Inspiration from Nuklear RawFB

PNTR_NUKLEAR_API void pntr_nuklear_draw_polygon_fill(pntr_image* dst, const struct nk_vec2i *pnts, int count, pntr_color col) {
    int i = 0;
    #define MAX_POINTS 64
    int left = 10000, top = 10000, bottom = 0, right = 0;
    int nodes, nodeX[MAX_POINTS], pixelX, pixelY, j, swap ;

    if (count == 0) return;
    if (count > MAX_POINTS)
        count = MAX_POINTS;

    /* Get polygon dimensions */
    for (i = 0; i < count; i++) {
        if (left > pnts[i].x)
            left = pnts[i].x;
        if (right < pnts[i].x)
            right = pnts[i].x;
        if (top > pnts[i].y)
            top = pnts[i].y;
        if (bottom < pnts[i].y)
            bottom = pnts[i].y;
    } bottom++; right++;

    /* Polygon scanline algorithm released under public-domain by Darel Rex Finley, 2007 */
    /*  Loop through the rows of the image. */
    for (pixelY = top; pixelY < bottom; pixelY ++) {
        nodes = 0; /*  Build a list of nodes. */
        j = count - 1;
        for (i = 0; i < count; i++) {
            if (((pnts[i].y < pixelY) && (pnts[j].y >= pixelY)) ||
                ((pnts[j].y < pixelY) && (pnts[i].y >= pixelY))) {
                nodeX[nodes++]= (int)((float)pnts[i].x
                     + ((float)pixelY - (float)pnts[i].y) / ((float)pnts[j].y - (float)pnts[i].y)
                     * ((float)pnts[j].x - (float)pnts[i].x));
            } j = i;
        }

        /*  Sort the nodes, via a simple “Bubble” sort. */
        i = 0;
        while (i < nodes - 1) {
            if (nodeX[i] > nodeX[i+1]) {
                swap = nodeX[i];
                nodeX[i] = nodeX[i+1];
                nodeX[i+1] = swap;
                if (i) i--;
            } else i++;
        }
        /*  Fill the pixels between node pairs. */
        for (i = 0; i < nodes; i += 2) {
            if (nodeX[i+0] >= right) break;
            if (nodeX[i+1] > left) {
                if (nodeX[i+0] < left) nodeX[i+0] = left ;
                if (nodeX[i+1] > right) nodeX[i+1] = right;
                for (pixelX = nodeX[i]; pixelX < nodeX[i + 1]; pixelX++)
                    //nk_rawfb_ctx_setpixel(rawfb, pixelX, pixelY, col);
                    pntr_draw_point(dst, pixelX, pixelY, col);

            }
        }
    }
    #undef MAX_POINTS
}

/**
 * @internal
 */
PNTR_NUKLEAR_API void pntr_nuklear_draw_stroke_curve(pntr_image* rawfb,
    const struct nk_vec2i p1, const struct nk_vec2i p2,
    const struct nk_vec2i p3, const struct nk_vec2i p4,
    const unsigned int num_segments, const unsigned short line_thickness,
    pntr_color col)
{
    unsigned int i_step, segments;
    float t_step;
    struct nk_vec2i last = p1;

    segments = PNTR_MAX(num_segments, 1);
    t_step = 1.0f/(float)segments;
    for (i_step = 1; i_step <= segments; ++i_step) {
        float t = t_step * (float)i_step;
        float u = 1.0f - t;
        float w1 = u*u*u;
        float w2 = 3*u*u*t;
        float w3 = 3*u*t*t;
        float w4 = t * t *t;
        float x = w1 * p1.x + w2 * p2.x + w3 * p3.x + w4 * p4.x;
        float y = w1 * p1.y + w2 * p2.y + w3 * p3.y + w4 * p4.y;
        // TODO: Add line_thickness to pntr_nuklear_draw_stroke_curve
        pntr_draw_line(rawfb, last.x, last.y, (int)x, (int)y, col);
        last.x = (short)x; last.y = (short)y;
    }
}
RobLoach / pntr

Inspiration from Nuklear RawFB #174
