FileImageDataProvider will throw IllegalArgumentException on Windows 200% scale with SVG image

[Phillipus]

With a display set to 200% scaling on Windows calling GC.drawImage(Image image, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY, int destWidth, int destHeight) when using a FileImageDataProvider can cause an IllegalArgumentException.

import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class FileImageDataProviderIllegalArgumentException {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setSize(800, 600);

        Image image = FileImageDataProvider.createImage(FileImageDataProviderIllegalArgumentException.class, "GEF.svg");
        int width = image.getBounds().width;
        int height = image.getBounds().height;
        
        shell.addPaintListener(event -> {
            GC gc = event.gc;
            gc.drawImage(image, 0, 0, width, height, 0, 0, width, height);
        });

        shell.open();

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

Use this SVG image with the Snippet:

See eclipse-platform/eclipse.platform.swt#2916

FileImageDataProvider.getImageData() should really return null for zoom 200 and FileImageDataProvider.createImageData() should check for null InputStream:

	@Override
	public ImageData getImageData(int zoom) {
		if (zoom == 100) { //$NON-NLS-1$
			return createImageData(basePath + '.' + fileExtension);
		}
		if (zoom == 200) {
			return createImageData(basePath + "@2x." + fileExtension); //$NON-NLS-1$
		}
		return null;
	}

    private ImageData createImageData(String name) {
        try (InputStream stream = clazz.getResourceAsStream(name)) {
            return stream != null ? new ImageData(stream) : null;
        } catch (IOException ioe) {
            return null;
        }
    }

[HeikoKlare]

Out of curiosity: what is the purpose of FileImageDataProvider at all? Wouldn't instantiating SWT's ImageFileNameProvider returning the given path for zoom=100 yield the same results (and even consider that a @2x file may not be present, that a @1.5x file may be present and the like)? It would even support properly rendering SVGs at any zoom.

[ptziegler]

The FileImageDataProvider is an internal class. It is only intended to be used for the Checkbox and Graph class and nothing else. Though it doesn't make sense to use this provider for SVG-based images, which is addressed by #942.

what is the purpose of FileImageDataProvider at all?

It serves the same purpose as ImageDescriptor.createFromFile(Class,String), which can't be used in Draw2D as it doesn't reference JFace.

Wouldn't instantiating SWT's ImageFileNameProvider returning the given path for zoom=100 yield the same results (and even consider that a @2x file may not be present, that a @1.5x file may be present and the like)? It would even support properly rendering SVGs at any zoom.

This provider is only used in the Checkbox and Graph class, which are using images in the classpath. The ImageFileNameProvider works with file paths encoded as String, not URI, which is why it's not an option.

That's also the reason why the provider is so minimalistic. We always have a 100% and 200% PNG file for those classes (and nothing more), which is why any additional checks are unnecessary.

[ptziegler]

That said, a similar issue is also tracked via #874.

[Phillipus]

That said, a similar issue is also tracked via #874.

Is the root cause eclipse-platform/eclipse.platform.swt#2916 ?

[ptziegler]

Is the root cause eclipse-platform/eclipse.platform.swt#2916 ?

No. It's (likely) because the surface used by the GC hasn't been resized after the zoom change. It's similar as both times, the surface is improperly sized, but not because of an ImageDataProvider.