From b7ec4ea16071d4d6d06c503c1890f4868e4f033f Mon Sep 17 00:00:00 2001
From: Maciej Suminski <maciej.suminski@cern.ch>
Date: Fri, 10 Jun 2016 17:07:12 +0200
Subject: [PATCH] Corrected the last instance check in OPENGL_GAL.

---
 common/gal/opengl/opengl_gal.cpp | 21 +++++++++++++++++----
 include/gal/opengl/opengl_gal.h  |  1 +
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/common/gal/opengl/opengl_gal.cpp b/common/gal/opengl/opengl_gal.cpp
index d6b5d444a1..4a6180cf93 100644
--- a/common/gal/opengl/opengl_gal.cpp
+++ b/common/gal/opengl/opengl_gal.cpp
@@ -51,6 +51,7 @@ static void InitTesselatorCallbacks( GLUtesselator* aTesselator );
 static const int glAttributes[] = { WX_GL_RGBA, WX_GL_DOUBLEBUFFER, WX_GL_DEPTH_SIZE, 8, 0 };
 
 wxGLContext* OPENGL_GAL::glMainContext = NULL;
+int OPENGL_GAL::instanceCounter = 0;
 GLuint OPENGL_GAL::fontTexture = 0;
 bool OPENGL_GAL::isBitmapFontLoaded = false;
 SHADER* OPENGL_GAL::shader = NULL;
@@ -74,6 +75,8 @@ OPENGL_GAL::OPENGL_GAL( wxWindow* aParent, wxEvtHandler* aMouseListener,
         glPrivContext = GL_CONTEXT_MANAGER::Get().CreateCtx( this, glMainContext );
     }
 
+    ++instanceCounter;
+
     // Check if OpenGL requirements are met
     runTest();
 
@@ -142,6 +145,7 @@ OPENGL_GAL::~OPENGL_GAL()
 {
     GL_CONTEXT_MANAGER::Get().LockCtx( glPrivContext );
 
+    --instanceCounter;
     glFlush();
     gluDeleteTess( tesselator );
     ClearCache();
@@ -151,9 +155,18 @@ OPENGL_GAL::~OPENGL_GAL()
     delete nonCachedManager;
     delete overlayManager;
 
+    GL_CONTEXT_MANAGER::Get().UnlockCtx( glPrivContext );
+
+    // If it was the main context, then it will be deleted
+    // when the last OpenGL GAL instance is destroyed (a few lines below)
+    if( glPrivContext != glMainContext )
+        GL_CONTEXT_MANAGER::Get().DestroyCtx( glPrivContext );
+
     // Are destroying the last GAL instance?
-    if( glPrivContext == glMainContext )
+    if( instanceCounter == 0 )
     {
+        GL_CONTEXT_MANAGER::Get().LockCtx( glMainContext );
+
         if( isBitmapFontLoaded )
         {
             glDeleteTextures( 1, &fontTexture );
@@ -161,11 +174,11 @@ OPENGL_GAL::~OPENGL_GAL()
         }
 
         delete shader;
-        glMainContext = NULL;
+
+        GL_CONTEXT_MANAGER::Get().UnlockCtx( glMainContext );
+        GL_CONTEXT_MANAGER::Get().DestroyCtx( glMainContext );
     }
 
-    GL_CONTEXT_MANAGER::Get().UnlockCtx( glPrivContext );
-    GL_CONTEXT_MANAGER::Get().DestroyCtx( glPrivContext );
 }
 
 
diff --git a/include/gal/opengl/opengl_gal.h b/include/gal/opengl/opengl_gal.h
index 508e13a6e5..8e218c7281 100644
--- a/include/gal/opengl/opengl_gal.h
+++ b/include/gal/opengl/opengl_gal.h
@@ -275,6 +275,7 @@ private:
 
     static wxGLContext*     glMainContext;      ///< Parent OpenGL context
     wxGLContext*            glPrivContext;      ///< Canvas-specific OpenGL context
+    static int              instanceCounter;    ///< GL GAL instance counter
     wxEvtHandler*           mouseListener;
     wxEvtHandler*           paintListener;