<AWT Dev> RFR: 8040630 Popup menus and tooltips flicker with previous popup contents when first shown

[Sergey Bylokhov]

On 3/9/20 7:47 am, Alexander Zuev wrote:
>    as a workaround resetting the internal windows state will do. Question is - do we use OpenGL framework
> anywhere aside of OSX? I doubt we do. And does new Metal framework exhibit this problem? I know this
> question is probably not for you specifically, but still.

The OpenGL can be enabled on linux and windows as well. The
bug does not really OGL specific, it just a matter of chance that
OGL on macOS is slower than other pipelines on other platforms,
all depends on how faster the pipeline is able to redraw the window.
In theory all pipelines are affected.

>    Anyways - shouldn't we add some specific comments about what this code is workaround for so we don't
> forget to clean it up later when the main problem is gone (one way or another)?

The main issue cannot be gone, the only possible more generic
solution is to drop H/W caching.

> 
> /Alex
> 
> On 03-Feb-20 5:07, Sergey Bylokhov wrote:
>> Hello.
>> Please review the fix for jdk/client.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8040630
>> Fix: http://cr.openjdk.java.net/~serb/8040630/webrev.00
>>
>> This change is intended to fix the flickering of popup menus on
>> macOS. The root cause of the problem is that the native windows
>> for popup menus are cached internally. So when we show such a
>> cached window to the user he will see old content till the moment
>> we draw the new one.
>> As a fix we could
>>  - Drop the internal state(surface) of the window which contains the
>>    old content, as suggested in the current fix we set its size to 1x1 pixels.
>>  - Clean the old content by something like graphics.clearRect(), but
>>    since the draw operation is asynchronous it is possible it will
>>    not be completed when the user will see the popup.
>>  - Drop the caching completely, I am not sure that we really needed it,
>>    I have checked the performance PopupFactory.getPopup() when the
>>    cache is enabled/disabled and did not found a big difference. But
>>    since I plan to backport this to jdk11, I would like to minimize the
>>    fix, and drop the cache sometime later.
>>
>> Notes:
>>  - The easiest way to reproduce the bug is to run SwingSet2, and
>>    quickly open/reopen the "File" and "Look and feel" menu.
>>  - The bug is not really macOS specific, but java2D OGL pipeline"
>>    specific where the actual draw operations are asynchronous.
>>
>>
> 


-- 
Best regards, Sergey.