more X11/Linux debug-graphics fixes

btgui/GwenOpenGLTest/OpenGLSample.cpp

@@ -68,8 +68,8 @@ void MyMouseButtonCallback(int button, int state, float x, float y)
 	}
 }
 
-int sWidth = 1050;
-int sHeight = 768;
+int sWidth = 800;//1050;
+int sHeight = 600;//768;
 GLPrimitiveRenderer* primRenderer=0;
 //GwenOpenGL3CoreRenderer* gwenRenderer=0;
 Gwen::Renderer::Base* gwenRenderer =0;
@@ -308,7 +308,7 @@ int main()
 	b3gDefaultOpenGLWindow* window = new b3gDefaultOpenGLWindow();
 	window->setKeyboardCallback(keyCallback);
 	b3gWindowConstructionInfo wci;
-    wci.m_openglVersion = 2;
+    wci.m_openglVersion = 3;
 	wci.m_width = sWidth;
 	wci.m_height = sHeight;
 	//	wci.m_resizeCallback = MyResizeCallback;
@@ -324,14 +324,25 @@ int main()
         printf("Exit: Error cannot extract OpenGL version from GL_VERSION string\n");
         exit(0);
     }
-    if (majorGlVersion>=3)
+    if (majorGlVersion>=3 && wci.m_openglVersion>=3)
     {
         float retinaScale = 1.f;
 
 #ifndef __APPLE__
+#ifndef _WIN32
+    //we need glewExperimental on Linux
+    glewExperimental = GL_TRUE;
+#endif // _WIN32
         glewInit();
 #endif
 
+    //we ned to call glGetError twice, because of some Ubuntu/Intel/OpenGL issue
+
+    GLuint err = glGetError();
+    err = glGetError();
+    assert(err==GL_NO_ERROR);
+
+
         retinaScale = window->getRetinaScale();
 
         primRenderer = new GLPrimitiveRenderer(sWidth,sHeight);
@@ -410,7 +421,7 @@ int main()
 //	MSG msg;
 	while( !window->requestedExit() )
 	{
-        if (majorGlVersion<3)
+        if (majorGlVersion<3 || wci.m_openglVersion<3)
         {
             saveOpenGLState(sWidth,sHeight);
         }
@@ -503,7 +514,7 @@ int main()
 		}
 		window->endRendering();
 
-        if (majorGlVersion<3)
+        if (majorGlVersion<3 || wci.m_openglVersion<3)
         {
             restoreOpenGLState();
         }

btgui/OpenGLWindow/GLRenderToTexture.cpp

@@ -1,13 +1,26 @@
 
 ///See http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-14-render-to-texture/
 
-bool gIntelLinuxglDrawBufferWorkaround=false;
 
 #include "GLRenderToTexture.h"
 #include "Bullet3Common/b3Scalar.h" // for b3Assert
+#include <string.h>
+#include <stdio.h>
+
+bool gIntelLinuxglDrawBufferWorkaround=false;
+
 GLRenderToTexture::GLRenderToTexture()
 :m_framebufferName(0)
 {
+ const GLubyte* ven = glGetString(GL_VENDOR);
+	printf("ven = %s\n",ven);
+
+ if (strncmp((const char*)ven,"Intel",5)==0)
+       {
+               printf("Workaround for some crash in the Intel OpenGL driver on Linux/Ubuntu\n");
+               gIntelLinuxglDrawBufferWorkaround=true;
+       }
+
 }
 	
 void GLRenderToTexture::init(int width, int height, GLuint textureId, int renderTextureType)

btgui/OpenGLWindow/GLRenderToTexture.h

@@ -17,7 +17,6 @@ struct GLRenderToTexture
 	bool	m_initialized;
 	int		m_renderTextureType;
 public:
-		
 	GLRenderToTexture();
 	
 	void init(int width, int height, GLuint textureId, int renderTextureType=RENDERTEXTURE_COLOR);

btgui/OpenGLWindow/X11OpenGLWindow.cpp

@@ -15,7 +15,6 @@
 #include <unistd.h>
 
 #include <pthread.h>
-extern bool gIntelLinuxglDrawBufferWorkaround;
 
 GLint                   att[] = { GLX_RGBA, GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, None };
 static bool forceOpenGL3 = true;
@@ -235,11 +234,6 @@ void X11OpenGLWindow::enableOpenGL()
     const GLubyte* ven = glGetString(GL_VENDOR);
     printf("GL_VENDOR=%s\n", ven);
 
-    if (strncmp((const char*)ven,"Intel",5)==0)
-	{
-		printf("Workaround for some crash in the Intel OpenGL driver on Linux/Ubuntu\n");
-		gIntelLinuxglDrawBufferWorkaround=true;
-	}
     const GLubyte* ren = glGetString(GL_RENDERER);
     printf("GL_RENDERER=%s\n",ren);
     const GLubyte* ver = glGetString(GL_VERSION);
@@ -276,7 +270,10 @@ printf("createWindow\n");
 
     m_data->m_root = DefaultRootWindow(m_data->m_dpy);
 
-
+    if (ci.m_openglVersion < 3)
+    {
+        forceOpenGL3 = false;
+    }
 
     if (forceOpenGL3)
     {