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ReC98/platform/x86real/pc98/grcg.cpp

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[Platform] [PC-98] GRCG tile and color wrappers Choosing C++ RAII wrappers because there's at least one case where ZUN misplaced a manual grcg_off(). This implementation combines safety with the optimal instructions for both dynamic and static use cases. Part of P0232, funded by [Anonymous].
2023-02-23 22:48:19 +00:00
#include "platform.h"
#include "x86real.h"
#include "pc98.h"
#include "planar.h"
#include "platform/x86real/pc98/grcg.hpp"
[Maintenance] Introduce types for VRAM colors and their components Finally differentiating between colors and columns at least at the type level. Part of P0245, funded by [Anonymous], Blue Bolt, Ember2528, and Yanga.
2023-06-25 18:41:05 +00:00
void GRCG::setcolor(vc_t col)
[Platform] [PC-98] GRCG tile and color wrappers Choosing C++ RAII wrappers because there's at least one case where ZUN misplaced a manual grcg_off(). This implementation combines safety with the optimal instructions for both dynamic and static use cases. Part of P0232, funded by [Anonymous].
2023-02-23 22:48:19 +00:00
{
// By shifting each successive bit of [col] into the carry flag and using
// tile_register_from_carry(), we get the minimum of three instructions
// (SHR, SBB, OUT) per bitplane, with no register spills. Quite a beautiful
// optimization!
_AH = col;
outportb(0x7E, tile_register_from_carry(_AH >>= 1));
outportb(0x7E, tile_register_from_carry(_AH >>= 1));
outportb(0x7E, tile_register_from_carry(_AH >>= 1));
outportb(0x7E, tile_register_from_carry(_AH >>= 1));
}