From 036add8e9e7bafa4e1335481f70e46bf3f7c918d Mon Sep 17 00:00:00 2001
From: "Konstantin S. Matveyev" <root@zorro.ev>
Date: Fri, 18 Aug 2017 10:20:26 +0300
Subject: [PATCH] glClear should not be called with zero-mask in
 osgUtil::RenderStage::drawImplementation

---
 src/osgUtil/RenderStage.cpp | 58 +++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 28 deletions(-)

diff --git a/src/osgUtil/RenderStage.cpp b/src/osgUtil/RenderStage.cpp
index 2b707e57d..e05af611a 100644
--- a/src/osgUtil/RenderStage.cpp
+++ b/src/osgUtil/RenderStage.cpp
@@ -1342,40 +1342,42 @@ void RenderStage::drawImplementation(osg::RenderInfo& renderInfo,RenderLeaf*& pr
     if (_colorMask.valid()) _colorMask->apply(state);
     else glColorMask(GL_TRUE,GL_TRUE,GL_TRUE,GL_TRUE);
 
-    if (_clearMask & GL_COLOR_BUFFER_BIT)
+    if (_clearMask != 0)
     {
-        glClearColor( _clearColor[0], _clearColor[1], _clearColor[2], _clearColor[3]);
-    }
+        if (_clearMask & GL_COLOR_BUFFER_BIT)
+        {
+            glClearColor( _clearColor[0], _clearColor[1], _clearColor[2], _clearColor[3]);
+        }
 
-    if (_clearMask & GL_DEPTH_BUFFER_BIT)
-    {
-        #if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE) && !defined(OSG_GLES3_AVAILABLE)
-            glClearDepth( _clearDepth);
-        #else
-            glClearDepthf( _clearDepth);
+        if (_clearMask & GL_DEPTH_BUFFER_BIT)
+        {
+            #if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE) && !defined(OSG_GLES3_AVAILABLE)
+                glClearDepth( _clearDepth);
+            #else
+                glClearDepthf( _clearDepth);
+            #endif
+
+            glDepthMask ( GL_TRUE );
+            state.haveAppliedAttribute( osg::StateAttribute::DEPTH );
+        }
+
+        if (_clearMask & GL_STENCIL_BUFFER_BIT)
+        {
+            glClearStencil( _clearStencil);
+            glStencilMask ( ~0u );
+            state.haveAppliedAttribute( osg::StateAttribute::STENCIL );
+        }
+
+        #if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE) && !defined(OSG_GLES3_AVAILABLE) && !defined(OSG_GL3_AVAILABLE)
+            if (_clearMask & GL_ACCUM_BUFFER_BIT)
+            {
+                glClearAccum( _clearAccum[0], _clearAccum[1], _clearAccum[2], _clearAccum[3]);
+            }
         #endif
 
-        glDepthMask ( GL_TRUE );
-        state.haveAppliedAttribute( osg::StateAttribute::DEPTH );
+        glClear( _clearMask );
     }
 
-    if (_clearMask & GL_STENCIL_BUFFER_BIT)
-    {
-        glClearStencil( _clearStencil);
-        glStencilMask ( ~0u );
-        state.haveAppliedAttribute( osg::StateAttribute::STENCIL );
-    }
-
-    #if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE) && !defined(OSG_GLES3_AVAILABLE) && !defined(OSG_GL3_AVAILABLE)
-        if (_clearMask & GL_ACCUM_BUFFER_BIT)
-        {
-            glClearAccum( _clearAccum[0], _clearAccum[1], _clearAccum[2], _clearAccum[3]);
-        }
-    #endif
-
-
-    glClear( _clearMask );
-
     #ifdef USE_SCISSOR_TEST
         glDisable( GL_SCISSOR_TEST );
     #endif