MenuButton: support Mac look & feel

ui/views/controls/button/menu_button.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_CONTROLS_BUTTON_MENU_BUTTON_H_
 #define UI_VIEWS_CONTROLS_BUTTON_MENU_BUTTON_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 25 matching lines @@
     ~PressedLock();
 
    private:
     base::WeakPtr<MenuButton> menu_button_;
 
     DISALLOW_COPY_AND_ASSIGN(PressedLock);
   };
 
   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); }
 
   // Activate the button (called when the button is pressed). |event| is the
   // event triggering the activation, if any.
   bool Activate(const ui::Event* event);
 
   // Returns true if the event is of the proper type to potentially trigger an
   // action. Since MenuButtons have properties other than event type (like
   // last menu open time) to determine if an event is valid to activate the
   // menu, this is distinct from IsTriggerableEvent().
   virtual bool IsTriggerableEventType(const ui::Event& event);
 
   // Overridden from View:
   gfx::Size GetPreferredSize() const override;
   const char* GetClassName() const override;
   void OnPaint(gfx::Canvas* canvas) override;
   bool OnMousePressed(const ui::MouseEvent& event) override;
   void OnMouseReleased(const ui::MouseEvent& event) override;
   void OnMouseEntered(const ui::MouseEvent& event) override;
   void OnMouseExited(const ui::MouseEvent& event) override;
   void OnMouseMoved(const ui::MouseEvent& event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;
   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;
 
   // Overridden from CustomButton:
   bool IsTriggerableEvent(const ui::Event& event) override;
   bool ShouldEnterPushedState(const ui::Event& event) override;
   void StateChanged() override;
   void NotifyClick(const ui::Event& event) override;
 
   // Offset of the associated menu position.
   gfx::Point menu_offset_;
 
  private:
   friend class PressedLock;
 
   // Increment/decrement the number of "pressed" locks this button has, and
   // set the state accordingly. The ink drop is snapped to the final ACTIVATED
   // state if |snap_ink_drop_to_activated| is true, otherwise the ink drop will
   // be animated to the ACTIVATED state.
   void IncrementPressedLocked(bool snap_ink_drop_to_activated);
   void DecrementPressedLocked();
 
   // Compute the maximum X coordinate for the current screen. MenuButtons
   // 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
   // menu. There is no clean way to get the second click event because the
   // menu is displayed using a modal loop and, unlike regular menus in Windows,
   // the button is not part of the displayed menu.
   base::TimeTicks menu_closed_time_;
 
   // Our listener. Not owned.
   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.
   bool* destroyed_flag_;
 
   // The current number of "pressed" locks this button has.
   int pressed_lock_count_;
 
   // Used to let Activate() know if IncrementPressedLocked() was called.
   bool* increment_pressed_lock_called_;
 
   // True if the button was in a disabled state when a menu was run, and should
   // return to it once the press is complete. This can happen if, e.g., we
   // programmatically show a menu on a disabled button.
   bool should_disable_after_press_;
 
   base::WeakPtrFactory<MenuButton> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MenuButton);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_BUTTON_MENU_BUTTON_H_