MenuButton: support Mac look & feel

ui/views/controls/button/menu_button.h

Index: ui/views/controls/button/menu_button.h
diff --git a/ui/views/controls/button/menu_button.h b/ui/views/controls/button/menu_button.h
index 696a94146f3f9868e01e2eca55a00dfab53f5e8e..882a3406ae42259e5acaa4ee7d581b32007faddb 100644
--- a/ui/views/controls/button/menu_button.h
+++ b/ui/views/controls/button/menu_button.h
@@ -43,22 +43,12 @@ class VIEWS_EXPORT MenuButton : public LabelButton {
 
   static const char kViewClassName[];
 
-  // How much padding to put on the left and right of the menu marker.
-  static const int kMenuMarkerPaddingLeft;
-  static const int kMenuMarkerPaddingRight;
-
   // Create a Button.
   MenuButton(const base::string16& text,
              MenuButtonListener* menu_button_listener,
              bool show_menu_marker);
   ~MenuButton() override;
 
-  bool show_menu_marker() const { return show_menu_marker_; }
-  void set_menu_marker(const gfx::ImageSkia* menu_marker) {
-    menu_marker_ = menu_marker;
-  }
-  const gfx::ImageSkia* menu_marker() const { return menu_marker_; }
-
   const gfx::Point& menu_offset() const { return menu_offset_; }
   void set_menu_offset(int x, int y) { menu_offset_.SetPoint(x, y); }
 
@@ -85,11 +75,17 @@ class VIEWS_EXPORT MenuButton : public LabelButton {
   bool OnKeyPressed(const ui::KeyEvent& event) override;
   bool OnKeyReleased(const ui::KeyEvent& event) override;
   void GetAccessibleState(ui::AXViewState* state) override;
+  void OnEnabledChanged() override;
+  void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
 
  protected:
   // Paint the menu marker image.
   void PaintMenuMarker(gfx::Canvas* canvas);
 
+  // Subclasses that want to use a border can override this method.
+  virtual bool ShouldUsePlatformStyleBackground() const;
+  virtual bool ShouldUsePlatformStyleBorder() const;

[tapted, 2016/05/09 08:01:35]

So I think there is a nicer solution that doesn't use virtual methods to achieve
this. The big problem is that we need MenuButton to fit in with the stuff that
LabelButton is already doing. Except!

LabelButton doesn't have a background -- just a border, even when themed.

So I really think we need to do the same for MenuButton -- incorporate the
shinymodern themed background in with the border. I think it's dangerous to
think we can get away with only "half" being themed -- they need to match.

Yes, drawing background stuff in with the "border" is weird, but doing this
allows the parts of the theme to stay together and preserve consistency.

This approach should let us use the existing plumbing for this, in
LabelButton::border_is_themed_border_ -- maybe we will need an accessor for that
bool (e.g. so PlatformStyle can read it), or maybe we can just do it via an
UpdateThemedBorder override. See what LabelButton does -- I think we need to
align the approaches we use for adding style to these.

+
   // Overridden from LabelButton:
   gfx::Rect GetChildAreaBounds() override;
 
@@ -116,6 +112,10 @@ class VIEWS_EXPORT MenuButton : public LabelButton {
   // use this to make sure a menu is never shown off screen.
   int GetMaximumScreenXCoordinate();
 
+  // Returns the width of the "shoulder" of the MenuButton, which is the area
+  // containing the menu marker, and any padding surrounding it.
+  int GetShoulderWidth() const;
+
   // We use a time object in order to keep track of when the menu was closed.
   // The time is used for simulating menu behavior for the menu button; that
   // is, if the menu is shown and the button is pressed, we need to close the
@@ -128,10 +128,10 @@ class VIEWS_EXPORT MenuButton : public LabelButton {
   MenuButtonListener* listener_;
 
   // Whether or not we're showing a drop marker.
-  bool show_menu_marker_;
+  const bool show_menu_marker_;
 
   // The down arrow used to differentiate the menu button from normal buttons.
-  const gfx::ImageSkia* menu_marker_;
+  gfx::ImageSkia menu_marker_;
 
   // If non-null the destructor sets this to true. This is set while the menu is
   // showing and used to detect if the menu was deleted while running.