"Graphic is disposed" on Windows with pull/1496

[tobiasmelcher]

#1496 introduces an incompatibility which breaks existing implementations.

Following pattern is used where the base image is disposed directly after creating an instance of DecorationOverlayIcon.

Image tempImage = descriptor.createImage();

ImageDescriptor[] overlaysArray = new ImageDescriptor[6];
overlaysArray[IDecoration.BOTTOM_LEFT] = getDecorator(stateDecoratorLocation);
overlaysArray[IDecoration.TOP_RIGHT] = getDecorator(testPoolDecoratorLocation);

image = new DecorationOverlayIcon(tempImage, overlaysArray).createImage();
tempImage.dispose();  // <!--------------------------
this.imageCache.put(imageId, image);

This produces now a "Graphic is disposed" exception on Windows with following stack:

org.eclipse.swt.SWTException: Graphic is disposed
              at org.eclipse.swt.SWT.error(SWT.java:4922)
              at org.eclipse.swt.SWT.error(SWT.java:4837)
              at org.eclipse.swt.SWT.error(SWT.java:4808)
              at org.eclipse.swt.graphics.Image.getImageData(Image.java:1380)
              at org.eclipse.jface.resource.CompositeImageDescriptor$CachedImageImageDataProvider.getImageData(CompositeImageDescriptor.java:114)
              at org.eclipse.jface.resource.CompositeImageDescriptor.getZoomedImageData(CompositeImageDescriptor.java:457)
              at org.eclipse.jface.resource.CompositeImageDescriptor.drawImage(CompositeImageDescriptor.java:267)
              at org.eclipse.jface.viewers.DecorationOverlayIcon.drawCompositeImage(DecorationOverlayIcon.java:217)
              at org.eclipse.jface.resource.CompositeImageDescriptor.getImageData(CompositeImageDescriptor.java:375)
              at org.eclipse.swt.internal.DPIUtil.lambda$2(DPIUtil.java:543)
              at org.eclipse.swt.internal.DPIUtil.getElementAtZoom(DPIUtil.java:572)
              at org.eclipse.swt.internal.DPIUtil.validateAndGetImageDataAtZoom(DPIUtil.java:543)
              at org.eclipse.swt.graphics.Image.getImageMetadata(Image.java:768)
              at org.eclipse.swt.graphics.Image.getBounds(Image.java:1306)
              at org.eclipse.swt.graphics.Image.getBounds(Image.java:1301)
              at org.eclipse.swt.internal.ImageList.add(ImageList.java:61)
              at org.eclipse.swt.widgets.Button._setImage(Button.java:144)
              at org.eclipse.swt.widgets.Button.setImage(Button.java:875)

Could you please improve the enhancements of #1496 so that this exception does no longer occur?

Thanks and best regards,
Tobias

[HeikoKlare]

Thank you for reporting the issue, Tobias!

fyi @amartya4256 @akoch-yatta @fedejeanne

[akoch-yatta]

@tobiasmelcher thx for reporting that issue. I had a look into it, but I cannot reproduce a new issue with that. I took a simpler variant of your snippet:

public class Test {
	public static void main(String[] args) {
		Image tempImage = new Image(new Display(), 20, 20); 
		ImageDescriptor[] overlaysArray = new ImageDescriptor[6];

		Image image = new DecorationOverlayIcon(tempImage, overlaysArray).createImage();
		tempImage.dispose(); 
		image.getImageData(200);
		image.getImageData(100);
	}
}

With that I get the similar exception even in the 2022-12 release (just picked any old release).
The disposal check in Image::getImageData is quite old and the tempImage (in the snippet) is the exact same instance of the Image that is used in CompositeImageDescriptor.java:114 (wrapped into an ImageDataProvider). This indicates to me, that this image must not be disposed. Otherwise this exception will occur as soon as a second variant of the image must be created.

Perhaps my simplified snippet behaves different as in your use case, so do you have a complete reproducer for the that worked before in the same setup and setting? Please give me your full monitor setup then. My current assumption is, that your setup could cause that and the default cached variant of the ImageData is different than before, so the second variant shall be created.

Nevertheless, I didn't have a too deep look into the jface implementation, but it looks to me that disposing the tempImage will lead to issues when two different variants of that icon are requested based on the implementation in CachedImageImageDataProvider -> e.g. with two monitors (100 & 200) and the experimental rescaling at runtime set to true.

[tobiasmelcher]

@akoch-yatta, here the snippet to reproduce the problem

public class Snippet {
	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setText("Test");
		shell.setSize(300, 200);

		Image tempImage = new Image(display, 20, 20);
		ImageDescriptor[] overlaysArray = new ImageDescriptor[6];

		Image image = new DecorationOverlayIcon(tempImage, overlaysArray).createImage();
		tempImage.dispose();

		Button button = new Button(shell, SWT.PUSH);
		button.setImage(image);

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

The zoom value on my machine is 200.
I see following difference:

• before pull request Refactor Image for storing ImageMetadata #1496 CompositeImageDescriptor$CachedImageImageDataProvider.getImageData(int) line: 111 is called only once with zoom level value 200.
• on the current master branch CompositeImageDescriptor$CachedImageImageDataProvider.getImageData(int) line: 111 is called twice. First call with zoom level value 200, second call with value 100 and then the Exception is raised.
  Here the stack from the second call:

Thread [main] (Suspended (breakpoint at line 111 in CompositeImageDescriptor$CachedImageImageDataProvider))	
	CompositeImageDescriptor$CachedImageImageDataProvider.getImageData(int) line: 111	
	DecorationOverlayIcon(CompositeImageDescriptor).getZoomedImageData(ImageDataProvider) line: 457	
	DecorationOverlayIcon(CompositeImageDescriptor).drawImage(ImageDataProvider, int, int) line: 267	
	DecorationOverlayIcon.drawCompositeImage(int, int) line: 217	
	DecorationOverlayIcon(CompositeImageDescriptor).getImageData(int) line: 375	
	0x00000222a802bc10.getImageData(int) line: not available	
	DPIUtil.lambda$2(ImageDataProvider, Integer) line: 543	
	0x00000222a8029c00.apply(Object) line: not available	
	DPIUtil.getElementAtZoom(Function<Integer,T>, int) line: 572	
	DPIUtil.validateAndGetImageDataAtZoom(ImageDataProvider, int) line: 543	
	Image.getImageMetadata(int) line: 768	
	Image.getBounds(int) line: 1306	
	Image.getBounds() line: 1301	
	ImageList.add(Image) line: 61	
	Button._setImage(Image) line: 144	
	Button.setImage(Image) line: 875	
	Snippet.main(String[]) line: 25	

[akoch-yatta]

@tobiasmelcher Thx for the Snippet and the further analysis. The issue was that getBounds created new handles on demand instead of scaling existing ones. I created a PR for that.

I want to emphasize, that the underlyind issue remains. The implementation of CachedImageImageDataProvider relies on the baseImage (=tempImage) not being disposed. The exception will reappear if a second variant of the image is requested (see my Snippet). Could you open an issue for jface with your usecase? Perhaps it is intended, but if not the implementation could be changed to no rely on the passed image not being disposed.

[tobiasmelcher]

Hi colleagues,

the problem raised again. I am again getting the "Graphic is disposed" exception. Could you please fix again?

Thanks a lot,
Tobias

org.eclipse.swt.SWTException: Graphic is disposed
	at org.eclipse.swt.SWT.error(SWT.java:4932)
	at org.eclipse.swt.SWT.error(SWT.java:4847)
	at org.eclipse.swt.SWT.error(SWT.java:4818)
	at org.eclipse.swt.graphics.Image.getImageData(Image.java:1400)
	at org.eclipse.jface.resource.CompositeImageDescriptor$CachedImageImageDataProvider.getImageData(CompositeImageDescriptor.java:114)
	at org.eclipse.jface.resource.CompositeImageDescriptor.getZoomedImageData(CompositeImageDescriptor.java:457)
	at org.eclipse.jface.resource.CompositeImageDescriptor.drawImage(CompositeImageDescriptor.java:267)
	at org.eclipse.jface.viewers.DecorationOverlayIcon.drawCompositeImage(DecorationOverlayIcon.java:217)
	at org.eclipse.jface.resource.CompositeImageDescriptor.getImageData(CompositeImageDescriptor.java:375)
	at org.eclipse.swt.internal.DPIUtil.lambda$2(DPIUtil.java:538)
	at org.eclipse.swt.internal.DPIUtil.getElementAtZoom(DPIUtil.java:567)
	at org.eclipse.swt.internal.DPIUtil.validateAndGetImageDataAtZoom(DPIUtil.java:538)
	at org.eclipse.swt.graphics.Image$ImageDataProviderWrapper.getBounds(Image.java:2188)
	at org.eclipse.swt.graphics.Image.getBounds(Image.java:1322)
	at org.eclipse.swt.graphics.Image.getBounds(Image.java:1312)
	at org.eclipse.swt.widgets.Button.computeSizeInPixels(Button.java:361)

[HeikoKlare]

Thank you, @tobiasmelcher!

I can reproduce the issue at 200% with your snippet (#1639 (comment)). We will have a look.