Get mouse actions rather than just mouse state

application.go

@@ -70,6 +70,10 @@ type Application struct {
 	// event to be forwarded to the default mouse handler (nil if nothing should
 	// be forwarded).
 	mouseCapture func(event EventMouse) EventMouse
+
+	lastMouseX, lastMouseY int
+	lastMouseBtn           tcell.ButtonMask
+	lastMouseTarget        Primitive // nil if none
 }
 
 // EventKey is the key input event info.
@@ -77,11 +81,22 @@ type Application struct {
 // even though it's just an alias to *tcell.EventKey for backwards compatibility.
 type EventKey = *tcell.EventKey
 
+// MouseAction are bit flags indicating what the mouse is logically doing.
+type MouseAction int
+
+const (
+	MouseDown MouseAction = 1 << iota
+	MouseUp
+	MouseClick // Button1 only.
+	MouseMove  // The mouse position changed.
+)
+
 // EventMouse is the mouse event info.
 type EventMouse struct {
 	*tcell.EventMouse
 	Target      Primitive
 	Application *Application
+	Action      MouseAction
 }
 
 // IsZero returns true if this is a zero object.
@@ -304,11 +319,46 @@ EventLoop:
 				a.draw()
 			case *tcell.EventMouse:
 				atX, atY := event.Position()
-				ptarget := a.GetPrimitiveAtPoint(atX, atY) // p under mouse.
+				btn := event.Buttons()
+
+				var ptarget Primitive
+				if a.lastMouseBtn != 0 {
+					// While a button is down, the same primitive gets events.
+					ptarget = a.lastMouseTarget
+				}
 				if ptarget == nil {
-					ptarget = p // Fallback to focused.
+					ptarget = a.GetPrimitiveAtPoint(atX, atY) // p under mouse.
+					if ptarget == nil {
+						ptarget = p // Fallback to focused.
+					}
 				}
-				event2 := EventMouse{event, ptarget, a}
+				a.lastMouseTarget = ptarget
+
+				// Calculate mouse actions.
+				var act MouseAction
+				if atX != a.lastMouseX || atY != a.lastMouseY {
+					act |= MouseMove
+					a.lastMouseX = atX
+					a.lastMouseY = atY
+				}
+				btnDiff := btn ^ a.lastMouseBtn
+				if btnDiff != 0 {
+					if btn&btnDiff != 0 {
+						act |= MouseDown
+					}
+					if a.lastMouseBtn&btnDiff != 0 {
+						act |= MouseUp
+					}
+					if a.lastMouseBtn == tcell.Button1 && btn == 0 {
+						if ptarget == a.GetPrimitiveAtPoint(atX, atY) {
+							// Only if Button1 and mouse up over same p.
+							act |= MouseClick
+						}
+					}
+					a.lastMouseBtn = btn
+				}
+
+				event2 := EventMouse{event, ptarget, a, act}
 
 				// Intercept event.
 				if mouseCapture != nil {

button.go

@@ -140,7 +140,7 @@ func (b *Button) InputHandler() func(event *tcell.EventKey, setFocus func(p Prim
 func (b *Button) MouseHandler() func(event EventMouse) {
 	return b.WrapMouseHandler(func(event EventMouse) {
 		// Process mouse event.
-		if event.Buttons()&tcell.Button1 != 0 {
+		if event.Action&MouseClick != 0 {
 			if b.selected != nil {
 				b.selected()
 			}

checkbox.go

@@ -206,7 +206,7 @@ func (c *Checkbox) InputHandler() func(event *tcell.EventKey, setFocus func(p Pr
 func (c *Checkbox) MouseHandler() func(event EventMouse) {
 	return c.WrapMouseHandler(func(event EventMouse) {
 		// Process mouse event.
-		if event.Buttons()&tcell.Button1 != 0 {
+		if event.Action&MouseClick != 0 {
 			c.checked = !c.checked
 			if c.changed != nil {
 				c.changed(c.checked)

dropdown.go

@@ -476,12 +476,17 @@ func (d *DropDown) openList(setFocus func(Primitive), app *Application) {
 				if atX >= x && atY >= y && atX < x+w && atY < y+h {
 					// Mouse is within the list.
 					if handler := d.list.MouseHandler(); handler != nil {
+						if event.Action&MouseUp != 0 {
+							// Treat mouse up as click here.
+							// This allows you to expand and select in one go.
+							event.Action |= MouseClick
+						}
 						handler(event)
 						return EventMouse{} // handled
 					}
 				} else {
 					// Mouse not within the list.
-					if event.Buttons() != 0 {
+					if event.Action&MouseDown != 0 {
 						// If a mouse button was pressed, cancel this capture.
 						app.SetMouseCapture(nil)
 						d.closeList(event.SetFocus)
@@ -521,7 +526,7 @@ func (d *DropDown) HasFocus() bool {
 func (d *DropDown) MouseHandler() func(event EventMouse) {
 	return d.WrapMouseHandler(func(event EventMouse) {
 		// Process mouse event.
-		if event.Buttons()&tcell.Button1 != 0 {
+		if event.Action&MouseDown != 0 && event.Buttons()&tcell.Button1 != 0 {
 			//d.open = !d.open
 			//event.SetFocus(d)
 			if d.open {

inputfield.go

@@ -596,7 +596,7 @@ func (i *InputField) InputHandler() func(event *tcell.EventKey, setFocus func(p
 func (i *InputField) MouseHandler() func(event EventMouse) {
 	return i.WrapMouseHandler(func(event EventMouse) {
 		// Process mouse event.
-		if event.Buttons()&tcell.Button1 != 0 {
+		if event.Action&MouseDown != 0 {
 			event.SetFocus(i)
 		}
 	})

list.go

@@ -550,7 +550,7 @@ func (l *List) indexAtPoint(atX, atY int) int {
 func (l *List) MouseHandler() func(event EventMouse) {
 	return l.WrapMouseHandler(func(event EventMouse) {
 		// Process mouse event.
-		if event.Buttons()&tcell.Button1 != 0 {
+		if event.Action&MouseClick != 0 {
 			atX, atY := event.Position()
 			index := l.indexAtPoint(atX, atY)
 			if index != -1 {