Replacement for hardcoded font paths

findDejaVuSans.h

/* findDejaVuSans - Quick function to find DejaVuSans.ttf
 *
 * Copyright (c) 2019 Ethan Lee
 *
 * This software is provided 'as-is', without any express or implied warranty.
 * In no event will the authors be held liable for any damages arising from
 * the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 * claim that you wrote the original software. If you use this software in a
 * product, an acknowledgment in the product documentation would be
 * appreciated but is not required.
 *
 * 2. Altered source versions must be plainly marked as such, and must not be
 * misrepresented as being the original software.
 *
 * 3. This notice may not be removed or altered from any source distribution.
 *
 * Ethan "flibitijibibo" Lee <flibitijibibo@flibitijibibo.com>
 *
 */

/* Replace your existing DejaVuSans.ttf path with:
 *
 *	char fontPath[PATH_MAX];
 *	findDejaVuSans(fontPath, sizeof(fontPath));
 *
 * Be sure to only call this function once!
 */

#include <fontconfig/fontconfig.h>

#ifdef USE_SDL2
#include <SDL.h>
#define PRINTFILE(name) SDL_snprintf(path, len, "%s", name)
#define LOADSO(name) sofile = SDL_LoadObject(name)
#define LOADFN(name) SDL_LoadFunction(sofile, name)
#define UNLOADSO SDL_UnloadObject(sofile)
#else
#include <dlfcn.h>
#include <stdio.h>
#define PRINTFILE(name) snprintf(path, len, "%s", name)
#define LOADSO(name) sofile = dlopen(name, RTLD_NOW | RTLD_LOCAL)
#define LOADFN(name) dlsym(sofile, name)
#define UNLOADSO dlclose(sofile)
#endif

static inline void findDejaVuSans(char *path, size_t len)
{
	/* libfontconfig */
	void* sofile;
	FcPattern* (*fcNameParse)(const FcChar8*);
	FcBool (*fcConfigSubstitute)(FcConfig*, FcPattern*, FcMatchKind);
	void (*fcDefaultSubstitute)(FcPattern*);
	FcPattern* (*fcFontMatch)(FcConfig*, FcPattern*, FcResult*);
	FcFontSet* (*fcFontSetCreate)(void);
	FcBool (*fcFontSetAdd)(FcFontSet*, FcPattern*);
	void (*fcPatternDestroy)(FcPattern*);
	FcChar8* (*fcPatternFormat)(FcPattern*, const FcChar8*);
	void (*fcStrFree)(FcChar8*);
	void (*fcFontSetDestroy)(FcFontSet*);
	void (*fcFini)(void);

	FcPattern *parse = NULL, *match;
	FcFontSet *set = NULL;
	FcResult result;
	FcChar8 *file = NULL;

	/* Dynamically load Fontconfig */
	LOADSO("libfontconfig.so.1");
	if (sofile == NULL)
	{
		/* Couldn't find libfontconfig */
		goto fdvsError;
	}
	fcNameParse = LOADFN("FcNameParse");
	fcConfigSubstitute = LOADFN("FcConfigSubstitute");
	fcDefaultSubstitute = LOADFN("FcDefaultSubstitute");
	fcFontMatch = LOADFN("FcFontMatch");
	fcFontSetCreate = LOADFN("FcFontSetCreate");
	fcFontSetAdd = LOADFN("FcFontSetAdd");
	fcPatternDestroy = LOADFN("FcPatternDestroy");
	fcPatternFormat = LOADFN("FcPatternFormat");
	fcStrFree = LOADFN("FcStrFree");
	fcFontSetDestroy = LOADFN("FcFontSetDestroy");
	fcFini = LOADFN("FcFini");
	if (	(fcNameParse == NULL) ||
		(fcConfigSubstitute == NULL) ||
		(fcDefaultSubstitute == NULL) ||
		(fcFontMatch == NULL) ||
		(fcFontSetCreate == NULL) ||
		(fcFontSetAdd == NULL) ||
		(fcPatternDestroy == NULL) ||
		(fcPatternFormat == NULL) ||
		(fcStrFree == NULL) ||
		(fcFontSetDestroy == NULL) ||
		(fcFini == NULL)	)
	{
		/* Couldn't find Fontconfig functions */
		goto fdvsError;
	}

	/* Search setup */
	parse = fcNameParse((const FcChar8*) "DejaVuSans.ttf");
	if (parse == NULL)
	{
		/* Couldn't even parse the font name */
		goto fdvsError;
	}
	if (fcConfigSubstitute(0, parse, FcMatchPattern) == FcFalse)
	{
		/* Allocation failure */
		goto fdvsError;
	}
	fcDefaultSubstitute(parse);

	/* Execute search */
	match = fcFontMatch(0, parse, &result);
	if (match == NULL)
	{
		/* Didn't find a match */
		fcPatternDestroy(parse);
		fcFini();
		goto fdvsError;
	}
	set = fcFontSetCreate();
	if (set == NULL)
	{
		/* Allocation failure */
		goto fdvsError;
	}
	if (fcFontSetAdd(set, match) == FcFalse)
	{
		/* Allocation failure */
		goto fdvsError;
	}
	fcPatternDestroy(parse);
	parse = NULL;

	/* Generate file path string */
	file = fcPatternFormat(set->fonts[0], (const FcChar8*) "%{file}");
	if (file == NULL || file[0] == '\0')
	{
		/* Invalid format? Allocation failure? */
		fcFontSetDestroy(set);
		if (file != NULL)
		{
			fcStrFree(file);
		}
		fcFini();
		goto fdvsError;
	}

	/* Write path, clean up. We out. */
	PRINTFILE(file);
	fcStrFree(file);
	fcFontSetDestroy(set);
	fcFini();
	UNLOADSO;
	return;
fdvsError:
	if (sofile != NULL)
	{
		UNLOADSO;
	}
	/* Screw it, just write the SteamOS location */
	PRINTFILE("/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf");
}

#if 0 /* Example Program */
#include <stdio.h>
#include <limits.h>
int main(int argc, char **argv)
{
	char path[PATH_MAX];
	findDejaVuSans(path, sizeof(path));
	printf("%s\n", path);
	return 0;

}
#endif /* Example Program */