FrameBuffer Transition

module FrameBuffer

  def self.start(frames = 1, viewport_z = 10000)
    dispose unless disposed?
    this_frame =  Graphics.snap_to_bitmap
    @buffer = []
    @viewport = Viewport.new
    @viewport.z = viewport_z

    frames.times do
      sprite = Sprite.new(@viewport)
      sprite.bitmap = this_frame.clone
      sprite.x = Graphics.width / 2
      sprite.y = Graphics.height / 2
      sprite.ox = Graphics.width / 2
      sprite.oy = Graphics.height / 2
      @buffer.push(sprite)
    end

    this_frame.dispose
  end

  def self.dispose
    return if disposed?
    @buffer.each {|sprite| sprite.dispose}
    @viewport.dispose if @viewport
    @buffer = nil
  end

  def self.disposed?
    !@buffer
  end

  def self.cycle
    return if disposed?
    @buffer[-1].bitmap.dispose
    @buffer.each_index do |i|
      next if i == 0
      @buffer[i].bitmap = @buffer[i - 1].bitmap
    end

    @buffer[0].bitmap = Graphics.snap_to_bitmap
  end

  def self.refresh
    this_frame = Graphics.snap_to_bitmap
    @buffer.each do |sprite|
      sprite.bitmap.dispose
      sprite.bitmap = this_frame.clone
    end

    this_frame.dispose
  end

  def self.[](num)
    return nil if disposed?
    return @buffer[num]
  end
end

class Scene_Map < Scene_Base

  def pre_battle_scene
    Graphics.update
    Graphics.freeze
    FrameBuffer.start(3)
    FrameBuffer[0].z = 0
    FrameBuffer[0].zoom_x = 1
    FrameBuffer[0].zoom_y = 1
    FrameBuffer[0].opacity = 235
    FrameBuffer[0].angle = 0
    FrameBuffer[0].blend_type = 0
    FrameBuffer[1].z = 1
    FrameBuffer[1].zoom_x = 1.01
    FrameBuffer[1].zoom_y = 1.01
    FrameBuffer[1].opacity = 128
    FrameBuffer[1].angle = 359
    FrameBuffer[1].blend_type = 0
    FrameBuffer[2].z = 2
    FrameBuffer[2].zoom_x = 0.8
    FrameBuffer[2].zoom_y = 0.9
    FrameBuffer[2].opacity = 12
    FrameBuffer[2].angle = 12
    FrameBuffer[2].blend_type = 1
    @spriteset.dispose_characters
    BattleManager.save_bgm_and_bgs
    Sound.play_battle_start
  end

  def perform_battle_transition
    Graphics.transition(1)
    (0..60).each do |i|
      Graphics.brightness = 255
      FrameBuffer.refresh
      Graphics.frame_reset
      Graphics.brightness = 255 - (255 * ((i - 40) / 20.0)) if i > 40
      Graphics.update
    end

    FrameBuffer.dispose
    Graphics.freeze
    BattleManager.play_battle_bgm
  end
end