WIP - Gutterless resize on Windows

ui/views/widget/desktop_aura/desktop_window_tree_host_win.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 "ui/views/widget/desktop_aura/desktop_window_tree_host_win.h"
 
 #include "base/win/metro.h"
 #include "third_party/skia/include/core/SkPath.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_property.h"
 #include "ui/base/cursor/cursor_loader_win.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/win/shell.h"
+#include "ui/base/window_resize_helper.h"
 #include "ui/compositor/compositor_constants.h"
 #include "ui/compositor/paint_context.h"
 #include "ui/gfx/geometry/insets.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/path.h"
 #include "ui/gfx/path_win.h"
 #include "ui/gfx/win/dpi.h"
 #include "ui/native_theme/native_theme_aura.h"
 #include "ui/native_theme/native_theme_win.h"
@@ skipping 873 matching lines @@
 }
 
 void DesktopWindowTreeHostWin::HandleWindowSizeChanged() {
   // A resize may not have occurred if the window size happened not to have
   // changed (can occur on Windows 10 when snapping a window to the side of
   // the screen). In that case do a resize to the current size to reenable
   // swaps.
   if (compositor())
     compositor()->SetScaleAndSize(compositor()->device_scale_factor(),
                                   compositor()->size());
+
+  // If the window size has changed and this is a visible window, we may
+  // want to try to immediately produce a frame.
+  MaybeWaitForFrame();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHostWin, private:
 
 Widget* DesktopWindowTreeHostWin::GetWidget() {
   return native_widget_delegate_->AsWidget();
 }
 
 const Widget* DesktopWindowTreeHostWin::GetWidget() const {
@@ skipping 21 matching lines @@
   for (index = window()->children().begin();
        index != window()->children().end();
        ++index) {
     if ((*index)->GetProperty(aura::client::kModalKey) !=
         ui:: MODAL_TYPE_NONE && (*index)->TargetVisibility())
       return true;
   }
   return false;
 }
 
+void DesktopWindowTreeHostWin::MaybeWaitForFrame() {
+  if (!compositor())
+    return;
+
+  const gfx::Size target_size = compositor()->size();
+
+  if (!compositor()->IsVisible() ||
+      compositor()->last_swapped_frame_size() == target_size) {
+    return;
+  }
+
+  const int kPaintMsgTimeoutMS = 55;

[piman, 2015/12/15 07:15:36]

Any specific reason for 55 vs 50?
My gut feeling is that we should use the same value on all platforms, unless
there is a good reason not to.

+  const base::TimeTicks start_time = base::TimeTicks::Now();
+  const base::TimeTicks timeout_time =
+      start_time + base::TimeDelta::FromMilliseconds(kPaintMsgTimeoutMS);
+
+  ui::WindowResizeHelper* resize_helper = ui::WindowResizeHelper::Get();
+  for (base::TimeTicks now = start_time; now < timeout_time;
+       now = base::TimeTicks::Now()) {
+    if (!resize_helper->WaitForSingleTaskToRun(timeout_time - now))
+      return;  // Timeout.
+
+    // Since the UI thread is blocked, the size shouldn't change.
+    DCHECK(target_size == compositor()->size());
+    if (compositor()->last_swapped_frame_size() == target_size) {
+      return;  // Frame arrived.
+    }
+  }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHost, public:
 
 // static
 DesktopWindowTreeHost* DesktopWindowTreeHost::Create(
     internal::NativeWidgetDelegate* native_widget_delegate,
     DesktopNativeWidgetAura* desktop_native_widget_aura) {
   return new DesktopWindowTreeHostWin(native_widget_delegate,
                                       desktop_native_widget_aura);
 }
 
 }  // namespace views