Customize GenericBase

This guide builds on the whole series: you have a fully working Mystery Gift scene. Back in the scene guide we wrote a minimal MysteryGiftBase that only changed the background. Here we finish it -- a themed button bar and ctrl buttons -- which is the last change to the scene.

Principle

GenericBase is the foundation of every UI scene: background, button bar, ctrl buttons and win_text. Never rebuild these from scratch -- subclass GenericBase and override its private methods. It uses the Template Method pattern: hardcoded values are extracted into private methods you can override.

For the ctrl buttons, use inheritance (a nested subclass), never prepend: prepend is global and would change the buttons of every scene in the game.

Overridable methods

Need	Class	Method to override	Default value
Different background	GenericBase subclass	background_filename	'team/Fond'
Different button bar	GenericBase subclass	button_background_filename	'tcard/button_background'
No background animation	GenericBase subclass	create_background_animation	Scrolling animation
Custom ctrl button class	GenericBase subclass	control_button_class	ControlButton
Different button texture	ControlButton subclass	button_texture	'buttons'

Finishing MysteryGiftBase

Update scripts/20 MysteryGift/003 GamePlay/000 Base.rb to its full version:

module UI
  # Custom base UI for the Mystery Gift scene
  class MysteryGiftBase < GenericBase
    private

    # Return the background filename
    # @return [String]
    def background_filename
      return 'mystery_gift/background'
    end

    # Return the button background filename
    # @return [String]
    def button_background_filename
      return 'mystery_gift/button_background'
    end

    # Return the class used to create control buttons
    # @return [Class]
    def control_button_class
      return ControlButton
    end

    # Disable the background scroll animation
    def create_background_animation; end

    # Return the default cache used by control buttons
    # @return [Symbol]
    def control_button_default_cache
      return :interface
    end

    # Custom control button with mystery gift theme
    class ControlButton < GenericBase::ControlButton
      private

      # Use the mystery gift button texture
      # @return [String]
      def button_texture
        return 'mystery_gift/buttons'
      end
    end
  end
end

• background_filename and create_background_animation were there from the scene guide; we add the rest now.
• button_background_filename returns the themed bottom bar (graphics/interface/mystery_gift/button_background.png).
• control_button_class returns the nested ControlButton subclass; the inherited create_control_button uses it automatically -- no need to rewrite button creation.
• The nested ControlButton subclasses GenericBase::ControlButton and only overrides button_texture to use mystery_gift/buttons. It inherits everything else (pressed state, key icon, label).
• control_button_default_cache returns :interface so the button texture loads from graphics/interface/ like the rest of our assets, instead of the default pokedex cache. No need to override initialize.
• The buttons texture follows the 2×2 spritesheet format described in the setup guide (A/X/Y column, B column; normal row, pressed row; 1px transparent separators).

Why inheritance, not prepend

prepend inserts a module into the lookup chain of the original class -- it affects all ControlButtons in the game, in every scene. A nested subclass only affects the scene that instantiates it: Mystery Gift creates its local ControlButton, while the team, the PC and every other scene keep GenericBase::ControlButton untouched.

GenericBaseMultiMode

When different scene states need different button labels, use GenericBaseMultiMode instead of GenericBase:

texts = [
  [scene_text(0), nil, nil, scene_text(1)],          # mode 0: Confirm + Back
  [scene_text(2), scene_text(3), nil, scene_text(1)] # mode 1: Edit + Delete + Back
]
keys = [%i[A X Y B], %i[A X Y B]]
@base_ui = UI::GenericBaseMultiMode.new(@viewport, texts, keys)

@base_ui.mode = 1  # switch to Edit + Delete + Back

• All button configurations are passed at construction; switch with mode= and the labels update. Mystery Gift does not need it (its buttons never change), but it is the tool to reach for when they do.

Try it

Open the scene one last time:

GamePlay.open_mystery_gift

The bottom bar and the A/B buttons now use the Mystery Gift theme. The scene is complete: browse claimed gifts with the keyboard or mouse, enter a code with A, and watch the banner on a successful claim.

Conclusion

• Always subclass GenericBase for a custom background and button bar -- override background_filename, button_background_filename, create_background_animation.
• Customize button textures with a nested subclass of GenericBase::ControlButton -- never prepend, which is global.
• Override control_button_class to return your subclass; no need to rewrite create_control_button.
• Custom button textures follow the 2×2 spritesheet format.
• Use GenericBaseMultiMode when a scene needs different button labels per state.