Switch event type for dragging and drop all but the last drag event i…

…n a series

event.go

@@ -45,3 +45,16 @@ type SimpleEventFunc func()
 func (fn SimpleEventFunc) Execute() {
 	fn()
 }
+
+type DragEventFunc struct {
+	wid Draggable
+	ev  *DragEvent
+}
+
+func NewDragEventFunc(wid Draggable, ev *DragEvent) *DragEventFunc {
+	return &DragEventFunc{wid, ev}
+}
+
+func (drag *DragEventFunc) Execute() {
+	drag.wid.Dragged(drag.ev)
+}

internal/driver/common/window.go

@@ -30,8 +30,32 @@ func (w *Window) QueueEvent(fn fyne.EventFunc) {
 // RunEventQueue runs the event queue. This should called inside a go routine.
 // This function blocks.
 func (w *Window) RunEventQueue() {
-	for fn := range w.eventQueue.Out() {
-		fn.Execute()
+	for evfn := range w.eventQueue.Out() {
+		if dragfn, ok := evfn.(*fyne.DragEventFunc); ok {
+			evfn = nil
+
+			L: for {
+				select {
+				case nevfn := <- w.eventQueue.Out():
+					ndragfn, ok := nevfn.(*fyne.DragEventFunc)
+					if !ok {
+						evfn = nevfn
+						break L
+					}
+					dragfn = ndragfn
+				default:
+					break L
+				}
+			}
+
+			dragfn.Execute()
+			if evfn != nil {
+				evfn.Execute()
+			}
+			continue
+		}
+
+		evfn.Execute()
 	}
 }
 

internal/driver/glfw/window.go

@@ -451,8 +451,7 @@ func (w *window) processMouseMoved(xpos float64, ypos float64) {
 			ev.AbsolutePosition = mousePos
 			ev.Position = mousePos.Subtract(mouseDraggedOffset).Add(draggedObjDelta)
 			ev.Dragged = fyne.NewDelta(mousePos.X-mouseDragPos.X, mousePos.Y-mouseDragPos.Y)
-			wd := mouseDragged
-			w.QueueEvent(fyne.SimpleEventFunc(func() { wd.Dragged(ev) }))
+			w.QueueEvent(fyne.NewDragEventFunc(mouseDragged, ev))
 		}
 
 		w.mouseLock.Lock()

internal/driver/mobile/driver.go

@@ -387,7 +387,7 @@ func (d *driver) tapMoveCanvas(w *window, x, y float32, tapID touch.Sequence) {
 	pos := fyne.NewPos(tapX, tapY+tapYOffset)
 
 	w.canvas.tapMove(pos, int(tapID), func(wid fyne.Draggable, ev *fyne.DragEvent) {
-		w.QueueEvent(fyne.SimpleEventFunc(func() { wid.Dragged(ev) }))
+		w.QueueEvent(fyne.NewDragEventFunc(wid, ev))
 	})
 }