How to implement new renderer?

[trogmaniac]

Where would i have to "hook in" if i wanted to write a new renderer, e.g. using GDI+? Somehow i expected to find methods to draw primitives in the renderer that i could easily replace with GDI+ calls. But i guess that was a little too optimistic :)

Thanks.

[memononen]

The render loop is quite simple, take a look at: https://github.com/memononen/nanosvg/blob/master/src/nanosvgrast.h#L1244

To draw the shapes, something like this could work:

NSVGpath* path;
for (path = shape->paths; path != NULL; path = path->next) {
    for (i = 0; i < path->npts-1; i += 3) {
        float* p = &path->pts[i*2];
        drawBezier(p[0]*scale,p[1]*scale, p[2]*scale,p[3]*scale, p[4]*scale,p[5]*scale, p[6]*scale,p[7]*scale, 0, 0);
    }
}

or if your API is like html canvas:

NSVGpath* path;
for (path = shape->paths; path != NULL; path = path->next) {
    moveTo(path->pts[0]*scale, path->pts[1]*scale);
    for (i = 0; i < path->npts-1; i += 3) {
        float* p = &path->pts[i*2];
        drawBezierTo(p[2]*scale,p[3]*scale, p[4]*scale,p[5]*scale, p[6]*scale,p[7]*scale, 0, 0);
    }
}

That should get you started, mapping the color and gradients is a little more effort, but not too bad.

[trogmaniac]

I saw that loop, but didn't know how to collect the other informations about colors, gradients etc. I'll try to study the rasterizer code some more. Thanks.

[memononen]

NanoSVG header should give you some idea how the paints are structured, and color helper functions should give you idea how to "decode" an RGBA color from the uint color of the paint: https://github.com/memononen/nanosvg/blob/master/src/nanosvgrast.h#L818

Using the uint for color is a bit silly here, it has historical significance. I'm going to change that to a struct as I get time to do so.