Implement focus events

_demos/mouse.go

@@ -129,12 +129,14 @@ func main() {
 	s.SetStyle(defStyle)
 	s.EnableMouse()
 	s.EnablePaste()
+	s.EnableFocus()
 	s.Clear()
 
 	posfmt := "Mouse: %d, %d  "
 	btnfmt := "Buttons: %s"
 	keyfmt := "Keys: %s"
 	pastefmt := "Paste: [%d] %s"
+	focusfmt := "Focus: %s"
 	white := tcell.StyleDefault.
 		Foreground(tcell.ColorMidnightBlue).Background(tcell.ColorLightCoral)
 
@@ -148,9 +150,10 @@ func main() {
 	pstr := ""
 	ecnt := 0
 	pasting := false
+	focus := true // assume we are focused when we start
 
 	for {
-		drawBox(s, 1, 1, 42, 7, white, ' ')
+		drawBox(s, 1, 1, 42, 8, white, ' ')
 		emitStr(s, 2, 2, white, "Press ESC twice to exit, C to clear.")
 		emitStr(s, 2, 3, white, fmt.Sprintf(posfmt, mx, my))
 		emitStr(s, 2, 4, white, fmt.Sprintf(btnfmt, bstr))
@@ -162,6 +165,12 @@ func main() {
 		}
 		emitStr(s, 2, 6, white, fmt.Sprintf(pastefmt, len(pstr), ps))
 
+		fstr := "false"
+		if focus {
+			fstr = "true"
+		}
+		emitStr(s, 2, 7, white, fmt.Sprintf(focusfmt, fstr))
+
 		s.Show()
 		bstr = ""
 		ev := s.PollEvent()
@@ -315,6 +324,8 @@ func main() {
 			lchar = ch
 			s.SetContent(w-1, h-1, 'M', nil, st)
 			mx, my = x, y
+		case *tcell.EventFocus:
+			focus = ev.Focused
 		default:
 			s.SetContent(w-1, h-1, 'X', nil, st)
 		}

console_win.go

@@ -282,6 +282,10 @@ func (s *cScreen) EnablePaste() {}
 
 func (s *cScreen) DisablePaste() {}
 
+func (s *cScreen) EnableFocus() {}
+
+func (s *cScreen) DisableFocus() {}
+
 func (s *cScreen) Fini() {
 	s.disengage()
 }

focus.go

@@ -0,0 +1,28 @@
+// 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.
+// You may obtain a copy of the license at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tcell
+
+// EventFocus is a focus event. It is sent when the terminal window (or tab)
+// gets or loses focus.
+type EventFocus struct {
+	*EventTime
+
+	// True if the window received focus, false if it lost focus
+	Focused bool
+}
+
+func NewEventFocus(focused bool) *EventFocus {
+	return &EventFocus{Focused: focused}
+}

screen.go

@@ -139,6 +139,12 @@ type Screen interface {
 	// DisablePaste disables bracketed paste mode.
 	DisablePaste()
 
+	// EnableFocus enables reporting of focus events, if your terminal supports it.
+	EnableFocus()
+
+	// DisableFocus disables reporting of focus events.
+	DisableFocus()
+
 	// HasMouse returns true if the terminal (apparently) supports a
 	// mouse.  Note that the return value of true doesn't guarantee that
 	// a mouse/pointing device is present; a false return definitely

simulation.go

@@ -325,6 +325,12 @@ func (s *simscreen) DisablePaste() {
 	s.paste = false
 }
 
+func (s *simscreen) EnableFocus() {
+}
+
+func (s *simscreen) DisableFocus() {
+}
+
 func (s *simscreen) Size() (int, int) {
 	s.Lock()
 	w, h := s.back.Size()

terminfo/terminfo.go

@@ -230,6 +230,8 @@ type Terminfo struct {
 	EnterUrl                string
 	ExitUrl                 string
 	SetWindowSize           string
+	EnableFocusReporting    string
+	DisableFocusReporting   string
 }
 
 const (

tscreen.go

@@ -153,6 +153,8 @@ type tScreen struct {
 	enterUrl     string
 	exitUrl      string
 	setWinSize   string
+	enableFocus  string
+	disableFocus string
 	cursorStyles map[CursorStyle]string
 	cursorStyle  CursorStyle
 	saved        *term.State
@@ -161,6 +163,7 @@ type tScreen struct {
 	wg           sync.WaitGroup
 	mouseFlags   MouseFlags
 	pasteEnabled bool
+	focusEnabled bool
 
 	sync.Mutex
 }
@@ -366,6 +369,17 @@ func (t *tScreen) prepareExtendedOSC() {
 	} else if t.ti.Mouse != "" {
 		t.setWinSize = "\x1b[8;%p1%p2%d;%dt"
 	}
+
+	if t.ti.EnableFocusReporting != "" {
+		t.enableFocus = t.ti.EnableFocusReporting
+	} else if t.ti.Mouse != "" {
+		t.enableFocus = "\x1b[?1004h"
+	}
+	if t.ti.DisableFocusReporting != "" {
+		t.disableFocus = t.ti.DisableFocusReporting
+	} else if t.ti.Mouse != "" {
+		t.disableFocus = "\x1b[?1004l"
+	}
 }
 
 func (t *tScreen) prepareCursorStyles() {
@@ -1043,6 +1057,32 @@ func (t *tScreen) enablePasting(on bool) {
 	}
 }
 
+func (t *tScreen) EnableFocus() {
+	t.Lock()
+	t.focusEnabled = true
+	t.enableFocusReporting()
+	t.Unlock()
+}
+
+func (t *tScreen) DisableFocus() {
+	t.Lock()
+	t.focusEnabled = false
+	t.disableFocusReporting()
+	t.Unlock()
+}
+
+func (t *tScreen) enableFocusReporting() {
+	if t.enableFocus != "" {
+		t.TPuts(t.enableFocus)
+	}
+}
+
+func (t *tScreen) disableFocusReporting() {
+	if t.disableFocus != "" {
+		t.TPuts(t.disableFocus)
+	}
+}
+
 func (t *tScreen) Size() (int, int) {
 	t.Lock()
 	w, h := t.w, t.h
@@ -1380,6 +1420,35 @@ func (t *tScreen) parseSgrMouse(buf *bytes.Buffer, evs *[]Event) (bool, bool) {
 	return true, false
 }
 
+func (t *tScreen) parseFocus(buf *bytes.Buffer, evs *[]Event) (bool, bool) {
+	state := 0
+	b := buf.Bytes()
+	for i := range b {
+		switch state {
+		case 0:
+			if b[i] != '\x1b' {
+				return false, false
+			}
+			state = 1
+		case 1:
+			if b[i] != '[' {
+				return false, false
+			}
+			state = 2
+		case 2:
+			if b[i] != 'I' && b[i] != 'O' {
+				return false, false
+			}
+			*evs = append(*evs, NewEventFocus(b[i] == 'I'))
+			_, _ = buf.ReadByte()
+			_, _ = buf.ReadByte()
+			_, _ = buf.ReadByte()
+			return true, true
+		}
+	}
+	return true, false
+}
+
 // parseXtermMouse is like parseSgrMouse, but it parses a legacy
 // X11 mouse record.
 func (t *tScreen) parseXtermMouse(buf *bytes.Buffer, evs *[]Event) (bool, bool) {
@@ -1556,6 +1625,12 @@ func (t *tScreen) collectEventsFromInput(buf *bytes.Buffer, expire bool) []Event
 			partials++
 		}
 
+		if part, comp := t.parseFocus(buf, &res); comp {
+			continue
+		} else if part {
+			partials++
+		}
+
 		// Only parse mouse records if this term claims to have
 		// mouse support
 
@@ -1804,6 +1879,9 @@ func (t *tScreen) engage() error {
 	t.stopQ = stopQ
 	t.enableMouse(t.mouseFlags)
 	t.enablePasting(t.pasteEnabled)
+	if t.focusEnabled {
+		t.enableFocusReporting()
+	}
 
 	ti := t.ti
 	t.TPuts(ti.EnterCA)
@@ -1853,6 +1931,7 @@ func (t *tScreen) disengage() {
 	t.TPuts(ti.ExitKeypad)
 	t.enableMouse(0)
 	t.enablePasting(false)
+	t.disableFocusReporting()
 
 	_ = t.tty.Stop()
 }