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GPU: Compute VRAM display width from GP1(06h) values

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Fixes overpadding in some specific cases, e.g. when cropping overscan in
Captain Commando.
This commit is contained in:
Albert Liu 2020-07-10 23:58:56 -07:00
parent 554237a6d1
commit c44e74db80
1 changed files with 9 additions and 18 deletions
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27
src/core/gpu.cpp
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@ -581,6 +581,12 @@ void GPU::UpdateCRTCDisplayParameters()
cs.display_width = (cs.horizontal_active_end - cs.horizontal_active_start) / cs.dot_clock_divider;
cs.display_height = (cs.vertical_active_end - cs.vertical_active_start) << height_shift;
// Determine number of pixels outputted from VRAM (align to 4-pixel boundary).
// TODO: Verify behavior if start > end and also if values are outside of the active video portion of scanline.
const u16 horizontal_display_ticks = horizontal_display_end - horizontal_display_start;
cs.display_vram_width =
(static_cast<u16>(std::round(horizontal_display_ticks / static_cast<float>(cs.dot_clock_divider))) + 2u) & ~3u;
// Determine if we need to adjust the VRAM rectangle (because the display is starting outside the visible area) or add
// padding.
u16 horizontal_skip_pixels;
@ -597,27 +603,12 @@ void GPU::UpdateCRTCDisplayParameters()
cs.display_vram_left = std::min<u16>(m_crtc_state.regs.X + horizontal_skip_pixels, VRAM_WIDTH - 1);
}
u16 horizontal_active_ticks;
if (horizontal_display_end <= cs.horizontal_active_end)
{
horizontal_active_ticks =
horizontal_display_end -
std::min(horizontal_display_end, std::max(horizontal_display_start, cs.horizontal_active_start));
}
else
{
horizontal_active_ticks =
cs.horizontal_active_end -
std::min(cs.horizontal_active_end, std::max(horizontal_display_start, cs.horizontal_active_start));
}
// align to 4-pixel boundary
cs.display_vram_width =
(static_cast<u16>(std::round(horizontal_active_ticks / static_cast<float>(cs.dot_clock_divider))) + 2u) & ~3u;
// apply the crop from the start (usually overscan)
cs.display_vram_width -= std::min(cs.display_vram_width, horizontal_skip_pixels);
// Apply crop from the end by shrinking VRAM rectangle width if display would end outside the visible area.
cs.display_vram_width = std::min<u16>(cs.display_vram_width, cs.display_width - cs.display_origin_left);
if (vertical_display_start >= cs.vertical_active_start)
{
cs.display_origin_top = (vertical_display_start - cs.vertical_active_start) << y_shift;