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[llpp.git] / glfont.c
blobf35a7d04fd982fc012a2ff8e0bbf2efabba5d3b0
1 /* This is a slightly modified
2 https://github.com/ccxvii/snippets/blob/master/glfont.c by Tor Andersson
3 */
4 /*
5 * A very simple font cache and rasterizer that uses freetype
6 * to draw fonts from a single OpenGL texture. The code uses
7 * a linear-probe hashtable, and writes new glyphs into
8 * the texture using glTexSubImage2D. When the texture fills
9 * up, or the hash table gets too crowded, everything is wiped.
11 * This is designed to be used for horizontal text only,
12 * and draws unhinted text with subpixel accurate metrics
13 * and kerning. As such, you should always call the drawing
14 * function with an identity transform that maps units
15 * to pixels accurately.
17 * If you wish to use it to draw arbitrarily transformed
18 * text, change the min and mag filters to GL_LINEAR and
19 * add a pixel of padding between glyphs and rows, and
20 * make sure to clear the texture when wiping the cache.
23 #include FT_ADVANCES_H
24 typedef int Rune; /* 32 bits */
26 #define PADDING 1 /* set to 0 to save some space but disallow arbitrary transforms */
28 #define MAXGLYPHS 4093 /* prime number for hash table goodness */
29 #define CACHESIZE 256
30 #define XPRECISION 4
31 #define YPRECISION 1
33 struct key
35 FT_Face face;
36 short size;
37 short gid;
38 short subx;
39 short suby;
42 struct glyph
44 signed char lsb, top, w, h;
45 short s, t;
46 float advance;
49 struct table
51 struct key key;
52 struct glyph glyph;
55 static FT_Library g_freetype_lib = NULL;
56 static struct table g_table[MAXGLYPHS];
57 static int g_table_load = 0;
58 static unsigned int g_cache_tex = 0;
59 static int g_cache_w = CACHESIZE;
60 static int g_cache_h = CACHESIZE;
61 static int g_cache_row_y = 0;
62 static int g_cache_row_x = 0;
63 static int g_cache_row_h = 0;
64 static int g_use_kern = 0;
66 static void init_font_cache(void)
68 int code;
70 code = FT_Init_FreeType(&g_freetype_lib);
71 if (code)
72 errx(1, "cannot initialize freetype");
74 glGenTextures(1, &g_cache_tex);
75 glBindTexture(GL_TEXTURE_2D, g_cache_tex);
76 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
77 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
78 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
79 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
80 glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, g_cache_w, g_cache_h, 0, GL_ALPHA, GL_UNSIGNED_BYTE, NULL);
83 static void clear_font_cache(void)
85 #if PADDING > 0
86 unsigned char *zero = calloc(g_cache_w, g_cache_h);
87 if (!zero)
88 err(1, "malloc zero (%u bytes failed)", g_cache_w * g_cache_h);
89 glBindTexture(GL_TEXTURE_2D, g_cache_tex);
90 glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, g_cache_w, g_cache_h, GL_ALPHA, GL_UNSIGNED_BYTE, zero);
91 free(zero);
92 #endif
94 memset(g_table, 0, sizeof(g_table));
95 g_table_load = 0;
97 g_cache_row_y = PADDING;
98 g_cache_row_x = PADDING;
99 g_cache_row_h = 0;
102 static void *filecontents (char *path, int *len)
104 int ret, fd;
105 void *res;
106 struct stat st;
107 ssize_t nread;
109 ret = stat(path, &st);
110 if (ret) err(1, "failed to stat `%s'", path);
111 if (st.st_size > INT_MAX) errx(1, "font `%s' is too big", path);
112 res = malloc(st.st_size);
113 if (!res)
114 err(1, "failed to allocate %llu bytes for `%s'",
115 st.st_size+0ull, path);
117 fd = open(path, O_RDONLY | O_BINARY);
118 if (fd < 0) err(1, "failed to open `%s'", path);
120 nread = read(fd, res, st.st_size);
121 if (nread - st.st_size)
122 err(1, "read %llu failed, ret=%zd", st.st_size+0llu, nread);
124 *len = (int) st.st_size;
125 return res;
128 static FT_Face load_font(char *fontname)
130 FT_Face face;
131 int code, len;
132 void *base;
134 if (g_freetype_lib == NULL)
136 init_font_cache();
137 clear_font_cache();
140 base = filecontents(fontname, &len);
141 code = FT_New_Memory_Face(g_freetype_lib, base, len, 0, &face);
142 if (code)
144 errx(1, "FT_New_Memory_Face for `%s' failed: %d",
145 fontname, code);
148 FT_Select_Charmap(face, ft_encoding_unicode);
149 return face;
152 static FT_Face UNUSED_ATTR load_builtin_font(const void *base, int len)
154 FT_Face face;
155 int code;
157 if (g_freetype_lib == NULL)
159 init_font_cache();
160 clear_font_cache();
163 code = FT_New_Memory_Face(g_freetype_lib, base, len, 0, &face);
164 if (code)
166 errx (1, "failed to load builtin font: %d\n", code);
167 return NULL;
170 FT_Select_Charmap(face, ft_encoding_unicode);
171 return face;
174 static void UNUSED_ATTR free_font(FT_Face face)
176 clear_font_cache();
177 FT_Done_Face(face);
180 static unsigned int hashfunc(struct key *key)
182 unsigned char *buf = (unsigned char *)key;
183 unsigned int len = sizeof(struct key);
184 unsigned int h = 0;
185 while (len--)
186 h = *buf++ + (h << 6) + (h << 16) - h;
187 return h;
190 static unsigned int lookup_table(struct key *key)
192 unsigned int pos = hashfunc(key) % MAXGLYPHS;
193 while (1)
195 if (!g_table[pos].key.face) /* empty slot */
196 return pos;
197 if (!memcmp(key, &g_table[pos].key, sizeof(struct key))) /* matching slot */
198 return pos;
199 pos = (pos + 1) % MAXGLYPHS;
203 static struct glyph * lookup_glyph(FT_Face face, int size, int gid, int subx, int suby)
205 FT_Vector subv;
206 struct key key;
207 unsigned int pos;
208 int code;
209 int w, h;
212 * Look it up in the table
215 key.face = face;
216 key.size = size;
217 key.gid = gid;
218 key.subx = subx;
219 key.suby = suby;
221 pos = lookup_table(&key);
222 if (g_table[pos].key.face)
223 return &g_table[pos].glyph;
226 * Render the bitmap
228 #ifdef FFP
229 glEnd();
230 #endif
232 subv.x = subx;
233 subv.y = suby;
235 FT_Set_Transform(face, NULL, &subv);
237 code = FT_Load_Glyph(face, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING);
238 if (code < 0)
239 return NULL;
241 code = FT_Render_Glyph(face->glyph, FT_RENDER_MODE_LIGHT);
242 if (code < 0)
243 return NULL;
245 w = face->glyph->bitmap.width;
246 h = face->glyph->bitmap.rows;
249 * Find an empty slot in the texture
252 if (g_table_load == (MAXGLYPHS * 3) / 4)
254 lprintf("font cache table full, clearing cache");
255 clear_font_cache();
256 pos = lookup_table(&key);
259 if (h + PADDING > g_cache_h || w + PADDING > g_cache_w)
260 errx(1, "rendered glyph exceeds cache dimensions");
262 if (g_cache_row_x + w + PADDING > g_cache_w)
264 g_cache_row_y += g_cache_row_h + PADDING;
265 g_cache_row_x = PADDING;
266 g_cache_row_h = 0;
268 if (g_cache_row_y + h + PADDING > g_cache_h)
270 lprintf("font cache texture full, clearing cache");
271 clear_font_cache();
272 pos = lookup_table(&key);
276 * Copy bitmap into texture
279 memcpy(&g_table[pos].key, &key, sizeof(struct key));
280 g_table[pos].glyph.w = face->glyph->bitmap.width;
281 g_table[pos].glyph.h = face->glyph->bitmap.rows;
282 g_table[pos].glyph.lsb = face->glyph->bitmap_left;
283 g_table[pos].glyph.top = face->glyph->bitmap_top;
284 g_table[pos].glyph.s = g_cache_row_x;
285 g_table[pos].glyph.t = g_cache_row_y;
286 g_table[pos].glyph.advance = face->glyph->advance.x / 64.0;
287 g_table_load ++;
289 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
290 glPixelStorei(GL_UNPACK_ROW_LENGTH, face->glyph->bitmap.pitch);
291 glTexSubImage2D(GL_TEXTURE_2D, 0, g_cache_row_x, g_cache_row_y, w, h,
292 GL_ALPHA, GL_UNSIGNED_BYTE, face->glyph->bitmap.buffer);
293 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
295 #ifdef FFP
296 glBegin(GL_QUADS);
297 #endif
298 g_cache_row_x += w + PADDING;
299 if (g_cache_row_h < h + PADDING)
300 g_cache_row_h = h + PADDING;
302 return &g_table[pos].glyph;
305 static float draw_glyph(FT_Face face, int size, int gid, float x, float y)
307 struct glyph *glyph;
308 int subx = (x - floor(x)) * XPRECISION;
309 int suby = (y - floor(y)) * YPRECISION;
310 #ifndef FFP
311 GLfloat *t = state.texcoords;
312 GLfloat *v = state.vertices;
313 #endif
314 float s0, t0, s1, t1, xc, yc;
316 subx = (subx * 64) / XPRECISION;
317 suby = (suby * 64) / YPRECISION;
319 glyph = lookup_glyph(face, size, gid, subx, suby);
320 if (!glyph)
321 return 0.0;
323 s0 = (float) glyph->s / g_cache_w;
324 t0 = (float) glyph->t / g_cache_h;
325 s1 = (float) (glyph->s + glyph->w) / g_cache_w;
326 t1 = (float) (glyph->t + glyph->h) / g_cache_h;
327 xc = floor(x) + glyph->lsb;
328 yc = floor(y) - glyph->top + glyph->h;
330 #ifndef FFP
331 t[0] = s0; t[1] = t0; v[0] = xc; v[1] = yc - glyph->h;
332 t[2] = s1; t[3] = t0; v[2] = xc + glyph->w; v[3] = yc - glyph->h;
333 t[4] = s0; t[5] = t1; v[4] = xc; v[5] = yc;
334 t[6] = s1; t[7] = t1; v[6] = xc + glyph->w; v[7] = yc;
336 glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
337 #else
338 glTexCoord2f(s0, t0); glVertex2f(xc, yc - glyph->h);
339 glTexCoord2f(s1, t0); glVertex2f(xc + glyph->w, yc - glyph->h);
340 glTexCoord2f(s1, t1); glVertex2f(xc + glyph->w, yc);
341 glTexCoord2f(s0, t1); glVertex2f(xc, yc);
342 #endif
344 return glyph->advance;
347 static float measure_string(FT_Face face, float fsize, char *str)
349 int size = fsize * 64;
350 FT_Fixed advance;
351 Rune ucs, gid;
352 float w = 0.0;
353 int left = 0;
355 FT_Set_Char_Size(face, size, size, 72, 72);
357 while (*str)
359 str += fz_chartorune(&ucs, str);
360 gid = FT_Get_Char_Index(face, ucs);
361 FT_Get_Advance(face, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING, &advance);
362 w += advance / 65536.0;
363 if (g_use_kern) {
364 FT_Vector kern;
366 FT_Get_Kerning(face, left, gid, FT_KERNING_UNFITTED, &kern);
367 w += kern.x / 64.0;
369 left = gid;
372 return w;
375 static float draw_string(FT_Face face, float fsize, float x, float y, char *str)
377 int size = fsize * 64;
378 Rune ucs, gid;
379 int left = 0;
381 FT_Set_Char_Size(face, size, size, 72, 72);
383 glBindTexture(GL_TEXTURE_2D, g_cache_tex);
384 #ifdef FFP
385 glBegin(GL_QUADS);
386 #else
387 glVertexPointer(2, GL_FLOAT, 0, state.vertices);
388 glTexCoordPointer(2, GL_FLOAT, 0, state.texcoords);
389 #endif
390 while (*str)
392 str += fz_chartorune(&ucs, str);
393 gid = FT_Get_Char_Index(face, ucs);
394 x += draw_glyph(face, size, gid, x, y);
395 if (g_use_kern) {
396 FT_Vector kern;
398 FT_Get_Kerning(face, left, gid, FT_KERNING_UNFITTED, &kern);
399 x += kern.x / 64.0;
401 left = gid;
404 #ifdef FFP
405 glEnd();
406 #endif
408 return x;
411 Local Variables:
412 c-file-style: "linux"
413 End: