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

Alexander Scherbatiy alexandr.scherbatiy at oracle.com
Fri Aug 10 07:00:38 PDT 2012

Could you review the updated fix:

The comments are below:

On 8/7/2012 6:47 PM, Mike Swingler wrote:
> I noticed that, NSWindow's windowNumber is NSInteger, which is 32 bits wide on 32-bit and 64 bits wide on 64-bit. Chopping that to a simple 32 bit int is probably not what you intended to do.
> Also, have you considered simply calling -[NSWindow setAcceptsMouseMovedEvents:YES] in -[AWTView initWithRect:], and then removing the calls that flip it on and off in -[AWTView mouseEntered:] and -[AWTView mouseExited"]? This would also require a change in Java_sun_lwawt_macosx_CPlatformWindow_nativeSetNSWindowBounds(), which has a comment that states it only turns on mouse moved events if the window is currently under the mouse.
      I tried it. The result that I got is that a dragging mouse from 
one window to another does not generate mouse enter/exit events on the 
second window in case when tracking rect is used and the 
acceptsMouseMovedEvents flag is always set to YES.

> I would think that AppKit should be more than happy to send you mouse-over/enter/exited events as long as you say you want them. Was this approach tried and didn't work for some reason?
>> Hi, Alexander.
>> Probably all this stuff can be simplified? Can you try to change TrackingRect to TrackingArea with appropriate flags like NSTrackingEnabledDuringMouseDrag etc.
     I changed the TrackingRect to TrackingArea in the updated fix. It 
now generates the mouse enter/exit events on the second window during drag.
     So it is not necessary to generates such events from our side.

    The getTopmostWindowUnderMouse is necessary to handle mouse 
enter/exit events for component in case when a mouse is dragged from one 
window to another.
    Where the second window contains it's own components and the only 
way to know about tracking over them  are  drag events which receives 
the first window.

    I think that the LWWindowPeer class code can be simplified if we 
assume that window mouse enter/exit events are always come to the 
current window.
    So the component mouse enter/exit events can be tracked only in the 
current or topmost window.
    For this case I separated the global lastCommonMouseEventPeer which 
is necessary for the cursor manager and the local lastMouseEventPeer.

     According to the specification: The proper order of mouse-entered 
and mouse-exited events received by tracking-area objects in an 
application cannot be guaranteed.
    So it seems it is not possible to have one lastMouseEventPeer 
instead of two: lastCommonMouseEventPeer  and lastMouseEventPeer.

    And there are possible situations that we can receive mouse drag 
event between enter and exit.
    To handle this the isMouseOver flag is added to the LWWindowPeer 
class. So the component mouse  enter/exit events are not generated if 
the window mouse exited event is received and window mouse entered is not.

     There is the test: 
     It shows that even using the TrackingArea some mouse enter/exit 
events are not generateed in the following cases:
      - window is created under the mouse
      - window changes it's bounds so it becomes under the mouse

    For this cases it still necessary to generate mouse enter/exit 
events from our side.
    I just moved the related code to one method 


>> 07.08.2012 15:17, Alexander Scherbatiy wrote:
>>> 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.
>> -- 
>> Best regards, Sergey.

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