[win32] Use operations for Path manipulation

This commit refactors Path in the win32 implementation to better
support multiple handles for different zoom settings of a Path when
monitor-specific scaling is enabled. The previous implementation
only applied adaptions to the initial handle of the path and relied
on the path not to be changed afterwards. This doesn't cover all
scenarios and can lead to unexpected behavior when re-using Path
objects over different zoom settings.

Author: akoch-yatta

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/graphics/PathWin32Tests.java

@@ -13,6 +13,7 @@
  *******************************************************************************/
 package org.eclipse.swt.graphics;
 
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import java.util.*;
@@ -49,9 +50,11 @@ public void testHandlesExistForEachZoomLevelInHashMap() {
 		DPIUtil.setDeviceZoom(zoom);
 		Path path = new Path(display);
 		path.addArc(0, 0, 10, 10, 0, 90);
+		path.getHandle(zoom);
+		assertTrue("zoomLevelToHandle should contain initial zoom's handle", path.toString().contains(zoom + "="));
+		assertFalse("zoomLevelToHandle should not contains scaled handle", path.toString().contains(scaledZoom + "="));
 		path.getHandle(scaledZoom);
-		assertTrue("zoomLevelToHandle contains scaled handle", path.toString().contains(scaledZoom + "="));
-		assertTrue("zoomLevelToHandle contains initial zoom's handle", path.toString().contains(zoom + "="));
+		assertTrue("zoomLevelToHandle should contain scaled handle", path.toString().contains(scaledZoom + "="));
 	}
 
 	@Test
@@ -70,4 +73,22 @@ public void testBoundsAreScaledWRTZoomLevel() {
 		assertTrue("Height is scaled up wrt the scalingFactor", bounds.Height * scalingFactor == scaledBounds.Height);
 		assertTrue("Height is scaled up wrt the scalingFactor", bounds.Width * scalingFactor == scaledBounds.Width);
 	}
+
+	@Test
+	public void testCreatePathHandleWithDisposedPathInvolved() {
+		Display display = Display.getDefault();
+
+		Path path = new Path(display);
+		path.addArc(0, 0, 10, 10, 0, 90);
+
+		Path path2 = new Path(display);
+		path.addArc(0, 0, 30, 30, 0, 270);
+
+		path.addPath(path2);
+
+		path2.dispose();
+		path.getHandle(100);
+		path.getHandle(200);
+		path.dispose();
+	}
 }