Merge 88386 - 2011-06-08 John Bauman <jbauman@chromium.org>

Source/WebCore/platform/graphics/chromium/LayerTilerChromium.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 328 matching lines @@
         return;
 
     GraphicsContext3D* context = layerRendererContext();
     const LayerTilerChromium::Program* program = layerRenderer()->tilerProgram();
     GLC(context, context->useProgram(program->program()));
     GLC(context, context->uniform1i(program->fragmentShader().samplerLocation(), 0));
     GLC(context, context->activeTexture(GraphicsContext3D::TEXTURE0));
 
     int left, top, right, bottom;
     contentRectToTileIndices(contentRect, left, top, right, bottom);
+    IntRect layerRect = contentRectToLayerRect(contentRect);
     for (int j = top; j <= bottom; ++j) {
         for (int i = left; i <= right; ++i) {
             Tile* tile = tileAt(i, j);
             if (!tile)
                 continue;
 
             tile->texture()->bindTexture();
 
             TransformationMatrix tileMatrix(globalTransform);
 
             // Don't use tileContentRect here, as that contains the full
             // rect with border texels which shouldn't be drawn.
             IntRect tileRect = m_tilingData.tileBounds(m_tilingData.tileIndex(tile->i(), tile->j()));
+            IntRect displayRect = tileRect;
+            tileRect.intersect(layerRect);
+            // Keep track of how the top left has moved, so the texture can be
+            // offset the same amount.
+            IntSize offset = tileRect.minXMinYCorner() - displayRect.minXMinYCorner();
             tileRect.move(m_layerPosition.x(), m_layerPosition.y());
             tileMatrix.translate3d(tileRect.x() + tileRect.width() / 2.0, tileRect.y() + tileRect.height() / 2.0, 0);
 
-            IntPoint texOffset = m_tilingData.textureOffset(tile->i(), tile->j());
+            IntPoint texOffset = m_tilingData.textureOffset(tile->i(), tile->j()) + offset;
             float tileWidth = static_cast<float>(m_tileSize.width());
             float tileHeight = static_cast<float>(m_tileSize.height());
             float texTranslateX = texOffset.x() / tileWidth;
             float texTranslateY = texOffset.y() / tileHeight;
             float texScaleX = tileRect.width() / tileWidth;
             float texScaleY = tileRect.height() / tileHeight;
             // OpenGL coordinate system is bottom-up.
             // If tile texture is top-down, we need to flip the texture coordinates.
             if (m_textureUpdater->orientation() == LayerTextureUpdater::TopDownOrientation) {
                 texTranslateY += 1.0;
@@ skipping 37 matching lines @@
 
     GLC(context, context->uniform4f(program->vertexShader().texTransformLocation(),
         texTranslateX, texTranslateY, texScaleX, texScaleY));
 
     GLC(context, context->drawElements(GraphicsContext3D::TRIANGLES, 6, GraphicsContext3D::UNSIGNED_SHORT, 0));
 }
 
 } // namespace WebCore
 
 #endif // USE(ACCELERATED_COMPOSITING)