[win32] Refresh GC handle when related image

[akoch-yatta]

This PR adapts the behavior of the commonly used pattern of a GC that draw onto a plain image. In the windows implementation the monitor specific scaling could lead to issues with this pattern, because during creation time of an GC/Image combo it was not always clear with which zoom the final result will be drawn upon. This commit will redraw the GC on an image handle if a new zoom is requested. The handle for the old zoom of the image will be kept, but if another operation of the GC is executed it will only be applied on the new handle.

How to test

You can use this small windows specific snippet to force an image redraw with a different zoom

package org.eclipse.swt.snippets;

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class SnippetGcRedraw {

	public static void main (String [] args) {
		Display display = new Display ();
		Shell shell = new Shell (display);
		shell.setText("GC Redraw");
		shell.setLayout(new FillLayout());
		int width = 150, height = 200;
		Image image = new Image (display, width, height);

		GCData data = new GCData();
		GC gc = GC.win32_new(image, data);
		gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
		gc.fillRectangle (0, 0, width, height);
		gc.drawLine (0, 0, width, height);
		gc.drawLine (0, height, width, 0);
		gc.drawText ("Default Image", 10, 10);
		final Point origin = new Point (0, 0);
		final Canvas canvas = new Canvas (shell, SWT.NONE);
		canvas.addListener (SWT.Paint, e -> {
			GC gc2 = e.gc;
			gc2.getGCData().nativeZoom = 150;
			gc2.drawImage (image, origin.x, origin.y);
			gc2.getGCData().nativeZoom = 200;
			gc2.drawImage (image, origin.x + 300, origin.y);
		});
		shell.setSize (1000, 1000);
		shell.open ();
		while (!shell.isDisposed ()) {
			if (!display.readAndDispatch ()) display.sleep ();
		}
		gc.dispose ();
		image.dispose();
		display.dispose ();
	}
}

Before

If the image was used with a GC the same ImageData were used for all zooms

After

Left image is drawn for 150%, right is redrawn for 200%

This PR relies upon #2243 and must be merged after it. Only the latest commit is part of this PR

[github-actions]

Test Results

   545 files  ±0     545 suites  ±0   31m 46s ⏱️ - 2m 2s
 4 403 tests ±0   4 385 ✅ ±0   18 💤 ±0  0 ❌ ±0 
16 733 runs  ±0  16 593 ✅ ±0  140 💤 ±0  0 ❌ ±0 

Results for commit ad24d4a. ± Comparison against base commit e7478cd.

♻️ This comment has been updated with latest results.

[fedejeanne]

I tested it and it looks good.

I only have one question (#2263 (comment)) but even with that change, the code looks good.