Rendering issue when overwriting characters with a multi-rune character #976
Description
I'm testing this against tcell v3, commit a5d9742.
The following simple addition to the hello demo shows a rendering problem. We first draw two 'T' characters, and then we overwrite the first of these with a multi-rune emoji. On some terminals, the second T remains visible after this.
diff --git a/demos/hello/hello.go b/demos/hello/hello.go
index 5fa9a96..538e97e 100644
--- a/demos/hello/hello.go
+++ b/demos/hello/hello.go
@@ -29,6 +29,9 @@ func displayHelloWorld(s tcell.Screen) {
x := w/2 - 7
y := h/2 - 1
style := tcell.StyleDefault.Foreground(color.CadetBlue.TrueColor()).Background(color.White)
+ x_ := x
+ y_ := y - 2
+ s.PutStrStyled(x_, y_, "TT", tcell.StyleDefault.Foreground(color.Red))
s.PutStrStyled(x, y, "Hello, World!", style)
x = w/2 - 9
y += 2
@@ -39,6 +42,9 @@ func displayHelloWorld(s tcell.Screen) {
x += len("ESC")
s.PutStr(x, y, " to exit.")
s.Show()
+
+ s.PutStr(x_, y_, "⚠️")
+ s.Show()
}
// This program just prints "Hello, World!". Press ESC to exit.Rendering is as expected in ghostty and kitty, but the second 'T' remains visible in iTerm2 and alacritty:
I'm not knowledgable enough with terminal stuff to tell whether this is a bug in these terminals, or whether it's tcell's responsibility to clear out the second 'T' somehow in the second Show call.