Class: Amaterasu::GameBoy::Ppu::Modes::Rendering::BgWinFetcher

Inherits:
Object
  • Object
show all
Defined in:
lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb

Overview

Responsible for fetching Background and Window tiles, decoding the pixels and outputting them into the BG/WIN FIFO.

Despite the similarity it behaves differently than the SpriteFetcher.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(ppu, bg_win_fifo) ⇒ BgWinFetcher

Returns a new instance of BgWinFetcher.



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb', line 15

def initialize(ppu, bg_win_fifo)
  @ppu = ppu
  @bg_win_fifo = bg_win_fifo

  @step = :fetch_tile_index
  @bg_fetcher_x = 0
  @window_fetcher_x = 0
  @fetch_mode = :bg

  @fetch_duration = 6
  @sleep_duration = 2
  @warming_up     = true

  @tile_index     = nil
  @tile_data_low  = nil
  @tile_data_high = nil
  @tile_pixels    = nil
end

Instance Attribute Details

#fetch_mode ⇒ Object (readonly)

Returns the value of attribute fetch_mode.



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb', line 13

def fetch_mode
  @fetch_mode
end

#step ⇒ Object (readonly)

Returns the value of attribute step.



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb', line 13

def step
  @step
end

Instance Method Details

#activate_window! ⇒ Object 



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb', line 46

def activate_window!
  @bg_win_fifo.clear
  @fetch_mode = :window
  reset_cycle
end

#increment_window_y ⇒ Object 



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb', line 52

def increment_window_y
  return unless @window_drawed

  @ppu.window_y_count += 1
  @window_drawed = false
end

#reset_for_scanline ⇒ Object 



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb', line 59

def reset_for_scanline
  reset_cycle
  @fetch_mode = :bg
  @warming_up = true
  @bg_fetcher_x = 0
  @window_fetcher_x = 0
  increment_window_y
end

#tick ⇒ Object

Core fetch state machine.



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/bg_win_fetcher.rb', line 36

def tick
  case @step
  when :fetch_tile_index     then fetch_tile_index
  when :fetch_tile_data_low  then fetch_tile_data_low
  when :fetch_tile_data_high then fetch_tile_data_high
  when :push  then push
  when :sleep then sleep
  end
end