gtk3: mark mouse event as handled

src/gtk3/fresnel.gtk3.pas

@@ -409,7 +409,7 @@ var
   end;
 
 begin
-  Result:=false;
+  Result:=true;
   WSData:=Default(TFresnelMouseEventInit);
   MButton := Event^.button.button;
 
@@ -427,6 +427,7 @@ begin
   GDK_BUTTON_PRESS,GDK_DOUBLE_BUTTON_PRESS,GDK_TRIPLE_BUTTON_PRESS:
     begin
       EventId:=evtMouseDown;
+      //writeln('TGtk3WSForm.GtkEventMouseXY ',Event^.type_,' MButton=',MButton,' button.window=',hexstr(ptruint(Event^.button.window),16),' send_event=',Event^.button.send_event,' state=',integer(Event^.button.state),' time=',Event^.button.time);
       PressRelease;
       if MButton = GTK3_LEFT_BUTTON then
       begin