I'm trying to render a picture from an SVG file, using the graphics rendering library SDL2.
Problem is, my SVG files have text tags (sometimes, with additional effects), like in this example:
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="680.3215748031496" height="350.0788582677165">
<text xmlns="http://www.w3.org/2000/svg" transform="translate(263.9375,206.64214) scale(0.8792,0.8792)" font-size="40" xml:space="preserve" fill="#8c3600" fill-rule="nonzero" stroke="#8c3600" stroke-width="3" stroke-linecap="butt" stroke-linejoin="miter" stroke-miterlimit="10" stroke-dasharray="" stroke-dashoffset="0" font-family="Sans Serif" font-weight="normal" text-anchor="start" style="mix-blend-mode: normal">
<tspan x="0" dy="0">Text</tspan>
</text>
</svg>
My code to load SVG files is as follows:
uint8_t* textureData = /*Irrelevant function for me to load the file as a byte array*/
SDL_RWops *rw = SDL_RWFromMem(textureData, size);
SDL_Texture* tex = IMG_LoadTexture_RW(renderer, rw, true);
I'm using IMG_LoadTexture_RW to autodetect the image format, since I use many of them in my application. This gives me an SDL_Texture* to render.
But when rendering that SDL_Texture*, there's no text to be found on the picture rendered on screen.
I did link SDL_TTF and SDL_Image to my project, and looked for traces of this problem in the docs but couldn't find much.
I can't skip using SVG either, since those are provided on the fly by user-generated zip files that embed them.
As both SDL_image 3's code and SDL_image 2's code indicate, nanosvg is being used to parse and rasterize SVG files, which has no text support, and clearly doesn't plan to add it.
As a result, the only ways to render text tags found in SVGs using SDL_image, as of SDL 3.2, are:
To transform text tags into path tags beforehand. This can be done with tools like Inkscape, with the command (Tested with v1.4.2, old versions might require you to convert to a PDF first and then back to an SVG):
inkscape yourInputFile.svg --export-text-to-path --export-type=svg --export-filename=yourOutputFile.svg -l
Although Inkscape is written in C++, it doesn't seem to be easy to integrate within other C++ programs, though. I could find other pieces of code that perform a similar task, but only in PHP and JavaScript and they didn't seem to do a perfect job. So for what it is, interacting with Inkscape might be the best option.
To use a nanosvg fork or a project based on it which supports text rendering, although most of them are unmaintained (well, it's not like nanosvg was maintained either...) and very old. Not to mention, integrating them into SDL might be a very tedious task, and isn't great if relying on a custom SDL_image build doesn't suit you.
If none of those solutions seem good to you, you can always try to work on a cleaner solution by implementing this directly into SDL_image and sending them a pull request so other developers can benefit from it, and to allow such a feature to be officially supported!