linux_aura: Improve window drag performance.

ui/views/widget/desktop_aura/x11_desktop_window_move_client.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/x11_desktop_window_move_client.h"
 
 #include <X11/Xlib.h>
 // Get rid of a macro from Xlib.h that conflicts with Aura's RootWindow class.
 #undef RootWindow
 
 #include "base/debug/stack_trace.h"
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_pump_x11.h"
 #include "base/run_loop.h"
 #include "ui/aura/env.h"
 #include "ui/aura/root_window.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/events/event.h"
 #include "ui/gfx/screen.h"
 
+namespace {
+
+// Delay moving the window.
+//
+// When we receive a mouse move event, we have to have it processed in a
+// different run through the message pump because moving the window will
+// otherwise prevent tasks from running.
+//
+// This constant was derived with playing with builds of chrome; it has no
+// theoretical justification.
+//
+// TODO(erg): This helps with the performance of dragging windows, but it
+// doesn't really solve the hard problems, which is that various calls to X11,
+// such as XQueryPointer, ui::IsWindowVisible() and ui::WindowContainsPoint()
+// take a while to get replies and block in the process. I've seen all of the
+// above take as long as 20ms to respond.
+const int kMoveDelay = 3;
+
+}  // namespace
+
 namespace views {
 
 X11DesktopWindowMoveClient::X11DesktopWindowMoveClient()
     : move_loop_(this),
       root_window_(NULL) {
 }
 
 X11DesktopWindowMoveClient::~X11DesktopWindowMoveClient() {}
 
 void X11DesktopWindowMoveClient::OnMouseMovement(XMotionEvent* event) {
   gfx::Point cursor_point(event->x_root, event->y_root);
   gfx::Point system_loc = cursor_point - window_offset_;
-  root_window_->SetHostBounds(gfx::Rect(
-      system_loc, root_window_->GetHostSize()));
+
+  gfx::Rect target_rect(system_loc, root_window_->GetHostSize());
+
+  window_move_timer_.Start(
+      FROM_HERE,
+      base::TimeDelta::FromMilliseconds(kMoveDelay),
+      base::Bind(&X11DesktopWindowMoveClient::SetHostBounds,
+                 base::Unretained(this),
+                 target_rect));
 }
 
 void X11DesktopWindowMoveClient::OnMouseReleased() {
   EndMoveLoop();
 }
 
 void X11DesktopWindowMoveClient::OnMoveLoopEnded() {
   root_window_ = NULL;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopRootWindowHostLinux, aura::client::WindowMoveClient implementation:
 
 aura::client::WindowMoveResult X11DesktopWindowMoveClient::RunMoveLoop(
     aura::Window* source,
     const gfx::Vector2d& drag_offset,
     aura::client::WindowMoveSource move_source) {
   window_offset_ = drag_offset;
   root_window_ = source->GetDispatcher();
 
   bool success = move_loop_.RunMoveLoop(source, root_window_->last_cursor());
   return success ? aura::client::MOVE_SUCCESSFUL : aura::client::MOVE_CANCELED;
 }
 
 void X11DesktopWindowMoveClient::EndMoveLoop() {
+  window_move_timer_.Stop();
   move_loop_.EndMoveLoop();
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// DesktopRootWindowHostLinux, private:
+
+void X11DesktopWindowMoveClient::SetHostBounds(const gfx::Rect& rect) {
+  root_window_->SetHostBounds(rect);
+}
+
 }  // namespace views