cc: Don't use partial updates for scrollbars when they are not allowed.

cc/scrollbar_layer.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 "cc/scrollbar_layer.h"
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/layer_painter.h"
 #include "cc/layer_tree_host.h"
@@ skipping 229 matching lines @@
     if (!m_thumb)
         m_thumb = m_thumbUpdater->createResource(layerTreeHost()->contentsTextureManager());
 }
 
 void ScrollbarLayer::updatePart(CachingBitmapContentLayerUpdater* painter, LayerUpdater::Resource* resource, const gfx::Rect& rect, ResourceUpdateQueue& queue, RenderingStats& stats)
 {
     // Skip painting and uploading if there are no invalidations and
     // we already have valid texture data.
     if (resource->texture()->haveBackingTexture() &&
         resource->texture()->size() == rect.size() &&
-        m_updateRect.IsEmpty())
+        !isDirty())
         return;
 
     // We should always have enough memory for UI.
     DCHECK(resource->texture()->canAcquireBackingTexture());
     if (!resource->texture()->canAcquireBackingTexture())
         return;
 
     // Paint and upload the entire part.
     gfx::Rect paintedOpaqueRect;
     painter->prepareToUpdate(rect, rect.size(), contentsScaleX(), contentsScaleY(), paintedOpaqueRect, stats);
     if (!painter->pixelsDidChange() && resource->texture()->haveBackingTexture()) {
         TRACE_EVENT_INSTANT0("cc","ScrollbarLayer::updatePart no texture upload needed");
         return;
     }
 
+    bool partialUpdatesAllowed = layerTreeHost()->settings().maxPartialTextureUpdates > 0;
+    if (!partialUpdatesAllowed)
+      resource->texture()->returnBackingTexture();
+
     gfx::Vector2d destOffset(0, 0);
-    resource->update(queue, rect, destOffset, false, stats);
+    resource->update(queue, rect, destOffset, partialUpdatesAllowed, stats);
 }
 
 gfx::Rect ScrollbarLayer::scrollbarLayerRectToContentRect(const gfx::Rect& layerRect) const
 {
     // Don't intersect with the bounds as in layerRectToContentRect() because
     // layerRect here might be in coordinates of the containing layer.
     gfx::RectF contentRect = gfx::ScaleRect(layerRect, contentsScaleX(), contentsScaleY());
     return gfx::ToEnclosingRect(contentRect);
 }
 
@@ skipping 17 matching lines @@
     }
     if (m_thumb) {
         gfx::Size thumbSize = scrollbarLayerRectToContentRect(m_geometry->thumbRect(m_scrollbar.get())).size();
         m_thumb->texture()->setDimensions(thumbSize, m_textureFormat);
         m_thumb->texture()->setRequestPriority(PriorityCalculator::uiPriority(drawsToRoot));
     }
 }
 
 void ScrollbarLayer::update(ResourceUpdateQueue& queue, const OcclusionTracker*, RenderingStats& stats)
 {
+    m_dirtyRect.Union(m_updateRect);

[enne (OOO), 2012/12/17 20:59:02]

What does adding m_dirtyRect enable you to do that m_updateRect didn't?

[danakj, 2012/12/17 21:27:06]

it lets you return when visibleContentRect() is empty (ie scrollbar is not
visible) and then paint it when it becomes visible.

[enne (OOO), 2012/12/17 21:36:45]

Ah, ok.  I see.  :)

     if (contentBounds().IsEmpty())
         return;
+    if (visibleContentRect().IsEmpty())
+        return;
+    if (!isDirty())
+        return;
 
     createUpdaterIfNeeded();
 
     gfx::Rect contentRect = scrollbarLayerRectToContentRect(gfx::Rect(m_scrollbar->location(), bounds()));
     updatePart(m_backTrackUpdater.get(), m_backTrack.get(), contentRect, queue, stats);
     if (m_foreTrack && m_foreTrackUpdater)
         updatePart(m_foreTrackUpdater.get(), m_foreTrack.get(), contentRect, queue, stats);
 
     // Consider the thumb to be at the origin when painting.
-    WebKit::WebRect thumbRect = m_geometry->thumbRect(m_scrollbar.get());
-    gfx::Rect originThumbRect = scrollbarLayerRectToContentRect(gfx::Rect(0, 0, thumbRect.width, thumbRect.height));
+    gfx::Rect thumbRect = m_geometry->thumbRect(m_scrollbar.get());
+    gfx::Rect originThumbRect = scrollbarLayerRectToContentRect(gfx::Rect(thumbRect.size()));
     if (!originThumbRect.IsEmpty())
         updatePart(m_thumbUpdater.get(), m_thumb.get(), originThumbRect, queue, stats);
+
+    m_dirtyRect = gfx::RectF();
 }
 
 }  // namespace cc