macOS delay on incomplete escape sequences to avoid spurious escape keypress detection #132

api.go

@@ -8,6 +8,7 @@ import "os"
 import "os/signal"
 import "syscall"
 import "runtime"
+import "time"
 
 // public API
 
@@ -253,8 +254,8 @@ func CellBuffer() []Cell {
 // NOTE: This API is experimental and may change in future.
 func ParseEvent(data []byte) Event {
 	event := Event{Type: EventKey}
-	ok := extract_event(data, &event)
-	if !ok {
+	status := extract_event(data, &event, false)
+	if status != event_extracted {
 		return Event{Type: EventNone, N: event.N}
 	}
 	return event
@@ -303,34 +304,65 @@ func PollRawEvent(data []byte) Event {
 
 // Wait for an event and return it. This is a blocking function call.
 func PollEvent() Event {
+	// Constant governing macOS specific behavior. See https://github.com/nsf/termbox-go/issues/132
+	// This is an arbitrary delay which hopefully will be enough time for any lagging
+	// partial escape sequences to come through.
+	const esc_wait_delay = 50 * time.Millisecond
+
 	var event Event
+	var esc_wait_timer *time.Timer
+	var esc_timeout <-chan time.Time
 
 	// try to extract event from input buffer, return on success
 	event.Type = EventKey
-	ok := extract_event(inbuf, &event)
+	status := extract_event(inbuf, &event, true)
 	if event.N != 0 {
 		copy(inbuf, inbuf[event.N:])
 		inbuf = inbuf[:len(inbuf)-event.N]
 	}
-	if ok {
+	if status == event_extracted {
 		return event
+	} else if status == esc_wait {
+		esc_wait_timer = time.NewTimer(esc_wait_delay)
+		esc_timeout = esc_wait_timer.C
 	}
 
 	for {
 		select {
 		case ev := <-input_comm:
+			if esc_wait_timer != nil {
+				if !esc_wait_timer.Stop() {
+					<-esc_wait_timer.C
+				}
+				esc_wait_timer = nil
+			}
+
 			if ev.err != nil {
 				return Event{Type: EventError, Err: ev.err}
 			}
 
 			inbuf = append(inbuf, ev.data...)
 			input_comm <- ev
-			ok := extract_event(inbuf, &event)
+			status := extract_event(inbuf, &event, true)
+			if event.N != 0 {
+				copy(inbuf, inbuf[event.N:])
+				inbuf = inbuf[:len(inbuf)-event.N]
+			}
+			if status == event_extracted {
+				return event
+			} else if status == esc_wait {
+				esc_wait_timer = time.NewTimer(esc_wait_delay)
+				esc_timeout = esc_wait_timer.C
+			}
+		case <-esc_timeout:
+			esc_wait_timer = nil
+
+			status := extract_event(inbuf, &event, false)
 			if event.N != 0 {
 				copy(inbuf, inbuf[event.N:])
 				inbuf = inbuf[:len(inbuf)-event.N]
 			}
-			if ok {
+			if status == event_extracted {
 				return event
 			}
 		case <-interrupt_comm:

escwait.go

+// +build !darwin
+
+package termbox
+
+// On all systems other than macOS, disable behavior which will wait before
+// deciding that the escape key was pressed, to account for partially send
+// escape sequences, especially with regard to lengthy mouse sequences.
+// See https://github.com/nsf/termbox-go/issues/132
+func enable_wait_for_escape_sequence() bool {
+	return false
+}

escwait_darwin.go

+package termbox
+
+// On macOS, enable behavior which will wait before deciding that the escape
+// key was pressed, to account for partially send escape sequences, especially
+// with regard to lengthy mouse sequences.
+// See https://github.com/nsf/termbox-go/issues/132
+func enable_wait_for_escape_sequence() bool {
+	return true
+}

termbox.go

@@ -41,6 +41,14 @@ type input_event struct {
 	err  error
 }
 
+type extract_event_res int
+
+const (
+	event_not_extracted extract_event_res = iota
+	event_extracted
+	esc_wait
+)
+
 var (
 	// term specific sequences
 	keys  []string
@@ -440,17 +448,27 @@ func extract_raw_event(data []byte, event *Event) bool {
 	return true
 }
 
-func extract_event(inbuf []byte, event *Event) bool {
+func extract_event(inbuf []byte, event *Event, allow_esc_wait bool) extract_event_res {
 	if len(inbuf) == 0 {
 		event.N = 0
-		return false
+		return event_not_extracted
 	}
 
 	if inbuf[0] == '\033' {
 		// possible escape sequence
 		if n, ok := parse_escape_sequence(event, inbuf); n != 0 {
 			event.N = n
-			return ok
+			if ok {
+				return event_extracted
+			} else {
+				return event_not_extracted
+			}
+		}
+
+		// possible partially read escape sequence; trigger a wait if appropriate
+		if enable_wait_for_escape_sequence() && allow_esc_wait {
+			event.N = 0
+			return esc_wait
 		}
 
 		// it's not escape sequence, then it's Alt or Esc, check input_mode
@@ -461,17 +479,17 @@ func extract_event(inbuf []byte, event *Event) bool {
 			event.Key = KeyEsc
 			event.Mod = 0
 			event.N = 1
-			return true
+			return event_extracted
 		case input_mode&InputAlt != 0:
 			// if we're in alt mode, set Alt modifier to event and redo parsing
 			event.Mod = ModAlt
-			ok := extract_event(inbuf[1:], event)
-			if ok {
+			status := extract_event(inbuf[1:], event, false)
+			if status == event_extracted {
 				event.N++
 			} else {
 				event.N = 0
 			}
-			return ok
+			return status
 		default:
 			panic("unreachable")
 		}
@@ -486,7 +504,7 @@ func extract_event(inbuf []byte, event *Event) bool {
 		event.Ch = 0
 		event.Key = Key(inbuf[0])
 		event.N = 1
-		return true
+		return event_extracted
 	}
 
 	// the only possible option is utf8 rune
@@ -494,10 +512,10 @@ func extract_event(inbuf []byte, event *Event) bool {
 		event.Ch = r
 		event.Key = 0
 		event.N = n
-		return true
+		return event_extracted
 	}
 
-	return false
+	return event_not_extracted
 }
 
 func fcntl(fd int, cmd int, arg int) (val int, err error) {