From 2896c1898127256193d49c80a56ba7188fad0e33 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Wed, 14 Aug 2024 08:50:44 +0200
Subject: [PATCH] osc: regression: fix OSC-111 handling of alpha changes

When the background alpha changes from fully opaque, to transparent,
or vice versa, we need to do more than just repaint the affected
cells.

For example, we need to create new surfaces with the correct pixel
format.

OSC-11 (set background color) already does this, but the same alpha
checking logic was missing in OSC-111 (reset background color).

Fixes #1801
---
 CHANGELOG.md |  7 +++++++
 osc.c        | 11 ++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6d7d6614..fe82d2ff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -72,6 +72,13 @@
 ### Deprecated
 ### Removed
 ### Fixed
+
+* Regression: OSC-111 not handling alpha changes correctly, causing
+  visual glitches ([#1801][1801]).
+
+[1801]: https://codeberg.org/dnkl/foot/issues/1801
+
+
 ### Security
 ### Contributors
 
diff --git a/osc.c b/osc.c
index 53597d0f..3c5f7616 100644
--- a/osc.c
+++ b/osc.c
@@ -1381,13 +1381,22 @@ osc_dispatch(struct terminal *term)
         term_damage_color(term, COLOR_DEFAULT, 0);
         break;
 
-    case 111: /* Reset default text background color */
+    case 111: { /* Reset default text background color */
         LOG_DBG("resetting background color");
+        bool alpha_changed = term->colors.alpha != term->conf->colors.alpha;
+
         term->colors.bg = term->conf->colors.bg;
         term->colors.alpha = term->conf->colors.alpha;
+
+        if (alpha_changed) {
+            wayl_win_alpha_changed(term->window);
+            term_font_subpixel_changed(term);
+        }
+
         term_damage_color(term, COLOR_DEFAULT, 0);
         term_damage_margins(term);
         break;
+    }
 
     case 112:
         LOG_DBG("resetting cursor color");