From 5685a176747711d0330f1251ad297b13e0621a37 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Sat, 27 Apr 2019 16:47:59 +0000
Subject: lib/ui: introduce Invalidatable

Many Drawable implementations have their own Invalidate and OnInvalidate
functions, with an unexported onInvalidate field. However OnInvalidate and
Invalidate are usually not called in the same goroutine. This results in a race
on this field, e.g.:

    Read at 0x00c000094748 by goroutine 7:
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList.func1()
          /home/simon/src/aerc2/widgets/dirlist.go:85 +0x56
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start.func1()
          /home/simon/src/aerc2/widgets/spinner.go:93 +0x1bb

    Previous write at 0x00c000094748 by main goroutine:
      [failed to restore the stack]

    Goroutine 7 (running) created at:
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start()
          /home/simon/src/aerc2/widgets/spinner.go:46 +0x8f
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList()
          /home/simon/src/aerc2/widgets/dirlist.go:37 +0x286
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAccountView()
          /home/simon/src/aerc2/widgets/account.go:50 +0x5ca
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAerc()
          /home/simon/src/aerc2/widgets/aerc.go:60 +0x800
      main.main()
          /home/simon/src/aerc2/aerc.go:65 +0x33e

To fix this, introduce a new type, Invalidatable, which protects the field.
Unfortunately the Drawable must be passed to the callback function in
Invalidate, so we still need to re-implement this in each Invalidatable user.
---
 widgets/terminal.go | 36 +++++++++++++++---------------------
 1 file changed, 15 insertions(+), 21 deletions(-)

(limited to 'widgets/terminal.go')

diff --git a/widgets/terminal.go b/widgets/terminal.go
index 84f80e3..63c105f 100644
--- a/widgets/terminal.go
+++ b/widgets/terminal.go
@@ -88,20 +88,20 @@ func init() {
 }
 
 type Terminal struct {
-	closed       bool
-	cmd          *exec.Cmd
-	colors       map[tcell.Color]tcell.Color
-	ctx          *ui.Context
-	cursorPos    vterm.Pos
-	cursorShown  bool
-	damage       []vterm.Rect
-	destroyed    bool
-	err          error
-	focus        bool
-	onInvalidate func(d ui.Drawable)
-	pty          *os.File
-	start        chan interface{}
-	vterm        *vterm.VTerm
+	ui.Invalidatable
+	closed      bool
+	cmd         *exec.Cmd
+	colors      map[tcell.Color]tcell.Color
+	ctx         *ui.Context
+	cursorPos   vterm.Pos
+	cursorShown bool
+	damage      []vterm.Rect
+	destroyed   bool
+	err         error
+	focus       bool
+	pty         *os.File
+	start       chan interface{}
+	vterm       *vterm.VTerm
 
 	OnClose func(err error)
 	OnStart func()
@@ -225,10 +225,6 @@ func (term *Terminal) Destroy() {
 	term.destroyed = true
 }
 
-func (term *Terminal) OnInvalidate(cb func(d ui.Drawable)) {
-	term.onInvalidate = cb
-}
-
 func (term *Terminal) Invalidate() {
 	if term.vterm != nil {
 		width, height := term.vterm.Size()
@@ -239,9 +235,7 @@ func (term *Terminal) Invalidate() {
 }
 
 func (term *Terminal) invalidate() {
-	if term.onInvalidate != nil {
-		term.onInvalidate(term)
-	}
+	term.DoInvalidate(term)
 }
 
 func (term *Terminal) Draw(ctx *ui.Context) {
-- 
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