cc: Remove texture scaling and clear edge texels of a layer.

cc/picture_pile_impl.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/trace_event.h"
 #include "cc/debug_colors.h"
 #include "cc/picture_pile_impl.h"
 #include "cc/region.h"
 #include "cc/rendering_stats.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkSize.h"
 #include "ui/gfx/rect_conversions.h"
+#include "ui/gfx/size_conversions.h"
 #include "ui/gfx/skia_util.h"
 
 namespace cc {
 
 scoped_refptr<PicturePileImpl> PicturePileImpl::Create() {
   return make_scoped_refptr(new PicturePileImpl());
 }
 
 PicturePileImpl::PicturePileImpl()
     : slow_down_raster_scale_factor_for_debug_(0) {
@@ skipping 30 matching lines @@
   }
   clone->min_contents_scale_ = min_contents_scale_;
   clone->set_slow_down_raster_scale_factor(
       slow_down_raster_scale_factor_for_debug_);
 
   return clone;
 }
 
 void PicturePileImpl::Raster(
     SkCanvas* canvas,
-    gfx::Rect content_rect,
+    gfx::Rect canvas_rect,
     float contents_scale,
     int64* total_pixels_rasterized) {
 
   DCHECK(contents_scale >= min_contents_scale_);
 
 #ifndef NDEBUG
   // Any non-painted areas will be left in this color.
   canvas->clear(DebugColors::NonPaintedFillColor());
 #endif  // NDEBUG
 
   canvas->save();
-  canvas->translate(-content_rect.x(), -content_rect.y());
-  canvas->clipRect(gfx::RectToSkRect(content_rect));
+  canvas->translate(-canvas_rect.x(), -canvas_rect.y());
 
+  gfx::SizeF total_content_size = gfx::ScaleSize(tiling_.total_size(),
+                                                 contents_scale);
+  gfx::Rect total_content_rect(gfx::ToCeiledSize(total_content_size));
+  gfx::Rect content_rect = total_content_rect;
+  content_rect.Intersect(canvas_rect);
+
+  // Clear one texel inside the right/bottom edge of the content rect,
+  // as it may only be partially covered by the picture playback.
+  // Also clear one texel outside the right/bottom edge of the content rect,
+  // as it may get blended in by linear filtering when zoomed in.
+  gfx::Rect deflated_content_rect = total_content_rect;
+  deflated_content_rect.Inset(0, 0, 1, 1);
+
+  gfx::Rect canvas_outside_content_rect = canvas_rect;
+  canvas_outside_content_rect.Subtract(deflated_content_rect);
+
+  if (!canvas_outside_content_rect.IsEmpty()) {
+    gfx::Rect inflated_content_rect = total_content_rect;
+    inflated_content_rect.Inset(0, 0, -1, -1);
+    canvas->clipRect(gfx::RectToSkRect(inflated_content_rect),
+                     SkRegion::kReplace_Op);
+    canvas->clipRect(gfx::RectToSkRect(deflated_content_rect),
+                     SkRegion::kDifference_Op);
+    canvas->drawColor(background_color_, SkXfermode::kSrc_Mode);
+  }
+
+  // Rasterize the collection of relevant picture piles.
   gfx::Rect layer_rect = gfx::ToEnclosingRect(
       gfx::ScaleRect(content_rect, 1.f / contents_scale));
 
+  canvas->clipRect(gfx::RectToSkRect(content_rect),
+                   SkRegion::kReplace_Op);
   Region unclipped(content_rect);
   for (TilingData::Iterator tile_iter(&tiling_, layer_rect);
        tile_iter; ++tile_iter) {
     PictureListMap::iterator map_iter =
         picture_list_map_.find(tile_iter.index());
     if (map_iter == picture_list_map_.end())
       continue;
     PictureList& pic_list= map_iter->second;
     if (pic_list.empty())
       continue;
@@ skipping 115 matching lines @@
       if (!(*i)->LayerRect().Intersects(layer_rect) || !(*i)->HasRecording())
         continue;
       if (!(*i)->IsCheapInRect(layer_rect))
         return false;
     }
   }
   return true;
 }
 
 }  // namespace cc