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Scale down new-mode coordinates; add note to self.

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This commit is contained in:
Thomas Harte 2023-02-21 22:28:39 -05:00
parent 6a2cda7074
commit ef5d05db53
1 changed files with 14 additions and 1 deletions
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15
Components/9918/Implementation/Draw.hpp
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@ -109,6 +109,19 @@ void Base<personality>::draw_sprites(LineBuffer &buffer, int start, int end, int
}
}
// Mode 2 logic, as I currently understand it, as a note for my future self:
//
// If a sprite is marked as 'CC' then it doesn't collide, but its colour value is
// ORd with those of all lower-numbered sprites down to the next one that is visible on
// that line and not marked CC.
//
// If no previous sprite meets that criteria, no pixels are displayed. But if one does
// then pixels are displayed even where they don't overlap with the earlier sprites.
//
// ... so in terms of my loop above, I guess I need temporary storage to accumulate
// an OR mask up until I hit a non-CC sprite, at which point I composite everything out?
// I'm not immediately sure whether I can appropriately reuse sprite_buffer, but possibly?
// MARK: - TMS9918
template <Personality personality>
@ -331,7 +344,7 @@ void Base<personality>::draw_yamaha(LineBuffer &buffer, int start, int end) {
draw_sprites<
SpriteMode::Mode2,
mode == ScreenMode::YamahaGraphics5 || mode == ScreenMode::YamahaGraphics6
>(buffer, start, end);
>(buffer, start >> 2, end >> 2);
}
template <Personality personality>