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use better variable names in reg bg render func

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Matthew Berry 2021-05-23 14:47:44 -07:00
parent 65ea773adb
commit 2f983c5045
1 changed files with 13 additions and 13 deletions
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26
src/crab/gba/ppu.cr
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@ -146,23 +146,23 @@ module GBA
bgvofs = @bgvofs[bg]
bghofs = @bghofs[bg]
tw, th = case bgcnt.screen_size
when 0b00 then {0x0FF, 0x0FF} # 32x32
when 0b01 then {0x1FF, 0x0FF} # 64x32
when 0b10 then {0x0FF, 0x1FF} # 32x64
when 0b11 then {0x1FF, 0x1FF} # 64x64
else raise "Impossible bgcnt screen size: #{bgcnt.screen_size}"
end
bg_width, bg_height = case bgcnt.screen_size
when 0b00 then {0x0FF, 0x0FF} # 32x32
when 0b01 then {0x1FF, 0x0FF} # 64x32
when 0b10 then {0x0FF, 0x1FF} # 32x64
when 0b11 then {0x1FF, 0x1FF} # 64x64
else raise "Impossible bgcnt screen size: #{bgcnt.screen_size}"
end
screen_base = 0x800_u32 * bgcnt.screen_base_block
character_base = bgcnt.character_base_block.to_u32 * 0x4000
effective_row = (@vcount.to_u32 + bgvofs.offset) & th
ty = effective_row >> 3
character_base = 0x4000_u32 * bgcnt.character_base_block
effective_row = (@vcount.to_u32 + bgvofs.offset) & bg_height
tile_y = effective_row >> 3
240.times do |col|
effective_col = (col + bghofs.offset) & tw
tx = effective_col >> 3
effective_col = (col + bghofs.offset) & bg_width
tile_x = effective_col >> 3
se_idx = se_index(tx, ty, bgcnt.screen_size)
se_idx = se_index(tile_x, tile_y, bgcnt.screen_size)
screen_entry = @vram[screen_base + se_idx * 2 + 1].to_u16 << 8 | @vram[screen_base + se_idx * 2]
tile_id = bits(screen_entry, 0..9)