Redraw when change-footer changes line count

Mirror of the earlier change-header fix. The inline footer slot's row
budget depends on footer content length, but resizeIfNeeded() tolerates
a shorter-than-wanted inline window, so extra lines get clipped. Drive
a redraw on length change to re-run the layout.

src/terminal.go

@@ -1816,14 +1816,16 @@ func (t *Terminal) changeHeader(header string) bool {
 	return needFullRedraw
 }
 
-func (t *Terminal) changeFooter(footer string) {
+func (t *Terminal) changeFooter(footer string) bool {
 	var lines []string
 	if len(footer) > 0 {
 		lines = strings.Split(strings.TrimSuffix(footer, "\n"), "\n")
 	}
+	needFullRedraw := len(t.footer) != len(lines)
 	t.footer = lines
 	t.clickFooterLine = 0
 	t.clickFooterColumn = 0
+	return needFullRedraw
 }
 
 // UpdateHeader updates the header
@@ -6796,7 +6798,12 @@ func (t *Terminal) Loop() error {
 				})
 			case actChangeFooter, actTransformFooter, actBgTransformFooter:
 				capture(false, func(footer string) {
-					t.changeFooter(footer)
+					if t.changeFooter(footer) && t.footerBorderShape == tui.BorderInline {
+						// resizeIfNeeded() tolerates a shorter-than-wanted inline
+						// window, so a length change can leave the inline slot
+						// stale. Force a redraw to re-run the layout.
+						req(reqRedraw)
+					}
 					req(reqFooter)
 				})
 			case actChangeHeaderLabel, actTransformHeaderLabel, actBgTransformHeaderLabel: