Tiling priorities in Android Webview.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 02fb92fb735dce8d5048487eebe38ab6800c7706..cc975bf74373c9b5575ca965d0f19ef65ada4a47 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -198,6 +198,8 @@ void PictureLayerImpl::AppendQuads(
       render_pass, scaled_content_bounds, shared_quad_state, append_quads_data);
 
   if (ShowDebugBorders()) {
+    SkColor color;

[enne (OOO), 2014/07/24 19:25:19]

?

[hush (inactive), 2014/07/24 23:29:37]

This is just a minor performance improvement. Don't create a temp variable for
each time in the iteration?

On 2014/07/24 19:25:19, enne wrote:

[enne (OOO), 2014/07/24 23:34:29]

There's not performance improvement here.  Neither SkColor nor float has a
constructor to call, so it's just pushing the stack to make space.  By keeping
them in the inner loop you get better readability (in my opinion) by knowing
that they are scoped to a single loop iteration.

If you want to make unrelated changes, please put them in separate patches.

[hush (inactive), 2014/07/24 23:48:07]

Okay. I will just revert this part.
On 2014/07/24 23:34:29, enne wrote:

+    float width;
     for (PictureLayerTilingSet::CoverageIterator iter(
              tilings_.get(),
              max_contents_scale,
@@ -205,8 +207,6 @@ void PictureLayerImpl::AppendQuads(
              ideal_contents_scale_);
          iter;
          ++iter) {
-      SkColor color;
-      float width;
       if (*iter && iter->IsReadyToDraw()) {
         ManagedTileState::TileVersion::Mode mode =
             iter->GetTileVersionForDrawing().mode();
@@ -399,8 +399,10 @@ void PictureLayerImpl::UpdateTiles(
   // resourceless software draw, so don't update them.
   if (!layer_tree_impl()->resourceless_software_draw()) {
     visible_rect_for_tile_priority_ = visible_content_rect();
-    viewport_size_for_tile_priority_ = layer_tree_impl()->DrawViewportSize();
+    viewport_rect_for_tile_priority_ = layer_tree_impl()->ExternalTilingRect();
     screen_space_transform_for_tile_priority_ = screen_space_transform();
+    screen_space_transform_for_tile_priority_.ConcatTransform(

[enne (OOO), 2014/07/24 19:25:19]

It seems a little bit like this viewport_rect_for_tile_priority_ and
screen_space_transform_for_tile_priority_ are a bit redundant.  It's not like
tile priorities are that smart about crazy perspective or rotation (they're just
treated as scales, but the scale comes from the content scale of the layer, not
the transform).  So it seems like you could just do this transform once and use
a transformed viewport rect here rather than a viewport + transform?

[hush (inactive), 2014/07/24 23:29:37]

Yeah right. I will do this based on your other comment in LTHI:
Combine "ExternalTilingRect" and "ExternalTilingTransform" into one function
"ViewportRectForTilingPriority" in layer_tree_impl. It will be the external
tiling rect inversely transformed from screen space into view space. Then
picture layer impl will just use ViewportRectForTilingPriority().
On 2014/07/24 19:25:19, enne wrote:

+        layer_tree_impl()->ExternalTilingTransform());
   }
 
   if (!CanHaveTilings()) {
@@ -457,16 +459,23 @@ void PictureLayerImpl::UpdateTilePriorities(
   if (!tiling_needs_update)
     return;
 
-  // Use visible_content_rect, unless it's empty. If it's empty, then
-  // try to inverse project the viewport into layer space and use that.
+  // If visible_rect_for_tile_priority_ is empty or
+  // LayerTreeImpl::ExternalTilingRect is set to be different from the device
+  // viewport, try to inverse project the viewport into layer space and use
+  // that. Otherwise just use visible_rect_for_tile_priority_
   gfx::Rect visible_rect_in_content_space = visible_rect_for_tile_priority_;
-  if (visible_rect_in_content_space.IsEmpty()) {
+  if (visible_rect_in_content_space.IsEmpty() ||
+      layer_tree_impl()->DeviceViewport() != viewport_rect_for_tile_priority_ ||
+      !layer_tree_impl()->ExternalTilingTransform().IsIdentity()) {
     gfx::Transform screen_to_layer(gfx::Transform::kSkipInitialization);
+
     if (screen_space_transform_for_tile_priority_.GetInverse(
             &screen_to_layer)) {
+      // Transform from screen space to content space.
       visible_rect_in_content_space =
           gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
-              screen_to_layer, gfx::Rect(viewport_size_for_tile_priority_)));
+              screen_to_layer, viewport_rect_for_tile_priority_));
+
       visible_rect_in_content_space.Intersect(gfx::Rect(content_bounds()));
     }
   }