feat: `systemPreferences.getColor` should return RGBA instead of RGB (#38960)

* fix: return RGBA hex value from `SystemPreferences.getColor`

* docs: update docs to match changes of last commit

* fix: GetColor on windows now returns RGBA too

* fix: update tests for getColor RGBA on Windows

---------

Co-authored-by: John Kleinschmidt <[email protected]>

docs/api/system-preferences.md

@@ -306,7 +306,7 @@ This API is only available on macOS 10.14 Mojave or newer.
     * `window-background` - The background of a window.
     * `window-frame-text` - The text in the window's titlebar area.
 
-Returns `string` - The system color setting in RGB hexadecimal form (`#ABCDEF`).
+Returns `string` - The system color setting in RGBA hexadecimal form (`#RRGGBBAA`).
 See the [Windows docs][windows-colors] and the [macOS docs][macos-colors] for more details.
 
 The following colors are only available on macOS 10.14: `find-highlight`, `selected-content-background`, `separator`, `unemphasized-selected-content-background`, `unemphasized-selected-text-background`, and `unemphasized-selected-text`.

shell/browser/api/electron_api_system_preferences_mac.mm

@@ -540,7 +540,7 @@ std::string SystemPreferences::GetColor(gin_helper::ErrorThrower thrower,
   }
 
   if (sysColor)
-    return ToRGBHex(skia::NSSystemColorToSkColor(sysColor));
+    return ToRGBAHex(skia::NSSystemColorToSkColor(sysColor));
   return "";
 }
 

shell/browser/api/electron_api_system_preferences_win.cc

@@ -133,7 +133,7 @@ std::string SystemPreferences::GetColor(gin_helper::ErrorThrower thrower,
       });
 
   if (const auto* iter = Lookup.find(color); iter != Lookup.end())
-    return ToRGBHex(color_utils::GetSysSkColor(iter->second));
+    return ToRGBAHex(color_utils::GetSysSkColor(iter->second));
 
   thrower.ThrowError("Unknown color: " + color);
   return "";

spec/api-system-preferences-spec.ts

@@ -17,8 +17,8 @@ describe('systemPreferences module', () => {
       }).to.throw('Unknown color: not-a-color');
     });
 
-    it('returns a hex RGB color string', () => {
-      expect(systemPreferences.getColor('window')).to.match(/^#[0-9A-F]{6}$/i);
+    it('returns a hex RGBA color string', () => {
+      expect(systemPreferences.getColor('window')).to.match(/^#[0-9A-F]{8}$/i);
     });
   });