terminal: avoid races between close and draw

Fix races where a goroutine calls Terminal.Draw and another one calls
Terminal.Close or Terminal.Destroy. The closing thread will eventually
set term.vterm to nil just before the drawing thread calls
term.vterm.Draw(), causing this crash:

Error: runtime error: invalid memory address or nil pointer dereference

goroutine 1 [running]:
panic({0xb09140, 0x10b5860})
        runtime/panic.go:890 +0x263
git.sr.ht/~rockorager/tcell-term.(*VT).Draw(0x0)
        git.sr.ht/~rockorager/tcell-term@v0.8.0/vt.go:424 +0x50
git.sr.ht/~rjarry/aerc/widgets.(*Terminal).draw(0xc001c658b0)
        git.sr.ht/~rjarry/aerc/widgets/terminal.go:116 +0x29
git.sr.ht/~rjarry/aerc/widgets.(*Terminal).Draw(0xc001c658b0, 0xc002b08150)
        git.sr.ht/~rjarry/aerc/widgets/terminal.go:108 +0x1b4
git.sr.ht/~rjarry/aerc/lib/ui.(*Grid).Draw(0xc001d0c360, 0xc0008ddb30)
        git.sr.ht/~rjarry/aerc/lib/ui/grid.go:126 +0x225
git.sr.ht/~rjarry/aerc/widgets.(*Composer).Draw(0xc001c13180, 0xc0008ddb30)
        git.sr.ht/~rjarry/aerc/widgets/compose.go:747 +0x8f
git.sr.ht/~rjarry/aerc/lib/ui.(*TabContent).Draw(0xc0003cc5b0, 0xc0008ddb30)
        git.sr.ht/~rjarry/aerc/lib/ui/tab.go:468 +0x1f4
git.sr.ht/~rjarry/aerc/lib/ui.(*Grid).Draw(0xc0001b2900, 0xc000037050)
        git.sr.ht/~rjarry/aerc/lib/ui/grid.go:126 +0x225
git.sr.ht/~rjarry/aerc/widgets.(*Aerc).Draw(0xc000000180, 0xc000037050)
        git.sr.ht/~rjarry/aerc/widgets/aerc.go:193 +0x209
git.sr.ht/~rjarry/aerc/lib/ui.(*UI).Render(0xc000414040)
        git.sr.ht/~rjarry/aerc/lib/ui/ui.go:105 +0x62
main.main()
        git.sr.ht/~rjarry/aerc/main.go:279 +0xbac

Use an atomic to determine if the terminal is closed or not. Never set
vterm to nil (it is not necessary).

Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Koni Marti <koni.marti@gmail.com>
Reviewed-by: Tim Culverhouse <tim@timculverhouse.com>

0 files changed, 0 insertions, 0 deletions