renderDiscRow()

template<typename PixelT, bool Overwrite>

void fl::gfx::detail::renderDiscRow ( PixelT * buf, int w, int py, fl::i32 d2_row, const DiscCtx< PixelT > & f )

inline

Render one scanline of a disc using incremental d².

Templated on Overwrite for compile-time dispatch (no per-pixel branch). Uses (n+1)² = n² + 2n + 1 identity — zero multiplies in the inner loop.

Definition at line 280 of file primitives.h.

                                                                 {
    PixelT* ptr = &buf[py * w + f.xmin];
    fl::i32 d2 = d2_row;
    fl::i32 xd = f.xdelta0;
    int px = f.xmin;
    // Phase 1: Skip outside pixels (left, d2 decreasing)
    while (px <= f.xmax && d2 >= f.rout2) {
        d2 += xd; xd += 131072; ++ptr; ++px;
    }
    // Phase 2: Outer AA fringe (left)
    while (px <= f.xmax && d2 >= f.rin2 && d2 < f.rout2) {
        fl::u16 diff = static_cast<fl::u16>(static_cast<fl::u32>(f.rout2 - d2) >> f.band_shift);
        fl::u8 br = static_cast<fl::u8>((diff * f.band_inv) >> 8);
        PixelT c = f.color; c.nscale8(br);
        if (Overwrite) *ptr = c; else *ptr += c;
        d2 += xd; xd += 131072; ++ptr; ++px;
    }
    // Phase 3: Full brightness interior (d2 hits minimum, then increases)
    while (px <= f.xmax && d2 < f.rin2) {
        if (Overwrite) *ptr = f.color; else *ptr += f.color;
        d2 += xd; xd += 131072; ++ptr; ++px;
    }
    // Phase 4: Outer AA fringe (right, d2 increasing)
    while (px <= f.xmax && d2 < f.rout2) {
        fl::u16 diff = static_cast<fl::u16>(static_cast<fl::u32>(f.rout2 - d2) >> f.band_shift);
        fl::u8 br = static_cast<fl::u8>((diff * f.band_inv) >> 8);
        PixelT c = f.color; c.nscale8(br);
        if (Overwrite) *ptr = c; else *ptr += c;
        d2 += xd; xd += 131072; ++ptr; ++px;
    }
}

References fl::FL_NO_EXCEPT, and renderDiscRow().

Referenced by drawDiscCore(), and renderDiscRow().

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