Use AutoScaleMethod "smooth" by default for fractional scaling

Currently, AutoScaleMethod "nearest" is used by default, leading to
jagged image scaling results. The method "Ssooth" is only used on GTK
with a fractional scaling value not being a multiple of 100.
The reason for not using "smooth" scaling on all platform was a bug
regarding icon transparency that has long been resolved.

With this change, AutoScaleMethod "smooth" is used by default in
fractional scaling scenarios (i.e., with deviceZoom not being an integer
multiple of 100) and when using monitor-specific scaling on Windows. To
still use "nearest" in these scenarios, it can be activated via system
property.

Author: HeikoKlare

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/internal/DPIUtil.java

@@ -79,10 +79,9 @@ private static enum AutoScaleMethod { AUTO, NEAREST, SMOOTH }
 	 * <li>"nearest": nearest-neighbor interpolation, may look jagged</li>
 	 * <li>"smooth": smooth edges, may look blurry</li>
 	 * </ul>
-	 * The current default is to use "nearest", except on
-	 * GTK when the deviceZoom is not an integer multiple of 100%.
-	 * The smooth strategy currently doesn't work on Win32 and Cocoa, see
-	 * <a href="https://bugs.eclipse.org/493455">bug 493455</a>.
+	 * The current default is to use "nearest" on Cocoa or when deviceZoom is an
+	 * integer multiple of 100% and if monitor-specific scaling on Windows is not
+	 * used, and "smooth" otherwise.
 	 */
 	private static final String SWT_AUTOSCALE_METHOD = "swt.autoScale.method";
 
@@ -605,7 +604,7 @@ public static void setDeviceZoom (int nativeDeviceZoom) {
 	DPIUtil.deviceZoom = deviceZoom;
 	System.setProperty("org.eclipse.swt.internal.deviceZoom", Integer.toString(deviceZoom));
 	if (deviceZoom != 100 && autoScaleMethodSetting == AutoScaleMethod.AUTO) {
-		if (deviceZoom / 100 * 100 == deviceZoom || !"gtk".equals(SWT.getPlatform())) {
+		if ((deviceZoom / 100 * 100 == deviceZoom && !isMonitorSpecificScalingActive()) || "cocoa".equals(SWT.getPlatform())) {
 			autoScaleMethod = AutoScaleMethod.NEAREST;
 		} else {
 			autoScaleMethod = AutoScaleMethod.SMOOTH;