[Windows] [Tree] Column icons and text overlaps in multi resolution monitor setup

[glasedom]

Eclipse: 4.38
OS: Windows 11
Monitor Setup: Primary Monitor 100% (1920x1080), Second Monitor 150% (3840x2160)

In our RCP application we have some views and editors where the icons and text of tree cells are overlapped in a monitor setup with multiple resolutions.
I have created a mini snippet that demonstrates the problem.

• I verified I can reproduce this issue against latest Integration Build of Eclipse SDK (eclipse-SDK-I20260208-1140-win32-x86_64)

Steps to reproduce

Open the given sample program.
The tree looks like this:

Move the window from the primary monitor to the second monitor.
You can see that icon and text overlaps in the second column.

If you move the window back to the primary monitor the icon and text still overlaps.

Here is the sample snippet:

import java.io.File;

import org.eclipse.jface.action.Action;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.viewers.ArrayContentProvider;
import org.eclipse.jface.viewers.DelegatingStyledCellLabelProvider;
import org.eclipse.jface.viewers.DelegatingStyledCellLabelProvider.IStyledLabelProvider;
import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.jface.viewers.StyledString;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.jface.viewers.TreeViewerColumn;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.TreeColumn;

public class CellIconError {

	public CellIconError(Shell shell) {
		final TreeViewer v = new TreeViewer(shell, SWT.BORDER | SWT.FULL_SELECTION);
		v.setContentProvider(new DummyContentProvider());

		TreeColumn column = new TreeColumn(v.getTree(), SWT.NONE);
		column.setWidth(200);
		column.setText("Column 1");
		TreeViewerColumn viewerColumn = new TreeViewerColumn(v, column);
		viewerColumn.setLabelProvider(new DelegatingStyledCellLabelProvider(new DummyLabelProvider()));

		column = new TreeColumn(v.getTree(), SWT.NONE);
		column.setWidth(200);
		column.setText("Column 2");
		viewerColumn = new TreeViewerColumn(v, column);
		viewerColumn.setLabelProvider(new DelegatingStyledCellLabelProvider(new DummyLabelProviderWithCellImage()));

		v.setInput(new File[] { new File("C:\\") });
		v.getTree().setLinesVisible(true);
		v.getTree().setHeaderVisible(true);
	}

	public static void main(String[] args) {
		System.setProperty("swt.autoScale.updateOnRuntime", "true");
		Display display = new Display();
		
		JFaceResources.getImageRegistry().put("stop", ImageDescriptor.createFromURLSupplier(true, () -> {
			return Action.class.getResource("images/stop.png");
		}));

		Shell shell = new Shell(display);
		shell.setLayout(new FillLayout());
		new CellIconError(shell);
		shell.setSize(600, 150);
		shell.open();

		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) {
				display.sleep();
			}
		}

		display.dispose();
	}
	
	public static class DummyLabelProvider extends LabelProvider implements IStyledLabelProvider {

		@Override
		public StyledString getStyledText(Object element) {
			return new StyledString(element.toString());
		}
		
	}

	public static class DummyLabelProviderWithCellImage extends LabelProvider implements IStyledLabelProvider {

		@Override
		public StyledString getStyledText(Object element) {
			return new StyledString(element.toString());
		}
		
		@Override
		public Image getImage(Object element) {
			return JFaceResources.getImage("stop");
		}

	}
	
	public static class DummyContentProvider extends ArrayContentProvider implements ITreeContentProvider {

		@Override
		public Object[] getChildren(Object parentElement) {
			return new Object[0];
		}

		@Override
		public Object getParent(Object element) {
			return null;
		}

		@Override
		public boolean hasChildren(Object element) {
			return false;
		}
		
	}

}

[HeikoKlare]

Here is a plain SWT snippet to reproduce the issue:

public class Snippet392 {

	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setLayout(new FillLayout());

		Tree tree = new Tree(shell, SWT.BORDER | SWT.FULL_SELECTION);
		tree.setLinesVisible(true);
		TreeColumn column1 = new TreeColumn(tree, SWT.NONE);
		column1.setWidth(200);
		TreeColumn column2 = new TreeColumn(tree, SWT.NONE);
		column2.setWidth(200);

		Image imageColumn1 = new Image(display, Snippet392.class.getResourceAsStream("eclipse.png"));
		Image imageColumn2 = new Image(display, Snippet392.class.getResourceAsStream("pause.gif"));

		TreeItem item = new TreeItem(tree, SWT.None);
		item.setText(0, "Hello");
		item.setImage(0, imageColumn1);
		item.setText(1, "World");
		item.setImage(1, imageColumn2);

		shell.setSize(600, 150);
		shell.open();

		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) {
				display.sleep();
			}
		}

		display.dispose();
	}

}

The issue is caused by TreeItem.handleDPIChange() not updating the images. Just adding the according update is insufficient as the setImage(int, Image) implementation also seems to be flawed: when setting an image for column 1, it will also be set for column 0 (adds it in images [0]), so without any further changes a DPI change would set the image of the second column also for the first column.

The implementation for Table works as expected because unlike in the Tree implementation the image list is not cleaned up upon DPI change. This may lead to blurry scaled images in a table or at least an image list with a wrong zoom being used, which should also be checked when addressing this reported issue.

[HeikoKlare]

I've moved this issue to SWT as it's reproducible with a plain SWT Tree and is thus rooted and needs to be fixed in SWT.

[HeikoKlare]

@glasedom your issue should be fixed with the combination of:

• [Win32] Update images of tree columns upon DPI change #3076
• [Win32] Avoid faulty setting of image list at OS on Tree.setOrientation #3077

Are you able to verify that?

[glasedom]

With both changes together (#3076 and #3077) our views look good again.
Many thanks Heiko, great job!

[HeikoKlare]

Great, thank you for the feedback.

Would it be important for you to both these fixes in the upcoming 2026-03 release? I would be fine with merging the PR that ensures that the images do not disappear upon DPI change:

• [Win32] Update images of tree columns upon DPI change #3076

But since we are already approaching milestone 3 and the time for detecting potential side-effects/regressions is limited, I am a bit hesitant to merge the other PR, as that one is more invasive and has a higher risk of undetected error:

• [Win32] Avoid faulty setting of image list at OS on Tree.setOrientation #3077

[glasedom]

I have absolutely no problem with this approach.
#3076 in 2026-03 and #3077 in 2026-06 sounds good for me.