[Win32] Correct bounds/size value of child shells #2862

In point/pixel conversions for bounds/sizes of controls, the parent
control's zoom is used to adhere to the most appropriate context when
having auto-scale disabled controls. This, however, leads to child
shells using the zoom of the parent shells, which can be placed on a
different monitor with a different zoom, such that the bounds/sizes of
such child shells are wrongly scaled.

With this change, shells always use their own zoom for bounds/sizes
calculations instead of the one of a potential parent shell.

Fixes #2862

Author: HeikoKlare

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/widgets/ControlWin32Tests.java

@@ -356,4 +356,16 @@ void testChildFillsScrollableWithBadlyRoundedClientArea() {
 		assertTrue(clientAreaInPixels.height <= childBoundsInPixels.y + childBoundsInPixels.height);
 	}
 
+	@Test
+	void testChildShellGetSize() {
+		Win32DPIUtils.setMonitorSpecificScaling(true);
+		Display display = Display.getDefault();
+		Shell shell = new Shell(display);
+		shell.nativeZoom = 150;
+		Shell childShell = new Shell(shell);
+		childShell.nativeZoom = 100;
+		childShell.setSize(300, 300);
+		assertEquals(300, childShell.getSizeInPixels().x);
+	}
+
 }

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

@@ -4886,7 +4886,7 @@ int getShellZoom() {
 	return nativeZoom;
 }
 
-private int computeGetBoundsZoom() {
+int computeGetBoundsZoom() {
 	if (parent != null && !autoScaleDisabled) {
 		return parent.getZoom();
 	}

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

@@ -2787,4 +2787,14 @@ LRESULT WM_WINDOWPOSCHANGING (long wParam, long lParam) {
 	return result;
 }
 
+@Override
+int computeBoundsZoom() {
+	return getZoom();
+}
+
+@Override
+int computeGetBoundsZoom() {
+	return getZoom();
+}
+
 }