Bug 1794626: Create invert_colors telemetry probe and maintain its value via LookAndFeel r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D159292

toolkit/components/telemetry/Scalars.yaml

@@ -83,6 +83,24 @@ a11y:
     release_channel_collection: opt-out
     keyed: false
 
+  invert_colors:
+    bug_numbers:
+      - 1794626
+    description: >
+      Boolean tracking if the user has an invert colors OS
+      setting enabled.
+    expires: never
+    kind: boolean
+    notification_emails:
+      - accessibility@mozilla.com
+      - mreschenberg@mozilla.com
+    products:
+      - 'firefox'
+    record_in_processes:
+      - 'main'
+    release_channel_collection: opt-out
+    keyed: false
+
   theme:
     bug_numbers:
       - 1022528

widget/cocoa/nsLookAndFeel.h

@@ -24,6 +24,15 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
     return 0x2022;
   }
 
+  void RecordLookAndFeelSpecificTelemetry() override {
+    RecordAccessibilityTelemetry();
+  }
+
+  // Having a separate, static method allows us to rely on the same
+  // chunk of telemetry logging code at initialization and when we
+  // recieve an event that changes the value of our telemetry probe.
+  static void RecordAccessibilityTelemetry();
+
  protected:
   static bool SystemWantsDarkTheme();
   static bool IsSystemOrientationRTL();

widget/cocoa/nsLookAndFeel.mm

@@ -18,6 +18,7 @@
 #include "mozilla/FontPropertyTypes.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/StaticPrefs_widget.h"
+#include "mozilla/Telemetry.h"
 #include "mozilla/widget/WidgetMessageUtils.h"
 #include "SDKDeclarations.h"
 
@@ -576,6 +577,14 @@ bool nsLookAndFeel::NativeGetFont(FontID aID, nsString& aFontName, gfxFontStyle&
   NS_OBJC_END_TRY_BLOCK_RETURN(false);
 }
 
+void nsLookAndFeel::RecordAccessibilityTelemetry() {
+  if ([[NSWorkspace sharedWorkspace]
+          respondsToSelector:@selector(accessibilityDisplayShouldInvertColors)]) {
+    bool val = [[NSWorkspace sharedWorkspace] accessibilityDisplayShouldInvertColors];
+    Telemetry::ScalarSet(Telemetry::ScalarID::A11Y_INVERT_COLORS, val);
+  }
+}
+
 @implementation MOZLookAndFeelDynamicChangeObserver
 
 + (void)startObserving {
@@ -663,6 +672,10 @@ bool nsLookAndFeel::NativeGetFont(FontID aID, nsString& aFontName, gfxFontStyle&
 }
 
 - (void)mediaQueriesChanged {
+  // Changing`Invert Colors` sends AccessibilityDisplayOptionsDidChangeNotifications.
+  // We monitor that setting via telemetry, so call into that
+  // recording method here.
+  nsLookAndFeel::RecordAccessibilityTelemetry();
   LookAndFeel::NotifyChangedAllWindows(widget::ThemeChangeKind::MediaQueriesOnly);
 }