refactor lib/ui/tab to ensure staying in bounds

Fix a few potential out of bounds by placing proper checks, which should
be relevant if all tabs are removed for some reason.

Also avoid iterating all tabs in the invalidate handler, since we are
only interested in whether it's the selected tab either way

1 files changed, 21 insertions, 8 deletions

diff --git a/lib/ui/tab.go b/lib/ui/tab.go
index f18b0ac..8f08978 100644
--- a/lib/ui/tab.go
+++ b/lib/ui/tab.go
@@ -40,14 +40,13 @@ func (tabs *Tabs) Add(content Drawable, name string) {
 }
 
 func (tabs *Tabs) invalidateChild(d Drawable) {
-	for i, tab := range tabs.Tabs {
-		if tab.Content == d {
-			if i == tabs.Selected {
-				if tabs.onInvalidateContent != nil {
-					tabs.onInvalidateContent(tabs.TabContent)
-				}
-			}
-			return
+	if tabs.Selected >= len(tabs.Tabs) {
+		return
+	}
+
+	if tabs.Tabs[tabs.Selected].Content == d {
+		if tabs.onInvalidateContent != nil {
+			tabs.onInvalidateContent(tabs.TabContent)
 		}
 	}
 }
@@ -59,10 +58,18 @@ func (tabs *Tabs) Remove(content Drawable) {
 			break
 		}
 	}
+	/* Force the selected index into the existing range */
+	if tabs.Selected >= len(tabs.Tabs) {
+		tabs.Select(len(tabs.Tabs) - 1)
+	}
 	tabs.TabStrip.Invalidate()
 }
 
 func (tabs *Tabs) Select(index int) {
+	if tabs.Selected >= len(tabs.Tabs) {
+		panic("Tried to set tab index to a non-existing element")
+	}
+
 	if tabs.Selected != index {
 		tabs.Selected = index
 		tabs.TabStrip.Invalidate()
@@ -101,6 +108,12 @@ func (strip *TabStrip) OnInvalidate(onInvalidate func(d Drawable)) {
 }
 
 func (content *TabContent) Draw(ctx *Context) {
+	if content.Selected >= len(content.Tabs) {
+		width := ctx.Width()
+		height := ctx.Height()
+		ctx.Fill(0, 0, width, height, ' ', tcell.StyleDefault)
+	}
+
 	tab := content.Tabs[content.Selected]
 	tab.Content.Draw(ctx)
 }