Implementation of device metrics emulation in render view.

cc/layers/heads_up_display_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/layers/heads_up_display_layer.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/trees/layer_tree_host.h"
+#include "ui/gfx/size_conversions.h"
 
 namespace cc {
 
 scoped_refptr<HeadsUpDisplayLayer> HeadsUpDisplayLayer::Create() {
   return make_scoped_refptr(new HeadsUpDisplayLayer());
 }
 
 HeadsUpDisplayLayer::HeadsUpDisplayLayer() {}
 
 HeadsUpDisplayLayer::~HeadsUpDisplayLayer() {}
 
 void HeadsUpDisplayLayer::PrepareForCalculateDrawProperties(
     gfx::Size device_viewport, float device_scale_factor) {
   gfx::Size device_viewport_in_layout_pixels = gfx::Size(
       device_viewport.width() / device_scale_factor,
       device_viewport.height() / device_scale_factor);
 
+  if (parent()) {
+    // The root layer may have the transform set. As we still want to be shown

[aelias_OOO_until_Jul13, 2013/09/13 23:51:44]

This should be addressed on the Blink side instead.  You can set a inverse
transform on the HUD layer there or change where the transform is applied so
that the HUD layer isn't under it.

[dgozman, 2013/09/19 10:17:11]

AFAIK, blink doesn't know about the HUD layer. Ideally, we should place HUD
layer as a sibling to blink root layer. Not sure if that's the right choice
though. WDYT?

+    // at the corner of visible viewport, apply inverted transform to it.
+    gfx::Transform invert;
+    gfx::RectF rect(device_viewport_in_layout_pixels);
+    if (parent()->transform().TransformRectReverse(&rect)) {
+      device_viewport_in_layout_pixels = gfx::ToFlooredSize(rect.size());
+    }
+  }
+
   gfx::Size bounds;
   gfx::Transform matrix;
   matrix.MakeIdentity();
 
   if (layer_tree_host()->debug_state().ShowHudRects()) {
     int max_texture_size =
         layer_tree_host()->GetRendererCapabilities().max_texture_size;
     bounds.SetSize(std::min(max_texture_size,
                             device_viewport_in_layout_pixels.width()),
                    std::min(max_texture_size,
@@ skipping 14 matching lines @@
     LayerTreeImpl* tree_impl) {
   return HeadsUpDisplayLayerImpl::Create(tree_impl, layer_id_).
       PassAs<LayerImpl>();
 }
 
 std::string HeadsUpDisplayLayer::DebugName() {
   return std::string("Heads Up Display Layer");
 }
 
 }  // namespace cc