[8] Review request for 7171045 [macosx] There are no enter or exit events reported against 8b39 for MouseEventsDuringDrag.

[Alexander Scherbatiy]

bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7171045
webrev: http://cr.openjdk.java.net/~alexsch/7171045/webrev.01/

This is a regression after the fix 7154048 [macosx] At least drag twice, 
the toolbar can be dragged to the left side.

In the case where a toolbar is created under a mouse and it is dragged 
over the initial window the mouse enter/exit events should not be 
generated for the components which are under the toolbar.

The current fix is supposed to solve this regression and also to fix 
generation of mouse enter/exit events for all cases where a mouse is 
dragged from one window to another or a new window is created under a 
mouse (like it is implemented for toolbar).

Let's see the following cases
1) Mouse is dragged from a window and back to the same window.
   The Mac OS X system generates a mouse exit event only the first time 
when a mouse is dragged from a window and does not generate mouse 
enter/exit events next times during one drag trace.

2) Mouse is dragged from one window to another.
   The Mac OS X system does not generate mouse enter/exit events for the 
second window.

3) Mouse is dragged from one window to another and released.
   In this case the Mac OS X system generates mouse enter event for the 
second window only after releasing the mouse.

4) Clicking on window creates a new window after that the new window is 
dragged (toolbar dragging).

However the Java system generates mouse enter/exit events each time when 
a mouse is dragged over any window.

To fix this the following methods are introduced:
- Get topmost window under mouse
- Synthesize mouse enter/exit events for all windows


The dispatchMouseEvent method from the LWWindowPeer class is handled 
previous and next components and is able to generate mouse enter/exit 
events for them.
However the the AWTView native class contains isMouseOver flag which 
value becomes inconsistent if we do not updated it. Because of this the 
fix generates the mouse enter/exit window events on the native side.

Generating mouse enter/exit events always should be in order where mouse 
exit events are generated before the mouse enter events.

The synthesizeMouseEnteredExitedEventsForAllWindows method tries to 
generate mouse enter/exit events for all windows during mouse drag or 
window creation/window bounds changing.
However only those windows which isMouseOver flag is differ from the 
isTopMostWindowUnderMouse state are affected.
This method also tries to generate both mouse enter and exit event for 
the same window but only one of them can be applicable because the 
isTopMostWindowUnderMouse state is not changed for these calls.

So the window enter/exit events now are always generated from the native 
system and component enter/exit events are generated in the LWWindowPeer 
class.

LWWindowPeer class now uses three links to components: current, last and 
topmostUnderMouse. All of them are necessary because in case when a 
mouse is dragged from one window to another the current component 
receives drag events and last and topmostUnderMouse links handle 
components mouse exit/enter events on the second window.

Thanks,
Alexandr.