textinput: fix crash when scrolling back in command history

Pressing up while in command mode, calls TextInput.Set() with the
previous command in the history. If the command exceeds the current
terminal width, there is a scroll mechanism that puts the cursor at the
end of the text (see ensureScroll()). However, the offset used to
perform the draw is not the current scroll value but the "previous" one.
When the one before last command required a longer scroll offset than
the current command length, this causes a crash:

 Error: runtime error: slice bounds out of range [348:5]

 git.sr.ht/~rjarry/aerc/lib/ui.(*TextInput).Draw(0xc0017ce000, 0xc005460570)
         git.sr.ht/~rjarry/aerc/lib/ui/textinput.go:111 +0x525
 git.sr.ht/~rjarry/aerc/widgets.(*ExLine).Draw(0x30?, 0xc01de13b08?)
         git.sr.ht/~rjarry/aerc/widgets/exline.go:76 +0x1d
 git.sr.ht/~rjarry/aerc/lib/ui.(*Stack).Draw(0xc0003f0ff0?, 0x0?)
         git.sr.ht/~rjarry/aerc/lib/ui/stack.go:30 +0x49
 git.sr.ht/~rjarry/aerc/lib/ui.(*Grid).Draw(0xc00038c240, 0xc0003f0ff0)
         git.sr.ht/~rjarry/aerc/lib/ui/grid.go:126 +0x225
 git.sr.ht/~rjarry/aerc/widgets.(*Aerc).Draw(0xc0003f4000, 0xc0003f0ff0)
         git.sr.ht/~rjarry/aerc/widgets/aerc.go:176 +0x1d2
 git.sr.ht/~rjarry/aerc/lib/ui.(*UI).Render(0xc0003a0000)
         git.sr.ht/~rjarry/aerc/lib/ui/ui.go:110 +0x63
 main.main()
         git.sr.ht/~rjarry/aerc/aerc.go:255 +0x9c5

There are actually two distinct issues here:

1) The scroll offset used for drawing must be the current one, not the
   one from the previous ensureScoll() call.

2) The scroll offset must be reset when changing the text with
   TextInput.Set(). Other methods that change the text actually call
   ensureScroll but they make incremental changes to the text, since Set
   completely overwrites everything, it makes more sense to set the
   scroll offset to 0.

Reported-by: Adam Cooper <adam@theadamcooper.com>
Signed-off-by: Robin Jarry <robin@jarry.cc>
Acked-by: Tim Culverhouse <tim@timculverhouse.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/lib/ui/textinput.go b/lib/ui/textinput.go
index bcfe4a83..2b23f15d 100644
--- a/lib/ui/textinput.go
+++ b/lib/ui/textinput.go
@@ -89,6 +89,7 @@ func (ti *TextInput) StringRight() string {
 func (ti *TextInput) Set(value string) *TextInput {
 	ti.text = []rune(value)
 	ti.index = len(ti.text)
+	ti.scroll = 0
 	return ti
 }
 
@@ -97,11 +98,10 @@ func (ti *TextInput) Invalidate() {
 }
 
 func (ti *TextInput) Draw(ctx *Context) {
-	scroll := ti.scroll
-	if !ti.focus {
-		scroll = 0
-	} else {
+	scroll := 0
+	if ti.focus {
 		ti.ensureScroll()
+		scroll = ti.scroll
 	}
 	ti.ctx = ctx // gross