lite-xl/tests/stb_font_render_test.c

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#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "SDL_surface.h"
#include "stb_truetype.h"
#define MAX_GLYPHSET 256
typedef struct { uint8_t b, g, r, a; } RenColor;
typedef struct { int x, y, width, height; } RenRect;
struct RenImage {
RenColor *pixels;
int width, height;
};
typedef struct RenImage RenImage;
typedef struct {
RenImage *image;
stbtt_bakedchar glyphs[256];
} GlyphSet;
struct RenFont {
void *data;
stbtt_fontinfo stbfont;
GlyphSet *sets[MAX_GLYPHSET];
float size;
int height;
};
typedef struct RenFont RenFont;
static void* check_alloc(void *ptr) {
if (!ptr) {
fprintf(stderr, "Fatal error: memory allocation failed\n");
exit(EXIT_FAILURE);
}
return ptr;
}
RenImage* ren_new_image(int width, int height) {
assert(width > 0 && height > 0);
RenImage *image = malloc(sizeof(RenImage) + width * height * sizeof(RenColor));
check_alloc(image);
image->pixels = (void*) (image + 1);
image->width = width;
image->height = height;
return image;
}
void ren_free_image(RenImage *image) {
free(image);
}
RenFont* ren_load_font(const char *filename, float size) {
RenFont *font = NULL;
FILE *fp = NULL;
/* init font */
font = check_alloc(calloc(1, sizeof(RenFont)));
font->size = size;
/* load font into buffer */
fp = fopen(filename, "rb");
if (!fp) { return NULL; }
/* get size */
fseek(fp, 0, SEEK_END); int buf_size = ftell(fp); fseek(fp, 0, SEEK_SET);
/* load */
font->data = check_alloc(malloc(buf_size));
int _ = fread(font->data, 1, buf_size, fp); (void) _;
fclose(fp);
fp = NULL;
/* init stbfont */
int ok = stbtt_InitFont(&font->stbfont, font->data, 0);
if (!ok) { goto fail; }
/* get height and scale */
int ascent, descent, linegap;
fprintf(stderr, "Requesting font size: %g\n", size);
stbtt_GetFontVMetrics(&font->stbfont, &ascent, &descent, &linegap);
float scale = stbtt_ScaleForMappingEmToPixels(&font->stbfont, size);
fprintf(stderr, "Font metrics ascent: %d descent: %d, linegap: %d scale: %g\n", ascent, descent, linegap, scale);
font->height = (ascent - descent + linegap) * scale + 0.5;
fprintf(stderr, "Font height: %d\n", font->height);
return font;
fail:
if (fp) { fclose(fp); }
if (font) { free(font->data); }
free(font);
return NULL;
}
static GlyphSet* load_glyphset(RenFont *font, int idx) {
GlyphSet *set = check_alloc(calloc(1, sizeof(GlyphSet)));
/* init image */
int width = 128;
int height = 128;
retry:
set->image = ren_new_image(width, height);
/* load glyphs */
float s =
stbtt_ScaleForMappingEmToPixels(&font->stbfont, 1) /
stbtt_ScaleForPixelHeight(&font->stbfont, 1);
int res = stbtt_BakeFontBitmap(
font->data, 0, font->size * s, (void*) set->image->pixels,
width, height, idx * 256, 256, set->glyphs);
/* retry with a larger image buffer if the buffer wasn't large enough */
if (res < 0) {
width *= 2;
height *= 2;
ren_free_image(set->image);
goto retry;
}
/* adjust glyph yoffsets and xadvance */
int ascent, descent, linegap;
stbtt_GetFontVMetrics(&font->stbfont, &ascent, &descent, &linegap);
float scale = stbtt_ScaleForMappingEmToPixels(&font->stbfont, font->size);
int scaled_ascent = ascent * scale + 0.5;
for (int i = 0; i < 256; i++) {
set->glyphs[i].yoff += scaled_ascent;
set->glyphs[i].xadvance = floor(set->glyphs[i].xadvance);
}
/* convert 8bit data to 32bit */
for (int i = width * height - 1; i >= 0; i--) {
uint8_t n = *((uint8_t*) set->image->pixels + i);
set->image->pixels[i] = (RenColor) { .r = 255, .g = 255, .b = 255, .a = n };
}
return set;
}
int main(int argc, char *argv[]) {
if (argc < 3) {
fprintf(stderr, "usage: %s <font-filename> <size>\n", argv[0]);
return 1;
}
const char *filename = argv[1];
const int size = atoi(argv[2]);
RenFont *font = ren_load_font(filename, size);
GlyphSet *set = load_glyphset(font, 0);
SDL_Surface *surface = SDL_CreateRGBSurfaceWithFormatFrom(
set->image->pixels,
set->image->width, set->image->height, 32, set->image->width * 4,
SDL_PIXELFORMAT_RGBA32);
SDL_SaveBMP(surface, "stb-glyphset.bmp");
return 0;
}