Bug 1223144 - Scale texture coordinates in CompositorOGL for non POT textures. r=mwoodrow

gfx/layers/opengl/CompositorOGL.cpp

@@ -412,6 +412,21 @@ CompositorOGL::Initialize()
   return true;
 }
 
+/*
+ * Returns a size that is equal to, or larger than and closest to,
+ * aSize where both width and height are powers of two.
+ * If the OpenGL setup is capable of using non-POT textures,
+ * then it will just return aSize.
+ */
+static IntSize
+CalculatePOTSize(const IntSize& aSize, GLContext* gl)
+{
+  if (CanUploadNonPowerOfTwo(gl))
+    return aSize;
+
+  return IntSize(NextPowerOfTwo(aSize.width), NextPowerOfTwo(aSize.height));
+}
+
 // |aRect| is the rectangle we want to draw to. We will draw it with
 // up to 4 draw commands if necessary to avoid wrapping.
 // |aTexCoordRect| is the rectangle from the texture that we want to
@@ -424,10 +439,26 @@ CompositorOGL::BindAndDrawQuadWithTextureRect(ShaderProgramOGL *aProg,
                                               const Rect& aTexCoordRect,
                                               TextureSource *aTexture)
 {
+  Rect scaledTexCoordRect = aTexCoordRect;
+
+  // If the OpenGL setup does not support non-power-of-two textures then the
+  // texture's width and height will have been increased to the next
+  // power-of-two (unless already a power of two). In that case we must scale
+  // the texture coordinates to account for that.
+  if (!CanUploadNonPowerOfTwo(mGLContext)) {
+    const IntSize& textureSize = aTexture->GetSize();
+    const IntSize potSize = CalculatePOTSize(textureSize, mGLContext);
+    if (potSize != textureSize) {
+      const float xScale = (float)textureSize.width / (float)potSize.width;
+      const float yScale = (float)textureSize.height / (float)potSize.height;
+      scaledTexCoordRect.Scale(xScale, yScale);
+    }
+  }
+
   Rect layerRects[4];
   Rect textureRects[4];
   size_t rects = DecomposeIntoNoRepeatRects(aRect,
-                                            aTexCoordRect,
+                                            scaledTexCoordRect,
                                             &layerRects,
                                             &textureRects);
 
@@ -572,21 +603,6 @@ GetFrameBufferInternalFormat(GLContext* gl,
   return LOCAL_GL_RGBA;
 }
 
-/*
- * Returns a size that is larger than and closest to aSize where both
- * width and height are powers of two.
- * If the OpenGL setup is capable of using non-POT textures, then it
- * will just return aSize.
- */
-static IntSize
-CalculatePOTSize(const IntSize& aSize, GLContext* gl)
-{
-  if (CanUploadNonPowerOfTwo(gl))
-    return aSize;
-
-  return IntSize(NextPowerOfTwo(aSize.width), NextPowerOfTwo(aSize.height));
-}
-
 void
 CompositorOGL::ClearRect(const gfx::Rect& aRect)
 {

gfx/thebes/gfxUtils.h

@@ -336,8 +336,8 @@ IsPowerOfTwo(int aNumber)
 }
 
 /**
- * Returns the first integer greater than |aNumber| which is a power of two
- * Undefined for |aNumber| < 0
+ * Returns the first integer greater than or equal to |aNumber| which is a
+ * power of two. Undefined for |aNumber| < 0.
  */
 static inline int
 NextPowerOfTwo(int aNumber)