Bug 576215 - [Wayland] Mouse events not received as on other platforms

This patch addresses mouse events not being the same between x11 and
Wayland. The issue was MouseMove events were being left out of the queue
which prevented them from being sent out. Passes AllNonBrowserTests and
DnD example works as expected.

The Wayland behavior is not 100% the same as x11 due to the initial
MouseDown event being cached before being sent out. However, as soon as
the mouse begins to move, the down message pops up, and the behavior is
as expected.

Change-Id: I090953be3bf592c4161ec497a53e47964904fe45
Signed-off-by: jmajano <[email protected]>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.swt/+/186019
Tested-by: Platform Bot <[email protected]>
Reviewed-by: Alexander Kurtakov <[email protected]>

Author: joel-majano

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

@@ -4999,7 +4999,13 @@ boolean sendMouseEvent (int type, int button, int count, int detail, boolean sen
 				sendOrPost(SWT.MouseDown, mouseDownEvent);
 			}
 		}
-		return true;
+		/* This checks for Wayland, a previous MouseDown || MouseMove in the
+		 * dragDetectionQueue and it checks if the current event is MouseMove
+		 * This will prevent them from not being queued, which caused
+		 * Bug 576215 - [Wayland] Mouse events not received as on other platforms.
+		 * In x11 this will always return true as before.
+		 */
+		if( (OS.isX11() || (dragDetectionQueue == null) || (type != SWT.MouseMove)) ) return true;
 	}
 	Event event = new Event ();
 	event.time = time;