Monitor Position Offset for multi zoom level

This commit introduces the offsetting of the monitor position to obtain
the absolute and scaled down bounds of the monitor for seamlessly
translating the positioning of the shell at any zoom levels. With this,
we fix several behaviour in multi zoom - multi monitor set up for win32,
such as, proper positioning of the shell and the overlay on dragging,
opening of a new window in the right monitor,etc.

contributes to #62 and #127

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Display.java

@@ -1687,7 +1687,8 @@ public Control getCursorControl () {
  */
 public Point getCursorLocation () {
 	checkDevice ();
-	return DPIUtil.autoScaleDown(getCursorLocationInPixels());
+	Point pt = getCursorLocationInPixels();
+	return getLocationInPointWithMonitorOffset(pt.x, pt.y);
 }
 
 Point getCursorLocationInPixels () {
@@ -1696,6 +1697,22 @@ Point getCursorLocationInPixels () {
 	return new Point (pt.x, pt.y);
 }
 
+Point getLocationInPixelsWithMonitorOffset(int x, int y) {
+	Monitor monitor = getContainingMonitor(x, y);
+	int zoom = DPIUtil.getZoomForAutoscaleProperty(monitor.zoom);
+	x = DPIUtil.scaleUp(x - monitor.clientX, zoom) + monitor.clientX;
+	y = DPIUtil.scaleUp(y - monitor.clientY, zoom) + monitor.clientY;
+	return new Point(x, y);
+}
+
+Point getLocationInPointWithMonitorOffset(int x, int y) {
+	Monitor monitor = getContainingMonitorInPixelsCoordiate(x, y);
+	int zoom = DPIUtil.getZoomForAutoscaleProperty(monitor.zoom);
+	x = DPIUtil.scaleDown(x - monitor.clientX, zoom) + monitor.clientX;
+	y = DPIUtil.scaleDown(y - monitor.clientY, zoom) + monitor.clientY;
+	return new Point(x, y);
+}
+
 /**
  * Returns an array containing the recommended cursor sizes.
  *
@@ -2183,8 +2200,8 @@ Monitor getMonitor (long hmonitor) {
 		System.err.println("***WARNING: GetDpiForMonitor: SWT could not get valid monitor scaling factor.");
 		result = 100;
 	}
-	monitor.setBounds(DPIUtil.scaleDown(boundsInPixels, autoscaleZoom));
-	monitor.setClientArea(DPIUtil.scaleDown(clientAreaInPixels, autoscaleZoom));
+	monitor.setBounds(getBoundsInPointsWithMonitorOffset(boundsInPixels, autoscaleZoom));
+	monitor.setClientArea(getBoundsInPointsWithMonitorOffset(clientAreaInPixels, autoscaleZoom));
 	/*
 	 * Always return true monitor zoom value as fetched from native, else will lead
 	 * to scaling issue on OS Win8.1 and above, for more details refer bug 537614.
@@ -2193,6 +2210,13 @@ Monitor getMonitor (long hmonitor) {
 	return monitor;
 }
 
+private Rectangle getBoundsInPointsWithMonitorOffset(Rectangle boundsInPixels, int zoom) {
+	Rectangle bounds = DPIUtil.scaleDown(boundsInPixels, zoom);
+	bounds.x = boundsInPixels.x;
+	bounds.y = boundsInPixels.y;
+	return bounds;
+}
+
 /**
  * Returns an array of monitors attached to the device.
  *
@@ -5262,4 +5286,18 @@ Monitor getContainingMonitor(int x, int y) {
 	}
 	return getPrimaryMonitor();
 }
+
+Monitor getContainingMonitorInPixelsCoordiate(int xInPixels, int yInPixels) {
+	Monitor[] monitors = getMonitors();
+	for (Monitor current : monitors) {
+		Rectangle clientArea = DPIUtil.scaleUp(current.getClientArea(), DPIUtil.getZoomForAutoscaleProperty(current.zoom));
+		clientArea.x = current.clientX;
+		clientArea.y = current.clientY;
+		if (clientArea.contains(xInPixels, yInPixels)) {
+			return current;
+		}
+	}
+	return getPrimaryMonitor();
+}
+
 }

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Shell.java

@@ -1579,30 +1579,61 @@ private void updateNativeZoomBeforePositionChange(int x, int y) {
 	}
 }
 
+@Override
+public Rectangle getBounds() {
+	Rectangle boundsInPixels = getBoundsInPixels ();
+	Rectangle bounds = DPIUtil.scaleDown(boundsInPixels, getZoom());
+	Point pointWithMonitorOffset = display.getLocationInPointWithMonitorOffset(boundsInPixels.x, boundsInPixels.y);
+	bounds.x = pointWithMonitorOffset.x;
+	bounds.y = pointWithMonitorOffset.y;
+	return bounds;
+}
+
+@Override
+public Point getLocation() {
+	Point locationInPixels = getLocationInPixels();
+	Point location = display.getLocationInPointWithMonitorOffset(locationInPixels.x, locationInPixels.y);
+	return location;
+}
+
 @Override
 public void setLocation(Point location) {
 	if (location == null) error (SWT.ERROR_NULL_ARGUMENT);
 	updateNativeZoomBeforePositionChange(location.x, location.y);
-	super.setLocation(location);
+	location = display.getLocationInPixelsWithMonitorOffset(location.x, location.y);
+	setLocationInPixels(location.x, location.y);
 }
 
 @Override
 public void setLocation(int x, int y) {
 	updateNativeZoomBeforePositionChange(x, y);
-	super.setLocation(x, y);
+	Point location = display.getLocationInPixelsWithMonitorOffset(x, y);
+	x = location.x;
+	y = location.y;
+	setLocationInPixels(x, y);
 }
 
 @Override
 public void setBounds(Rectangle rect) {
 	if (rect == null) error (SWT.ERROR_NULL_ARGUMENT);
 	updateNativeZoomBeforePositionChange(rect.x, rect.y);
-	super.setBounds(rect);
+	Rectangle scaledBounds = DPIUtil.scaleUp(rect, getZoom());
+	Point topLeft = display.getLocationInPixelsWithMonitorOffset(rect.x, rect.y);
+	scaledBounds.x = topLeft.x;
+	scaledBounds.y = topLeft.y;
+	setBoundsInPixels(scaledBounds);
 }
 
 @Override
 public void setBounds(int x, int y, int width, int height) {
 	updateNativeZoomBeforePositionChange(x, y);
-	super.setBounds(x, y, width, height);
+	int zoom = getZoom();
+	Point topLeft = display.getLocationInPixelsWithMonitorOffset(x, y);
+	x = topLeft.x;
+	y = topLeft.y;
+	width = DPIUtil.scaleUp(width, zoom);
+	height = DPIUtil.scaleUp(height, zoom);
+	setBoundsInPixels(x, y, width, height);
 }
 
 @Override