[Win32] MultiZoomCoordinateSystemMapper: zero-sized rectangle handling

The MultiZoomCoordinateSystemMapper currently produces a devide-by-zero
error when transforming a rectangle of zero size. This can, for example,
happen when a (dummy) shell with width=height=0 is created and its
bounds are passed to the mapper.

This change ensures that the problematic calculation is avoided in case
width or height are zeroi by just taking the x/y coordinate into
account.

Author: HeikoKlare

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/widgets/CoordinateSystemMapperTests.java

@@ -210,6 +210,15 @@ void translateRectangleInPixelsInBothMonitorsBackAndForthShouldBeTheSame(Coordin
 		assertEquals(rectInPxs, mapper.translateToDisplayCoordinates(rectInPts, monitors[0].getZoom()));
 	}
 
+	@ParameterizedTest
+	@MethodSource("provideCoordinateSystemMappers")
+	void translateRectangleInPixelsForZeroSize(CoordinateSystemMapper mapper) {
+		setupMonitors(mapper);
+		Rectangle rectInPts = createExpectedRectangle(mapper, 0, 0, 0, 0, monitors[0]);
+		Rectangle rectInPxs = mapper.translateToDisplayCoordinates(rectInPts, monitors[0].getZoom());
+		assertEquals(rectInPts, mapper.translateFromDisplayCoordinates(rectInPxs, monitors[0].getZoom()));
+	}
+
 	private Point createExpectedPoint(CoordinateSystemMapper mapper, int x, int y, Monitor monitor) {
 		if (mapper instanceof SingleZoomCoordinateSystemMapper) {
 			return new Point(x, y);

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

@@ -192,6 +192,9 @@ private Monitor getContainingMonitorForPoints(int x, int y) {
 	}
 
 	private Monitor getContainingMonitorForPoints(int x, int y, int width, int height) {
+		if (width <= 0 || height <= 0) {
+			return getContainingMonitorForPoints(x, y);
+		}
 		Monitor[] monitors = monitorSupplier.get();
 		Monitor selectedMonitor = null;
 		int highestIntersectionRatio = 0;