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Desugar loops in PPU#render_bg and extract common shift computation

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This commit is contained in:
Benoit Daloze 2017-03-05 19:48:53 +01:00
parent 7991a71cb3
commit cb70d8d451
1 changed files with 11 additions and 8 deletions
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19
lib/waterfoul/ppu.rb
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@ -281,7 +281,8 @@ module Waterfoul
# relative line number offset
tile_line_offset = tile_line * 2
palette = $mmu.read_memory_byte 0xFF47
0.upto(31) do |x|
x = 0
while x < 32
tile = 0
if tiles_select == 0x8800
tile = signed_value $mmu.read_byte(map_select + y_offset + x)
@ -297,18 +298,20 @@ module Waterfoul
byte_1 = $mmu.read_byte tile_address
byte_2 = $mmu.read_byte (tile_address + 1)
0.upto(7) do |pixelx|
buffer_addr = line_pixel_offset + pixelx - scx
next if buffer_addr >= Screen::SCREEN_WIDTH
pixel = (byte_1 & (0x1 << (7 - pixelx)) > 0) ? 1 : 0
pixel |= (byte_2 & (0x1 << (7 - pixelx)) > 0) ? 2 : 0
pixelx = 0
buffer_addr = line_pixel_offset - scx
while pixelx < 8 and buffer_addr < Screen::SCREEN_WIDTH
shift = 0x1 << (7 - pixelx)
pixel = (byte_1 & shift > 0) ? 1 : 0
pixel |= (byte_2 & shift > 0) ? 2 : 0
position = line_width + buffer_addr
color = (palette >> (pixel * 2)) & 0x3
@framebuffer[position] = rgb(color)
pixelx += 1
buffer_addr = line_pixel_offset + pixelx - scx
end
x += 1
end
else
0.upto(Screen::SCREEN_WIDTH - 1) do |i|