BUG: Don't leak GL state for face culling.

This addresses bug 12588, where backface culling would leak and cause
text to fail to be rendered. The added test fails until the patch is
applied to PostRender in vtkOpenGLProperty.

Change-Id: I63ced0363b33914d23a92527d9a2cf70963649f7

Rendering/Testing/Cxx/CMakeLists.txt

@@ -19,6 +19,7 @@ IF(VTK_USE_DISPLAY)
     LoadOpenGLExtension.cxx
     TestActorLightingFlag.cxx
     TestAnimationScene.cxx
+    TestBackfaceCulling.cxx
     TestBlurAndSobelPasses.cxx
     TestDynamic2DLabelMapper.cxx
     TestFBO.cxx

Rendering/Testing/Cxx/TestBackfaceCulling.cxx

+/*=========================================================================
+
+  Program:   Visualization Toolkit
+  Module:    TestBackfaceCulling.cxx
+
+  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
+  All rights reserved.
+  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notice for more information.
+
+=========================================================================*/
+// This tests backface culling with a text actor.
+//
+
+#include "vtkTestUtilities.h"
+#include "vtkRegressionTestImage.h"
+
+#include "vtkRenderWindowInteractor.h"
+#include "vtkRenderWindow.h"
+#include "vtkRenderer.h"
+#include "vtkCamera.h"
+#include "vtkSphereSource.h"
+#include "vtkActor.h"
+#include "vtkProperty.h"
+#include "vtkPolyDataMapper.h"
+#include "vtkTextActor.h"
+#include "vtkTextProperty.h"
+#include "vtkNew.h"
+
+int TestBackfaceCulling(int argc, char* argv[])
+{
+  vtkNew<vtkRenderWindowInteractor> iren;
+  vtkNew<vtkRenderWindow> renWin;
+  iren->SetRenderWindow(renWin.GetPointer());
+  vtkNew<vtkRenderer> renderer;
+  renWin->AddRenderer(renderer.GetPointer());
+  renderer->SetBackground(0.0, 0.0, 0.5);
+  renWin->SetSize(300, 300);
+
+  // Set up the sphere
+  vtkNew<vtkSphereSource> sphere;
+  vtkNew<vtkPolyDataMapper> mapper;
+  vtkNew<vtkActor> actor;
+  mapper->SetInput(sphere->GetOutput());
+  actor->SetMapper(mapper.GetPointer());
+  actor->GetProperty()->SetColor(0, 1, 0);
+  actor->GetProperty()->SetBackfaceCulling(1);
+  renderer->AddActor(actor.GetPointer());
+
+  // Set up the text renderer.
+  vtkNew<vtkTextActor> text;
+  renderer->AddActor(text.GetPointer());
+  text->SetInput("Can you see me?");
+  text->SetDisplayPosition(3, 4);
+
+  renWin->Render();
+  renderer->ResetCamera();
+
+  renWin->Render();
+
+  int retVal = vtkRegressionTestImage(renWin.GetPointer());
+  if (retVal == vtkRegressionTester::DO_INTERACTOR)
+    {
+    iren->Start();
+    }
+
+  return !retVal;
+}

Rendering/vtkOpenGLProperty.cxx

@@ -614,6 +614,13 @@ void vtkOpenGLProperty::PostRender(vtkActor *actor, vtkRenderer *renderer)
 {
   vtkOpenGLRenderer *oRenderer=static_cast<vtkOpenGLRenderer *>(renderer);
   vtkShaderProgram2 *prog=oRenderer->GetShaderProgram();
+
+  // Reset the face culling now we are done, leaking into text actor etc.
+  if (this->BackfaceCulling || this->FrontfaceCulling)
+    {
+    glDisable(GL_CULL_FACE);
+    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+    }
   
   if(this->CurrentShaderProgram2!=0) // ie if shaders are supported
     {