Dialogs open with wrong zoom level

[ptziegler]

Describe the bug

When switch between different zoom levels, the Dialog seems to remember the previous/initial zoom level. When the dialog is openend, the contents of this dialog are scaled based on the previous zoom and then rescaled to match the monitor zoom.

To Reproduce

I'm not sure about the exact steps, as I only noticed this problem some time later. But I switched between 100%, 125% and 150% zoom on my second monitor for some tests and then reverted back to 100%.

Expected behavior

The dialog should already be at the correct zoom level when opened.

Screenshots

Recording.2025-10-08.154557.mp4

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)

Windows 11

Version since
2025-12 M1

[ptziegler]

The inverse also seems to be true. I've changed my monitor zoom to 125% and restarted the IDE. Now everything is rescaled from 100% -> 125% after the dialog was opened.

Recording.2025-10-08.160019.mp4

[HeikoKlare]

Thank you for reporting this! I faced the same issue yesterday and was about to document it in an issue. This happens because we introduced async processing of DPI change events:

• Make DPI_CHANGED event handling async  #2520

Unfortunately, (child) shells seem to be created with primary monitor zoom (or whatever monitor they are initialized on) and then (asynchronously) process the DPI change event to the monitor they are placed on. Before this was asynchronous, you did not see the additional relayouting, but now you will notice it. We will work on that.

[fedejeanne]

How to reproduce

Warning

The issue is not reproducible in the Runtime Workspace (run configuration) that can be started from the IDE but it is reproducible in the IDE and in the SDK (see downloads)

Setup

• 2 monitors with different zooms

Steps

• Open the SDK / IDE by double clicking in the eclipse.exe in the File Explorer
• Open Type Dialog (Ctrl + Shift + T) or Resource Dialog (Ctrl + Shift + R) or the Plug-in Selection dialog (as shown in the original description)
• Move the dialog to the monitor were the File Explorer is not in and close it
• Open the dialog again (it should remember its position and open in the same monitor were you closed it) --> The issue happens, there's a re-layouting

Current findings

• The issue is not reproducible using the Runtime Workspace application that one can start from the IDE
• The issue is not reproducible with the "console version": eclipsec.exe
• The issue depends on were the child shell (pop-up dialog) is, the location of the parent shell (the Workbench window) does not play a role.
• The issue happens because a WM_DPICHANGED event is triggered and the code reaches this method Shell.handleMonitorSpecificDpiChange(int, Rectangle)

Stack trace

Thread [main] (Suspended (breakpoint at line 4974 in Control))	
	Shell(Control).handleMonitorSpecificDpiChange(int, Rectangle) line: 4974	
	Shell(Control).WM_DPICHANGED(long, long) line: 5002	
	Shell(Control).windowProc(long, int, long, long) line: 4894	
	Shell(Canvas).windowProc(long, int, long, long) line: 336	
	Shell(Decorations).windowProc(long, int, long, long) line: 1499	
	Shell.windowProc(long, int, long, long) line: 2378	
	Display.windowProc(long, long, long, long) line: 5125	
	OS.SetWindowPos(long, long, int, int, int, int, int) line: not available [native method]	
	Shell(Control).setBoundsInPixels(int, int, int, int, int, boolean) line: 3250	
	Shell(Composite).setBoundsInPixels(int, int, int, int, int, boolean) line: 1062	
	Shell(Decorations).setBoundsInPixels(int, int, int, int, int, boolean) line: 775	
	Shell.setBoundsInPixels(int, int, int, int, int, boolean) line: 1619	
	Shell(Control).setBoundsInPixels(int, int, int, int, int) line: 3211	
	Shell(Control).setBoundsInPixels(int, int, int, int) line: 3207	
	Shell.setBounds(Rectangle) line: 1595	
	OpenTypeSelectionDialog(Window).initializeBounds() line: 764	
	OpenTypeSelectionDialog(Dialog).initializeBounds() line: 717	
	OpenTypeSelectionDialog(Window).create() line: 435	
	OpenTypeSelectionDialog(Dialog).create() line: 1088	
	OpenTypeSelectionDialog(SelectionStatusDialog).create() line: 155	
	OpenTypeSelectionDialog(FilteredItemsSelectionDialog).create() line: 352	
	OpenTypeSelectionDialog(FilteredTypesSelectionDialog).create() line: 417	
	OpenTypeSelectionDialog(Window).open() line: 788	
	OpenTypeSelectionDialog(FilteredTypesSelectionDialog).open() line: 441	
	OpenTypeAction.runWithEvent(Event) line: 83	
	OpenTypeAction.runWithEvent(IAction, Event) line: 170	
	ActionDelegateHandlerProxy.execute(ExecutionEvent) line: 273	
	E4HandlerProxy.execute(IEclipseContext, Map, Event, IEvaluationContext) line: 98	
	0x000002e6dba48800.invokeVirtual(Object, Object, Object, Object, Object, Object) line: not available	
	0x000002e6dba4a000.invoke(Object, Object, Object) line: not available	
	Invokers$Holder.invokeExact_MT(Object, Object, Object, Object) line: not available	
	DirectMethodHandleAccessor.invokeImpl(Object, Object[]) line: 157	
	DirectMethodHandleAccessor.invoke(Object, Object[]) line: 103	
	Method.invoke(Object, Object...) line: 580	
	MethodRequestor.execute() line: 58	
	InjectorImpl.invokeUsingClass(Object, Class<?>, Class<Annotation>, Object, PrimaryObjectSupplier, PrimaryObjectSupplier, boolean, boolean, boolean) line: 305	
	InjectorImpl.invoke(Object, Class<Annotation>, Object, PrimaryObjectSupplier, PrimaryObjectSupplier) line: 237	
	ContextInjectionFactory.invoke(Object, Class<Annotation>, IEclipseContext, IEclipseContext, Object) line: 174	
	WorkbenchHandlerServiceHandler(HandlerServiceHandler).execute(ExecutionEvent) line: 165	
	Command.executeWithChecks(ExecutionEvent) line: 488	
	ParameterizedCommand.executeWithChecks(Object, Object) line: 484	
	HandlerServiceImpl.executeHandler(ParameterizedCommand, IEclipseContext) line: 204	
	KeyBindingDispatcher.executeCommand(ParameterizedCommand, Event) line: 320	
	KeyBindingDispatcher.press(List<KeyStroke>, Event) line: 580	
	KeyBindingDispatcher.processKeyEvent(List<KeyStroke>, Event) line: 661	
	KeyBindingDispatcher.filterKeySequenceBindings(Event) line: 450	
	KeyBindingDispatcher$KeyDownFilter.handleEvent(Event) line: 104	
	EventTable.sendEvent(Event) line: 91	
	Display.filterEvent(Event) line: 1335	
	StyledText(Widget).sendEvent(Event) line: 1220	
	StyledText(Widget).sendEvent(int, Event, boolean) line: 1245	
	StyledText(Widget).sendEvent(int, Event) line: 1230	
	StyledText(Widget).sendKeyEvent(int, int, long, long, Event) line: 1272	
	StyledText(Widget).sendKeyEvent(int, int, long, long) line: 1268	
	StyledText(Widget).wmChar(long, long, long) line: 1755	
	StyledText(Control).WM_CHAR(long, long) line: 4922	
	StyledText(Canvas).WM_CHAR(long, long) line: 341	
	StyledText(Control).windowProc(long, int, long, long) line: 4799	
	StyledText(Canvas).windowProc(long, int, long, long) line: 336	
	Display.windowProc(long, long, long, long) line: 5125	
	OS.DispatchMessage(MSG) line: not available [native method]	
	Display.readAndDispatch() line: 3741	
	PartRenderingEngine$5.run() line: 1147	
	Realm.runWithDefault(Realm, Runnable) line: 339	
	PartRenderingEngine.run(MApplicationElement, IEclipseContext) line: 1038	
	E4Workbench.createAndRunUI(MApplicationElement) line: 153	
	Workbench.lambda$3(Display, WorkbenchAdvisor, int[]) line: 677	
	Lambda.run() line: not available	
	Realm.runWithDefault(Realm, Runnable) line: 339	
	Workbench.createAndRunWorkbench(Display, WorkbenchAdvisor) line: 583	
	PlatformUI.createAndRunWorkbench(Display, WorkbenchAdvisor) line: 173	
	IDEApplication.start(IApplicationContext) line: 185	
	EclipseAppHandle.run(Object) line: 219	
	EclipseAppLauncher.runApplication(Object) line: 149	
	EclipseAppLauncher.start(Object) line: 115	
	EclipseStarter.run(Object) line: 467	
	EclipseStarter.run(String[], Runnable) line: 298	
	DirectMethodHandle$Holder.invokeStatic(Object, Object, Object) line: not available	
	0x000002e6db016800.invoke(Object, Object, Object, Object) line: not available	
	0x000002e6db016c00.invokeExact_MT(Object, Object, Object, Object, Object) line: not available	
	DirectMethodHandleAccessor.invokeImpl(Object, Object[]) line: 155	
	DirectMethodHandleAccessor.invoke(Object, Object[]) line: 103	
	Method.invoke(Object, Object...) line: 580	
	Main.invokeFramework(String[], URL[]) line: 627	
	Main.basicRun(String[]) line: 575	
	Main.run(String[]) line: 1431	
	Main.main(String[]) line: 1403

• When reaching line Shell.setBounds(Rectangle) line: 1595 in the stack trace, the result of getZoom() is the zoom of the monitor were the SDK / IDE was started (i.e. were the File Explorer is)
• The value of the parameter newNativeZoom when reaching Control.handleMonitorSpecificDpiChange(int, Rectangle) is the zoom of the monitor were the child shell is
• If the child shell opens on the same monitor were the File Explorer is then the method Control.handleMonitorSpecificDpiChange(int, Rectangle) is never reached.

@akoch-yatta feel free to offer any insights, in the meantime I'll try to see if it's possible to somehow let the child shell know that it's been opened in a monitor with a zoom that requires re-layouting before the shell is set to be visible, as we discussed in our call.

[ptziegler]

As an additional comment: The problem doesn't only affect dialogs but also happens when e.g. switching perspective, where a rescaling of e.g. the Package Explorer view can be seen.

[ptziegler]

20251014-0752-29.9341420.mp4

[HeikoKlare]

As an additional comment: The problem doesn't only affect dialogs but also happens when e.g. switching perspective, where a rescaling of e.g. the Package Explorer view can be seen.

Yes, that's even a different issue we are currently also having a look at.

[fedejeanne]

Further insights

• The child shell is first created, then the WM_DPICHANGED happens and then the shell is made visible ✅
• After the child shell is set to be visible, deferred layouts come into play and all children widgets (composites, buttons, text fields, labels) of the popup dialog start receiving WM_WINDOWPOSCHANGING / WM_WINDOWPOSCHANGED events. This is when one notices the issue: when the contents of the dialog start resizing.
• When paying close attention, one can notice in both of the videos provided by @ptziegler that the dialog itself is not resized, only its content.