Fixed alpha-blended drawables getting incorrect alpha values when rendered through a RenderImage

Replaced internal calls to glewIsSupported with the corresponding constants (faster checks)

git-svn-id: https://sfml.svn.sourceforge.net/svnroot/sfml/branches/sfml2@1264 4e206d99-4929-0410-ac5d-dfc041789085

src/SFML/Graphics/Batch.cpp

@@ -90,14 +90,28 @@ void Batch::Render(GeometryRenderer& renderer) const
     {
         GLCheck(glEnable(GL_BLEND));
 
-        // @todo the resulting alpha may not be correct, which matters when target is a RenderImage.
-        //       find a fix for this (glBlendFuncSeparate -- but not supported by every graphics card)
         switch (myBlendMode)
         {
+            // Alpha blending
+            // glBlendFuncSeparateEXT is used when available to avoid an incorrect alpha value when the target
+            // is a RenderImage -- in this case the alpha value must be written directly to the target buffer
             default :
-            case Blend::Alpha :    GLCheck(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)); break;
-            case Blend::Add :      GLCheck(glBlendFunc(GL_SRC_ALPHA, GL_ONE));                 break;
-            case Blend::Multiply : GLCheck(glBlendFunc(GL_DST_COLOR, GL_ZERO));                break;
+            case Blend::Alpha :
+                if (GLEW_EXT_blend_func_separate)
+                    GLCheck(glBlendFuncSeparateEXT(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ZERO));
+                else
+                    GLCheck(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+                break;
+
+            // Additive blending
+            case Blend::Add :
+                GLCheck(glBlendFunc(GL_SRC_ALPHA, GL_ONE));
+                break;
+
+            // Multiplicative blending
+            case Blend::Multiply :
+                GLCheck(glBlendFunc(GL_DST_COLOR, GL_ZERO));
+                break;
         }
     }
 

src/SFML/Graphics/GeometryRendererVA.cpp

@@ -38,7 +38,7 @@ bool GeometryRendererVA::IsSupported()
 {
     priv::EnsureGlewInit();
 
-    return glewIsSupported("GL_EXT_vertex_array") != 0;
+    return GLEW_EXT_vertex_array != 0;
 }
 
 
@@ -47,8 +47,6 @@ GeometryRendererVA::GeometryRendererVA() :
 myIndices(NULL)
 {
     priv::EnsureGlewInit();
-
-    myCanLock = glewIsSupported("GL_EXT_compiled_vertex_array") != 0;
 }
 
 
@@ -71,7 +69,7 @@ void GeometryRendererVA::Begin(const float* vertices, std::size_t verticesCount,
     GLCheck(glTexCoordPointer(2, GL_FLOAT, stride, vertices + 6));
 
     // Lock (compile) the vertex array if supported
-    if (myCanLock)
+    if (GLEW_EXT_compiled_vertex_array)
         GLCheck(glLockArraysEXT(0, verticesCount / 8));
 
     // Store indices for later use
@@ -83,7 +81,7 @@ void GeometryRendererVA::Begin(const float* vertices, std::size_t verticesCount,
 void GeometryRendererVA::End()
 {
     // Unlock the vertex array if it was locked
-    if (myCanLock)
+    if (GLEW_EXT_compiled_vertex_array)
         GLCheck(glUnlockArraysEXT());
 }
 

src/SFML/Graphics/GeometryRendererVA.hpp

@@ -96,7 +96,6 @@ public :
     ////////////////////////////////////////////////////////////
     // Member data
     ////////////////////////////////////////////////////////////
-    bool                myCanLock; ///< Is geometry locking supported?
     const unsigned int* myIndices; ///< Pointer to the indices to render
 };
 

src/SFML/Graphics/GeometryRendererVBO.cpp

@@ -37,7 +37,7 @@ bool GeometryRendererVBO::IsSupported()
 {
     priv::EnsureGlewInit();
 
-    return glewIsSupported("GL_ARB_vertex_buffer_object") != 0;
+    return GLEW_ARB_vertex_buffer_object != 0;
 }
 
 

src/SFML/Graphics/Image.cpp

@@ -584,7 +584,7 @@ unsigned int Image::GetValidTextureSize(unsigned int size)
     // Make sure that GLEW is initialized
     priv::EnsureGlewInit();
 
-    if (glewIsSupported("GL_ARB_texture_non_power_of_two") != 0)
+    if (GLEW_ARB_texture_non_power_of_two)
     {
         // If hardware supports NPOT textures, then just return the unmodified size
         return size;

src/SFML/Graphics/RenderImageImplFBO.cpp

@@ -75,7 +75,7 @@ bool RenderImageImplFBO::IsSupported()
     // Make sure that GLEW is initialized
     priv::EnsureGlewInit();
 
-    return glewIsSupported("GL_EXT_framebuffer_object") != 0;
+    return GLEW_EXT_framebuffer_object != 0;
 }
 
 

src/SFML/Graphics/Shader.cpp

@@ -309,10 +309,10 @@ bool Shader::IsAvailable()
     // Make sure that GLEW is initialized
     priv::EnsureGlewInit();
 
-    return glewIsSupported("GL_ARB_shading_language_100") != 0 &&
-           glewIsSupported("GL_ARB_shader_objects")       != 0 &&
-           glewIsSupported("GL_ARB_vertex_shader")        != 0 &&
-           glewIsSupported("GL_ARB_fragment_shader")      != 0;
+    return GLEW_ARB_shading_language_100 &&
+           GLEW_ARB_shader_objects       &&
+           GLEW_ARB_vertex_shader        &&
+           GLEW_ARB_fragment_shader;
 }
 
 

src/SFML/Graphics/Win32/RenderImageImplPBuffer.cpp

@@ -79,8 +79,7 @@ bool RenderImageImplPBuffer::IsSupported()
     // Make sure that GLEW is initialized
     priv::EnsureGlewInit();
 
-    return wglewIsSupported("WGL_ARB_pbuffer") &&
-           wglewIsSupported("WGL_ARB_pixel_format");
+    return WGLEW_ARB_pbuffer && WGLEW_ARB_pixel_format;
 }