Refactor event polling code.

This centralizes much of the logic (hopefully reducing duplication)
for polling events and the queue.  This will make it easier to make
further design changes to express a better, simpler, API to consumers.

While here addressed missing logic to handle Fini correctly on Windows.

Author: gdamore

console_win.go

@@ -33,7 +33,6 @@ type cScreen struct {
 	out        syscall.Handle
 	cancelflag syscall.Handle
 	scandone   chan struct{}
-	evch       chan Event
 	quit       chan struct{}
 	curx       int
 	cury       int
@@ -53,11 +52,11 @@ type cScreen struct {
 	oomode      uint32
 	cells       CellBuffer
 
-	finiOnce sync.Once
-
 	mouseEnabled bool
 	wg           sync.WaitGroup
+	eventQ       chan Event
 	stopQ        chan struct{}
+	finiOnce     sync.Once
 
 	sync.Mutex
 }
@@ -146,7 +145,7 @@ const (
 	vtSgr0                    = "\x1b[0m"
 	vtBold                    = "\x1b[1m"
 	vtUnderline               = "\x1b[4m"
-	vtBlink                   = "\x1b[5m" // Not sure this is processed
+	vtBlink                   = "\x1b[5m" // Not sure if this is processed
 	vtReverse                 = "\x1b[7m"
 	vtSetFg                   = "\x1b[38;5;%dm"
 	vtSetBg                   = "\x1b[48;5;%dm"
@@ -179,7 +178,7 @@ func NewConsoleScreen() (Screen, error) {
 }
 
 func (s *cScreen) Init() error {
-	s.evch = make(chan Event, 10)
+	s.eventQ = make(chan Event, 10)
 	s.quit = make(chan struct{})
 	s.scandone = make(chan struct{})
 
@@ -286,7 +285,10 @@ func (s *cScreen) EnableFocus() {}
 func (s *cScreen) DisableFocus() {}
 
 func (s *cScreen) Fini() {
-	s.disengage()
+	s.finiOnce.Do(func() {
+		close(s.quit)
+		s.disengage()
+	})
 }
 
 func (s *cScreen) disengage() {
@@ -356,52 +358,6 @@ func (s *cScreen) engage() error {
 	return nil
 }
 
-func (s *cScreen) PostEventWait(ev Event) {
-	s.evch <- ev
-}
-
-func (s *cScreen) PostEvent(ev Event) error {
-	select {
-	case s.evch <- ev:
-		return nil
-	default:
-		return ErrEventQFull
-	}
-}
-
-func (s *cScreen) ChannelEvents(ch chan<- Event, quit <-chan struct{}) {
-	defer close(ch)
-	for {
-		select {
-		case <-quit:
-			return
-		case <-s.stopQ:
-			return
-		case ev := <-s.evch:
-			select {
-			case <-quit:
-				return
-			case <-s.stopQ:
-				return
-			case ch <- ev:
-			}
-		}
-	}
-}
-
-func (s *cScreen) PollEvent() Event {
-	select {
-	case <-s.stopQ:
-		return nil
-	case ev := <-s.evch:
-		return ev
-	}
-}
-
-func (s *cScreen) HasPendingEvent() bool {
-	return len(s.evch) > 0
-}
-
 type cursorInfo struct {
 	size    uint32
 	visible uint32
@@ -701,6 +657,13 @@ func mrec2btns(mbtns, flags uint32) ButtonMask {
 	return btns
 }
 
+func (s *cScreen) postEvent(ev Event) {
+	select {
+	case s.eventQ <- ev:
+	case <-s.quit:
+	}
+}
+
 func (s *cScreen) getConsoleInput() error {
 	// cancelFlag comes first as WaitForMultipleObjects returns the lowest index
 	// in the event that both events are signalled.
@@ -743,19 +706,17 @@ func (s *cScreen) getConsoleInput() error {
 			krec.mod = getu32(rec.data[12:])
 
 			if krec.isdown == 0 || krec.repeat < 1 {
-				// its a key release event, ignore it
+				// it's a key release event, ignore it
 				return nil
 			}
 			if krec.ch != 0 {
 				// synthesized key code
 				for krec.repeat > 0 {
 					// convert shift+tab to backtab
 					if mod2mask(krec.mod) == ModShift && krec.ch == vkTab {
-						s.PostEventWait(NewEventKey(KeyBacktab, 0,
-							ModNone))
+						s.postEvent(NewEventKey(KeyBacktab, 0, ModNone))
 					} else {
-						s.PostEventWait(NewEventKey(KeyRune, rune(krec.ch),
-							mod2mask(krec.mod)))
+						s.postEvent(NewEventKey(KeyRune, rune(krec.ch), mod2mask(krec.mod)))
 					}
 					krec.repeat--
 				}
@@ -767,8 +728,7 @@ func (s *cScreen) getConsoleInput() error {
 				return nil
 			}
 			for krec.repeat > 0 {
-				s.PostEventWait(NewEventKey(key, rune(krec.ch),
-					mod2mask(krec.mod)))
+				s.postEvent(NewEventKey(key, rune(krec.ch), mod2mask(krec.mod)))
 				krec.repeat--
 			}
 
@@ -781,14 +741,13 @@ func (s *cScreen) getConsoleInput() error {
 			mrec.flags = getu32(rec.data[12:])
 			btns := mrec2btns(mrec.btns, mrec.flags)
 			// we ignore double click, events are delivered normally
-			s.PostEventWait(NewEventMouse(int(mrec.x), int(mrec.y), btns,
-				mod2mask(mrec.mod)))
+			s.postEvent(NewEventMouse(int(mrec.x), int(mrec.y), btns, mod2mask(mrec.mod)))
 
 		case resizeEvent:
 			var rrec resizeRecord
 			rrec.x = geti16(rec.data[0:])
 			rrec.y = geti16(rec.data[2:])
-			s.PostEventWait(NewEventResize(int(rrec.x), int(rrec.y)))
+			s.postEvent(NewEventResize(int(rrec.x), int(rrec.y)))
 
 		default:
 		}
@@ -1128,7 +1087,10 @@ func (s *cScreen) resize() {
 		uintptr(s.out),
 		uintptr(1),
 		uintptr(unsafe.Pointer(&r)))
-	_ = s.PostEvent(NewEventResize(w, h))
+	select {
+	case s.eventQ <- NewEventResize(w, h):
+	default:
+	}
 }
 
 func (s *cScreen) clearScreen(style Style, vtEnable bool) {
@@ -1298,3 +1260,11 @@ func (s *cScreen) Tty() (Tty, bool) {
 func (s *cScreen) GetCells() *CellBuffer {
 	return &s.cells
 }
+
+func (s *cScreen) EventQ() chan Event {
+	return s.eventQ
+}
+
+func (s *cScreen) StopQ() <-chan struct{} {
+	return s.stopQ
+}

screen.go

@@ -1,4 +1,4 @@
-// Copyright 2022 The TCell Authors
+// Copyright 2023 The TCell Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use file except in compliance with the License.
@@ -314,11 +314,6 @@ type screenImpl interface {
 	HideCursor()
 	SetCursorStyle(CursorStyle)
 	Size() (width, height int)
-	ChannelEvents(ch chan<- Event, quit <-chan struct{})
-	PollEvent() Event
-	HasPendingEvent() bool
-	PostEvent(ev Event) error
-	PostEventWait(ev Event)
 	EnableMouse(...MouseFlags)
 	DisableMouse()
 	EnablePaste()
@@ -351,6 +346,15 @@ type screenImpl interface {
 	// GetCells returns a pointer to the underlying CellBuffer that the implementation uses.
 	// Various methods will write to these for performance, but will use the lock to do so.
 	GetCells() *CellBuffer
+
+	// StopQ is closed when the screen is shut down via Fini.  It remains open if the screen
+	// is merely suspended.
+	StopQ() <-chan struct{}
+
+	// EventQ delivers events.  Events are posted to this by the screen in response to
+	// key presses, resizes, etc.  Application code receives events from this via the
+	// Screen.PollEvent, Screen.ChannelEvents APIs.
+	EventQ() chan Event
 }
 
 type baseScreen struct {
@@ -417,3 +421,52 @@ func (b *baseScreen) LockRegion(x, y, width, height int, lock bool) {
 	}
 	b.Unlock()
 }
+
+func (b *baseScreen) ChannelEvents(ch chan<- Event, quit <-chan struct{}) {
+	defer close(ch)
+	for {
+		select {
+		case <-quit:
+			return
+		case <-b.StopQ():
+			return
+		case ev := <-b.EventQ():
+			select {
+			case <-quit:
+				return
+			case <-b.StopQ():
+				return
+			case ch <- ev:
+			}
+		}
+	}
+}
+
+func (b *baseScreen) PollEvent() Event {
+	select {
+	case <-b.StopQ():
+		return nil
+	case ev := <-b.EventQ():
+		return ev
+	}
+}
+
+func (b *baseScreen) HasPendingEvent() bool {
+	return len(b.EventQ()) > 0
+}
+
+func (b *baseScreen) PostEventWait(ev Event) {
+	select {
+	case b.EventQ() <- ev:
+	case <-b.StopQ():
+	}
+}
+
+func (b *baseScreen) PostEvent(ev Event) error {
+	select {
+	case b.EventQ() <- ev:
+		return nil
+	default:
+		return ErrEventQFull
+	}
+}

simulation.go

@@ -309,68 +309,29 @@ func (s *simscreen) resize() {
 	if w != ow || h != oh {
 		s.back.Resize(w, h)
 		ev := NewEventResize(w, h)
-		s.PostEvent(ev)
+		s.postEvent(ev)
 	}
 }
 
 func (s *simscreen) Colors() int {
 	return 256
 }
 
-func (s *simscreen) ChannelEvents(ch chan<- Event, quit <-chan struct{}) {
-	defer close(ch)
-	for {
-		select {
-		case <-quit:
-			return
-		case <-s.quit:
-			return
-		case ev := <-s.evch:
-			select {
-			case <-quit:
-				return
-			case <-s.quit:
-				return
-			case ch <- ev:
-			}
-		}
-	}
-}
-
-func (s *simscreen) PollEvent() Event {
-	select {
-	case <-s.quit:
-		return nil
-	case ev := <-s.evch:
-		return ev
-	}
-}
-
-func (s *simscreen) HasPendingEvent() bool {
-	return len(s.evch) > 0
-}
-
-func (s *simscreen) PostEventWait(ev Event) {
-	s.evch <- ev
-}
-
-func (s *simscreen) PostEvent(ev Event) error {
+func (s *simscreen) postEvent(ev Event) {
 	select {
 	case s.evch <- ev:
-		return nil
-	default:
-		return ErrEventQFull
+	case <-s.quit:
 	}
 }
 
 func (s *simscreen) InjectMouse(x, y int, buttons ButtonMask, mod ModMask) {
 	ev := NewEventMouse(x, y, buttons, mod)
-	s.PostEvent(ev)
+	s.postEvent(ev)
 }
 
 func (s *simscreen) InjectKey(key Key, r rune, mod ModMask) {
 	ev := NewEventKey(key, r, mod)
-	s.PostEvent(ev)
+	s.postEvent(ev)
 }
 
 func (s *simscreen) InjectKeyBytes(b []byte) bool {
@@ -381,7 +342,7 @@ outer:
 		if b[0] >= ' ' && b[0] <= 0x7F {
 			// printable ASCII easy to deal with -- no encodings
 			ev := NewEventKey(KeyRune, rune(b[0]), ModNone)
-			s.PostEvent(ev)
+			s.postEvent(ev)
 			b = b[1:]
 			continue
 		}
@@ -393,7 +354,7 @@ outer:
 				mod = ModCtrl
 			}
 			ev := NewEventKey(Key(b[0]), 0, mod)
-			s.PostEvent(ev)
+			s.postEvent(ev)
 			b = b[1:]
 			continue
 		}
@@ -407,7 +368,7 @@ outer:
 				r, _ := utf8.DecodeRune(utfb[:nout])
 				if r != utf8.RuneError {
 					ev := NewEventKey(KeyRune, r, ModNone)
-					s.PostEvent(ev)
+					s.postEvent(ev)
 				}
 				b = b[nin:]
 				continue outer
@@ -526,3 +487,11 @@ func (s *simscreen) Tty() (Tty, bool) {
 func (s *simscreen) GetCells() *CellBuffer {
 	return &s.back
 }
+
+func (s *simscreen) EventQ() chan Event {
+	return s.evch
+}
+
+func (s *simscreen) StopQ() <-chan struct{} {
+	return s.quit
+}