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remove use of mod operator in render_reg_bg

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Matthew Berry 2021-01-29 00:02:13 -08:00
parent 512e81289e
commit f21091d375
1 changed files with 6 additions and 6 deletions
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12
src/crab/ppu.cr
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@ -129,19 +129,19 @@ class PPU
pal_buf = @layer_palettes[bg]
tw, th = case @bgcnt[bg].screen_size
when 0b00 then {32, 32} # 32x32
when 0b01 then {64, 32} # 64x32
when 0b10 then {32, 64} # 32x64
when 0b11 then {64, 64} # 64x64
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[bg].screen_size}"
end
screen_base = 0x800_u32 * @bgcnt[bg].screen_base_block
character_base = @bgcnt[bg].character_base_block.to_u32 * 0x4000
effective_row = (@vcount.to_u32 + @bgvofs[bg].value) % (th << 3)
effective_row = (@vcount.to_u32 + @bgvofs[bg].value) & th
ty = effective_row >> 3
240.times do |col|
effective_col = (col + @bghofs[bg].value) % (tw << 3)
effective_col = (col + @bghofs[bg].value) & tw
tx = effective_col >> 3
se_idx = se_index(tx, ty, @bgcnt[bg].screen_size)