Once again permit TAB navigation to pinned head button on Mac...

... But still don't let the ruler accept focus from a click on any platform

src/widgets/Ruler.cpp

@@ -3284,3 +3284,16 @@ void AdornedRulerPanel::GetMaxSize(wxCoord *width, wxCoord *height)
 {
    mRuler.GetMaxSize(width, height);
 }
+
+bool AdornedRulerPanel::s_AcceptsFocus{ false };
+
+auto AdornedRulerPanel::TemporarilyAllowFocus() -> TempAllowFocus {
+   s_AcceptsFocus = true;
+   return std::move(TempAllowFocus{ &s_AcceptsFocus });
+}
+
+void AdornedRulerPanel::SetFocusFromKbd()
+{
+   auto temp = TemporarilyAllowFocus();
+   SetFocus();
+}

src/widgets/Ruler.h

@@ -294,8 +294,9 @@ public:
 
    ~AdornedRulerPanel();
 
-   bool AcceptsFocus() const override { return false; }
+   bool AcceptsFocus() const override { return s_AcceptsFocus; }
-   bool AcceptsFocusFromKeyboard() const override { return false; }
+   bool AcceptsFocusFromKeyboard() const override { return true; }
+   void SetFocusFromKbd() override;
 
 public:
    int GetRulerHeight() { return GetRulerHeight(mShowScrubbing); }
@@ -357,6 +358,14 @@ public:
    void DoDrawIndicator(wxDC * dc, wxCoord xx, bool playing, int width, bool scrub, bool seek);
    void UpdateButtonStates();
 
+private:
+   static bool s_AcceptsFocus;
+   struct Resetter { void operator () (bool *p) const { if(p) *p = false; } };
+   using TempAllowFocus = std::unique_ptr<bool, Resetter>;
+
+public:
+   static TempAllowFocus TemporarilyAllowFocus();
+
 private:
    QuickPlayIndicatorOverlay *GetOverlay();
    void ShowOrHideQuickPlayIndicator(bool show);