shell.getMonitor().zoom returning wrong zoom sometimes when frequently switching between two different zoom level monitors

[ShahzaibIbrahim]

Monitor zoom returning wrong value when moving between two different zoom level monitors. This happens when swt.autoScale.updateOnRuntime is false. This could lead to weird behavior in some of the widgets that are using custom drawing.

Steps to reproduce

• Add this line System.out.println("Monitor Zoom in Button= " + this.getShell().getMonitor().zoom); in WM_SIZE method in Button.class.
• Go to ControlExample.java and add the line OS.setTheme(true);
• Run the ControlExample.java with swt.autoScale.updateOnRuntime=false
• Move the window between two monitors frequently and check the console if it returns the correct zoom level all the time.

This issue was found during testing the menuItem in Dark theme PR: eclipse-platform/eclipse.platform.swt#1405 (comment). The vertical alignment was broken in some cases when getMonitor().zoom returned the wrong zoom level.

[fedejeanne]

@ShahzaibIbrahim could you please mention the issue (or comment) to which this finding is related? IIRC it was a comment from Heiko.