SpriteConverter.hh

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/*
TODO:
- Implement sprite pixels in Graphic 5.
*/
 
#ifndef SPRITECONVERTER_HH
#define SPRITECONVERTER_HH
 
#include "SpriteChecker.hh"
#include "DisplayMode.hh"
#include "view.hh"
#include "narrow.hh"
#include <concepts>
#include <cstdint>
#include <span>
 
namespace openmsx {
 
template<std::unsigned_integral Pixel>
class SpriteConverter
{
public:
        // TODO: Move some methods to .cc?
 
        explicit SpriteConverter(SpriteChecker& spriteChecker_,
                                 std::span<const Pixel, 16> pal)
                : spriteChecker(spriteChecker_)
                , palette(pal)
        {
        }
 
        void setTransparency(bool enabled)
        {
                transparency = enabled;
        }
 
        void setDisplayMode(DisplayMode newMode)
        {
                mode = newMode;
        }
 
        void setPalette(std::span<const Pixel, 16> newPalette)
        {
                palette = newPalette;
        }
 
        static bool clipPattern(int& x, SpriteChecker::SpritePattern& pattern,
                                int minX, int maxX)
        {
                int before = minX - x;
                if (before > 0) {
                        if (before >= 32) {
                                // 32 pixels before minX -> not visible
                                return false;
                        }
                        pattern <<= before;
                        x = minX;
                }
                int after = maxX - x;
                if (after < 32) {
                        // close to maxX (or past)
                        if (after <= 0) {
                                // past maxX -> not visible
                                return false;
                        }
                        auto mask = narrow_cast<int>(0x80000000);
                        pattern &= (mask >> (after - 1));
                }
                return true; // visible
        }
 
        void drawMode1(int absLine, int minX, int maxX, std::span<Pixel> pixelPtr)
        {
                // Determine sprites visible on this line.
                auto visibleSprites = spriteChecker.getSprites(absLine);
                // Optimisation: return at once if no sprites on this line.
                // Lines without any sprites are very common in most programs.
                if (visibleSprites.empty()) return;
 
                // Render using overdraw.
                for (const auto& si : view::reverse(visibleSprites)) {
                        // Get sprite info.
                        Pixel colIndex = si.colorAttrib & 0x0F;
                        // Don't draw transparent sprites in sprite mode 1.
                        // Verified on real V9958: TP bit also has effect in
                        // sprite mode 1.
                        if (colIndex == 0 && transparency) continue;
                        Pixel color = palette[colIndex];
                        SpriteChecker::SpritePattern pattern = si.pattern;
                        int x = si.x;
                        // Clip sprite pattern to render range.
                        if (!clipPattern(x, pattern, minX, maxX)) continue;
                        // Convert pattern to pixels.
                        Pixel* p = &pixelPtr[x];
                        while (pattern) {
                                // Draw pixel if sprite has a dot.
                                if (pattern & 0x80000000) {
                                        *p = color;
                                }
                                // Advancing behaviour.
                                pattern <<= 1;
                                p++;
                        }
                }
        }
 
        template<unsigned MODE>
        void drawMode2(int absLine, int minX, int maxX, std::span<Pixel> pixelPtr)
        {
                // Determine sprites visible on this line.
                auto visibleSprites = spriteChecker.getSprites(absLine);
                // Optimisation: return at once if no sprites on this line.
                // Lines without any sprites are very common in most programs.
                if (visibleSprites.empty()) return;
                std::span visibleSpritesWithSentinel{visibleSprites.data(),
                                                     visibleSprites.size() +1};
 
                // Sprites with CC=1 are only visible if preceded by a sprite
                // with CC=0. Therefor search for first sprite with CC=0.
                int first = 0;
                do {
                        if ((visibleSprites[first].colorAttrib & 0x40) == 0) [[likely]] {
                                break;
                        }
                        ++first;
                } while (first < int(visibleSprites.size()));
                for (int i = narrow<int>(visibleSprites.size() - 1); i >= first; --i) {
                        const SpriteChecker::SpriteInfo& info = visibleSprites[i];
                        int x = info.x;
                        SpriteChecker::SpritePattern pattern = info.pattern;
                        // Clip sprite pattern to render range.
                        if (!clipPattern(x, pattern, minX, maxX)) continue;
                        uint8_t c = info.colorAttrib & 0x0F;
                        if (c == 0 && transparency) continue;
                        while (pattern) {
                                if (pattern & 0x80000000) {
                                        uint8_t color = c;
                                        // Merge in any following CC=1 sprites.
                                        for (int j = i + 1; /*sentinel*/; ++j) {
                                                const SpriteChecker::SpriteInfo& info2 =
                                                        visibleSpritesWithSentinel[j];
                                                if (!(info2.colorAttrib & 0x40)) break;
                                                unsigned shift2 = x - info2.x;
                                                if ((shift2 < 32) &&
                                                   ((info2.pattern << shift2) & 0x80000000)) {
                                                        color |= info2.colorAttrib & 0x0F;
                                                }
                                        }
                                        if constexpr (MODE == DisplayMode::GRAPHIC5) {
                                                Pixel pixL = palette[color >> 2];
                                                Pixel pixR = palette[color & 3];
                                                pixelPtr[x * 2 + 0] = pixL;
                                                pixelPtr[x * 2 + 1] = pixR;
                                        } else {
                                                Pixel pix = palette[color];
                                                if constexpr (MODE == DisplayMode::GRAPHIC6) {
                                                        pixelPtr[x * 2 + 0] = pix;
                                                        pixelPtr[x * 2 + 1] = pix;
                                                } else {
                                                        pixelPtr[x] = pix;
                                                }
                                        }
                                }
                                ++x;
                                pattern <<= 1;
                        }
                }
        }
 
private:
        SpriteChecker& spriteChecker;
 
        std::span<const Pixel, 16> palette;
 
        bool transparency;
 
        DisplayMode mode;
};
 
} // namespace openmsx
 
#endif