[Aura] Translate web contents area to nearest physical pixel boundary

content/browser/renderer_host/render_widget_host_view_aura.cc

 // Copyright (c) 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 "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_number_conversions.h"
+#include "cc/layers/layer.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/output/copy_output_result.h"
 #include "cc/resources/texture_mailbox.h"
 #include "cc/trees/layer_tree_settings.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
 #include "content/browser/accessibility/browser_accessibility_state_impl.h"
 #include "content/browser/frame_host/frame_tree.h"
 #include "content/browser/frame_host/frame_tree_node.h"
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/browser/gpu/compositor_util.h"
@@ skipping 581 matching lines @@
   aura::Window* root = window_->GetRootWindow();
   if (root) {
     aura::client::ScreenPositionClient* screen_position_client =
         aura::client::GetScreenPositionClient(root);
     if (screen_position_client) {
       screen_position_client->ConvertPointFromScreen(
           window_->parent(), &relative_origin);
     }
   }
 
+  SnapToPhysicalPixelBoundary();
   InternalSetBounds(gfx::Rect(relative_origin, rect.size()));
 }
 
 gfx::NativeView RenderWidgetHostViewAura::GetNativeView() const {
   return window_;
 }
 
 gfx::NativeViewId RenderWidgetHostViewAura::GetNativeViewId() const {
 #if defined(OS_WIN)
   aura::WindowTreeHost* host = window_->GetHost();
@@ skipping 329 matching lines @@
 }
 
 void RenderWidgetHostViewAura::EndFrameSubscription() {
   delegated_frame_host_->EndFrameSubscription();
 }
 
 void RenderWidgetHostViewAura::AcceleratedSurfaceInitialized(int host_id,
                                                              int route_id) {
 }
 
+void RenderWidgetHostViewAura::SnapToPhysicalPixelBoundary() {
+  // The top left corner of our view in window coordinates might not land on a
+  // device pixel boundary if we have a non-integer device scale. In that case,
+  // to avoid the web contents area looking blurry we translate the web contents
+  // in the +x, +y direction to land on the nearest pixel boundary. This may
+  // cause the bottom and right edges to be clipped slightly, but that's ok.
+  gfx::Point view_offset_dips = window_->GetBoundsInRootWindow().origin();
+  gfx::PointF view_offset = view_offset_dips;
+  view_offset.Scale(current_device_scale_factor_);
+  gfx::PointF view_offset_snapped(std::ceil(view_offset.x()),
+                                  std::ceil(view_offset.y()));
+
+  gfx::Vector2dF fudge = view_offset_snapped - view_offset;
+  fudge.Scale(1.0 / current_device_scale_factor_);
+  gfx::Transform fudge_transform;
+  fudge_transform.Translate(fudge.x(), fudge.y());
+  GetLayer()->cc_layer()->SetTransform(fudge_transform);
+}
+
 void RenderWidgetHostViewAura::InternalSetBounds(const gfx::Rect& rect) {
   if (HasDisplayPropertyChanged(window_))
     host_->InvalidateScreenInfo();
 
   // Don't recursively call SetBounds if this bounds update is the result of
   // a Window::SetBoundsInternal call.
   if (!in_bounds_changed_)
     window_->SetBounds(rect);
   host_->WasResized();
   delegated_frame_host_->WasResized();
@@ skipping 1404 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewBase, public:
 
 // static
 void RenderWidgetHostViewBase::GetDefaultScreenInfo(WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }
 
 }  // namespace content