Deliver mouse release after a drag

Releasing a mouse button was delivered as a plain mouse-move (hover)
event: the release processing resets dragState to NOT_DRAGGING, after
which the event fell into the NOT_DRAGGING branch. Views therefore had
no way of telling that a drag gesture ended, which the upcoming
drag-based features (range selection, commit reordering) need.

Deliver the release as a real mouse event with the MouseRelease key
and normalize its modifiers to ModNone, so release bindings also match
modified drags. Make recordClickInfo ignore it: a release is the end of
a click, not a click of its own, and must not break double-click
detection.

pkg/gocui/gui.go

@@ -1773,6 +1773,12 @@ func (g *Gui) recordClickInfo(x, y int, key KeyName, v *View) bool {
 		g.lastClick = nil
 		return false
 	}
+	// A release ends a gesture but is not a click of its own; it must leave
+	// the click info of the press that started it alone, or no double click
+	// could ever be detected.
+	if key == MouseRelease {
+		return false
+	}
 
 	clickInfo := &clickInfo{
 		x:        x,

pkg/gocui/tcell_driver.go

@@ -202,7 +202,6 @@ const (
 
 var (
 	lastMouseKey tcell.ButtonMask = tcell.ButtonNone
-	lastMouseMod tcell.ModMask    = tcell.ModNone
 	dragState                     = NOT_DRAGGING
 	lastX                         = 0
 	lastY                         = 0
@@ -367,10 +366,10 @@ func gocuiEventFromTcellEvent(tev tcell.Event) GocuiEvent {
 		// process button events (not wheel events)
 		button &= tcell.ButtonMask(0xff)
 		newButtonPress := false
+		buttonReleased := false
 		if button != tcell.ButtonNone && lastMouseKey == tcell.ButtonNone {
 			newButtonPress = true
 			lastMouseKey = button
-			lastMouseMod = tev.Modifiers()
 			switch button {
 			case tcell.ButtonPrimary:
 				mouseKey = MouseLeft
@@ -388,6 +387,7 @@ func gocuiEventFromTcellEvent(tev tcell.Event) GocuiEvent {
 		switch tev.Buttons() {
 		case tcell.ButtonNone:
 			if lastMouseKey != tcell.ButtonNone {
+				buttonReleased = true
 				switch lastMouseKey {
 				case tcell.ButtonPrimary:
 					dragState = NOT_DRAGGING
@@ -395,14 +395,13 @@ func gocuiEventFromTcellEvent(tev tcell.Event) GocuiEvent {
 				case tcell.ButtonMiddle:
 				default:
 				}
-				mouseMod = Modifier(lastMouseMod)
-				lastMouseMod = tcell.ModNone
+				mouseMod = ModNone
 				lastMouseKey = tcell.ButtonNone
 			}
 		default:
 		}
 
-		if !wheeling {
+		if !wheeling && !buttonReleased {
 			switch dragState {
 			case NOT_DRAGGING:
 				return GocuiEvent{

pkg/gocui/tcell_driver_test.go

@@ -32,16 +32,25 @@ func TestMouseReleaseAfterDragIsMouseEvent(t *testing.T) {
 	gocuiEventFromTcellEvent(tcell.NewEventMouse(1, 3, tcell.ButtonPrimary, tcell.ModNone))
 	releaseEvent := gocuiEventFromTcellEvent(tcell.NewEventMouse(1, 3, tcell.ButtonNone, tcell.ModNone))
 
-	/* EXPECTED:
 	assert.Equal(t, eventMouse, releaseEvent.Type)
 	assert.Equal(t, MouseRelease, releaseEvent.Key.KeyName())
-	ACTUAL: */
-	assert.Equal(t, eventMouseMove, releaseEvent.Type)
+}
+
+func TestMouseReleaseDoesNotKeepPressModifiers(t *testing.T) {
+	t.Cleanup(resetMouseState)
+	resetMouseState()
+
+	gocuiEventFromTcellEvent(tcell.NewEventMouse(1, 2, tcell.ButtonPrimary, tcell.ModAlt))
+	gocuiEventFromTcellEvent(tcell.NewEventMouse(1, 3, tcell.ButtonPrimary, tcell.ModAlt))
+	releaseEvent := gocuiEventFromTcellEvent(tcell.NewEventMouse(1, 3, tcell.ButtonNone, tcell.ModAlt))
+
+	assert.Equal(t, eventMouse, releaseEvent.Type)
+	assert.Equal(t, MouseRelease, releaseEvent.Key.KeyName())
+	assert.Equal(t, ModNone, releaseEvent.Key.Mod())
 }
 
 func resetMouseState() {
 	lastMouseKey = tcell.ButtonNone
-	lastMouseMod = tcell.ModNone
 	dragState = NOT_DRAGGING
 	lastX = 0
 	lastY = 0