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vid_ega: Fix CCLK/2 rendering in 4bpp graphics modes

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Required for 64KB-variant 640x350 2bpp modes (BIOS modes 0x0F, 0x10).
This does need some address decoding fixes to break the 16K-word barrier, though - those are coming.
This commit is contained in:
Ben Russell 2023-03-20 19:32:10 +00:00
parent b5f0692483
commit 77ba033fd9
1 changed files with 20 additions and 15 deletions
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35
src/video/vid_ega_render.c
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@ -336,7 +336,7 @@ ega_render_2bpp_highres(ega_t *ega)
void
ega_render_4bpp_lowres(ega_t *ega)
{
int x, oddeven;
int x, secondcclk;
uint8_t dat, edat[4];
uint32_t addr, *p;
@ -349,16 +349,19 @@ ega_render_4bpp_lowres(ega_t *ega)
ega->firstline_draw = ega->displine;
ega->lastline_draw = ega->displine;
secondcclk = 0;
for (x = 0; x <= (ega->hdisp + ega->scrollcache); x += 16) {
addr = ega->remap_func(ega, ega->ma);
oddeven = 0;
if (ega->seqregs[1] & 4) {
oddeven = (addr & 4) ? 1 : 0;
edat[0] = ega->vram[addr | oddeven];
edat[2] = ega->vram[addr | oddeven | 0x2];
edat[1] = edat[3] = 0;
ega->ma += 2;
// FIXME: Verify the behaviour of planes 1,3 on actual hardware
edat[0] = ega->vram[(addr | 0) ^ secondcclk];
edat[1] = ega->vram[(addr | 1) ^ secondcclk];
edat[2] = ega->vram[(addr | 2) ^ secondcclk];
edat[3] = ega->vram[(addr | 3) ^ secondcclk];
secondcclk = (secondcclk + 1) & 1;
if (secondcclk == 0)
ega->ma += 4;
} else {
*(uint32_t *) (&edat[0]) = *(uint32_t *) (&ega->vram[addr]);
ega->ma += 4;
@ -388,7 +391,7 @@ ega_render_4bpp_lowres(ega_t *ega)
void
ega_render_4bpp_highres(ega_t *ega)
{
int x, oddeven;
int x, secondcclk;
uint8_t dat, edat[4];
uint32_t addr, *p;
@ -401,16 +404,18 @@ ega_render_4bpp_highres(ega_t *ega)
ega->firstline_draw = ega->displine;
ega->lastline_draw = ega->displine;
secondcclk = 0;
for (x = 0; x <= (ega->hdisp + ega->scrollcache); x += 8) {
addr = ega->remap_func(ega, ega->ma);
oddeven = 0;
if (ega->seqregs[1] & 4) {
oddeven = (addr & 4) ? 1 : 0;
edat[0] = ega->vram[addr | oddeven];
edat[2] = ega->vram[addr | oddeven | 0x2];
edat[1] = edat[3] = 0;
ega->ma += 2;
// FIXME: Verify the behaviour of planes 1,3 on actual hardware
edat[0] = ega->vram[(addr | 0) ^ secondcclk];
edat[1] = ega->vram[(addr | 1) ^ secondcclk];
edat[2] = ega->vram[(addr | 2) ^ secondcclk];
edat[3] = ega->vram[(addr | 3) ^ secondcclk];
secondcclk = (secondcclk + 1) & 1;
if (secondcclk == 0)
ega->ma += 4;
} else {
*(uint32_t *) (&edat[0]) = *(uint32_t *) (&ega->vram[addr]);
ega->ma += 4;