dialog: avoid panic when window is too small

Avoid negative offsets and limit height to the parent context height.

Fixes: https://todo.sr.ht/~rjarry/aerc/142
Reported-by: Akspecs <akspecs@gmail.com>
Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Koni Marti <koni.marti@gmail.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/widgets/selector.go b/widgets/selector.go
index deefdfbf..fb8c8094 100644
--- a/widgets/selector.go
+++ b/widgets/selector.go
@@ -206,8 +206,20 @@ func (gp *SelectorDialog) ContextHeight() (func(int) int, func(int) int) {
 	totalHeight := 2 // title + empty line
 	totalHeight += strings.Count(gp.prompt, "\n") + 1
 	totalHeight += 2 // empty line + selector
-	start := func(h int) int { return h/2 - totalHeight/2 }
-	height := func(h int) int { return totalHeight }
+	start := func(h int) int {
+		s := h/2 - totalHeight/2
+		if s < 0 {
+			s = 0
+		}
+		return s
+	}
+	height := func(h int) int {
+		if totalHeight > h {
+			return h
+		} else {
+			return totalHeight
+		}
+	}
 	return start, height
 }