Bug 575521 - Draw to a clipped context backed by the surface uploaded to OpenGL using APPLE_client_storage to avoid slowdowns in glTexSubImage2D. r=jrmuizel a=b

gfx/thebes/GLContext.cpp

@@ -534,8 +534,7 @@ BasicTextureImage::BeginUpdate(nsIntRegion& aRegion)
         mUpdateRect = aRegion.GetBounds();
     }
 
-    // the basic impl can't upload updates to disparate regions,
-    // only rects
+    // the basic impl can only upload updates to rectangles
     aRegion = nsIntRegion(mUpdateRect);
 
     nsIntSize rgnSize = mUpdateRect.Size();
@@ -614,6 +613,12 @@ BasicTextureImage::EndUpdate()
           DEBUG_GL_ERROR_CHECK(mGLContext);
         }
     } else {
+        // By default, mUpdateOffset is initialized to (0, 0), so we will
+        // upload from the origin of the update surface. Subclasses can set
+        // mUpdateOffset in an overridden BeginUpdate or EndUpdate to change
+        // this.
+        unsigned char* data = uploadImage->Data() + mUpdateOffset.x * 4 +
+                                                    mUpdateOffset.y * uploadImage->Stride();
         mGLContext->fTexSubImage2D(LOCAL_GL_TEXTURE_2D,
                                    0,
                                    mUpdateRect.x,
@@ -622,7 +627,7 @@ BasicTextureImage::EndUpdate()
                                    mUpdateRect.height,
                                    LOCAL_GL_RGBA,
                                    LOCAL_GL_UNSIGNED_BYTE,
-                                   uploadImage->Data());
+                                   data);
     }
     mUpdateContext = NULL;
 

gfx/thebes/GLContext.h

@@ -268,6 +268,7 @@ protected:
         : TextureImage(aTexture, aSize, aContentType)
         , mTextureInited(PR_FALSE)
         , mGLContext(aContext)
+        , mUpdateOffset(0, 0)
     {}
 
     virtual already_AddRefed<gfxASurface>
@@ -281,6 +282,9 @@ protected:
     nsRefPtr<gfxImageSurface> mBackingSurface;
     nsRefPtr<gfxContext> mUpdateContext;
     nsIntRect mUpdateRect;
+
+    // The offset into the update surface at which the update rect is located.
+    nsIntPoint mUpdateOffset;
 };
 
 struct THEBES_API ContextFormat

gfx/thebes/GLContextProviderCGL.mm

@@ -272,6 +272,51 @@ class TextureImageCGL : public BasicTextureImage
                                           GLContext*);
 
 protected:
+    virtual gfxContext*
+    BeginUpdate(nsIntRegion& aRegion)
+    {
+        ImageFormat format;
+        if (GetContentType() == gfxASurface::CONTENT_COLOR)
+            format = gfxASurface::ImageFormatRGB24;
+        else
+            format = gfxASurface::ImageFormatARGB32;
+
+        if (!mTextureInited || !mBackingSurface || !mUpdateSurface ||
+            nsIntSize(mBackingSurface->Width(), mBackingSurface->Height()) < mSize ||
+            mBackingSurface->Format() != format)
+        {
+            mUpdateSurface = nsnull;
+            mClippedRect = nsIntRect(0, 0, 0, 0);
+            // We need to (re)create our backing store. Let the base class to that.
+            return BasicTextureImage::BeginUpdate(aRegion);
+        }
+
+        // the basic impl can only upload updates to rectangles
+        mUpdateRect = aRegion.GetBounds();
+        aRegion = nsIntRegion(mUpdateRect);
+
+        if (!nsIntRect(nsIntPoint(0, 0), mSize).Contains(mUpdateRect)) {
+            NS_ERROR("update outside of image");
+            return NULL;
+        }
+
+        mUpdateContext = new gfxContext(mUpdateSurface);
+        mUpdateContext->Clip(gfxRect(mUpdateRect.x, mUpdateRect.y,
+                                     mUpdateRect.width, mUpdateRect.height));
+        mUpdateOffset = mUpdateRect.TopLeft();
+
+        return mUpdateContext;
+    }
+
+    virtual PRBool
+    EndUpdate()
+    {
+        if (!mUpdateSurface)
+            mUpdateSurface = mUpdateContext->OriginalSurface();
+
+        return BasicTextureImage::EndUpdate();
+    }
+
     virtual already_AddRefed<gfxASurface>
     CreateUpdateSurface(const gfxIntSize& aSize, ImageFormat aFmt)
     {
@@ -313,6 +358,7 @@ private:
     {}
 
     ImageFormat mUpdateFormat;
+    nsRefPtr<gfxASurface> mUpdateSurface;
 };
 
 already_AddRefed<TextureImage>