Ignores mouse motion events when mouse is pressed or drag and drop is in progress

ui/views/corewm/tooltip_controller.cc

Index: ui/views/corewm/tooltip_controller.cc
diff --git a/ui/views/corewm/tooltip_controller.cc b/ui/views/corewm/tooltip_controller.cc
index 500466fdf4d646c69ccba8f31c98ef85a8f9496c..9cb56c2cf76f4e732dcb2bb91722c8b6c20db02d 100644
--- a/ui/views/corewm/tooltip_controller.cc
+++ b/ui/views/corewm/tooltip_controller.cc
@@ -28,6 +28,10 @@ namespace {
 const int kTooltipTimeoutMs = 500;
 const int kDefaultTooltipShownTimeoutMs = 10000;
 
+// Delay mouse events so that they are dispatched if there are no mouse location
+// events pending. Even a short delay delays them until the mouse is steady.
+const int kMouseMoveDelay = 10;
+
 // Returns true if |target| is a valid window to get the tooltip from.
 // |event_target| is the original target from the event and |target| the window
 // at the same location.
@@ -46,9 +50,10 @@ bool IsValidTarget(aura::Window* event_target, aura::Window* target) {
 // Returns the target (the Window tooltip text comes from) based on the event.
 // If a Window other than event.target() is returned, |location| is adjusted
 // to be in the coordinates of the returned Window.
-aura::Window* GetTooltipTarget(const ui::MouseEvent& event,
+aura::Window* GetTooltipTarget(ui::EventType event_type,
+                               aura::Window* target,
                                gfx::Point* location) {
-  switch (event.type()) {
+  switch (event_type) {
     case ui::ET_MOUSE_CAPTURE_CHANGED:
       // On windows we can get a capture changed without an exit. We need to
       // reset state when this happens else the tooltip may incorrectly show.
@@ -57,7 +62,7 @@ aura::Window* GetTooltipTarget(const ui::MouseEvent& event,
       return NULL;
     case ui::ET_MOUSE_MOVED:
     case ui::ET_MOUSE_DRAGGED: {
-      aura::Window* event_target = static_cast<aura::Window*>(event.target());
+      aura::Window* event_target = target;
       if (!event_target)
         return NULL;
 
@@ -83,7 +88,7 @@ aura::Window* GetTooltipTarget(const ui::MouseEvent& event,
 
       // If |target| has capture all events go to it, even if the mouse is
       // really over another window. Find the real window the mouse is over.
-      gfx::Point screen_loc(event.location());
+      gfx::Point screen_loc(*location);
       aura::client::GetScreenPositionClient(event_target->GetRootWindow())->
           ConvertPointToScreen(event_target, &screen_loc);
       gfx::Screen* screen = gfx::Screen::GetScreenFor(event_target);
@@ -185,14 +190,14 @@ void TooltipController::OnMouseEvent(ui::MouseEvent* event) {
     case ui::ET_MOUSE_EXITED:
     case ui::ET_MOUSE_MOVED:
     case ui::ET_MOUSE_DRAGGED: {
-      curr_mouse_loc_ = event->location();
-      aura::Window* target = GetTooltipTarget(*event, &curr_mouse_loc_);
-      SetTooltipWindow(target);
-      if (tooltip_timer_.IsRunning())
-        tooltip_timer_.Reset();
-
-      if (tooltip_->IsVisible())
-        UpdateIfRequired();
+      last_mouse_location_ = event->location();
+      mouse_event_timer_.Start(
+          FROM_HERE,
+          base::TimeDelta::FromMilliseconds(kMouseMoveDelay),
+          base::Bind(&TooltipController::DispatchMouseEvent,

[sky, 2014/05/08 19:05:55]

What happens if we enter some sort of nested message loop that prevents this
from executing?

[varkha, 2014/05/13 19:30:55]

We would need to synchronously process any pending mouse move before going into
a nested loop. We could trigger it in DesktopNativeWidgetAura::RunMoveLoop().

+                     base::Unretained(this),
+                     event->type(),
+                     static_cast<aura::Window*>(event->target())));

[sky, 2014/05/08 19:05:55]

What if window is destroyed between now and when this is processed?

[varkha, 2014/05/13 19:30:55]

We could maintain a set of windows for which we have a pending dispatch, watch
for them being destroyed and check if a window is still in the set when doing
dispatch. I cannot think of a degenerate case where this set would be
significantly long. Does this seem like a right approach to you?

       break;
     }
     case ui::ET_MOUSE_PRESSED:
@@ -239,6 +244,18 @@ void TooltipController::OnWindowDestroyed(aura::Window* window) {
 ////////////////////////////////////////////////////////////////////////////////
 // TooltipController private:
 
+void TooltipController::DispatchMouseEvent(ui::EventType event_type,
+                                           aura::Window* target) {
+  curr_mouse_loc_ = last_mouse_location_;
+  target = GetTooltipTarget(event_type, target, &curr_mouse_loc_);
+  SetTooltipWindow(target);
+  if (tooltip_timer_.IsRunning())
+    tooltip_timer_.Reset();
+
+  if (tooltip_->IsVisible())
+    UpdateIfRequired();
+}
+
 void TooltipController::TooltipTimerFired() {
   UpdateIfRequired();
 }