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

[Pankaj Bansal]

Looks good to me.

-Pankaj


On 03/02/20 7:37 AM, 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.
>
>