RFR: JDK-8255439: System Tray icons get corrupted when windows scaling changes

[Harshitha Onkar]

On Fri, 29 Apr 2022 00:36:15 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

> Did you have a chance to check why the WM_DPICHANGED does not work, any specific cases? It is used by checking the scale change for windows in AWT, and no issues were reported for that as far as I know.

When DPI gets changed, many events are generated one after the other. By setting delays at various places in code I  observed that, the timing of triggering tray icon update could have effects on how it is rendered. 

When DPI is changed, along with `WM_DPICHANGED` msg the tray icon window's procedure receives `WMPOSCHANGING` and if we trigger a tray icon update before this, the icon gets distorted. I believe the cause for distortion might be - adding an icon to the system tray while it is still changing its size and position (WMPOSCHANGING) due to DPI changes. 

By triggering the update after `WMPOSCHANGING`, the tray icon gets added when all the updates to the System Tray are completed.

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PR: https://git.openjdk.java.net/jdk/pull/8441