Bug 1736218 - Expose theme-derived color-scheme to privileged code. r=Gijs

This will be needed to determine whether following the Firefox theme
would produce light or dark colors.

Differential Revision: https://phabricator.services.mozilla.com/D140221

toolkit/xre/nsAppRunner.cpp

@@ -1684,6 +1684,13 @@ nsXULAppInfo::GetChromeColorSchemeIsDark(bool* aResult) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsXULAppInfo::GetContentThemeDerivedColorSchemeIsDark(bool* aResult) {
+  *aResult =
+      LookAndFeel::ThemeDerivedColorSchemeForContent() == ColorScheme::Dark;
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsXULAppInfo::GetDrawInTitlebar(bool* aResult) {
   *aResult = LookAndFeel::DrawInTitlebar();

widget/LookAndFeel.h

@@ -390,6 +390,7 @@ class LookAndFeel {
 
   enum class ChromeColorSchemeSetting { Light, Dark, System };
   static ChromeColorSchemeSetting ColorSchemeSettingForChrome();
+  static ColorScheme ThemeDerivedColorSchemeForContent();
 
   static ColorScheme ColorSchemeForChrome() {
     MOZ_ASSERT(sColorSchemeInitialized);

widget/nsXPLookAndFeel.cpp

@@ -1159,6 +1159,17 @@ auto LookAndFeel::ColorSchemeSettingForChrome() -> ChromeColorSchemeSetting {
   }
 }
 
+ColorScheme LookAndFeel::ThemeDerivedColorSchemeForContent() {
+  switch (StaticPrefs::browser_theme_content_theme()) {
+    case 0:  // Dark
+      return ColorScheme::Dark;
+    case 1:  // Light
+      return ColorScheme::Light;
+    default:
+      return ColorSchemeForChrome();
+  }
+}
+
 void LookAndFeel::RecomputeColorSchemes() {
   sColorSchemeInitialized = true;
 
@@ -1186,14 +1197,7 @@ void LookAndFeel::RecomputeColorSchemes() {
         break;  // Use the browser theme.
     }
 
-    switch (StaticPrefs::browser_theme_content_theme()) {
-      case 0:  // Dark
-        return ColorScheme::Dark;
-      case 1:  // Light
-        return ColorScheme::Light;
-      default:
-        return ColorSchemeForChrome();
-    }
+    return ThemeDerivedColorSchemeForContent();
   }();
 }
 

xpcom/system/nsIXULRuntime.idl

@@ -348,6 +348,9 @@ interface nsIXULRuntime : nsISupports
   /** Whether the chrome color-scheme is dark */
   readonly attribute boolean chromeColorSchemeIsDark;
 
+  /** Whether the content color-scheme derived from the app theme is dark */
+  readonly attribute boolean contentThemeDerivedColorSchemeIsDark;
+
   /** Whether we should draw over the titlebar */
   readonly attribute boolean drawInTitlebar;
 
@@ -396,4 +399,4 @@ nsIXULRuntime::ContentWin32kLockdownState GetWin32kLockdownState();
 
 }
 
-%}
+%}