Fix GTK4 shell location.

We cannot determine the location of the shell using Window Handle on
GTK4. Instead store the user set location in case of GTK4 and returns
the same values when client asks for location.
Note that setting location itself works fine on GTK4.

see #2498

Author: raghucssit

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

@@ -133,6 +133,7 @@ public class Shell extends Decorations {
 	boolean ignoreFocusOut, ignoreFocusIn;
 	boolean ignoreFocusOutAfterGrab, grabbedFocus;
 	Region originalRegion;
+	private final Point location = new Point(0, 0);
 
 	static final int MAXIMUM_TRIM = 128;
 	static final int BORDER = 3;
@@ -3461,4 +3462,43 @@ Point getSurfaceOrigin () {
 	return super.getSurfaceOrigin( );
 }
 
+@Override
+public void setLocation(int x, int y) {
+	super.setLocation(x, y);
+	if (GTK.GTK4) {
+		this.location.x = x;
+		this.location.y = y;
+	}
+}
+@Override
+public void setLocation(Point location) {
+	super.setLocation(location);
+	if (GTK.GTK4) {
+		this.location.x = location.x;
+		this.location.y = location.y;
+	}
+}
+
+@Override
+void setLocationInPixels(int x, int y) {
+	super.setLocationInPixels(x, y);
+	if (GTK.GTK4) {
+		this.location.x = x;
+		this.location.y = y;
+	}
+}
+
+@Override
+void setLocationInPixels(Point location) {
+	super.setLocationInPixels(location);
+	if (GTK.GTK4) {
+		this.location.x = location.x;
+		this.location.y = location.y;
+	}
+}
+
+@Override
+public Point getLocation() {
+	return GTK.GTK4 ? location : super.getLocation();
+}
 }