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ugui/text_rendering/font.c

196 lines
4.9 KiB

#define _POSIX_C_SOURCE 200809l
#define STB_TRUETYPE_IMPLEMENTATION
#define STBTT_STATIC
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include <grapheme.h>
#include <assert.h>
#include "font.h"
#include "stb_truetype.h"
#include "stb_image_write.h"
#include "util.h"
#include "generic_cache.h"
static inline unsigned int hash(unsigned int code)
{
// identity map the ascii range
return code < 128 ? code : hash_u32(code);
}
CACHE_DECL(cache, struct font_glyph, hash, hash_cmp_u32)
#define UTF8(c) (c&0x80)
#define BDEPTH 1
#define BORDER 4
// FIXME: as of now only monospaced fonts work correctly since no kerning information
// is stored
struct priv {
stbtt_fontinfo stb;
float scale;
int baseline;
unsigned char *bitmap;
struct cache c;
};
#define PRIV(x) ((struct priv *)x->priv)
struct font_atlas * font_init(void)
{
struct font_atlas *p = emalloc(sizeof(struct font_atlas));
memset(p, 0, sizeof(struct font_atlas));
p->priv = emalloc(sizeof(struct priv));
memset(p->priv, 0, sizeof(struct priv));
PRIV(p)->c = cache_init();
return p;
}
// loads a font into memory, storing all the ASCII characters in the atlas, each font
// atlas structure holds glyphs of a specific size in pixels
// NOTE: size includes ascend and descend (so 12 does not mean that 'A' is 12px tall)
int font_load(struct font_atlas *atlas, const char *path, int size)
{
if (!atlas || !path)
return -1;
int err;
dump_file(path, &(atlas->file), &(atlas->file_size));
err = stbtt_InitFont(&(PRIV(atlas)->stb), (unsigned char *)atlas->file, 0);
ERROR(err == 0, -1);
int ascent, descent, linegap, baseline;
int x0,y0,x1,y1;
float scale;
stbtt_GetFontVMetrics(&(PRIV(atlas)->stb), &ascent, &descent, &linegap);
stbtt_GetFontBoundingBox(&(PRIV(atlas)->stb), &x0, &y0, &x1, &y1);
scale = stbtt_ScaleForPixelHeight(&(PRIV(atlas)->stb), size);
baseline = scale * -y0;
atlas->glyph_max_w = (scale*x1) - (scale*x0);
atlas->glyph_max_h = (baseline+scale*y1) - (baseline+scale*y0);
atlas->atlas = emalloc(CACHE_SIZE*BDEPTH*atlas->glyph_max_w*atlas->glyph_max_h);
memset(atlas->atlas, 0, CACHE_SIZE*BDEPTH*atlas->glyph_max_w*atlas->glyph_max_h);
PRIV(atlas)->baseline = atlas->glyph_max_h - baseline;
PRIV(atlas)->scale = scale;
PRIV(atlas)->bitmap = emalloc(BDEPTH*atlas->glyph_max_w*atlas->glyph_max_h);
// FIXME: make this a square atlas
atlas->width = atlas->glyph_max_w*CACHE_SIZE/4;
atlas->height = atlas->glyph_max_h*4;
atlas->size = size;
// preallocate all ascii characters
for (char c = ' '; c <= '~'; c++) {
if (!font_get_glyph_texture(atlas, c, NULL))
return -1;
}
return 0;
}
int font_free(struct font_atlas *atlas)
{
efree(atlas->atlas);
efree(atlas->file);
efree(PRIV(atlas)->bitmap);
cache_free(&PRIV(atlas)->c);
efree(atlas->priv);
efree(atlas);
return 0;
}
// TODO: time and take the median of the time it takes to generate the cache and
// the time it takes to draw the glyph
const struct font_glyph * font_get_glyph_texture(struct font_atlas *atlas, unsigned int code, int *updated)
{
int _u = 0;
if (!updated) updated = &_u;
const struct font_glyph *r;
if ((r = cache_search(&PRIV(atlas)->c, code)) != NULL) {
*updated = 0;
return r;
}
*updated = 1;
// generate the sdf and put it into the cache
// TODO: generate the whole block at once
int idx = stbtt_FindGlyphIndex(&PRIV(atlas)->stb, code);
int x0,y0,x1,y1,gw,gh,l,off_x,off_y,adv,base;
base = atlas->glyph_max_h - PRIV(atlas)->baseline;
stbtt_GetGlyphBitmapBoxSubpixel(
&PRIV(atlas)->stb,
idx,
PRIV(atlas)->scale,
PRIV(atlas)->scale,
0,0,
&x0,&y0,
&x1, &y1);
gw = x1 - x0;
gh = y1 - y0;
stbtt_GetGlyphHMetrics(&PRIV(atlas)->stb, idx, &adv, &l);
adv *= PRIV(atlas)->scale;
off_x = PRIV(atlas)->scale*l;
off_y = atlas->glyph_max_h+y0;
stbtt_MakeGlyphBitmapSubpixel(
&PRIV(atlas)->stb,
PRIV(atlas)->bitmap,
atlas->glyph_max_w,
atlas->glyph_max_h,
atlas->glyph_max_w,
PRIV(atlas)->scale,
PRIV(atlas)->scale,
0, 0,
idx);
// TODO: bounds check usign atlas height
// TODO: clear spot area in the atlas before writing on it
unsigned int spot = cache_get(&PRIV(atlas)->c);
unsigned int ty = ((atlas->glyph_max_w * spot) / atlas->width) * atlas->glyph_max_h;
unsigned int tx = (atlas->glyph_max_w * spot) % atlas->width;
unsigned int w = atlas->width;
unsigned char *a = (void *)atlas->atlas;
//printf("max:%d %d spot:%d : %d %d %d %d\n", atlas->glyph_max_w, atlas->glyph_max_h, spot, tx, ty, off_x, off_y);
for (int y = 0; y < gh; y++) {
for (int x = 0; x < gw; x++) {
int c, r;
r = (ty+y)*w;
c = tx+x;
a[r+c] = PRIV(atlas)->bitmap[y*atlas->glyph_max_w+x];
}
}
// FIXME: get the advance
struct font_glyph g = {
.codepoint = code,
.u = tx,
.v = ty,
.w = gw,
.h = gh,
.x = off_x,
.y = off_y-base,
.a = adv,
};
return cache_insert(&PRIV(atlas)->c, &g, g.codepoint, spot);
}
void font_dump(const struct font_atlas *atlas, const char *path)
{
stbi_write_png(
path,
atlas->width,
atlas->height,
BDEPTH,
atlas->atlas,
BDEPTH*atlas->width);
}