From 73382cbc58e7f43941b311094d4fe6b1a0988cab Mon Sep 17 00:00:00 2001
From: kgv <kgv@opencascade.com>
Date: Sun, 24 Jan 2021 18:31:54 +0300
Subject: [PATCH] 0032081: Visualization - WebGL sample errors when run in
 Safari browser

---
 samples/webgl/CMakeLists.txt  |  3 ++-
 src/OpenGl/OpenGl_Context.cxx | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/samples/webgl/CMakeLists.txt b/samples/webgl/CMakeLists.txt
index 3a32e698da..7838293f5c 100644
--- a/samples/webgl/CMakeLists.txt
+++ b/samples/webgl/CMakeLists.txt
@@ -14,7 +14,8 @@ endif()
 
 # customize build
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s WASM=1")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s USE_WEBGL2=1")
+#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s USE_WEBGL2=1")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s MAX_WEBGL_VERSION=2")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s ALLOW_MEMORY_GROWTH=1")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --bind")
 #set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s SAFE_HEAP=1")
diff --git a/src/OpenGl/OpenGl_Context.cxx b/src/OpenGl/OpenGl_Context.cxx
index 097e12fefe..d4f12d0270 100644
--- a/src/OpenGl/OpenGl_Context.cxx
+++ b/src/OpenGl/OpenGl_Context.cxx
@@ -1156,6 +1156,20 @@ void OpenGl_Context::ReadGlVersion (Standard_Integer& theGlVerMajor,
   // read numbers
   theGlVerMajor = atoi (aMajorStr);
   theGlVerMinor = atoi (aMinorStr);
+#if defined(__EMSCRIPTEN__)
+  if (theGlVerMajor >= 3)
+  {
+    if (!toCheckVer3
+     || ::strstr (aVerStr, "WebGL 1.0") != NULL)
+    {
+      Message::SendWarning() << "Warning! OpenGL context reports version " << theGlVerMajor << "." << theGlVerMinor
+                             << " but WebGL 2.0 was unavailable\n"
+                             << "Fallback to OpenGL ES 2.0 will be used instead of reported version";
+      theGlVerMajor = 2;
+      theGlVerMinor = 0;
+    }
+  }
+#endif
 
   if (theGlVerMajor <= 0)
   {
-- 
2.39.5