From 90781493fcd035df2a3a25617fe31d7a0fa8218b Mon Sep 17 00:00:00 2001
From: Oriol Brufau <obrufau@igalia.com>
Date: Wed, 17 May 2023 00:35:27 +0200
Subject: [PATCH] style: Make the -moz-toolbar-prefers-color-scheme a tri-state

This will allow detecting the system theme, which allows fixing some of
the blocked bugs.

Note that when using the system theme we will still match light or dark
appropriately, so this shouldn't change behavior just yet.

Differential Revision: https://phabricator.services.mozilla.com/D113516
---
 components/style/gecko/media_features.rs | 42 +++++++++++++++++++-----
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/components/style/gecko/media_features.rs b/components/style/gecko/media_features.rs
index f6703bc9b3f..4c23620dd15 100644
--- a/components/style/gecko/media_features.rs
+++ b/components/style/gecko/media_features.rs
@@ -406,18 +406,42 @@ fn eval_prefers_color_scheme(device: &Device, query_value: Option<PrefersColorSc
     }
 }
 
+/// Values for the -moz-toolbar-prefers-color-scheme media feature.
+#[derive(Clone, Copy, Debug, FromPrimitive, Parse, PartialEq, ToCss)]
+#[repr(u8)]
+enum ToolbarPrefersColorScheme {
+    Dark,
+    Light,
+    System,
+}
+
 /// The color-scheme of the toolbar in the current Firefox theme. This is based
 /// on a pref managed by the front-end.
-fn eval_toolbar_prefers_color_scheme(_: &Device, query_value: Option<PrefersColorScheme>) -> bool {
-    let prefers_color_scheme = if static_prefs::pref!("browser.theme.dark-toolbar-theme") {
-        PrefersColorScheme::Dark
-    } else {
-        PrefersColorScheme::Light
+fn eval_toolbar_prefers_color_scheme(d: &Device, query_value: Option<ToolbarPrefersColorScheme>) -> bool {
+    let toolbar_value = match static_prefs::pref!("browser.theme.toolbar-theme") {
+        0 => ToolbarPrefersColorScheme::Dark,
+        1 => ToolbarPrefersColorScheme::Light,
+        _ => ToolbarPrefersColorScheme::System,
     };
 
+    let query_value = match query_value {
+        Some(v) => v,
+        None => return true,
+    };
+
+    if query_value == toolbar_value {
+        return true;
+    }
+
+    if toolbar_value != ToolbarPrefersColorScheme::System {
+        return false;
+    }
+
+    // System might match light and dark as well.
     match query_value {
-        Some(v) => prefers_color_scheme == v,
-        None => true,
+        ToolbarPrefersColorScheme::Dark => eval_prefers_color_scheme(d, Some(PrefersColorScheme::Dark)),
+        ToolbarPrefersColorScheme::Light => eval_prefers_color_scheme(d, Some(PrefersColorScheme::Light)),
+        ToolbarPrefersColorScheme::System => true,
     }
 }
 
@@ -617,7 +641,7 @@ macro_rules! lnf_int_feature {
 /// In order to use them you need to make sure that the pref defined as a static
 /// pref, with `rust: true`. The feature name needs to be defined in
 /// `StaticAtoms.py` just like the others. In order to support dynamic changes,
-/// you also need to add them to kBoolMediaQueryPrefs in nsXPLookAndFeel.cpp
+/// you also need to add them to kMediaQueryPrefs in nsXPLookAndFeel.cpp
 macro_rules! bool_pref_feature {
     ($feature_name:expr, $pref:tt) => {{
         fn __eval(_: &Device, query_value: Option<bool>, _: Option<RangeOrOperator>) -> bool {
@@ -852,7 +876,7 @@ pub static MEDIA_FEATURES: [MediaFeatureDescription; 62] = [
     feature!(
         atom!("-moz-toolbar-prefers-color-scheme"),
         AllowsRanges::No,
-        keyword_evaluator!(eval_toolbar_prefers_color_scheme, PrefersColorScheme),
+        keyword_evaluator!(eval_toolbar_prefers_color_scheme, ToolbarPrefersColorScheme),
         ParsingRequirements::CHROME_AND_UA_ONLY,
     ),