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 "likely.hh"
#include "openmsx.hh"

namespace openmsx {

template <class Pixel>
class SpriteConverter
{
public:
        // TODO: Move some methods to .cc?

        explicit SpriteConverter(SpriteChecker& spriteChecker_)
                : spriteChecker(spriteChecker_)
        {
        }

        void setTransparency(bool enabled)
        {
                transparency = enabled;
        }

        void setDisplayMode(DisplayMode newMode)
        {
                mode = newMode;
        }

        void setPalette(const Pixel* 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;
                        }
                        int mask = 0x80000000;
                        pattern &= (mask >> (after - 1));
                }
                return true; // visible
        }

        void drawMode1(int absLine, int minX, int maxX,
                       Pixel* __restrict pixelPtr) __restrict
        {
                // Determine sprites visible on this line.
                const SpriteChecker::SpriteInfo* visibleSprites;
                int visibleIndex =
                        spriteChecker.getSprites(absLine, visibleSprites);
                // Optimisation: return at once if no sprites on this line.
                // Lines without any sprites are very common in most programs.
                if (visibleIndex == 0) return;

                // Render using overdraw.
                while (visibleIndex--) {
                        // Get sprite info.
                        const SpriteChecker::SpriteInfo* sip =
                                &visibleSprites[visibleIndex];
                        Pixel colIndex = sip->colorAttrib & 0x0F;
                        // Don't draw transparent sprites in sprite mode 1.
                        // TODO: Verify on real V9938 that sprite mode 1 indeed
                        //       ignores the transparency bit.
                        if (colIndex == 0) continue;
                        Pixel color = palette[colIndex];
                        SpriteChecker::SpritePattern pattern = sip->pattern;
                        int x = sip->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,
                       Pixel* __restrict pixelPtr) __restrict
        {
                // Determine sprites visible on this line.
                const SpriteChecker::SpriteInfo* visibleSprites;
                int visibleIndex =
                        spriteChecker.getSprites(absLine, visibleSprites);
                // Optimisation: return at once if no sprites on this line.
                // Lines without any sprites are very common in most programs.
                if (visibleIndex == 0) return;

                // 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 (likely((visibleSprites[first].colorAttrib & 0x40) == 0)) {
                                break;
                        }
                        ++first;
                } while (first < visibleIndex);
                for (int i = visibleIndex - 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;
                        byte c = info.colorAttrib & 0x0F;
                        if (c == 0 && transparency) continue;
                        while (pattern) {
                                if (pattern & 0x80000000) {
                                        byte color = c;
                                        // Merge in any following CC=1 sprites.
                                        for (int j = i + 1; /*sentinel*/; ++j) {
                                                const SpriteChecker::SpriteInfo& info2 =
                                                        visibleSprites[j];
                                                if (!(info2.colorAttrib & 0x40)) break;
                                                unsigned shift2 = x - info2.x;
                                                if ((shift2 < 32) &&
                                                   ((info2.pattern << shift2) & 0x80000000)) {
                                                        color |= info2.colorAttrib & 0x0F;
                                                }
                                        }
                                        if (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 (MODE == DisplayMode::GRAPHIC6) {
                                                        pixelPtr[x * 2 + 0] = pix;
                                                        pixelPtr[x * 2 + 1] = pix;
                                                } else {
                                                        pixelPtr[x] = pix;
                                                }
                                        }
                                }
                                ++x;
                                pattern <<= 1;
                        }
                }
        }

private:
        SpriteChecker& spriteChecker;

        const Pixel* palette;

        bool transparency;

        DisplayMode mode;
};

} // namespace openmsx

#endif