StackOverflowError in Image when auto-scaling differs from device zoom

[HeikoKlare]

Description and Reproduction
Scaling image data can lead to a stack overflow error since this change:

• A strict check 200% image data is double the size of 100% image data eclipse-platform/eclipse.platform.swt#2249

The regression is documented with a reproduction in:

• StackOverflowError in Image when auto-scaling differs from device zoom eclipse-platform/eclipse.platform.swt#2353

Expected Behavior
No stack overflow should happen when scaling image data

Additional knowledge
The modified code is obviously problematic but the original code also seems to be incorrect. The ImageDataProvider used for image data to scale returned that same image data for every zoom, which potentially led to drawing the image data at a wrong size via Image.drawScaled and the subsequent call of GC#drawImage. So we should properly check what is really supposed to happen here and we should add according regression tests to capture different scenarios.

[fedejeanne]

@HeikoKlare , @akoch-yatta , I assigned you since I can't judge at a technical level (see my comment). At least one of you should take a look at the PR before merging it.

Thank you in advance