From 45c636ec33695f046de8bbc793f7c6e5f533bdff Mon Sep 17 00:00:00 2001
From: Timon Ringwald <timon.ringwald@mequen.de>
Date: Mon, 4 Apr 2022 14:47:15 +0200
Subject: [PATCH] thread safety for event loop and redraw loop

---
 screen.go | 86 ++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 54 insertions(+), 32 deletions(-)

diff --git a/screen.go b/screen.go
index eb44bb3..79750eb 100644
--- a/screen.go
+++ b/screen.go
@@ -9,10 +9,14 @@ import (
 )
 
 type Screen struct {
-	scr    tcell.Screen
-	buf    *ViewBuffer
-	stopCh chan error
-	Root   View
+	scr tcell.Screen
+	buf *ViewBuffer
+
+	stopCh   chan error
+	redrawCh chan struct{}
+
+	// Root is the root view which is currently shown on screen
+	Root View
 
 	// KeyPressed is called every time a key or key-combination is pressed.
 	KeyPressed func(event *KeyEvent) (consumed bool)
@@ -28,32 +32,18 @@ func NewScreen(root View) (*Screen, error) {
 	}
 
 	s := &Screen{
-		Root:   root,
-		scr:    scr,
-		stopCh: make(chan error, 1),
+		Root:     root,
+		scr:      scr,
+		stopCh:   make(chan error, 1),
+		redrawCh: make(chan struct{}, 1),
 	}
 
 	go s.eventloop()
+	go s.drawloop()
 
 	return s, nil
 }
 
-func (s *Screen) eventloop() {
-	for evt := s.scr.PollEvent(); evt != nil; evt = s.scr.PollEvent() {
-		switch event := evt.(type) {
-		case *tcell.EventResize:
-			go s.Redraw()
-		case *tcell.EventKey:
-			go s.onKeyPressed(event)
-		case *tcell.EventMouse:
-			go s.onMouseClicked(convertMouseEvent(event))
-		default:
-			s.StopWithError(errors.New(fmt.Sprintf("%#v", event)))
-		}
-	}
-	s.StopWithError(errors.New("unknown error occured"))
-}
-
 func (s *Screen) Start() error {
 	err := s.scr.Init()
 	if err != nil {
@@ -99,13 +89,45 @@ func convertMouseEvent(original *tcell.EventMouse) *MouseEvent {
 }
 
 func (s *Screen) Redraw() {
-	w, h := s.scr.Size()
-
-	if s.buf == nil || s.buf.Width() != w || s.buf.Height() != h {
-		s.buf = buf2d.NewBuffer(w, h, DefaultRune)
-	}
-
-	rw, rh := s.Root.Layout()
-	s.Root.Draw(truncateBuffer(s.buf, rw, rh))
-	drawBuffer(s.scr, s.buf)
+	s.redrawCh <- struct{}{}
+}
+
+func (s *Screen) eventloop() {
+	defer s.stopOnPanic()
+
+	for evt := s.scr.PollEvent(); evt != nil; evt = s.scr.PollEvent() {
+		switch event := evt.(type) {
+		case *tcell.EventResize:
+			go s.Redraw()
+		case *tcell.EventKey:
+			go s.onKeyPressed(event)
+		case *tcell.EventMouse:
+			go s.onMouseClicked(convertMouseEvent(event))
+		default:
+			s.StopWithError(errors.New(fmt.Sprintf("%#v", event)))
+		}
+	}
+	s.StopWithError(errors.New("unknown error occured"))
+}
+
+func (s *Screen) drawloop() {
+	defer s.stopOnPanic()
+
+	for range s.redrawCh {
+		w, h := s.scr.Size()
+
+		if s.buf == nil || s.buf.Width() != w || s.buf.Height() != h {
+			s.buf = buf2d.NewBuffer(w, h, DefaultRune)
+		}
+
+		rw, rh := s.Root.Layout()
+		s.Root.Draw(truncateBuffer(s.buf, rw, rh))
+		drawBuffer(s.scr, s.buf)
+	}
+}
+
+func (s *Screen) stopOnPanic() {
+	if err := recover(); err != nil {
+		s.StopWithError(fmt.Errorf("%v", err))
+	}
 }