Dispatches mouse movement messages in posted task to improve dragging smoothness

ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc

Index: ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
diff --git a/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc b/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
index 3f48b8993b7e83b6f4a9ddd878f6a85951fbb4bb..f03dcd1a0da045d114260d15937fc1b6d3bc621f 100644
--- a/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
+++ b/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
@@ -8,6 +8,7 @@
 // Get rid of a macro from Xlib.h that conflicts with Aura's RootWindow class.
 #undef RootWindow
 
+#include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_pump_x11.h"
 #include "base/run_loop.h"
@@ -56,7 +57,9 @@ X11WholeScreenMoveLoop::X11WholeScreenMoveLoop(
     : delegate_(delegate),
       in_move_loop_(false),
       should_reset_mouse_flags_(false),
-      grab_input_window_(None) {
+      grab_input_window_(None),
+      weak_factory_(this) {
+  last_xmotion_.type = NoEventMask;

[sadrul, 2014/03/27 19:25:09]

Set this to LASTEvent instead.

[varkha, 2014/03/27 21:00:54]

Done.

 }
 
 X11WholeScreenMoveLoop::~X11WholeScreenMoveLoop() {}
@@ -64,6 +67,13 @@ X11WholeScreenMoveLoop::~X11WholeScreenMoveLoop() {}
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHostLinux, MessagePumpDispatcher implementation:
 
+void X11WholeScreenMoveLoop::DispatchMouseMovement() {
+  if (!weak_factory_.HasWeakPtrs())
+    return;
+  weak_factory_.InvalidateWeakPtrs();

[sadrul, 2014/03/27 19:25:09]

Add a CHECK that last_xmotion_.type == MotionNotify

[varkha, 2014/03/27 21:00:54]

Done.

+  delegate_->OnMouseMovement(&last_xmotion_);

[sadrul, 2014/03/27 19:25:09]

set last_xmotion_.type back to LASTEvent here?

[varkha, 2014/03/27 21:00:54]

Done.

+}
+
 uint32_t X11WholeScreenMoveLoop::Dispatch(const base::NativeEvent& event) {
   XEvent* xev = event;
 
@@ -77,20 +87,29 @@ uint32_t X11WholeScreenMoveLoop::Dispatch(const base::NativeEvent& event) {
             screen->GetCursorScreenPoint() - drag_offset_);
         drag_widget_->SetBounds(gfx::Rect(location, drag_image_.size()));
       }
-      delegate_->OnMouseMovement(&xev->xmotion);
+      last_xmotion_ = xev->xmotion;
+      if (!weak_factory_.HasWeakPtrs()) {
+        base::MessageLoopForUI::current()->PostTask(

[sadrul, 2014/03/27 19:25:09]

Add a comment here why we do this.

[varkha, 2014/03/27 21:00:54]

Done.

+            FROM_HERE,
+            base::Bind(&X11WholeScreenMoveLoop::DispatchMouseMovement,
+                       weak_factory_.GetWeakPtr()));
+      }
       break;
     }
     case ButtonRelease: {
       if (xev->xbutton.button == Button1) {
         // Assume that drags are being done with the left mouse button. Only
         // break the drag if the left mouse button was released.
+        DispatchMouseMovement();
         delegate_->OnMouseReleased();
       }
       break;
     }
     case KeyPress: {
-      if (ui::KeyboardCodeFromXKeyEvent(xev) == ui::VKEY_ESCAPE)
+      if (ui::KeyboardCodeFromXKeyEvent(xev) == ui::VKEY_ESCAPE) {
+        weak_factory_.InvalidateWeakPtrs();

[sadrul, 2014/03/27 19:25:09]

Should this happen in EndMoveLoop() instead?

Also, this should reset last_motion_.type to LASTEvent

[varkha, 2014/03/27 21:00:54]

Done.

         EndMoveLoop();
+      }
       break;
     }
   }