summaryrefslogtreecommitdiff
path: root/platform/gl/gl-font.c
blob: f744fb4824d94cf71d79369cbda9083473496bca (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
/*
 * A very simple font cache and rasterizer that uses FreeType
 * to draw fonts from a single OpenGL texture. The code uses
 * a linear-probe hashtable, and writes new glyphs into
 * the texture using glTexSubImage2D. When the texture fills
 * up, or the hash table gets too crowded, the cache is emptied.
 *
 * This is designed to be used for horizontal text only,
 * and draws unhinted text with subpixel accurate metrics
 * and kerning. As such, you should always call the drawing
 * function with an orthogonal transform that maps units
 * to pixels accurately.
 */

#include "gl-app.h"

#include "mupdf/pdf.h" /* for builtin fonts */

#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_ADVANCES_H

#define PADDING 1		/* set to 0 to save some space but disallow arbitrary transforms */

#define MAXGLYPHS 4093	/* prime number for hash table goodness */
#define CACHESIZE 1024
#define XPRECISION 4
#define YPRECISION 1

struct key
{
	FT_Face face;
	short gid;
	short subx;
	short suby;
};

struct glyph
{
	char lsb, top, w, h;
	short s, t;
	float advance;
};

struct table
{
	struct key key;
	struct glyph glyph;
};

static FT_Library g_freetype_lib = NULL;
static struct table g_table[MAXGLYPHS];
static int g_table_load = 0;
static unsigned int g_cache_tex = 0;
static int g_cache_w = CACHESIZE;
static int g_cache_h = CACHESIZE;
static int g_cache_row_y = 0;
static int g_cache_row_x = 0;
static int g_cache_row_h = 0;

static FT_Face g_helvetica = NULL;
static FT_Face g_droidsansfallback = NULL;

static void clear_font_cache(void)
{
#if PADDING > 0
	unsigned char *zero = malloc(g_cache_w * g_cache_h);
	memset(zero, 0, g_cache_w * g_cache_h);
	glBindTexture(GL_TEXTURE_2D, g_cache_tex);
	glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, g_cache_w, g_cache_h, GL_ALPHA, GL_UNSIGNED_BYTE, zero);
	free(zero);
#endif

	memset(g_table, 0, sizeof(g_table));
	g_table_load = 0;

	g_cache_row_y = PADDING;
	g_cache_row_x = PADDING;
	g_cache_row_h = 0;
}

void ui_init_fonts(fz_context *ctx, float pixelsize)
{
	int fontsize = pixelsize * 64;
	unsigned char *data;
	unsigned int size;
	int code;
	int index;

	code = FT_Init_FreeType(&g_freetype_lib);
	if (code)
		fz_throw(ctx, FZ_ERROR_GENERIC, "cannot initialize freetype");

	glGenTextures(1, &g_cache_tex);
	glBindTexture(GL_TEXTURE_2D, g_cache_tex);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, g_cache_w, g_cache_h, 0, GL_ALPHA, GL_UNSIGNED_BYTE, NULL);

	clear_font_cache();

	data = pdf_lookup_builtin_font(ctx, "Times-Roman", &size);
	code = FT_New_Memory_Face(g_freetype_lib, data, size, 0, &g_helvetica);
	if (code)
		fz_throw(ctx, FZ_ERROR_GENERIC, "cannot load helvetica");

	data = pdf_lookup_substitute_cjk_font(ctx, 0, 0, 0, &size, &index);
	code = FT_New_Memory_Face(g_freetype_lib, data, size, 0, &g_droidsansfallback);
	if (code)
		fz_throw(ctx, FZ_ERROR_GENERIC, "cannot load droid sans fallback");

	FT_Select_Charmap(g_helvetica, ft_encoding_unicode);
	FT_Select_Charmap(g_droidsansfallback, ft_encoding_unicode);

	FT_Set_Char_Size(g_helvetica, fontsize, fontsize, 72, 72);
	FT_Set_Char_Size(g_droidsansfallback, fontsize, fontsize, 72, 72);
}

void ui_finish_fonts(fz_context *ctx)
{
	clear_font_cache();
	FT_Done_Face(g_helvetica);
	FT_Done_Face(g_droidsansfallback);
}

static unsigned int hashfunc(struct key *key)
{
	unsigned char *buf = (unsigned char *)key;
	unsigned int len = sizeof(struct key);
	unsigned int h = 0;
	while (len--)
		h = *buf++ + (h << 6) + (h << 16) - h;
	return h;
}

static unsigned int lookup_table(struct key *key)
{
	unsigned int pos = hashfunc(key) % MAXGLYPHS;
	while (1)
	{
		if (!g_table[pos].key.face) /* empty slot */
			return pos;
		if (!memcmp(key, &g_table[pos].key, sizeof(struct key))) /* matching slot */
			return pos;
		pos = (pos + 1) % MAXGLYPHS;
	}
}

static struct glyph *lookup_glyph(FT_Face face, int gid, int subx, int suby)
{
	FT_Vector subv;
	struct key key;
	unsigned int pos;
	int code;
	int w, h;

	/*
	 * Look it up in the table
	 */

	memset(&key, 0, sizeof key);
	key.face = face;
	key.gid = gid;
	key.subx = subx;
	key.suby = suby;

	pos = lookup_table(&key);
	if (g_table[pos].key.face)
		return &g_table[pos].glyph;

	/*
	 * Render the bitmap
	 */

	glEnd();

	subv.x = subx;
	subv.y = suby;

	FT_Set_Transform(face, NULL, &subv);

	code = FT_Load_Glyph(face, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING);
	if (code < 0)
		return NULL;

	code = FT_Render_Glyph(face->glyph, FT_RENDER_MODE_NORMAL);
	if (code < 0)
		return NULL;

	w = face->glyph->bitmap.width;
	h = face->glyph->bitmap.rows;

	/*
	 * Find an empty slot in the texture
	 */

	if (g_table_load == (MAXGLYPHS * 3) / 4)
	{
		puts("font cache table full, clearing cache");
		clear_font_cache();
		pos = lookup_table(&key);
	}

	if (h + PADDING > g_cache_h || w + PADDING > g_cache_w)
		return NULL;

	if (g_cache_row_x + w + PADDING > g_cache_w)
	{
		g_cache_row_y += g_cache_row_h + PADDING;
		g_cache_row_x = PADDING;
		g_cache_row_h = 0;
	}
	if (g_cache_row_y + h + PADDING > g_cache_h)
	{
		puts("font cache texture full, clearing cache");
		clear_font_cache();
		pos = lookup_table(&key);
	}

	/*
	 * Copy bitmap into texture
	 */

	memcpy(&g_table[pos].key, &key, sizeof(struct key));
	g_table[pos].glyph.w = face->glyph->bitmap.width;
	g_table[pos].glyph.h = face->glyph->bitmap.rows;
	g_table[pos].glyph.lsb = face->glyph->bitmap_left;
	g_table[pos].glyph.top = face->glyph->bitmap_top;
	g_table[pos].glyph.s = g_cache_row_x;
	g_table[pos].glyph.t = g_cache_row_y;
	g_table[pos].glyph.advance = face->glyph->advance.x / 64.0;
	g_table_load ++;

	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, face->glyph->bitmap.pitch);
	glTexSubImage2D(GL_TEXTURE_2D, 0, g_cache_row_x, g_cache_row_y, w, h,
			GL_ALPHA, GL_UNSIGNED_BYTE, face->glyph->bitmap.buffer);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);

	glBegin(GL_QUADS);

	g_cache_row_x += w + PADDING;
	if (g_cache_row_h < h + PADDING)
		g_cache_row_h = h + PADDING;

	return &g_table[pos].glyph;
}

static float ui_draw_glyph(FT_Face face, int gid, float x, float y)
{
	struct glyph *glyph;
	float s0, t0, s1, t1, xc, yc;

	int subx = (x - floor(x)) * XPRECISION;
	int suby = (y - floor(y)) * YPRECISION;
	subx = (subx * 64) / XPRECISION;
	suby = (suby * 64) / YPRECISION;

	glyph = lookup_glyph(face, gid, subx, suby);
	if (!glyph)
		return 0.0;

	s0 = (float) glyph->s / g_cache_w;
	t0 = (float) glyph->t / g_cache_h;
	s1 = (float) (glyph->s + glyph->w) / g_cache_w;
	t1 = (float) (glyph->t + glyph->h) / g_cache_h;
	xc = floor(x) + glyph->lsb;
	yc = floor(y) - glyph->top + glyph->h;

	glTexCoord2f(s0, t0); glVertex2f(xc, yc - glyph->h);
	glTexCoord2f(s1, t0); glVertex2f(xc + glyph->w, yc - glyph->h);
	glTexCoord2f(s1, t1); glVertex2f(xc + glyph->w, yc);
	glTexCoord2f(s0, t1); glVertex2f(xc, yc);

	return glyph->advance;
}

float ui_measure_character(fz_context *ctx, int ucs)
{
	FT_Fixed advance;
	FT_Face face;
	int gid;

	face = g_helvetica;
	gid = FT_Get_Char_Index(face, ucs);
	if (gid <= 0)
	{
		face = g_droidsansfallback;
		gid = FT_Get_Char_Index(face, ucs);
	}

	FT_Get_Advance(face, gid, FT_LOAD_NO_BITMAP | FT_LOAD_NO_HINTING, &advance);
	return advance / 65536.0f;
}

float ui_draw_character(fz_context *ctx, int ucs, float x, float y)
{
	FT_Face face;
	int gid;

	face = g_helvetica;
	gid = FT_Get_Char_Index(face, ucs);
	if (gid <= 0)
	{
		face = g_droidsansfallback;
		gid = FT_Get_Char_Index(face, ucs);
	}

	return ui_draw_glyph(face, gid, x, y);
}

void ui_begin_text(fz_context *ctx)
{
	glBindTexture(GL_TEXTURE_2D, g_cache_tex);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	glEnable(GL_BLEND);
	glEnable(GL_TEXTURE_2D);
	glBegin(GL_QUADS);
}

void ui_end_text(fz_context *ctx)
{
	glEnd();
	glDisable(GL_TEXTURE_2D);
	glDisable(GL_BLEND);
}

float ui_draw_string(fz_context *ctx, float x, float y, const char *str)
{
	int ucs;

	ui_begin_text(ctx);

	while (*str)
	{
		str += fz_chartorune(&ucs, str);
		x += ui_draw_character(ctx, ucs, x, y);
	}

	ui_end_text(ctx);

	return x;
}

float ui_measure_string(fz_context *ctx, char *str)
{
	int ucs;
	float x = 0;

	ui_begin_text(ctx);

	while (*str)
	{
		str += fz_chartorune(&ucs, str);
		x += ui_measure_character(ctx, ucs);
	}

	ui_end_text(ctx);

	return x;
}