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Implement Green Swap mode #260

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Implement Green Swap mode #260

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75dcf71
Implement Green Swap mode
andymcca Aug 25, 2024
a399366
Update video.cc
andymcca Aug 25, 2024
c01a75e
Change GRNSWP colors to RGB565
andymcca Aug 26, 2024
0f62c82
Correct GRNSWP color values and fix routine with swap buffer
andymcca Aug 26, 2024
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24 changes: 24 additions & 0 deletions video.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,11 @@ typedef struct
#define RENDER_COL32 2
#define RENDER_ALPHA 3

// GRNSWP colors
#define M_COLOR_RED 0xF800
#define M_COLOR_GREEN 0x07E0
#define M_COLOR_BLUE 0x001F
#define M_COLOR_ALPHA 0x0000

// Byte lengths of complete tiles and tile rows in 4bpp and 8bpp.

Expand Down Expand Up @@ -2286,6 +2291,7 @@ void update_scanline(void)
{
u32 pitch = get_screen_pitch();
u16 dispcnt = read_ioreg(REG_DISPCNT);
u16 grnswp = read_ioreg(REG_GRNSWP);
u32 vcount = read_ioreg(REG_VCOUNT);
u16 *screen_offset = get_screen_pixels() + (vcount * pitch);
u32 video_mode = dispcnt & 0x07;
Expand All @@ -2309,6 +2315,24 @@ void update_scanline(void)
else
render_scanline_window(screen_offset);

// Check for Undocumented Green Swap screen mode
if (grnswp) {
u16 swapbuffer = 0;
// Apply Green Swap to scanline in place for speed
for (u8 x = 0; x < pitch; x += 4) {
swapbuffer = screen_offset[x];
screen_offset[x] = screen_offset[x] & (M_COLOR_RED | M_COLOR_BLUE);
screen_offset[x] |= screen_offset[x + 1] & M_COLOR_GREEN;
screen_offset[x + 1] = screen_offset[x + 1] & (M_COLOR_RED | M_COLOR_BLUE);
screen_offset[x + 1] |= swapbuffer & M_COLOR_GREEN;
swapbuffer = screen_offset[x + 2];
screen_offset[x + 2] = screen_offset[x + 2] & (M_COLOR_RED | M_COLOR_BLUE);
screen_offset[x + 2] |= screen_offset[x + 3] & M_COLOR_GREEN;
screen_offset[x + 3] = screen_offset[x + 3] & (M_COLOR_RED | M_COLOR_BLUE);
screen_offset[x + 3] |= swapbuffer & M_COLOR_GREEN;
}
}

// Mode 0 does not use any affine params at all.
if (video_mode) {
// Account for vertical mosaic effect, by correcting affine references.
Expand Down