From 6993c34d5d2cb82e2c6384e0c0a999d632ce5068 Mon Sep 17 00:00:00 2001
From: Florian Rivoal <git@florian.rivoal.net>
Date: Mon, 17 Jun 2024 14:55:39 +0900
Subject: [PATCH] [css-ui-4] Define behavior for (semi) transparent accent
 colors

See #9852
---
 css-ui-4/Overview.bs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/css-ui-4/Overview.bs b/css-ui-4/Overview.bs
index 0276ca90250..a93187d6e04 100644
--- a/css-ui-4/Overview.bs
+++ b/css-ui-4/Overview.bs
@@ -2098,6 +2098,13 @@ Widget Accent Colors: the 'accent-color' property</h3>
 		</table>
 	</div>
 
+	If the color supplied is partially or fully transparent,
+	the user agent must first pre-compose it over the ''<system-color>/Canvas'' system color
+	and use the resulting (now opaque) color as the accent color.
+
+	Note: Although it may vary based on user settings,
+	''<system-color>/Canvas'' is typically white when in a [=light color scheme =]
+	and black when in a [=dark color scheme=].
 
 <h3 id="appearance-switching" caniuse="css-appearance">
 Switching appearance: the 'appearance' property</h3>