From 5850b1ced0bd1835ebed64fd1a88b2d8235ab95b Mon Sep 17 00:00:00 2001
From: Maciej Suminski <maciej.suminski@cern.ch>
Date: Fri, 10 Jun 2016 17:06:54 +0200
Subject: [PATCH] GL_CONTEXT_MANAGER: Call SetCurrent() only when a different
 context is used.

---
 common/gl_context_mgr.cpp | 18 +++++++++++-------
 include/gl_context_mgr.h  |  3 +++
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/common/gl_context_mgr.cpp b/common/gl_context_mgr.cpp
index 850158dbcf..4b048cc607 100644
--- a/common/gl_context_mgr.cpp
+++ b/common/gl_context_mgr.cpp
@@ -44,18 +44,22 @@ wxGLContext* GL_CONTEXT_MANAGER::CreateCtx( wxGLCanvas* aCanvas, const wxGLConte
 
 void GL_CONTEXT_MANAGER::DestroyCtx( wxGLContext* aContext )
 {
-    assert( m_glCtx != aContext );
-
-    if( m_glContexts.count( aContext ) && m_glCtx != aContext )
+    if( m_glContexts.count( aContext ) )
     {
         m_glContexts.erase( aContext );
         delete aContext;
     }
     else
     {
-        // Do not delete currently used or unknown GL contexts
+        // Do not delete unknown GL contexts
         assert( false );
     }
+
+    if( m_glCtx == aContext )
+    {
+        m_glCtx = NULL;
+        m_glCanvas = NULL;
+    }
 }
 
 
@@ -75,9 +79,10 @@ void GL_CONTEXT_MANAGER::LockCtx( wxGLContext* aContext, wxGLCanvas* aCanvas )
     m_glCtxMutex.lock();
     wxGLCanvas* canvas = aCanvas ? aCanvas : m_glContexts.at( aContext );
 
-    if( aContext != m_glCtx )
+    if( aContext != m_glCtx || canvas != m_glCanvas )
     {
         canvas->SetCurrent( *aContext );
+        m_glCanvas = canvas;
         m_glCtx = aContext;
     }
 }
@@ -90,7 +95,6 @@ void GL_CONTEXT_MANAGER::UnlockCtx( wxGLContext* aContext )
     if( m_glCtx == aContext )
     {
         m_glCtxMutex.unlock();
-        m_glCtx = NULL;
     }
     else
     {
@@ -100,7 +104,7 @@ void GL_CONTEXT_MANAGER::UnlockCtx( wxGLContext* aContext )
 
 
 GL_CONTEXT_MANAGER::GL_CONTEXT_MANAGER()
-    : m_glCtx( NULL )
+    : m_glCtx( NULL ), m_glCanvas( NULL )
 {
 }
 
diff --git a/include/gl_context_mgr.h b/include/gl_context_mgr.h
index de5f7d0bb4..de45cfab62 100644
--- a/include/gl_context_mgr.h
+++ b/include/gl_context_mgr.h
@@ -88,6 +88,9 @@ private:
     ///> Currently bound GL context.
     wxGLContext* m_glCtx;
 
+    ///> The canvas that uses the current GL context.
+    wxGLCanvas* m_glCanvas;
+
     ///> Lock to prevent unexpected GL context switching.
     MUTEX m_glCtxMutex;