Fix alpha when using `colors.transparent_background_colors`

The alpha is expected to be premultiplied from the text shader, so
we should apply it to the background color.

1 files changed, 3 insertions, 1 deletions

diff --git a/alacritty/res/text.f.glsl b/alacritty/res/text.f.glsl
index 5b4e3da6..3b8cd67c 100644
--- a/alacritty/res/text.f.glsl
+++ b/alacritty/res/text.f.glsl
@@ -18,7 +18,9 @@ void main() {
         }
 
         alphaMask = vec4(1.0);
-        color = vec4(bg.rgb, bg.a);
+
+        // Premultiply background color by alpha.
+        color = vec4(bg.rgb * bg.a, bg.a);
     } else if ((int(fg.a) & COLORED) != 0) {
         // Color glyphs, like emojis.
         vec4 glyphColor = texture(mask, TexCoords);