1 /* This is a slightly modified
2 https://github.com/ccxvii/snippets/blob/master/glfont.c by Tor Andersson
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 */
44 signed char lsb
, top
, w
, h
;
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)
69 code
= FT_Init_FreeType(&g_freetype_lib
);
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)
85 unsigned char *zero
= calloc(g_cache_w
, g_cache_h
);
87 err(1, "malloc zero (%u bytes failed)", g_cache_w
* g_cache_h
);
88 glBindTexture(GL_TEXTURE_2D
, g_cache_tex
);
89 glTexSubImage2D(GL_TEXTURE_2D
, 0, 0, 0, g_cache_w
, g_cache_h
, GL_ALPHA
, GL_UNSIGNED_BYTE
, zero
);
93 memset(g_table
, 0, sizeof(g_table
));
96 g_cache_row_y
= PADDING
;
97 g_cache_row_x
= PADDING
;
101 static FT_Face
load_font(char *fontname
)
106 if (g_freetype_lib
== NULL
)
112 code
= FT_New_Face (g_freetype_lib
, fontname
, 0, &face
);
114 fprintf (stderr
, "failed to load font `%s'\n", fontname
);
118 FT_Select_Charmap(face
, ft_encoding_unicode
);
122 static FT_Face
load_builtin_font(void *base
, int len
)
127 if (g_freetype_lib
== NULL
)
133 code
= FT_New_Memory_Face(g_freetype_lib
, base
, len
, 0, &face
);
135 fprintf (stderr
, "failed to load builtin font\n");
139 FT_Select_Charmap(face
, ft_encoding_unicode
);
143 static void UNUSED
free_font(FT_Face face
)
149 static unsigned int hashfunc(struct key
*key
)
151 unsigned char *buf
= (unsigned char *)key
;
152 unsigned int len
= sizeof(struct key
);
155 h
= *buf
++ + (h
<< 6) + (h
<< 16) - h
;
159 static unsigned int lookup_table(struct key
*key
)
161 unsigned int pos
= hashfunc(key
) % MAXGLYPHS
;
164 if (!g_table
[pos
].key
.face
) /* empty slot */
166 if (!memcmp(key
, &g_table
[pos
].key
, sizeof(struct key
))) /* matching slot */
168 pos
= (pos
+ 1) % MAXGLYPHS
;
172 static struct glyph
* lookup_glyph(FT_Face face
, int size
, int gid
, int subx
, int suby
)
181 * Look it up in the table
190 pos
= lookup_table(&key
);
191 if (g_table
[pos
].key
.face
)
192 return &g_table
[pos
].glyph
;
203 FT_Set_Transform(face
, NULL
, &subv
);
205 code
= FT_Load_Glyph(face
, gid
, FT_LOAD_NO_BITMAP
| FT_LOAD_NO_HINTING
);
209 code
= FT_Render_Glyph(face
->glyph
, FT_RENDER_MODE_LIGHT
);
213 w
= face
->glyph
->bitmap
.width
;
214 h
= face
->glyph
->bitmap
.rows
;
217 * Find an empty slot in the texture
220 if (g_table_load
== (MAXGLYPHS
* 3) / 4)
222 lprintf("font cache table full, clearing cache");
224 pos
= lookup_table(&key
);
227 if (h
+ PADDING
> g_cache_h
|| w
+ PADDING
> g_cache_w
)
228 errx(1, "rendered glyph exceeds cache dimensions");
230 if (g_cache_row_x
+ w
+ PADDING
> g_cache_w
)
232 g_cache_row_y
+= g_cache_row_h
+ PADDING
;
233 g_cache_row_x
= PADDING
;
235 if (g_cache_row_y
+ h
+ PADDING
> g_cache_h
)
237 lprintf("font cache texture full, clearing cache");
239 pos
= lookup_table(&key
);
243 * Copy bitmap into texture
246 memcpy(&g_table
[pos
].key
, &key
, sizeof(struct key
));
247 g_table
[pos
].glyph
.w
= face
->glyph
->bitmap
.width
;
248 g_table
[pos
].glyph
.h
= face
->glyph
->bitmap
.rows
;
249 g_table
[pos
].glyph
.lsb
= face
->glyph
->bitmap_left
;
250 g_table
[pos
].glyph
.top
= face
->glyph
->bitmap_top
;
251 g_table
[pos
].glyph
.s
= g_cache_row_x
;
252 g_table
[pos
].glyph
.t
= g_cache_row_y
;
253 g_table
[pos
].glyph
.advance
= face
->glyph
->advance
.x
/ 64.0;
256 glPixelStorei(GL_UNPACK_ALIGNMENT
, 1);
257 glPixelStorei(GL_UNPACK_ROW_LENGTH
, face
->glyph
->bitmap
.pitch
);
258 glTexSubImage2D(GL_TEXTURE_2D
, 0, g_cache_row_x
, g_cache_row_y
, w
, h
,
259 GL_ALPHA
, GL_UNSIGNED_BYTE
, face
->glyph
->bitmap
.buffer
);
260 glPixelStorei(GL_UNPACK_ROW_LENGTH
, 0);
264 g_cache_row_x
+= w
+ PADDING
;
265 if (g_cache_row_h
< h
+ PADDING
)
266 g_cache_row_h
= h
+ PADDING
;
268 return &g_table
[pos
].glyph
;
271 static float draw_glyph(FT_Face face
, int size
, int gid
, float x
, float y
)
274 int subx
= (x
- floor(x
)) * XPRECISION
;
275 int suby
= (y
- floor(y
)) * YPRECISION
;
276 subx
= (subx
* 64) / XPRECISION
;
277 suby
= (suby
* 64) / YPRECISION
;
279 glyph
= lookup_glyph(face
, size
, gid
, subx
, suby
);
283 float s0
= (float) glyph
->s
/ g_cache_w
;
284 float t0
= (float) glyph
->t
/ g_cache_h
;
285 float s1
= (float) (glyph
->s
+ glyph
->w
) / g_cache_w
;
286 float t1
= (float) (glyph
->t
+ glyph
->h
) / g_cache_h
;
287 float xc
= floor(x
) + glyph
->lsb
;
288 float yc
= floor(y
) - glyph
->top
+ glyph
->h
;
290 glTexCoord2f(s0
, t0
); glVertex2f(xc
, yc
- glyph
->h
);
291 glTexCoord2f(s1
, t0
); glVertex2f(xc
+ glyph
->w
, yc
- glyph
->h
);
292 glTexCoord2f(s1
, t1
); glVertex2f(xc
+ glyph
->w
, yc
);
293 glTexCoord2f(s0
, t1
); glVertex2f(xc
, yc
);
295 return glyph
->advance
;
298 static float measure_string(FT_Face face
, float fsize
, char *str
)
300 int size
= fsize
* 64;
307 FT_Set_Char_Size(face
, size
, size
, 72, 72);
311 str
+= chartorune(&ucs
, str
);
312 gid
= FT_Get_Char_Index(face
, ucs
);
313 FT_Get_Advance(face
, gid
, FT_LOAD_NO_BITMAP
| FT_LOAD_NO_HINTING
, &advance
);
314 w
+= advance
/ 65536.0;
315 FT_Get_Kerning(face
, left
, gid
, FT_KERNING_UNFITTED
, &kern
);
323 static float draw_string(FT_Face face
, float fsize
, float x
, float y
, char *str
)
325 int size
= fsize
* 64;
330 FT_Set_Char_Size(face
, size
, size
, 72, 72);
332 glBindTexture(GL_TEXTURE_2D
, g_cache_tex
);
337 str
+= chartorune(&ucs
, str
);
338 gid
= FT_Get_Char_Index(face
, ucs
);
339 x
+= draw_glyph(face
, size
, gid
, x
, y
);
340 FT_Get_Kerning(face
, left
, gid
, FT_KERNING_UNFITTED
, &kern
);