Add a custom mouse event wrapper around tcell's one

This wrapper implements the HasMotion() function which value is set by
the main application based on the previous mouse event.

application.go

@@ -38,6 +38,7 @@ type FocusableComponent interface {
 type Application struct {
 	screenLock   sync.RWMutex
 	screen       tcell.Screen
+	prevMouseEvt *tcell.EventMouse
 	root         Component
 	updates      chan interface{}
 	redrawTicker *time.Ticker
@@ -50,6 +51,7 @@ const queueSize = 255
 
 func NewApplication() *Application {
 	return &Application{
+		prevMouseEvt: &tcell.EventMouse{},
 		updates:      make(chan interface{}, queueSize),
 		redrawTicker: time.NewTicker(1 * time.Minute),
 		stop:         make(chan struct{}, 1),
@@ -132,7 +134,14 @@ func (app *Application) Start() error {
 					redraw = app.root.OnPasteEvent(customEvt)
 				}
 			case *tcell.EventMouse:
-				redraw = app.root.OnMouseEvent(event)
+				var customEvt customMouseEvent
+				if app.prevMouseEvt.Buttons() == event.Buttons() {
+					customEvt = customMouseEvent{event, true}
+				} else {
+					customEvt = customMouseEvent{event, false}
+				}
+				app.prevMouseEvt = event
+				redraw = app.root.OnMouseEvent(customEvt)
 			case *tcell.EventResize:
 				clear = true
 				redraw = true

eventhandler.go

@@ -51,6 +51,15 @@ type MouseEvent interface {
 	HasMotion() bool
 }
 
+type customMouseEvent struct {
+	*tcell.EventMouse
+	motion bool
+}
+
+func (cme customMouseEvent) HasMotion() bool {
+	return cme.motion
+}
+
 // SimpleEventHandler is a simple implementation of the event handling methods required for components.
 type SimpleEventHandler struct {
 	OnKey   func(event KeyEvent) bool