done by means of external link attributes, which store the path and the entry of external links.
471To sum up, standard documents alone provide access to the data framework. They also allow you to:
473 * Update external links
474 * Manage the saving and opening of data
475 * Manage the undo/redo functionality.
478@subsection occt_ocaf_4_2 The Application
dba69de2 480As a container for your data framework, you need a document, and your document must be contained in your application. This application will be a class inheriting from *TDocStd_Application*.
72b7576f 481
482@subsubsection occt_ocaf_4_2_1 Creating an application
484To create an application, use the following syntax.
72b7576f 486~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
487Handle(TDocStd_Application) app
488= new MyApplication_Application ();
dba69de2 490Note that *MyApplication_Application* is a class, which you have to create and which will inherit from *TDocStd_Application*.
72b7576f 491
492@subsubsection occt_ocaf_4_2_2 Creating a new document
dba69de2 494To the application which you declared in the previous example (4.2.1), you must add the document *doc* as an argument of *TDocStd_Application::NewDocument*.
72b7576f 495
72b7576f 496~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
497Handle(TDocStd_Document) doc;
498app->NewDocument("NewDocumentFormat", doc);
dba69de2 500
72b7576f 501@subsubsection occt_ocaf_4_2_3 Retrieving the application to which the document belongs
503To retrieve the application containing your document, you use the syntax below.
72b7576f 505~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
506app = Handle(TDocStd_Application)::DownCast
509@subsection occt_ocaf_4_3 The Document
511The document contains your data framework, and allows you to retrieve this framework, recover its main label, save it in a file, and open or close this file.
513@subsubsection occt_ocaf_4_3_1 Accessing the main label of the framework
dba69de2 515To access the main label in the data framework, you use *TDocStd_Document::Main* as in the example below. The main label is the first child of the root label in the data framework, and has the entry 0:1.
72b7576f 516
72b7576f 517~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
518TDF_Label label = doc->Main();
520@subsubsection occt_ocaf_4_3_2 Retrieving the document from a label in its framework
4ee1bdf4 522To retrieve the document from a label in its data framework, you use *TDocStd_Document::Get* as in the example below. The argument *label* passed to this method is an instantiation of *TDF_Label*.
72b7576f 523~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
524doc = TDocStd_Document::Get(label);
dba69de2 526
72b7576f 527@subsubsection occt_ocaf_4_3_3 Saving the document
4ee1bdf4 529If in your document you use only standard attributes (from the packages *TDF, TDataStd, TNaming, TFunction, TPrsStd* and *TDocStd*), you just do the following steps:
72b7576f 530
dba69de2 531* In your application class (which inherits class *TDocStd_Application*) implement two methods:
4ee1bdf4 532 + Formats (TColStd_SequenceOfExtendedString& theFormats), which append to a given sequence <i>\<theFormats\></i> your document format string, for example, "NewDocumentFormat" – this string is also set in the document creation command
dba69de2 533 + ResourcesName(), which returns a string with a name of resources file (this file contains a description about the extension of the document, storage/retrieval drivers GUIDs...), for example, "NewFormat"
534* Create the resource file (with name, for example, "NewFormat") with the following strings:
72b7576f 535
538NewDocumentFormat: New Document Format Version 1.0
539NewDocumentFormat.FileExtension: ndf
540NewDocumentFormat.StoragePlugin: bd696000-5b34-11d1-b5ba-00a0c9064368
541NewDocumentFormat.RetrievalPlugin: bd696001-5b34-11d1-b5ba-00a0c9064368
542NewDocumentFormatSchema: bd696002-5b34-11d1-b5ba-00a0c9064368
dba69de2 547* Create the resource file "Plugin" with GUIDs and corresponding plugin libraries, which looks like this:
72b7576f 548
551! Description of available plugins
552! ************
554b148e300-5740-11d1-a904-080036aaa103.Location: libFWOSPlugin.so
556! standard document drivers plugin
558bd696000-5b34-11d1-b5ba-00a0c9064368.Location: libPAppStdPlugin.so
559bd696001-5b34-11d1-b5ba-00a0c9064368.Location: libPAppStdPlugin.so
561! standard schema plugin
563bd696002-5b34-11d1-b5ba-00a0c9064368.Location: libPAppStdPlugin.so
565! standard attribute drivers plugin
56757b0b826-d931-11d1-b5da-00a0c9064368.Location: libPAppStdPlugin.so
56857b0b827-d931-11d1-b5da-00a0c9064368.Location: libPAppStdPlugin.so
dba69de2 571In order to set the paths for these files it is necessary to set the environments: *CSF_PluginDefaults* and *CSF_NewFormatDefaults*. For example, set the files in the directory *MyApplicationPath/MyResources*:
72b7576f 572
574setenv CSF_PluginDefaults MyApplicationPath/MyResources
575setenv CSF_NewFormatDefaults MyApplicationPath/MyResources
dba69de2 578Once these steps are taken you may run your application, create documents and Save/Open them. These resource files already exist in the OCAF (format "Standard").
72b7576f 579
e2b55410 580If you use your specific attributes from packages, for example, <i>P-, M-</i> and *TMyAttributePackage* (see @ref occt_ocaf_3_4_6 "Specific attribute creation") you must take some additional steps for the new plugin implementation:
72b7576f 581
e2b55410 5821. Add our *P* package to the standard schema. You can get an already existing (in Open CASCADE Technology sources) schema from *StdSchema* unit and add your package string to the cdl-file: package *PMyAttributePackage*.
5832. The next step consists in the implementation of an executable, which will connect our documents to our application and open/save them. Copy the package *PAppStdPlugin* and change its name to *MyTheBestApplicationPlugin*. In the *PLUGIN* macros type the name of your factory, which will be defined at the next step.
5843. *Factory* is a method, which returns drivers (standard drivers and our defined drivers from the *M* package) by a GUID. Copy the package to the location, where the standard factory is defined (it is PAppStd in the OCAF sources). Change its name to *MyTheBestSchemaLocation*. The *Factory()* method of the *PappStd* package checks the GUID set as its argument and returns the corresponding table of drivers. Set two new GUIDs for your determined storage and retrieval drivers. Append two *if* declarations inside the *Factory()* method, which should check whether the set GUID coincides with GUIDs defined by the *Factory()* method as far as our storage and retrieval drivers are concerned. If the GUID coincides with one of them, the method should return a table of storage or retrieval drivers respectively.
5854. Recompile all and add the strings with GUIDs to the *Plugin* file in accordance with your plugin library GUID.
72b7576f 586
587@subsubsection occt_ocaf_4_3_4 Opening the document from a file
e2b55410 589To open the document from a file where it has been previously saved, you can use *TDocStd_Application::Open* as in the example below. The arguments are the path of the file and the document saved in this file.
72b7576f 590
72b7576f 591~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
592app->Open("/tmp/example.caf", doc);
e2b55410 595@subsubsection occt_ocaf_4_3_5 Cutting, copying and pasting inside a document
597To cut, copy and paste inside a document, use the class *TDF_CopyLabel*.
599In fact, you must define a *Label*, which contains the temporary value of a cut or
600copy operation (say, in <i> Lab_Clipboard</i>). You must also define two other labels:
602* The data container (e.g. <i> Lab_source</i>)
603* The destination of the copy (e.g. <i> Lab_ Target</i> )
606 Copy = copy (Lab_Source => Lab_Clipboard)
607 Cut = copy + Lab_Source.ForgetAll() // command clear the contents of LabelSource.
608 Paste = copy (Lab_Clipboard => Lab_target)
611So we need a tool to copy all (or a part) of the content of a label and its sub-label,
612to another place defined by a label.
615 TDF_CopyLabel aCopy;
616 TDF_IDFilter aFilter (Standard_False);
618 //Don't copy TDataStd_TreeNode attribute
620 aFilter.Ignore(TDataStd_TreeNode::GetDefaultTreeID());
621 aCopy.Load(aSource, aTarget); aCopy.UseFilter(aFilter); aCopy.Perform();
623 // copy the data structure to clipboard
625 return aCopy.IsDone(); }
628The filter is used to forbid copying a specified type of attribute.
630You can also have a look at the class *TDF_Closure*, which can be useful to determine the dependencies of the part you want to cut from the document.
72b7576f 632@subsection occt_ocaf_4_4 External Links
dba69de2 634External links refer from one document to another. They allow you to update the copy of data framework later on.
72b7576f 635
dba69de2 636@image html /user_guides/ocaf/images/ocaf_image012.png "External links between documents"
637@image latex /user_guides/ocaf/images/ocaf_image012.png "External links between documents"
72b7576f 638
639Note that documents can be copied with or without a possibility of updating an external link.
641@subsubsection occt_ocaf_4_4_1 Copying the document
dba69de2 643#### With the possibility of updating it later
72b7576f 644
e2b55410 645To copy a document with a possibility of updating it later, you use *TDocStd_XLinkTool::CopyWithLink*.
72b7576f 646
72b7576f 647~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
648Handle(TDocStd_Document) doc1;
649Handle(TDocStd_Document) doc2;
651TDF_Label source = doc1->GetData()->Root();
652TDF_Label target = doc2->GetData()->Root();
653TDocStd_XLinkTool XLinkTool;
658Now the target document has a copy of the source document. The copy also has a link in order to update the content of the copy if the original changes.
e2b55410 660In the example below, something has changed in the source document. As a result, you need to update the copy in the target document. This copy is passed to *TDocStd_XLinkTool::UpdateLink* as the argument *target*.
72b7576f 661
72b7576f 662~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
dba69de2 666#### Without any link between the copy and the original
72b7576f 667
e2b55410 668You can also create a copy of the document with no link between the original and the copy. The syntax to use this option is *TDocStd_XLinkTool::Copy*. The copied document is again represented by the argument *target*, and the original – by *source.*
72b7576f 669
72b7576f 670~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
671XLinkTool.Copy(target, source);
676@section occt_ocaf_5_ OCAF Shape Attributes
677@subsection occt_ocaf_5_1 Overview
e2b55410 679A topological attribute can be seen as a hook into the topological structure. It is possible to attach data to define references to it.
681OCAF shape attributes are used for topology objects and their evolution access. All topological objects are stored in one *TNaming_UsedShapes* attribute at the root label of the data framework. This attribute contains a map with all topological shapes used in a given document.
72b7576f 682
e2b55410 683The user can add the *TNaming_NamedShape* attribute to other labels. This attribute contains references (hooks) to shapes from the *TNaming_UsedShapes* attribute and an evolution of these shapes. The *TNaming_NamedShape* attribute contains a set of pairs of hooks: to the *Old* shape and to a *New* shape (see the following figure). It allows not only to get the topological shapes by the labels, but also to trace the evolution of the shapes and to correctly update dependent shapes by the changed one.
72b7576f 684
685If a shape is newly created, then the old shape of a corresponding named shape is an empty shape. If a shape is deleted, then the new shape in this named shape is empty.
dba69de2 687@image html /user_guides/ocaf/images/ocaf_image013.png
688@image latex /user_guides/ocaf/images/ocaf_image013.png
72b7576f 689
e2b55410 690### Shape attributes in data framework.
72b7576f 692Different algorithms may dispose sub-shapes of the result shape at the individual labels depending on whether it is necessary to do so:
694* If a sub-shape must have some extra attributes (material of each face or color of each edge). In this case a specific sub-shape is placed to a separate label (usually to a sub-label of the result shape label) with all attributes of this sub-shape.
695* If the topological naming algorithm is needed, a necessary and sufficient set of sub-shapes is placed to child labels of the result shape label. As usual, for a basic solid and closed shells, all faces of the shape are disposed.
e2b55410 697*TNaming_NamedShape* may contain a few pairs of hooks with the same evolution. In this case the topology shape, which belongs to the named shape is a compound of new shapes.
72b7576f 698
e2b55410 699Consider the following example. Two boxes (solids) are fused into one solid (the result one). Initially each box was placed to the result label as a named shape, which has evolution PRIMITIVE and refers to the corresponding shape of the *TNaming_UsedShapes* map. The box result label has a material attribute and six child labels containing named shapes of Box faces.
72b7576f 700
dba69de2 701@image html /user_guides/ocaf/images/ocaf_image014.png "Resulting box"
702@image latex /user_guides/ocaf/images/ocaf_image014.png "Resulting box"
72b7576f 703
704After the fuse operation a modified result is placed to a separate label as a named shape, which refers to the old shape – one of the boxes, as well as to the new shape – the shape resulting from the fuse operation – and has evolution MODIFY (see the following figure).
8d44b0a0 706Named shapes, which contain information about modified faces, belong to the fuse result sub-labels: sub-label with tag 1 – modified faces from box 1, sub-label with tag 2 – modified faces from box 2.
72b7576f 707
dba69de2 708@image html /user_guides/ocaf/images/ocaf_image015.png
709@image latex /user_guides/ocaf/images/ocaf_image015.png
72b7576f 710
711This is necessary and sufficient information for the functionality of the right naming mechanism: any sub-shape of the result can be identified unambiguously by name type and set of labels, which contain named shapes:
e2b55410 713 * face F1’ as a modification of face F11
714 * face F1’’ as generation of face F12
72b7576f 715 * edges as an intersection of two contiguous faces
716 * vertices as an intersection of three contiguous faces
718After any modification of source boxes the application must automatically rebuild the naming entities: recompute the named shapes of the boxes (solids and faces) and fuse the resulting named shapes (solids and faces) that reference to the new named shapes.
720@subsection occt_ocaf_5_2 Services provided
722@subsubsection occt_ocaf_5_2_1 Registering shapes and their evolution
724When using TNaming_NamedShape to create attributes, the following fields of an attribute are filled:
dba69de2 726* A list of shapes called the "old" and the "new" shapes A new shape is recomputed as the value of the named shape. The meaning of this pair depends on the type of evolution.
e2b55410 727* The type of evolution, which is a term of the *TNaming_Evolution* enumeration used for the selected shapes that are placed to the separate label:
728 * PRIMITIVE – newly created topology, with no previous history;
729 * GENERATED – as usual, this evolution of a named shape means, that the new shape is created from a low-level old shape ( a prism face from an edge, for example );
730 * MODIFY – the new shape is a modified old shape;
731 * DELETE – the new shape is empty; the named shape with this evolution just indicates that the old shape topology is deleted from the model;
732 * SELECTED – a named shape with this evolution has no effect on the history of the topology.
72b7576f 733
734Only pairs of shapes with equal evolution can be stored in one named shape.
736@subsubsection occt_ocaf_5_2_2 Using naming resources
e2b55410 738The class *TNaming_Builder* allows you to create a named shape attribute. It has a label of a future attribute as an argument of the constructor. Respective methods are used for the evolution and setting of shape pairs. If for the same TNaming_Builder object a lot of pairs of shapes with the same evolution are given, then these pairs would be placed in the resulting named shape. After the creation of a new object of the TNaming_Builder class, an empty named shape is created at the given label.
72b7576f 739
72b7576f 740~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
dba69de2 741// a new empty named shape is created at "label"
72b7576f 742TNaming_Builder builder(label);
743// set a pair of shapes with evolution GENERATED
745// set another pair of shapes with the same evolution
747// get the result – TNaming_NamedShape attribute
748Handle(TNaming_NamedShape) ns = builder.NamedShape();
750@subsubsection occt_ocaf_5_2_3 Reading the contents of a named shape attribute
e2b55410 752You can use the method <i>TNaming_NamedShape::Evolution()</i> to get the evolution of this named shape and the method <i>TNaming_NamedShape::Get()</i> to get a compound of new shapes of all pairs of this named shape.
dba69de2 753
72b7576f 754More detailed information about the contents of the named shape or about the modification history of a topology can be obtained with the following:
e2b55410 755* *TNaming_Tool* provides a common high-level functionality for access to the named shapes contents:
756 * The method <i>GetShape(Handle(TNaming_NamedShape)) </i> returns a compound of new shapes of the given named shape;
757 * The method <i>CurrentShape(Handle(TNaming_NamedShape))</i> returns a compound of the shapes, which are latest versions of the shapes from the given named shape;
758 * The method <i>NamedShape(TopoDS_Shape,TDF_Label) </i> returns a named shape, which contains a given shape as a new shape. A given label is any label from the data framework – it just gives access to it.
759* *TNaming_Iterator* gives access to the named shape and hooks pairs.
72b7576f 760
72b7576f 761~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
762// create an iterator for a named shape
763TNaming_Iterator iter(namedshape);
764// iterate while some pairs are not iterated
765while(iter.More()) {
766// get the new shape from the current pair
767TopoDS_Shape newshape = iter.NewShape();
768// get the old shape from the current pair
769TopoDS_Shape oldshape = iter.OldShape();
770// do something...
772// go to the next pair
778@subsubsection occt_ocaf_5_2_4 Selection Mechanism
e2b55410 780One of user interfaces for topological naming resources is the *TNaming_Selector* class. You can use this class to:
72b7576f 781
782 * Store a selected shape on a label
783 * Access the named shape
784 * Update this naming
dba69de2 786Selector places a new named shape with evolution SELECTED to the given label. By the given context shape (main shape, which contains a selected sub-shape), its evolution and naming structure the selector creates a "name" of the selected shape – unique description how to find a selected topology.
72b7576f 787
e2b55410 788After any modification of a context shape and updating of the corresponding naming structure, you must call the method *TNaming_Selector::Solve*. If the naming structure is correct, the selector automatically updates the selected shape in the corresponding named shape, else it fails.
72b7576f 789
790@subsubsection occt_ocaf_5_2_5 Exploring shape evolution
e2b55410 792The class *TNaming_Tool* provides a toolkit to read current data contained in the attribute.
72b7576f 793
e2b55410 794If you need to create a topological attribute for existing data, use the method *NamedShape*.
72b7576f 795
72b7576f 796~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
797class MyPkg_MyClass
799public: Standard_Boolean SameEdge (const Handle(CafTest_Line)& L1, const Handle(CafTest_Line)& L2);
802Standard_Boolean CafTest_MyClass::SameEdge (const Handle(CafTest_Line)& L1, const Handle(CafTest_Line)& L2)
804 Handle(TNaming_NamedShape) NS1 = L1->NamedShape();
805 Handle(TNaming_NamedShape) NS2 = L2->NamedShape();
806 return BRepTools::Compare(NS1,NS2);
810@section occt_ocaf_6_ Standard Attributes
812@subsection occt_ocaf_6_1 Overview
e2b55410 814Standard attributes are ready-to-use attributes, which allow creating and modifying attributes for many basic data types. They are available in the packages *TDataStd, TDataXtd* and *TDF*. Each attribute belongs to one of four types:
72b7576f 815
e2b55410 816 * Geometric attributes;
817 * General attributes;
818 * Relationship attributes;
819 * Auxiliary attributes.
72b7576f 820
dba69de2 821### Geometric attributes
e2b55410 823 * **Axis** – simply identifies, that the concerned *TNaming_NamedShape* attribute with an axis shape inside belongs to the same label;
824 * **Constraint** – contains information about a constraint between geometries: used geometry attributes, type, value (if exists), plane (if exists), "is reversed", "is inverted" and "is verified" flags;
825 * **Geometry** – simply identifies, that the concerned *TNaming_NamedShape* attribute with a specified-type geometry belongs to the same label;
826 * **Plane** – simply identifies, that the concerned *TNaming_NamedShape* attribute with a plane shape inside belongs to the same label;
827 * **Point** – simply identifies, that the concerned *TNaming_NamedShape* attribute with a point shape inside belongs to the same label;
828 * **Shape** – simply identifies, that the concerned *TNaming_NamedShape* attribute belongs to the same label;
829 * **PatternStd** – identifies one of five available pattern models (linear, circular, rectangular, circular rectangular and mirror);
830 * **Position** – identifies the position in 3d global space.
72b7576f 831
dba69de2 832### General attributes
e2b55410 834 * **AsciiString** – contains AsciiString value;
835 * **BooleanArray** – contains an array of Boolean;
836 * **BooleanList** – contains a list of Boolean;
837 * **ByteArray** – contains an array of Byte (unsigned char) values;
838 * **Comment** – contains a string – some comment for a given label (or attribute);
839 * **Expression** – contains an expression string and a list of used variables attributes;
840 * **ExtStringArray** – contains an array of *ExtendedString* values;
841 * **ExtStringList** – contains a list of *ExtendedString* values;
842 * **Integer** – contains an integer value;
843 * **IntegerArray** – contains an array of integer values;
844 * **IntegerList** – contains a list of integer values;
845 * **IntPackedMap** – contains a packed map of integers;
846 * **Name** – contains a string – some name of a given label (or attribute);
847 * **NamedData** – may contain up to 6 of the following named data sets (vocabularies): *DataMapOfStringInteger, DataMapOfStringReal, DataMapOfStringString, DataMapOfStringByte, DataMapOfStringHArray1OfInteger* or *DataMapOfStringHArray1OfReal*;
848 * **NoteBook** – contains a *NoteBook* object attribute;
849 * **Real** – contains a real value;
850 * **RealArray** – contains an array of real values;
851 * **RealList** – contains a list of real values;
852 * **Relation** – contains a relation string and a list of used variables attributes;
853 * **Tick** – defines a boolean attribute;
854 * **Variable** – simply identifies, that a variable belongs to this label; contains the flag *is constraint* and a string of used units ("mm", "m"...);
855 * **UAttribute** – attribute with a user-defined GUID. As a rule, this attribute is used as a marker, which is independent of attributes at the same label (note, that attributes with the same GUIDs can not belong to the same label).
72b7576f 856
dba69de2 857### Relationship attributes
e2b55410 859 * **Reference** – contains reference to the label of its own data framework;
860 * **ReferenceArray** – contains an array of references;
861 * **ReferenceList** – contains a list of references;
862 * **TreeNode** – this attribute allows to create an internal tree in the data framework; this tree consists of nodes with the specified tree ID; each node contains references to the father, previous brother, next brother, first child nodes and tree ID.
72b7576f 863
dba69de2 864### Auxiliary attributes
e2b55410 866 * **Directory** – high-level tool attribute for sub-labels management;
867 * **TagSource** – this attribute is used for creation of new children: it stores the tag of the last-created child of the label and gives access to the new child label creation functionality.
72b7576f 868
e2b55410 869All attributes inherit class *TDF_Attribute*, so, each attribute has its own GUID and standard methods for attribute creation, manipulation, getting access to the data framework.
72b7576f 870
872@subsection occt_ocaf_6_2 Services common to all attributes
874@subsubsection occt_ocaf_6_2_1 Accessing GUIDs
876To access the GUID of an attribute, you can use two methods:
e2b55410 877 * Method *GetID* is the static method of a class. It returns the GUID of any attribute, which is an object of a specified class (for example, *TDataStd_Integer* returns the GUID of an integer attribute). Only two classes from the list of standard attributes do not support these methods: *TDataStd_TreeNode* and *TDataStd_Uattribute*, because the GUIDs of these attributes are variable.
dba69de2 878 * Method *ID* is the method of an object of an attribute class. It returns the GUID of this attribute. Absolutely all attributes have this method: only by this identifier you can discern the type of an attribute.
e2b55410 879
880To find an attribute attached to a specific label, you use the GUID of the attribute type you are looking for. This information can be found using the method <i> GetID</i> and the method <i> Find</i> for the label as follows:
883 Standard_GUID anID = MyAttributeClass::GetID();
884 Standard_Boolean HasAttribute = aLabel.Find(anID,anAttribute);
72b7576f 886
887@subsubsection occt_ocaf_6_2_2 Conventional Interface of Standard Attributes
889It is usual to create standard named methods for the attributes:
dba69de2 891 * Method *Set(label, [value])* is the static method, which allows to add an attribute to a given label. If an attribute is characterized by one value this method may set it.
892 * Method *Get()* returns the value of an attribute if it is characterized by one value.
893 * Method *Dump(Standard_OStream)* outputs debug information about a given attribute to a given stream.
72b7576f 894
dba69de2 895@section occt_ocaf_7 Visualization Attributes
72b7576f 896
897@subsection occt_ocaf_7_1 Overview
e2b55410 899Standard visualization attributes implement the Application Interactive Services (see @ref occt_user_guides__visualization "Visualization User's Guide"). in the context of Open CASCADE Technology Application Framework. Standard visualization attributes are AISViewer and Presentation and belong to the TPrsStd package.
72b7576f 900
901@subsection occt_ocaf_7_2 Services provided
903@subsubsection occt_ocaf_7_2_1 Defining an interactive viewer attribute
e2b55410 905The class *TPrsStd_AISViewer* allows you to define an interactive viewer attribute. There may be only one such attribute per one data framework and it is always placed to the root label. So, it could be set or found by any label ("access label") of the data framework. Nevertheless the default architecture can be easily extended and the user can manage several Viewers per one framework by himself.
72b7576f 906
e2b55410 907To initialize the AIS viewer as in the example below, use method *Find*.
72b7576f 908
72b7576f 909~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
dba69de2 910// "access" is any label of the data framework
72b7576f 911Handle(TPrsStd_AISViewer) viewer = TPrsStd_AISViewer::Find(access)
914@subsection occt_ocaf_7_2_2 Defining a presentation attribute
e2b55410 916The class *TPrsStd_AISPresentation* allows you to define the visual presentation of document labels contents. In addition to various visual fields (color, material, transparency, *isDisplayed*, etc.), this attribute contains its driver GUID. This GUID defines the functionality, which will update the presentation every time when needed.
72b7576f 917
918@subsubsection occt_ocaf_7_2_3 Creating your own driver
920The abstract class TPrsStd_Driver allows you to define your own driver classes. Simply redefine the Update method in your new class, which will rebuild the presentation.
e2b55410 922If your driver is placed to the driver table with the unique driver GUID, then every time the viewer updates presentations with a GUID identical to your driver’s GUID, the *Update* method of your driver for these presentations must be called:
dba69de2 923@image html /user_guides/ocaf/images/ocaf_image016.png
924@image latex /user_guides/ocaf/images/ocaf_image016.png
72b7576f 925
926As usual, the GUID of a driver and the GUID of a displayed attribute are the same.
928@subsubsection occt_ocaf_7_2_4 Using a container for drivers
e2b55410 930You frequently need a container for different presentation drivers. The class *TPrsStd_DriverTable* provides this service. You can add a driver to the table, see if one is successfully added, and fill it with standard drivers.
72b7576f 931
e2b55410 932To fill a driver table with standard drivers, first initialize the AIS viewer as in the example above, and then pass the return value of the method *InitStandardDrivers* to the driver table returned by the method *Get*. Then attach a *TNaming_NamedShape* to a label and set the named shape in the presentation attribute using the method *Set*. Then attach the presentation attribute to the named shape attribute, and the *AIS_InteractiveObject*, which the presentation attribute contains, will initialize its drivers for the named shape. This can be seen in the example below.
72b7576f 933
936DriverTable::Get() -> InitStandardDrivers();
937// next, attach your named shape to a label
939// here, attach the AISPresentation to NS.
dba69de2 942@section occt_ocaf_8 Function Services
72b7576f 943
944Function services aggregate data necessary for regeneration of a model. The function mechanism - available in the package TFunction - provides links between functions and any execution algorithms, which take their arguments from the data framework, and write their results inside the same framework.
946When you edit any application model, you have to regenerate the model by propagating the modifications. Each propagation step calls various algorithms. To make these algorithms independent of your application model, you need to use function services.
948Take, for example, the case of a modeling sequence made up of a box with the application of a fillet on one of its edges. If you change the height of the box, the fillet will need to be regenerated as well.
e2b55410 950See the white paper @ref occt_user_guides__ocaf_functionmechanism_wp "Application Framework Function Mechanism" for more information.
dba69de2 952@subsection occt_ocaf_8_1 Finding functions, their owners and roots
72b7576f 953
e2b55410 954The class *TFunction_Function* is an attribute, which stores a link to a function driver in the data framework. In the static table *TFunction_DriverTable* correspondence links between function attributes and drivers are stored.
72b7576f 955
e2b55410 956You can write your function attribute, a driver for such attribute, which updates the function result in accordance to a given map of changed labels, and set your driver with the GUID to the driver table.
72b7576f 957
e2b55410 958Then the solver algorithm of a data model can find the *Function* attribute on a corresponding label and call the *Execute* driver method to update the result of the function.
72b7576f 959
dba69de2 960@subsection occt_ocaf_8_2 Storing and accessing information about function status
72b7576f 961
e2b55410 962For updating algorithm optimization, each function driver has access to the *TFunction_Logbook* object that is a container for a set of touched, impacted and valid labels. Using this object a driver gets to know which arguments of the function were modified.
72b7576f 963
dba69de2 964@subsection occt_ocaf_8_3 Propagating modifications
72b7576f 965
e2b55410 966An application must implement its functions, function drivers and the common solver for parametric model creation. For example, check the following model:
72b7576f 967
dba69de2 968@image html /user_guides/ocaf/images/ocaf_image017.png
969@image latex /user_guides/ocaf/images/ocaf_image017.png
72b7576f 970
971The procedure of its creation is as follows:
972 * create a rectangular planar face F with height 100 and width 200
973 * create prism P using face F as a basis
974 * create fillet L at the edge of the prism
975 * change the width of F from 200 to 300:
976 * the solver for the function of face F starts
977 * the solver detects that an argument of the face *F* function has been modified
dba69de2 978 * the solver calls the driver of the face F function for a regeneration of the face
72b7576f 979 * the driver rebuilds face F and adds the label of the face *width* argument to the logbook as touched and the label of the function of face F as impacted
981 * the solver detects the function of P – it depends on the function of F
982 * the solver calls the driver of the prism P function
dba69de2 983 * the driver rebuilds prism P and adds the label of this prism to the logbook as impacted
984 * the solver detects the function of L – it depends on the function of P
72b7576f 985 * the solver calls the L function driver
986 * the driver rebuilds fillet L and adds the label of the fillet to the logbook as impacted
988@section occt_ocaf_9 XML Support
990Writing and reading XML files in OCCT is provided by LDOM package, which constitutes an integral part
991of XML OCAF persistence, which is the optional component provided on top of Open CASCADE Technology.
993The Light DOM (LDOM) package contains classes maintaining a data structure whose main principles conform to W3C DOM Level 1 Recommendations. The purpose of these classes as required by XML OCAF persistence schema is to:
e2b55410 994* Maintain a tree structure of objects in memory representing the XML document. The root of the structure is an object of the *LDOM_Document* type. This object contains all the data corresponding to a given XML document and contains one object of the *LDOM_Element* type named "document element". The document element contains other *LDOM_Element* objects forming a tree. Other types of nodes: *LDOM_Attr, LDOM_Text, LDOM_Comment* and *LDOM_CDATASection* - represent the corresponding XML types and serve as branches of the tree of elements.
995* Provide class *LDOM_Parser* to read XML files and convert them to *LDOM_Document* objects.
996* Provide class *LDOM_XmlWriter* to convert *LDOM_Document* to a character stream in XML format and store it in file.
72b7576f 997
998This package covers the functionality provided by numerous products known as "DOM parsers". Unlike most of them, LDOM was specifically developed to meet the following requirements:
999* To minimize the virtual memory allocated by DOM data structures. In average, the amount of memory of LDOM is the same as the XML file size (UTF-8).
1000* To minimize the time required for parsing and formatting XML, as well as for access to DOM data structures.
1002Both these requirements are important when XML files are processed by applications if these files are relatively large (occupying megabytes and even hundreds of megabytes). To meet the requirements, some limitations were imposed on the DOM Level 1 specification; these limitations are insignificant in applications like OCAF. Some of these limitations can be overridden in the course of future developments. The main limitations are:
e2b55410 1003* No Unicode support as well as various other encodings; only ASCII strings are used in DOM/XML. Note: There is a data type *TCollection_ExtendedString* for wide character data. This type is supported by *LDOM_String* as a sequence of numbers.
1004* Some superfluous methods are deleted: *getPreviousSibling, getParentNode,* etc.
72b7576f 1005* No resolution of XML Entities of any kind
1006* No support for DTD: the parser just checks for observance of general XML rules and never validates documents.
e2b55410 1007* Only 5 available types of DOM nodes: *LDOM_Element, LDOM_Attr, LDOM_Text, LDOM_Comment* and *LDOM_CDATASection*.
72b7576f 1008* No support of Namespaces; prefixed names are used instead of qualified names.
e2b55410 1009* No support of the interface *DOMException* (no exception when attempting to remove a non-existing node).
72b7576f 1010
1011LDOM is dependent on Kernel OCCT classes only. Therefore, it can be used outside OCAF persistence in various algorithms where DOM/XML support may be required.
1013@subsection occt_ocaf_9_1 Document Drivers
1015The drivers for document storage and retrieval manage conversion between a transient OCAF
e2b55410 1016Document in memory and its persistent reflection in a container (disk, memory, network). For XML Persistence, they are defined in the package XmlDrivers.
72b7576f 1017
1018The main methods (entry points) of these drivers are:
1019* *Write()* - for a storage driver;
1020* *Read()* - for a retrieval driver.
1022The most common case (which is implemented in XML Persistence) is writing/reading document to/from a regular OS file. Such conversion is performed in two steps:
1024First it is necessary to convert the transient document into another form (called persistent), suitable for writing into a file, and vice versa.
1025In XML Persistence LDOM_Document is used as the persistent form of an OCAF Document and the DOM_Nodes are the persistent objects.
1026An OCAF Document is a tree of labels with attributes. Its transformation into a persistent form can be functionally divided into two parts:
1027* Conversion of the labels structure, which is performed by the method XmlMDF::FromTo()
1028* Conversion of the attributes and their underlying objects, which is performed by the corresponding attribute drivers (one driver per attribute type).
1030The driver for each attribute is selected from a table of drivers, either by attribute
1031type (on storage) or by the name of the corresponding DOM_Element (on retrieval).
1032The table of drivers is created by by methods *XmlDrivers_DocumentStorageDriver::AttributeDrivers()*
1033and *XmlDrivers_DocumentRetrievalDriver::AttributeDrivers()*.
1035Then the persistent document is written into a file (or read from a file).
4ee1bdf4 1036In standard persistence Storage and FSD packages contain classes for writing/reading the persistent document into a file. In XML persistence *LDOMParser* and *LDOM_XmlWriter* are used instead.
72b7576f 1037
4ee1bdf4 1038Usually, the library containing document storage and retrieval drivers is loaded at run time by a plugin mechanism. To support this in XML Persistence, there is a plugin *XmlPlugin* and a *Factory()* method in the *XmlDrivers* package. This method compares passed GUIDs with known GUIDs and returns the corresponding driver or generates an exception if the GUID is unknown.
72b7576f 1039
1040The application defines which GUID is needed for document storage or retrieval and in which library it should be found. This depends on document format and application resources. Resources for XML Persistence and also for standard persistence are found in the StdResource unit. They are written for the XmlOcaf document format.
1042@subsection occt_ocaf_9_2 Attribute Drivers
4ee1bdf4 1044There is one attribute driver for XML persistence for each transient attribute from a set of standard OCAF attributes, with the exception of attribute types, which are never stored (pure transient). Standard OCAF attributes are collected in six packages, and their drivers also follow this distribution. Driver for attribute <i>T*_*</i> is called <i>XmlM*_*</i>. Conversion between transient and persistent form of attribute is performed by two methods *Paste()* of attribute driver.
72b7576f 1045
1046*XmlMDF_ADriver* is the root class for all attribute drivers.
4ee1bdf4 1048At the beginning of storage/retrieval process, one instance of each attribute driver is created and appended to driver table implemented as *XmlMDF_ADriverTable*. During OCAF Data storage, attribute drivers are retrieved from the driver table by the type of attribute. In the retrieval step, a data map is created linking names of *DOM_Elements* and attribute drivers, and then attribute drivers are sought in this map by *DOM_Element* qualified tag names.
72b7576f 1049
4ee1bdf4 1050Every transient attribute is saved as a *DOM_Element* (root element of OCAF attribute) with attributes and possibly sub-nodes. The name of the root element can be defined in the attribute driver as a string passed to the base class constructor. The default is the attribute type name. Similarly, namespace prefixes for each attribute can be set. There is no default value, but it is possible to pass NULL or an empty string to store attributes without namespace prefixes.
72b7576f 1051
4ee1bdf4 1052The basic class *XmlMDF_ADriver* supports errors reporting via the method *WriteMessage(const TCollection_ExtendedString&)*. It sends a message string to its message driver which is initialized in the constructor with a *Handle(CDM_MessageDriver)* passed from the application by Document Storage/Retrieval Driver.
72b7576f 1053
1054@subsection occt_ocaf_9_3 XML Document Structure
ba06f8bb 1056Every XML Document has one root element, which may have attributes and contain other nodes. In OCAF XML Documents the root element is named "document" and has attribute "format" with the name of the OCAF Schema used to generate the file. The standard XML format is "XmlOcaf". The following elements are sub-elements of \<document\> and should be unique entries as its sub-elements, in a specific order. The order is:
72b7576f 1057* **Element info** - contains strings identifying the format version and other parameters of the OCAF XML document. Normally, data under the element is used by persistence algorithms to correctly retrieve and initialize an OCAF document. The data also includes a copyright string.
ba06f8bb 1058* **Element comments** - consists of an unlimited number of \<comment\> sub-elements containing necessary comment strings.
72b7576f 1059* **Element label** is the root label of the document data structure, with the XML attribute "tag" equal to 0. It contains all the OCAF data (labels, attributes) as tree of XML elements. Every sub-label is identified by a tag (positive integer) defining a unique key for all sub-labels of a label. Every label can contain any number of elements representing OCAF attributes (see OCAF Attributes Representation below).
4ee1bdf4 1060* **Element shapes** - contains geometrical and topological entities in BRep format. These entities being referenced by OCAF attributes written under the element \<label\>. This element is empty if there are no shapes in the document. It is only output if attribute driver *XmlMNaming_NamedShapeDriver* has been added to drivers table by the *DocumentStorageDriver*.
72b7576f 1061
dba69de2 1062### OCAF Attributes Representation
72b7576f 1063
1064In XML documents, OCAF attributes are elements whose name identifies the OCAF attribute type. These elements may have a simple (string or number) or complex (sub-elements) structure, depending on the architecture of OCAF attribute. Every XML type for OCAF attribute possesses a unique positive integer "id" XML attribute identifying the OCAF attribute throughout the document. To ensure "id" uniqueness, the attribute name "id" is reserved and is only used to indicate and identify elements which may be referenced from other parts of the OCAF XML document.
1065For every standard OCAF attribute, its XML name matches the name of a C++ class in Transient data model. Generally, the XML name of OCAF attribute can be specified in the corresponding attribute driver.
1066XML types for OCAF attributes are declared with XML W3C Schema in a few XSD files where OCAF attributes are grouped by the package where they are defined.
dba69de2 1068### Example of resulting XML file
4ee1bdf4 1070The following example is a sample text from an XML file obtained by storing an OCAF document with two labels (0: and 0:2) and two attributes - *TDataStd_Name* (on label 0:) and *TNaming_NamedShape* (on label 0:2). The \<shapes\> section contents are replaced by an ellipsis.
72b7576f 1071
4ee1bdf4 1072~~~~
72b7576f 1073<?xml version="1.0" encoding="UTF-8"?>
1074<document format="XmlOcaf" xmlns="http://www.opencascade.org/OCAF/XML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1075xsi:schemaLocation="http://www.opencascade.org/OCAF/XML http://www.opencascade.org/OCAF/XML/XmlOcaf.xsd">
1077<info date="2001-10-04" schemav="0" objnb="3">
1078<iitem>Copyright: Open Cascade, 2001</iitem>
1079<iitem>STORAGE_VERSION: PCDM_ReadWriter_1</iitem>
1080<iitem>REFERENCE_COUNTER: 0</iitem>
1081<iitem>MODIFICATION_COUNTER: 1</iitem>
1084<label tag="0">
1085<TDataStd_Name id="1">Document_1</TDataStd_Name>
1086<label tag="2">
1087<TNaming_NamedShape id="2" evolution="primitive">
1090<shape tshape="+34" index="1"/>
ba06f8bb 1095\<shapes\>
72b7576f 1096...
4ee1bdf4 1100~~~~
72b7576f 1101
1102@subsection occt_ocaf_9_4 XML Schema
1104The XML Schema defines the class of a document.
1106The full structure of OCAF XML documents is described as a set of XML W3C Schema files with definitions of all XML element types. The definitions provided cannot be overridden. If any application defines new persistence schemas, it can use all the definitions from the present XSD files but if it creates new or redefines existing types, the definition must be done under other namespace(s).
1108There are other ways to declare XML data, different from W3C Schema, and it should be possible to use them to the extent of their capabilities of expressing the particular structure and constraints of our XML data model. However, it must be noted that the W3C Schema is the primary format for declarations and as such, it is the format supported for future improvements of Open CASCADE Technology, including the development of specific applications using OCAF XML persistence.
1110The Schema files (XSD) are intended for two purposes:
1111* documenting the data format of files generated by OCAF;
1112* validation of documents when they are used by external (non-OCAF) applications, e.g., to generate reports.
1114The Schema definitions are not used by OCAF XML Persistence algorithms when saving and restoring XML documents. There are internal checks to ensure validity when processing every type of data.
dba69de2 1116### Management of Namespaces
4ee1bdf4 1118Both the XML format and the XML OCAF persistence code are extensible in the sense that every new development can reuse everything that has been created in previous projects. For the XML format, this extensibility is supported by assigning names of XML objects (elements) to different XML Namespaces. Hence, XML elements defined in different projects (in different persistence libraries) can easily be combined into the same XML documents. An example is the XCAF XML persistence built as an extension to the Standard OCAF XML persistence <i>[File XmlXcaf.xsd]</i>. For the correct management of Namespaces it is necessary to:
dba69de2 1119* Define *targetNamespace* in the new XSD file describing the format.
4ee1bdf4 1120* Declare (in *XSD* files) all elements and types in the targetNamespace to appear without a namespace prefix; all other elements and types use the appropriate prefix (such as "ocaf:").
dba69de2 1121* Add (in the new *DocumentStorageDriver*) the *targetNamespace* accompanied with its prefix, using method *XmlDrivers_DocumentStorageDriver::AddNamespace*. The same is done for all namespaces objects which are used by the new persistence, with the exception of the "ocaf" namespace.
1122* Pass (in every OCAF attribute driver) the namespace prefix of the *targetNamespace* to the constructor of *XmlMDF_ADriver*.
72b7576f 1123
1124@section occt_ocaf_10 GLOSSARY
dba69de2 1126* **Application** - a document container holding all documents containing all application data.
1127* **Application data** - the data produced by an application, as opposed to data referring to it.
1128* **Associativity of data** - the ability to propagate modifications made to one document to other documents, which refer to such document. Modification propagation is:
72b7576f 1129 * unidirectional, that is, from the referenced to the referencing document(s), or
1130 * bi-directional, from the referencing to the referenced document and vice-versa.
dba69de2 1131* **Attribute** - a container for application data. An attribute is attached to a label in the hierarchy of the data framework.
1132* **Child** - a label created from another label, which by definition, is the father label.
1133* **Compound document** - a set of interdependent documents, linked to each other by means of external references. These references provide the associativity of data.
1134* **Data framework** - a tree-like data structure which in OCAF, is a tree of labels with data attached to them in the form of attributes. This tree of labels is accessible through the services of the *TDocStd_Document* class.
e2b55410 1135* **Document** - a container for a data framework which grants access to the data, and is, in its turn, contained by an application. A document also allows you to:
dba69de2 1136 * Manage modifications, providing Undo and Redo functions
1137 * Manage command transactions
1138 * Update external links
1139 * Manage save and restore options
1140 * Store the names of software extensions.
1141* **Driver** - an abstract class, which defines the communications protocol with a system.
e2b55410 1142* **Entry** - an ASCII character string containing the tag list of a label. For example:
72b7576f 1143
72b7576f 1144~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
dba69de2 1148* **External links** - references from one data structure to another data structure in another document.
72b7576f 1149To store these references properly, a label must also contain an external link attribute.
dba69de2 1150* **Father** - a label, from which other labels have been created. The other labels are, by definition, the children of this label.
1151* **Framework** - a group of co-operating classes which enable a design to be re-used for a given category of problem. The framework guides the architecture of the application by breaking it up into abstract classes, each of which has different responsibilities and collaborates in a predefined way. Application developer creates a specialized framework by:
72b7576f 1152 * defining new classes which inherit from these abstract classes
1153 * composing framework class instances
1154 * implementing the services required by the framework.
1156In C++, the application behavior is implemented in virtual functions redefined in these derived classes. This is known as overriding.
e2b55410 1158* **GUID** - Global Universal ID. A string of 37 characters intended to uniquely identify an object. For example:
72b7576f 1159
72b7576f 1160~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
dba69de2 1164* **Label** - a point in the data framework, which allows data to be attached to it by means of attributes. It has a name in the form of an entry, which identifies its place in the data framework.
1165* **Modified label** - containing attributes whose data has been modified.
1166* **Reference key** - an invariant reference, which may refer to any type of data used in an application. In its transient form, it is a label in the data framework, and the data is attached to it in the form of attributes. In its persistent form, it is an entry of the label. It allows an application to recover any entity in the current session or in a previous session.
1167* **Resource file** - a file containing a list of each document’s schema name and the storage and retrieval plug-ins for that document.
1168* **Root** - the starting point of the data framework. This point is the top label in the framework. It is represented by the [0] entry and is created at the same time with the document you are working on.
1169* **Scope** - the set of all the attributes and labels which depend on a given label.
1170* **Tag list** - a list of integers, which identify the place of a label in the data framework. This list is displayed in an entry.
1171* **Topological naming** - systematic referencing of topological entities so that these entities can still be identified after the models they belong to have gone through several steps in modeling. In other words, topological naming allows you to track entities through the steps in the modeling process. This referencing is needed when a model is edited and regenerated, and can be seen as a mapping of labels and name attributes of the entities in the old version of a model to those of the corresponding entities in its new version. Note that if the topology of a model changes during the modeling, this mapping may not fully coincide. A Boolean operation, for example, may split edges.
1172* **Topological tracking** - following a topological entity in a model through the steps taken to edit and regenerate that model.
1173* **Valid label** - in a data framework, this is a label, which is already recomputed in the scope of regeneration sequence and includes the label containing a feature which is to be recalculated. Consider the case of a box to which you first add a fillet, then a protrusion feature. For recalculation purposes, only valid labels of each construction stage are used. In recalculating a fillet, they are only those of the box and the fillet, not the protrusion feature which was added afterwards.
72b7576f 1174
dba69de2 1175@section occt_ocaf_11 Samples
1176@subsection occt_ocaf_11_1 Implementation of Attribute Transformation in a CDL file
72b7576f 1177
1179class Transformation from MyPackage inherits Attribute from TDF
dba69de2 1181 ---Purpose: This attribute implements a transformation data container.
72b7576f 1182
dba69de2 1185 Attribute from TDF,
1186 Label from TDF,
1187 GUID from Standard,
1188 RelocationTable from TDF,
1189 Pnt from gp,
1190 Ax1 from gp,
1191 Ax2 from gp,
1192 Ax3 from gp,
1193 Vec from gp,
1194 Trsf from gp,
1195 TrsfForm from gp
72b7576f 1196
dba69de2 1199 ---Category: Static methods
1200 -- ===============
1202 GetID (myclass)
1203 ---C++: return const &
1204 ---Purpose: The method returns a unique GUID of this attribute.
1205 -- By means of this GUID this attribute may be identified
1206 -- among other attributes attached to the same label.
1207 returns GUID from Standard;
1209 Set (myclass; theLabel : Label from TDF)
1210 ---Purpose: Finds or creates the attribute attached to <theLabel>.
1211 -- The found or created attribute is returned.
1212 returns Transformation from MyPackage;
1215 ---Category: Methods for access to the attribute data
1216 -- ========================================
1218 Get (me)
1219 ---Purpose: The method returns the transformation.
1220 returns Trsf from gp;
1223 ---Category: Methods for setting the data of transformation
1224 -- ==============================================
1226 SetRotation (me : mutable;
1227 theAxis : Ax1 from gp;
1228 theAngle : Real from Standard);
1229 ---Purpose: The method defines a rotation type of transformation.
1231 SetTranslation (me : mutable;
1232 theVector : Vec from gp);
1233 ---Purpose: The method defines a translation type of transformation.
1235 SetMirror (me : mutable;
1236 thePoint : Pnt from gp);
1237 ---Purpose: The method defines a point mirror type of transformation
1238 -- (point symmetry).
1240 SetMirror (me : mutable;
1241 theAxis : Ax1 from gp);
1242 ---Purpose: The method defines an axis mirror type of transformation
1243 -- (axial symmetry).
1245 SetMirror (me : mutable;
1246 thePlane : Ax2 from gp);
1247 ---Purpose: The method defines a point mirror type of transformation
1248 -- (planar symmetry).
1250 SetScale (me : mutable;
1251 thePoint : Pnt from gp;
1252 theScale : Real from Standard);
1253 ---Purpose: The method defines a scale type of transformation.
1255 SetTransformation (me : mutable;
1256 theCoordinateSystem1 : Ax3 from gp;
1257 theCoordinateSystem2 : Ax3 from gp);
1258 ---Purpose: The method defines a complex type of transformation
1259 -- from one co-ordinate system to another.
1262 ---Category: Overridden methods from TDF_Attribute
1263 -- =====================================
1265 ID (me)
1266 ---C++: return const &
1267 ---Purpose: The method returns a unique GUID of the attribute.
1268 -- By means of this GUID this attribute may be identified
1269 -- among other attributes attached to the same label.
1270 returns GUID from Standard;
1272 Restore (me: mutable;
1273 theAttribute : Attribute from TDF);
1274 ---Purpose: The method is called on Undo / Redo.
1275 -- It copies the content of <theAttribute>
1276 -- into this attribute (copies the fields).
1278 NewEmpty (me)
1279 ---Purpose: It creates a new instance of this attribute.
1280 -- It is called on Copy / Paste, Undo / Redo.
1281 returns mutable Attribute from TDF;
1283 Paste (me;
1284 theAttribute : mutable Attribute from TDF;
1285 theRelocationTable : mutable RelocationTable from TDF);
1286 ---Purpose:: The method is called on Copy / Paste.
1287 -- It copies the content of this attribute into
1288 -- <theAttribute> (copies the fields).
1290 Dump(me; anOS : in out OStream from Standard)
1291 ---C++: return;
1292 ---Purpose: Prints the content of this attribute into the stream.
1293 returns OStream from Standard is redefined;
1296 ---Category: Constructor
1297 -- ===========
1299 Create
1300 ---Purpose: The C++ constructor of this atribute class.
1301 -- Usually it is never called outside this class.
1302 returns mutable Transformation from MyPackage;
72b7576f 1303
dba69de2 1307 -- Type of transformation
1308 myType : TrsfForm from gp;
72b7576f 1309
dba69de2 1310 -- Axes (Ax1, Ax2, Ax3)
1311 myAx1 : Ax1 from gp;
1312 myAx2 : Ax2 from gp;
1313 myFirstAx3 : Ax3 from gp;
1314 mySecondAx3 : Ax3 from gp;
1316 -- Scalar values
1317 myAngle : Real from Standard;
1318 myScale : Real from Standard;
1320 -- Points
1321 myFirstPoint : Pnt from gp;
1322 mySecondPoint : Pnt from gp;
72b7576f 1323
1325end Transformation;
dba69de2 1328@subsection occt_ocaf_11_2 Implementation of Attribute Transformation in a CPP file
72b7576f 1330~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1331#include MyPackage_Transformation.ixx;
1334//function : GetID
dba69de2 1335//purpose : The method returns a unique GUID of this attribute.
1336// By means of this GUID this attribute may be identified
1337// among other attributes attached to the same label.
72b7576f 1338//=======================================================================
1339const Standard_GUID& MyPackage_Transformation::GetID()
dba69de2 1341 static Standard_GUID ID("4443368E-C808-4468-984D-B26906BA8573");
1342 return ID;
72b7576f 1343}
1346//function : Set
dba69de2 1347//purpose : Finds or creates the attribute attached to <theLabel>.
1348// The found or created attribute is returned.
72b7576f 1349//=======================================================================
1350Handle(MyPackage_Transformation) MyPackage_Transformation::Set(const TDF_Label& theLabel)
dba69de2 1352 Handle(MyPackage_Transformation) T;
1353 if (!theLabel.FindAttribute(MyPackage_Transformation::GetID(), T))
1354 {
1355 T = new MyPackage_Transformation();
1356 theLabel.AddAttribute(T);
1357 }
1358 return T;
72b7576f 1359}
1362//function : Get
dba69de2 1363//purpose : The method returns the transformation.
72b7576f 1364//=======================================================================
1365gp_Trsf MyPackage_Transformation::Get() const
dba69de2 1367 gp_Trsf transformation;
1368 switch (myType)
1369 {
1370 case gp_Identity:
1371 {
1372 break;
1373 }
1374 case gp_Rotation:
1375 {
1376 transformation.SetRotation(myAx1, myAngle);
1377 break;
1378 }
1379 case gp_Translation:
1380 {
1381 transformation.SetTranslation(myFirstPoint, mySecondPoint);
1382 break;
1383 }
1384 case gp_PntMirror:
1385 {
1386 transformation.SetMirror(myFirstPoint);
1387 break;
1388 }
1389 case gp_Ax1Mirror:
1390 {
1391 transformation.SetMirror(myAx1);
1392 break;
1393 }
1394 case gp_Ax2Mirror:
1395 {
1396 transformation.SetMirror(myAx2);
1397 break;
1398 }
1399 case gp_Scale:
1400 {
1401 transformation.SetScale(myFirstPoint, myScale);
1402 break;
1403 }
1404 case gp_CompoundTrsf:
1405 {
1406 transformation.SetTransformation(myFirstAx3, mySecondAx3);
1407 break;
1408 }
1409 case gp_Other:
1410 {
1411 break;
1412 }
1413 }
1414 return transformation;
72b7576f 1415}
1418//function : SetRotation
dba69de2 1419//purpose : The method defines a rotation type of transformation.
72b7576f 1420//=======================================================================
1421void MyPackage_Transformation::SetRotation(const gp_Ax1& theAxis, const Standard_Real theAngle)
dba69de2 1423 Backup();
1424 myType = gp_Rotation;
1425 myAx1 = theAxis;
1426 myAngle = theAngle;
72b7576f 1427}
1430//function : SetTranslation
dba69de2 1431//purpose : The method defines a translation type of transformation.
72b7576f 1432//=======================================================================
1433void MyPackage_Transformation::SetTranslation(const gp_Vec& theVector)
dba69de2 1435 Backup();
1436 myType = gp_Translation;
1437 myFirstPoint.SetCoord(0, 0, 0);
1438 mySecondPoint.SetCoord(theVector.X(), theVector.Y(), theVector.Z());
72b7576f 1439}
1442//function : SetMirror
dba69de2 1443//purpose : The method defines a point mirror type of transformation
1444// (point symmetry).
72b7576f 1445//=======================================================================
1446void MyPackage_Transformation::SetMirror(const gp_Pnt& thePoint)
dba69de2 1448 Backup();
1449 myType = gp_PntMirror;
1450 myFirstPoint = thePoint;
72b7576f 1451}
1454//function : SetMirror
dba69de2 1455//purpose : The method defines an axis mirror type of transformation
1456// (axial symmetry).
72b7576f 1457//=======================================================================
1458void MyPackage_Transformation::SetMirror(const gp_Ax1& theAxis)
dba69de2 1460 Backup();
1461 myType = gp_Ax1Mirror;
1462 myAx1 = theAxis;
72b7576f 1463}
1466//function : SetMirror
dba69de2 1467//purpose : The method defines a point mirror type of transformation
1468// (planar symmetry).
72b7576f 1469//=======================================================================
1470void MyPackage_Transformation::SetMirror(const gp_Ax2& thePlane)
dba69de2 1472 Backup();
1473 myType = gp_Ax2Mirror;
1474 myAx2 = thePlane;
72b7576f 1475}
1478//function : SetScale
dba69de2 1479//purpose : The method defines a scale type of transformation.
72b7576f 1480//=======================================================================
1481void MyPackage_Transformation::SetScale(const gp_Pnt& thePoint, const Standard_Real theScale)
dba69de2 1483 Backup();
1484 myType = gp_Scale;
1485 myFirstPoint = thePoint;
1486 myScale = theScale;
72b7576f 1487}
1490//function : SetTransformation
dba69de2 1491//purpose : The method defines a complex type of transformation
1492// from one co-ordinate system to another.
72b7576f 1493//=======================================================================
1494void MyPackage_Transformation::SetTransformation(const gp_Ax3& theCoordinateSystem1,
dba69de2 1495 const gp_Ax3& theCoordinateSystem2)
72b7576f 1496{
dba69de2 1497 Backup();
1498 myFirstAx3 = theCoordinateSystem1;
1499 mySecondAx3 = theCoordinateSystem2;
72b7576f 1500}
1503//function : ID
dba69de2 1504//purpose : The method returns a unique GUID of the attribute.
1505// By means of this GUID this attribute may be identified
1506// among other attributes attached to the same label.
72b7576f 1507//=======================================================================
1508const Standard_GUID& MyPackage_Transformation::ID() const
dba69de2 1510 return GetID();
72b7576f 1511}
1514//function : Restore
dba69de2 1515//purpose : The method is called on Undo / Redo.
1516// It copies the content of <theAttribute>
1517// into this attribute (copies the fields).
72b7576f 1518//=======================================================================
1519void MyPackage_Transformation::Restore(const Handle(TDF_Attribute)& theAttribute)
dba69de2 1521 Handle(MyPackage_Transformation) theTransformation = Handle(MyPackage_Transformation)::DownCast(theAttribute);
1522 myType = theTransformation->myType;
1523 myAx1 = theTransformation->myAx1;
1524 myAx2 = theTransformation->myAx2;
1525 myFirstAx3 = theTransformation->myFirstAx3;
1526 mySecondAx3 = theTransformation->mySecondAx3;
1527 myAngle = theTransformation->myAngle;
1528 myScale = theTransformation->myScale;
1529 myFirstPoint = theTransformation->myFirstPoint;
1530 mySecondPoint = theTransformation->mySecondPoint;
72b7576f 1531}
1534//function : NewEmpty
dba69de2 1535//purpose : It creates a new instance of this attribute.
1536// It is called on Copy / Paste, Undo / Redo.
72b7576f 1537//=======================================================================
1538Handle(TDF_Attribute) MyPackage_Transformation::NewEmpty() const
dba69de2 1539{
1540 return new MyPackage_Transformation();
72b7576f 1541}
1544//function : Paste
dba69de2 1545//purpose : The method is called on Copy / Paste.
1546// It copies the content of this attribute into
1547// <theAttribute> (copies the fields).
72b7576f 1548//=======================================================================
1549void MyPackage_Transformation::Paste(const Handle(TDF_Attribute)& theAttribute,
dba69de2 1550 const Handle(TDF_RelocationTable)& ) const
72b7576f 1551{
dba69de2 1552 Handle(MyPackage_Transformation) theTransformation = Handle(MyPackage_Transformation)::DownCast(theAttribute);
1553 theTransformation->myType = myType;
1554 theTransformation->myAx1 = myAx1;
1555 theTransformation->myAx2 = myAx2;
1556 theTransformation->myFirstAx3 = myFirstAx3;
1557 theTransformation->mySecondAx3 = mySecondAx3;
1558 theTransformation->myAngle = myAngle;
1559 theTransformation->myScale = myScale;
1560 theTransformation->myFirstPoint = myFirstPoint;
1561 theTransformation->mySecondPoint = mySecondPoint;
72b7576f 1562}
1565//function : Dump
dba69de2 1566//purpose : Prints the content of this attribute into the stream.
72b7576f 1567//=======================================================================
1568Standard_OStream& MyPackage_Transformation::Dump(Standard_OStream& anOS) const
dba69de2 1569{
1570 anOS = "Transformation: ";
1571 switch (myType)
1572 {
1573 case gp_Identity:
1574 {
1575 anOS = "gp_Identity";
1576 break;
1577 }
1578 case gp_Rotation:
1579 {
1580 anOS = "gp_Rotation";
1581 break;
1582 }
1583 case gp_Translation:
1584 {
1585 anOS = "gp_Translation";
1586 break;
1587 }
1588 case gp_PntMirror:
1589 {
1590 anOS = "gp_PntMirror";
1591 break;
1592 }
1593 case gp_Ax1Mirror:
1594 {
1595 anOS = "gp_Ax1Mirror";
1596 break;
1597 }
1598 case gp_Ax2Mirror:
1599 {
1600 anOS = "gp_Ax2Mirror";
1601 break;
1602 }
1603 case gp_Scale:
1604 {
1605 anOS = "gp_Scale";
1606 break;
1607 }
1608 case gp_CompoundTrsf:
1609 {
1610 anOS = "gp_CompoundTrsf";
1611 break;
1612 }
1613 case gp_Other:
1614 {
1615 anOS = "gp_Other";
1616 break;
1617 }
1618 }
1619 return anOS;
72b7576f 1620}
1623//function : MyPackage_Transformation
dba69de2 1624//purpose : A constructor.
72b7576f 1625//=======================================================================
dba69de2 1629~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1631@subsection occt_ocaf_11_3 Implementation of typical actions with standard OCAF attributes.
ba06f8bb 1633There are four sample files provided in the directory 'OpenCasCade/ros/samples/ocafsamples'. They present typical actions with OCAF services (mainly for newcomers).
dba69de2 1634The method *Sample()* of each file is not dedicated for execution 'as is', it is rather a set of logical actions using some OCAF services.
1636### TDataStd_Sample.cxx
1637This sample contains templates for typical actions with the following standard OCAF attributes:
1638- Starting with data framework;
1639- TDataStd_Integer attribute management;
1640- TDataStd_RealArray attribute management;
1641- TDataStd_Comment attribute management;
1642- TDataStd_Name attribute management;
1643- TDataStd_UAttribute attribute management;
1644- TDF_Reference attribute management;
1645- TDataXtd_Point attribute management;
1646- TDataXtd_Plane attribute management;
1647- TDataXtd_Axis attribute management;
1648- TDataXtd_Geometry attribute management;
1649- TDataXtd_Constraint attribute management;
1650- TDataStd_Directory attribute management;
1651- TDataStd_TreeNode attribute management.
1653### TDocStd_Sample.cxx
1654This sample contains template for the following typical actions:
1655- creating application;
1656- creating the new document (document contains a framework);
1657- retrieving the document from a label of its framework;
1658- filling a document with data;
1659- saving a document in the file;
1660- closing a document;
1661- opening the document stored in the file;
1662- copying content of a document to another document with possibility to update the copy in the future.
1664### TPrsStd_Sample.cxx
1665This sample contains template for the following typical actions:
1666- starting with data framework;
1667- setting the TPrsStd_AISViewer in the framework;
1668- initialization of aViewer;
1669- finding TPrsStd_AISViewer attribute in the DataFramework;
1670- getting AIS_InteractiveContext from TPrsStd_AISViewer;
1671- adding driver to the map of drivers;
1672- getting driver from the map of drivers;
ba06f8bb 1673- setting TNaming_NamedShape to \<ShapeLabel\>;
1674- setting the new TPrsStd_AISPresentation to \<ShapeLabel\>;
dba69de2 1675- displaying;
1676- erasing;
1677- updating and displaying presentation of the attribute to be displayed;
1678- setting a color to the displayed attribute;
1679- getting transparency of the displayed attribute;
1680- modify attribute;
1681- updating presentation of the attribute in viewer.
1683### TNaming_Sample.cxx
1684This sample contains template for typical actions with OCAF Topological Naming services.
1685The following scenario is used:
1686- data framework initialization;
1687- creating Box1 and pushing it as PRIMITIVE in DF;
1688- creating Box2 and pushing it as PRIMITIVE in DF;
1689- moving Box2 (applying a transformation);
1690- pushing the selected edges of the top face of Box1 in DF;
1691- creating a Fillet (using the selected edges) and pushing the result as a modification of Box1;
1692- creating a Cut (Box1, Box2) as a modification of Box1 and push it in DF;
1693- recovering the result from DF.