StackOverflowError in Image when auto-scaling differs from device zoom

[ptziegler]

To Reproduce

Run Snippet367 with -Dswt.autoScale=150.

Stacktrace:

Exception in thread "main" java.lang.StackOverflowError
	at org.eclipse.swt.internal.DPIUtil.getElementAtZoom(DPIUtil.java:289)
	at org.eclipse.swt.internal.DPIUtil.validateAndGetImageDataAtZoom(DPIUtil.java:260)
	at org.eclipse.swt.graphics.Image.initFromImageDataProvider(Image.java:797)
	at org.eclipse.swt.graphics.Image.<init>(Image.java:675)
	at org.eclipse.swt.internal.DPIUtil.autoScaleImageData(DPIUtil.java:156)
	at org.eclipse.swt.internal.DPIUtil.scaleImageData(DPIUtil.java:139)
	at org.eclipse.swt.graphics.Image.initFromImageDataProvider(Image.java:798)
	at org.eclipse.swt.graphics.Image.<init>(Image.java:675)
	at org.eclipse.swt.internal.DPIUtil.autoScaleImageData(DPIUtil.java:156)
	at org.eclipse.swt.internal.DPIUtil.scaleImageData(DPIUtil.java:139)
	at org.eclipse.swt.graphics.Image.initFromImageDataProvider(Image.java:798)
	at org.eclipse.swt.graphics.Image.<init>(Image.java:675)
...

Environment:

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

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

Version since

This is a regression introduced with 216f1ad.

[ptziegler]

A similar issue can be reproduced on Windows, also as a result of this commit. For this, simply execute Issue0445_HiDPISmoothScaling when your device zoom is something other than 200%.

Exception in thread "main" java.lang.StackOverflowError
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:651)
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
at org.eclipse.swt.graphics.GC.disposeOperations(GC.java:5968)
at org.eclipse.swt.graphics.GC.dispose(GC.java:5964)
at org.eclipse.swt.graphics.Image$ImageGcDrawerWrapper.newImageHandle(Image.java:2613)
at org.eclipse.swt.graphics.Image.getImageMetadata(Image.java:810)
at org.eclipse.swt.graphics.Image$ImageGcDrawerWrapper.newImageData(Image.java:2587)
at org.eclipse.swt.graphics.Image.getImageData(Image.java:1263)
at org.eclipse.swt.internal.DPIUtil.autoScaleImageData(DPIUtil.java:170)
at org.eclipse.swt.internal.DPIUtil.scaleImageData(DPIUtil.java:139)
at org.eclipse.swt.graphics.Image$BaseImageProviderWrapper.initializeHandleFromSource(Image.java:2292)
at org.eclipse.swt.graphics.Image$BaseImageProviderWrapper.newImageHandle(Image.java:2287)
at org.eclipse.swt.graphics.Image.getImageMetadata(Image.java:810)
at org.eclipse.swt.graphics.Image.win32_getHandle(Image.java:834)
at org.eclipse.swt.graphics.Image.createGdipImage(Image.java:858)
at org.eclipse.swt.graphics.GC.drawImage(GC.java:1201)
at org.eclipse.swt.graphics.GC$DrawImageToImageOperation.apply(GC.java:1194)
at org.eclipse.swt.graphics.GC.storeAndApplyOperationForExistingHandle(GC.java:5947)
at org.eclipse.swt.graphics.GC.drawImage(GC.java:1105)
at org.eclipse.swt.graphics.Image.drawScaled(Image.java:853)
at org.eclipse.swt.internal.DPIUtil$1.drawOn(DPIUtil.java:161)
at org.eclipse.swt.graphics.Image$ImageGcDrawerWrapper.newImageHandle(Image.java:2607)
at org.eclipse.swt.graphics.Image.getImageMetadata(Image.java:810)
at org.eclipse.swt.graphics.Image$ImageGcDrawerWrapper.newImageData(Image.java:2587)
at org.eclipse.swt.graphics.Image.getImageData(Image.java:1263)
at org.eclipse.swt.internal.DPIUtil.autoScaleImageData(DPIUtil.java:170)
at org.eclipse.swt.internal.DPIUtil.scaleImageData(DPIUtil.java:139)
...

[HeikoKlare]

Thank you for the report! We will have a look at this as soon as possible. The original code does also not seem fully sound to me, so let's see how we can properly fix it.