Fix keymap saving (again)
[llpp.git] / glfont.c
blob58552038aa6ceadac61472a9aefb35449da9d59e
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;
65 static void init_font_cache(void)
67 int code;
69 code = FT_Init_FreeType(&g_freetype_lib);
70 if (code)
71 errx(1, "cannot initialize freetype");
73 glGenTextures(1, &g_cache_tex);
74 glBindTexture(GL_TEXTURE_2D, g_cache_tex);
75 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
76 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
77 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
78 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
79 glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, g_cache_w, g_cache_h, 0, GL_ALPHA, GL_UNSIGNED_BYTE, NULL);
82 static void clear_font_cache(void)
84 #if PADDING > 0
85 unsigned char *zero = malloc(g_cache_w * g_cache_h);
86 memset(zero, 0, g_cache_w * g_cache_h);
87 glBindTexture(GL_TEXTURE_2D, g_cache_tex);
88 glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, g_cache_w, g_cache_h, GL_ALPHA, GL_UNSIGNED_BYTE, zero);
89 free(zero);
90 #endif
92 memset(g_table, 0, sizeof(g_table));
93 g_table_load = 0;
95 g_cache_row_y = PADDING;
96 g_cache_row_x = PADDING;
97 g_cache_row_h = 0;
100 static FT_Face load_font(char *fontname)
102 FT_Face face;
103 int code;
105 if (g_freetype_lib == NULL)
107 init_font_cache();
108 clear_font_cache();
111 code = FT_New_Face (g_freetype_lib, fontname, 0, &face);
112 if (code) {
113 fprintf (stderr, "failed to load font `%s'\n", fontname);
114 return NULL;
117 FT_Select_Charmap(face, ft_encoding_unicode);
118 return face;
121 static FT_Face load_builtin_font(void *base, int len)
123 FT_Face face;
124 int code;
126 if (g_freetype_lib == NULL)
128 init_font_cache();
129 clear_font_cache();
132 code = FT_New_Memory_Face(g_freetype_lib, base, len, 0, &face);
133 if (code) {
134 fprintf (stderr, "failed to load builtin font\n");
135 return NULL;
138 FT_Select_Charmap(face, ft_encoding_unicode);
139 return face;
142 static void UNUSED free_font(FT_Face face)
144 clear_font_cache();
145 FT_Done_Face(face);
148 static unsigned int hashfunc(struct key *key)
150 unsigned char *buf = (unsigned char *)key;
151 unsigned int len = sizeof(struct key);
152 unsigned int h = 0;
153 while (len--)
154 h = *buf++ + (h << 6) + (h << 16) - h;
155 return h;
158 static unsigned int lookup_table(struct key *key)
160 unsigned int pos = hashfunc(key) % MAXGLYPHS;
161 while (1)
163 if (!g_table[pos].key.face) /* empty slot */
164 return pos;
165 if (!memcmp(key, &g_table[pos].key, sizeof(struct key))) /* matching slot */
166 return pos;
167 pos = (pos + 1) % MAXGLYPHS;
171 static struct glyph * lookup_glyph(FT_Face face, int size, int gid, int subx, int suby)
173 FT_Vector subv;
174 struct key key;
175 unsigned int pos;
176 int code;
177 int w, h;
180 * Look it up in the table
183 key.face = face;
184 key.size = size;
185 key.gid = gid;
186 key.subx = subx;
187 key.suby = suby;
189 pos = lookup_table(&key);
190 if (g_table[pos].key.face)
191 return &g_table[pos].glyph;
194 * Render the bitmap
197 glEnd();
199 subv.x = subx;
200 subv.y = suby;
202 FT_Set_Transform(face, NULL, &subv);
204 code = FT_Load_Glyph(face, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING);
205 if (code < 0)
206 return NULL;
208 code = FT_Render_Glyph(face->glyph, FT_RENDER_MODE_LIGHT);
209 if (code < 0)
210 return NULL;
212 w = face->glyph->bitmap.width;
213 h = face->glyph->bitmap.rows;
216 * Find an empty slot in the texture
219 if (g_table_load == (MAXGLYPHS * 3) / 4)
221 lprintf("font cache table full, clearing cache");
222 clear_font_cache();
223 pos = lookup_table(&key);
226 if (h + PADDING > g_cache_h || w + PADDING > g_cache_w)
227 errx(1, "rendered glyph exceeds cache dimensions");
229 if (g_cache_row_x + w + PADDING > g_cache_w)
231 g_cache_row_y += g_cache_row_h + PADDING;
232 g_cache_row_x = PADDING;
234 if (g_cache_row_y + h + PADDING > g_cache_h)
236 lprintf("font cache texture full, clearing cache");
237 clear_font_cache();
238 pos = lookup_table(&key);
242 * Copy bitmap into texture
245 memcpy(&g_table[pos].key, &key, sizeof(struct key));
246 g_table[pos].glyph.w = face->glyph->bitmap.width;
247 g_table[pos].glyph.h = face->glyph->bitmap.rows;
248 g_table[pos].glyph.lsb = face->glyph->bitmap_left;
249 g_table[pos].glyph.top = face->glyph->bitmap_top;
250 g_table[pos].glyph.s = g_cache_row_x;
251 g_table[pos].glyph.t = g_cache_row_y;
252 g_table[pos].glyph.advance = face->glyph->advance.x / 64.0;
253 g_table_load ++;
255 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
256 glPixelStorei(GL_UNPACK_ROW_LENGTH, face->glyph->bitmap.pitch);
257 glTexSubImage2D(GL_TEXTURE_2D, 0, g_cache_row_x, g_cache_row_y, w, h,
258 GL_ALPHA, GL_UNSIGNED_BYTE, face->glyph->bitmap.buffer);
259 glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
261 glBegin(GL_QUADS);
263 g_cache_row_x += w + PADDING;
264 if (g_cache_row_h < h + PADDING)
265 g_cache_row_h = h + PADDING;
267 return &g_table[pos].glyph;
270 static float draw_glyph(FT_Face face, int size, int gid, float x, float y)
272 struct glyph *glyph;
273 int subx = (x - floor(x)) * XPRECISION;
274 int suby = (y - floor(y)) * YPRECISION;
275 subx = (subx * 64) / XPRECISION;
276 suby = (suby * 64) / YPRECISION;
278 glyph = lookup_glyph(face, size, gid, subx, suby);
279 if (!glyph)
280 return 0.0;
282 float s0 = (float) glyph->s / g_cache_w;
283 float t0 = (float) glyph->t / g_cache_h;
284 float s1 = (float) (glyph->s + glyph->w) / g_cache_w;
285 float t1 = (float) (glyph->t + glyph->h) / g_cache_h;
286 float xc = floor(x) + glyph->lsb;
287 float yc = floor(y) - glyph->top + glyph->h;
289 glTexCoord2f(s0, t0); glVertex2f(xc, yc - glyph->h);
290 glTexCoord2f(s1, t0); glVertex2f(xc + glyph->w, yc - glyph->h);
291 glTexCoord2f(s1, t1); glVertex2f(xc + glyph->w, yc);
292 glTexCoord2f(s0, t1); glVertex2f(xc, yc);
294 return glyph->advance;
297 static float measure_string(FT_Face face, float fsize, char *str)
299 int size = fsize * 64;
300 FT_Fixed advance;
301 FT_Vector kern;
302 Rune ucs, gid;
303 float w = 0.0;
304 int left = 0;
306 FT_Set_Char_Size(face, size, size, 72, 72);
308 while (*str)
310 str += chartorune(&ucs, str);
311 gid = FT_Get_Char_Index(face, ucs);
312 FT_Get_Advance(face, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING, &advance);
313 w += advance / 65536.0;
314 FT_Get_Kerning(face, left, gid, FT_KERNING_UNFITTED, &kern);
315 w += kern.x / 64.0;
316 left = gid;
319 return w;
322 static float draw_string(FT_Face face, float fsize, float x, float y, char *str)
324 int size = fsize * 64;
325 FT_Vector kern;
326 Rune ucs, gid;
327 int left = 0;
329 FT_Set_Char_Size(face, size, size, 72, 72);
331 glBindTexture(GL_TEXTURE_2D, g_cache_tex);
332 glBegin(GL_QUADS);
334 while (*str)
336 str += chartorune(&ucs, str);
337 gid = FT_Get_Char_Index(face, ucs);
338 x += draw_glyph(face, size, gid, x, y);
339 FT_Get_Kerning(face, left, gid, FT_KERNING_UNFITTED, &kern);
340 x += kern.x / 64.0;
341 left = gid;
344 glEnd();
346 return x;