summaryrefslogtreecommitdiff
path: root/source/pdf/pdf-layer.c
blob: 189b823bd71f95650cd969081b5804b9f7f6acb9 (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
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
#include "mupdf/fitz.h"
#include "mupdf/pdf.h"
#include "pdf-imp.h"

#include <string.h>

/*
	Notes on OCGs etc.

	PDF Documents may contain Optional Content Groups. Which of
	these is shown at any given time is dependent on which
	Optional Content Configuration Dictionary is in force at the
	time.

	A pdf_document, once loaded, contains some state saying which
	OCGs are enabled/disabled, and which 'Intent' (or 'Intents')
	a file is being used for. This information is held outside of
	the actual PDF file.

	An Intent (just 'View' or 'Design' or 'All', according to
	PDF 2.0, but theoretically more) says which OCGs to consider
	or ignore in calculating the visibility of content. The
	Intent (or Intents, for there can be an array) is set by the
	current OCCD.

	When first loaded, we turn all OCGs on, then load the default
	OCCD. This may turn some OCGs off, and sets the document Intent.

	Callers can ask how many OCCDs there are, read the names/creators
	for each, and then select any one of them. That updates which
	OCGs are selected, and resets the Intent.

	Once an OCCD has been selected, a caller can enumerate the
	'displayable configuration'. This is a list of labels/radio
	buttons/check buttons that can be used to enable/disable
	given OCGs. The caller can then enable/disable OCGs by
	asking to select (or toggle) given entries in that list.

	Thus the handling of radio button groups, and 'locked'
	elements is kept within the core of MuPDF.

	Finally, the caller can set the 'usage' for a document. This
	can be 'View', 'Print', or 'Export'.
*/

typedef struct
{
	pdf_obj *obj;
	int state;
} pdf_ocg_entry;

typedef struct
{
	int ocg;
	const char *name;
	int depth;
	unsigned int button_flags : 2;
	unsigned int locked : 1;
} pdf_ocg_ui;

struct pdf_ocg_descriptor_s
{
	int current;
	int num_configs;

	int len;
	pdf_ocg_entry *ocgs;

	pdf_obj *intent;
	const char *usage;

	int num_ui_entries;
	pdf_ocg_ui *ui;
};

int
pdf_count_layer_configs(fz_context *ctx, pdf_document *doc)
{
	/* If no OCProperties, then no OCGs */
	if (!doc || !doc->ocg)
		return 0;
	return doc->ocg->num_configs;
}

static int
count_entries(fz_context *ctx, pdf_obj *obj)
{
	int len = pdf_array_len(ctx, obj);
	int i;
	int count = 0;

	for (i = 0; i < len; i++)
	{
		pdf_obj *o = pdf_array_get(ctx, obj, i);
		if (pdf_mark_obj(ctx, o))
			continue;
		fz_try(ctx)
			count += (pdf_is_array(ctx, o) ? count_entries(ctx, o) : 1);
		fz_always(ctx)
			pdf_unmark_obj(ctx, o);
		fz_catch(ctx)
			fz_rethrow(ctx);
	}
	return count;
}

static pdf_ocg_ui *
populate_ui(fz_context *ctx, pdf_ocg_descriptor *desc, pdf_ocg_ui *ui, pdf_obj *order, int depth, pdf_obj *rbgroups, pdf_obj *locked)
{
	int len = pdf_array_len(ctx, order);
	int i, j;

	for (i = 0; i < len; i++)
	{
		pdf_obj *o = pdf_array_get(ctx, order, i);
		if (pdf_is_array(ctx, o))
		{
			if (pdf_mark_obj(ctx, o))
				continue;

			fz_try(ctx)
				ui = populate_ui(ctx, desc, ui, o, depth+1, rbgroups, locked);
			fz_always(ctx)
				pdf_unmark_obj(ctx, o);
			fz_catch(ctx)
				fz_rethrow(ctx);

			continue;
		}
		ui->depth = depth;
		if (pdf_is_string(ctx, o))
		{
			ui->ocg = -1;
			ui->name = pdf_to_str_buf(ctx, o);
			ui->button_flags = PDF_LAYER_UI_LABEL;
			ui->locked = 1;
			ui++;
			continue;
		}

		for (j = 0; j < desc->len; j++)
		{
			if (!pdf_objcmp_resolve(ctx, o, desc->ocgs[j].obj))
				break;
		}
		if (j == desc->len)
			continue; /* OCG not found in main list! Just ignore it */
		ui->ocg = j;
		ui->name = pdf_dict_get_string(ctx, o, PDF_NAME(Name), NULL);
		ui->button_flags = pdf_array_contains(ctx, o, rbgroups) ? PDF_LAYER_UI_RADIOBOX : PDF_LAYER_UI_CHECKBOX;
		ui->locked = pdf_array_contains(ctx, o, locked);
		ui++;
	}
	return ui;
}

static void
drop_ui(fz_context *ctx, pdf_ocg_descriptor *desc)
{
	if (!desc)
		return;

	fz_free(ctx, desc->ui);
	desc->ui = NULL;
}

static void
load_ui(fz_context *ctx, pdf_ocg_descriptor *desc, pdf_obj *ocprops, pdf_obj *occg)
{
	pdf_obj *order;
	pdf_obj *rbgroups;
	pdf_obj *locked;
	int count;

	/* Count the number of entries */
	order = pdf_dict_get(ctx, occg, PDF_NAME(Order));
	if (!order)
		order = pdf_dict_getp(ctx, ocprops, "D/Order");
	count = count_entries(ctx, order);
	rbgroups = pdf_dict_get(ctx, occg, PDF_NAME(RBGroups));
	if (!rbgroups)
		rbgroups = pdf_dict_getp(ctx, ocprops, "D/RBGroups");
	locked = pdf_dict_get(ctx, occg, PDF_NAME(Locked));

	desc->num_ui_entries = count;
	desc->ui = Memento_label(fz_calloc(ctx, count, sizeof(pdf_ocg_ui)), "pdf_ocg_ui");
	fz_try(ctx)
	{
		(void)populate_ui(ctx, desc, desc->ui, order, 0, rbgroups, locked);
	}
	fz_catch(ctx)
	{
		drop_ui(ctx, desc);
		fz_rethrow(ctx);
	}
}

void
pdf_select_layer_config(fz_context *ctx, pdf_document *doc, int config)
{
	int i, j, len, len2;
	pdf_ocg_descriptor *desc = doc->ocg;
	pdf_obj *obj, *cobj;
	pdf_obj *name;

	obj = pdf_dict_get(ctx, pdf_dict_get(ctx, pdf_trailer(ctx, doc), PDF_NAME(Root)), PDF_NAME(OCProperties));
	if (!obj)
	{
		if (config == 0)
			return;
		else
			fz_throw(ctx, FZ_ERROR_GENERIC, "Unknown Layer config (None known!)");
	}

	cobj = pdf_array_get(ctx, pdf_dict_get(ctx, obj, PDF_NAME(Configs)), config);
	if (!cobj)
	{
		if (config != 0)
			fz_throw(ctx, FZ_ERROR_GENERIC, "Illegal Layer config");
		cobj = pdf_dict_get(ctx, obj, PDF_NAME(D));
		if (!cobj)
			fz_throw(ctx, FZ_ERROR_GENERIC, "No default Layer config");
	}

	pdf_drop_obj(ctx, desc->intent);
	desc->intent = pdf_keep_obj(ctx, pdf_dict_get(ctx, cobj, PDF_NAME(Intent)));

	len = desc->len;
	name = pdf_dict_get(ctx, cobj, PDF_NAME(BaseState));
	if (pdf_name_eq(ctx, name, PDF_NAME(Unchanged)))
	{
		/* Do nothing */
	}
	else if (pdf_name_eq(ctx, name, PDF_NAME(OFF)))
	{
		for (i = 0; i < len; i++)
		{
			desc->ocgs[i].state = 0;
		}
	}
	else /* Default to ON */
	{
		for (i = 0; i < len; i++)
		{
			desc->ocgs[i].state = 1;
		}
	}

	obj = pdf_dict_get(ctx, cobj, PDF_NAME(ON));
	len2 = pdf_array_len(ctx, obj);
	for (i = 0; i < len2; i++)
	{
		pdf_obj *o = pdf_array_get(ctx, obj, i);
		for (j=0; j < len; j++)
		{
			if (!pdf_objcmp_resolve(ctx, desc->ocgs[j].obj, o))
			{
				desc->ocgs[j].state = 1;
				break;
			}
		}
	}

	obj = pdf_dict_get(ctx, cobj, PDF_NAME(OFF));
	len2 = pdf_array_len(ctx, obj);
	for (i = 0; i < len2; i++)
	{
		pdf_obj *o = pdf_array_get(ctx, obj, i);
		for (j=0; j < len; j++)
		{
			if (!pdf_objcmp_resolve(ctx, desc->ocgs[j].obj, o))
			{
				desc->ocgs[j].state = 0;
				break;
			}
		}
	}

	desc->current = config;

	drop_ui(ctx, desc);
	load_ui(ctx, desc, obj, cobj);
}

void
pdf_layer_config_info(fz_context *ctx, pdf_document *doc, int config_num, pdf_layer_config *info)
{
	pdf_obj *ocprops;
	pdf_obj *obj;

	if (!info)
		return;

	info->name = NULL;
	info->creator = NULL;

	if (doc == NULL || doc->ocg == NULL)
		return;
	if (config_num < 0 || config_num >= doc->ocg->num_configs)
		fz_throw(ctx, FZ_ERROR_GENERIC, "Invalid layer config number");

	ocprops = pdf_dict_getp(ctx, pdf_trailer(ctx, doc), "Root/OCProperties");
	if (!ocprops)
		return;

	obj = pdf_dict_get(ctx, ocprops, PDF_NAME(Configs));
	if (pdf_is_array(ctx, obj))
		obj = pdf_array_get(ctx, obj, config_num);
	else if (config_num == 0)
		obj = pdf_dict_get(ctx, ocprops, PDF_NAME(D));
	else
		fz_throw(ctx, FZ_ERROR_GENERIC, "Invalid layer config number");

	info->creator = pdf_dict_get_string(ctx, obj, PDF_NAME(Creator), NULL);
	info->name = pdf_dict_get_string(ctx, obj, PDF_NAME(Name), NULL);
}

void
pdf_drop_ocg(fz_context *ctx, pdf_document *doc)
{
	pdf_ocg_descriptor *desc;
	int i;

	if (!doc)
		return;
	desc = doc->ocg;
	if (!desc)
		return;

	drop_ui(ctx, desc);
	pdf_drop_obj(ctx, desc->intent);
	for (i = 0; i < desc->len; i++)
		pdf_drop_obj(ctx, desc->ocgs[i].obj);
	fz_free(ctx, desc->ocgs);
	fz_free(ctx, desc);
}

static void
clear_radio_group(fz_context *ctx, pdf_document *doc, pdf_obj *ocg)
{
	pdf_obj *rbgroups = pdf_dict_getp(ctx, pdf_trailer(ctx, doc), "Root/OCProperties/RBGroups");
	int len, i;

	len = pdf_array_len(ctx, rbgroups);
	for (i = 0; i < len; i++)
	{
		pdf_obj *group = pdf_array_get(ctx, rbgroups, i);

		if (pdf_array_contains(ctx, ocg, group))
		{
			int len2 = pdf_array_len(ctx, group);
			int j;

			for (j = 0; j < len2; j++)
			{
				pdf_obj *g = pdf_array_get(ctx, group, j);
				int k;
				for (k = 0; k < doc->ocg->len; k++)
				{
					pdf_ocg_entry *s = &doc->ocg->ocgs[k];

					if (!pdf_objcmp_resolve(ctx, s->obj, g))
						s->state = 0;
				}
			}
		}
	}
}

int pdf_count_layer_config_ui(fz_context *ctx, pdf_document *doc)
{
	if (doc == NULL || doc->ocg == NULL)
		return 0;

	return doc->ocg->num_ui_entries;
}

void pdf_select_layer_config_ui(fz_context *ctx, pdf_document *doc, int ui)
{
	pdf_ocg_ui *entry;

	if (doc == NULL || doc->ocg == NULL)
		return;

	if (ui < 0 || ui >= doc->ocg->num_ui_entries)
		fz_throw(ctx, FZ_ERROR_GENERIC, "Out of range UI entry selected");

	entry = &doc->ocg->ui[ui];
	if (entry->button_flags != PDF_LAYER_UI_RADIOBOX &&
		entry->button_flags != PDF_LAYER_UI_CHECKBOX)
		return;
	if (entry->locked)
		return;

	if (entry->button_flags == PDF_LAYER_UI_RADIOBOX)
		clear_radio_group(ctx, doc, doc->ocg->ocgs[entry->ocg].obj);

	doc->ocg->ocgs[entry->ocg].state = 1;
}

void pdf_toggle_layer_config_ui(fz_context *ctx, pdf_document *doc, int ui)
{
	pdf_ocg_ui *entry;
	int selected;

	if (doc == NULL || doc->ocg == NULL)
		return;

	if (ui < 0 || ui >= doc->ocg->num_ui_entries)
		fz_throw(ctx, FZ_ERROR_GENERIC, "Out of range UI entry toggled");

	entry = &doc->ocg->ui[ui];
	if (entry->button_flags != PDF_LAYER_UI_RADIOBOX &&
		entry->button_flags != PDF_LAYER_UI_CHECKBOX)
		return;
	if (entry->locked)
		return;

	selected = doc->ocg->ocgs[entry->ocg].state;

	if (entry->button_flags == PDF_LAYER_UI_RADIOBOX)
		clear_radio_group(ctx, doc, doc->ocg->ocgs[entry->ocg].obj);

	doc->ocg->ocgs[entry->ocg].state = !selected;
}

void pdf_deselect_layer_config_ui(fz_context *ctx, pdf_document *doc, int ui)
{
	pdf_ocg_ui *entry;

	if (doc == NULL || doc->ocg == NULL)
		return;

	if (ui < 0 || ui >= doc->ocg->num_ui_entries)
		fz_throw(ctx, FZ_ERROR_GENERIC, "Out of range UI entry deselected");

	entry = &doc->ocg->ui[ui];
	if (entry->button_flags != PDF_LAYER_UI_RADIOBOX &&
		entry->button_flags != PDF_LAYER_UI_CHECKBOX)
		return;
	if (entry->locked)
		return;

	doc->ocg->ocgs[entry->ocg].state = 0;
}

void
pdf_layer_config_ui_info(fz_context *ctx, pdf_document *doc, int ui, pdf_layer_config_ui *info)
{
	pdf_ocg_ui *entry;

	if (!info)
		return;

	info->depth = 0;
	info->locked = 0;
	info->selected = 0;
	info->text = NULL;
	info->type = 0;

	if (doc == NULL || doc->ocg == NULL)
		return;

	if (ui < 0 || ui >= doc->ocg->num_ui_entries)
		fz_throw(ctx, FZ_ERROR_GENERIC, "Out of range UI entry selected");

	entry = &doc->ocg->ui[ui];
	info->type = entry->button_flags;
	info->depth = entry->depth;
	info->selected = doc->ocg->ocgs[entry->ocg].state;
	info->locked = entry->locked;
	info->text = entry->name;
}

static int
ocg_intents_include(fz_context *ctx, pdf_ocg_descriptor *desc, const char *name)
{
	int i, len;

	if (strcmp(name, "All") == 0)
		return 1;

	/* In the absence of a specified intent, it's 'View' */
	if (!desc->intent)
		return (strcmp(name, "View") == 0);

	if (pdf_is_name(ctx, desc->intent))
	{
		const char *intent = pdf_to_name(ctx, desc->intent);
		if (strcmp(intent, "All") == 0)
			return 1;
		return (strcmp(intent, name) == 0);
	}
	if (!pdf_is_array(ctx, desc->intent))
		return 0;

	len = pdf_array_len(ctx, desc->intent);
	for (i=0; i < len; i++)
	{
		const char *intent = pdf_to_name(ctx, pdf_array_get(ctx, desc->intent, i));
		if (strcmp(intent, "All") == 0)
			return 1;
		if (strcmp(intent, name) == 0)
			return 1;
	}
	return 0;
}

int
pdf_is_hidden_ocg(fz_context *ctx, pdf_ocg_descriptor *desc, pdf_obj *rdb, const char *usage, pdf_obj *ocg)
{
	char event_state[16];
	pdf_obj *obj, *obj2, *type;

	/* Avoid infinite recursions */
	if (pdf_obj_marked(ctx, ocg))
		return 0;

	/* If no usage, everything is visible */
	if (!usage)
		return 0;

	/* If no ocg descriptor, everything is visible */
	if (!desc)
		return 0;

	/* If we've been handed a name, look it up in the properties. */
	if (pdf_is_name(ctx, ocg))
	{
		ocg = pdf_dict_get(ctx, pdf_dict_get(ctx, rdb, PDF_NAME(Properties)), ocg);
	}
	/* If we haven't been given an ocg at all, then we're visible */
	if (!ocg)
		return 0;

	fz_strlcpy(event_state, usage, sizeof event_state);
	fz_strlcat(event_state, "State", sizeof event_state);

	type = pdf_dict_get(ctx, ocg, PDF_NAME(Type));

	if (pdf_name_eq(ctx, type, PDF_NAME(OCG)))
	{
		/* An Optional Content Group */
		int default_value = 0;
		int len = desc->len;
		int i;
		pdf_obj *es;

		/* by default an OCG is visible, unless it's explicitly hidden */
		for (i = 0; i < len; i++)
		{
			if (!pdf_objcmp_resolve(ctx, desc->ocgs[i].obj, ocg))
			{
				default_value = !desc->ocgs[i].state;
				break;
			}
		}

		/* Check Intents; if our intent is not part of the set given
		 * by the current config, we should ignore it. */
		obj = pdf_dict_get(ctx, ocg, PDF_NAME(Intent));
		if (pdf_is_name(ctx, obj))
		{
			/* If it doesn't match, it's hidden */
			if (ocg_intents_include(ctx, desc, pdf_to_name(ctx, obj)) == 0)
				return 1;
		}
		else if (pdf_is_array(ctx, obj))
		{
			int match = 0;
			len = pdf_array_len(ctx, obj);
			for (i=0; i<len; i++) {
				match |= ocg_intents_include(ctx, desc, pdf_to_name(ctx, pdf_array_get(ctx, obj, i)));
				if (match)
					break;
			}
			/* If we don't match any, it's hidden */
			if (match == 0)
				return 1;
		}
		else
		{
			/* If it doesn't match, it's hidden */
			if (ocg_intents_include(ctx, desc, "View") == 0)
				return 1;
		}

		/* FIXME: Currently we do a very simple check whereby we look
		 * at the Usage object (an Optional Content Usage Dictionary)
		 * and check to see if the corresponding 'event' key is on
		 * or off.
		 *
		 * Really we should only look at Usage dictionaries that
		 * correspond to entries in the AS list in the OCG config.
		 * Given that we don't handle Zoom or User, or Language
		 * dicts, this is not really a problem. */
		obj = pdf_dict_get(ctx, ocg, PDF_NAME(Usage));
		if (!pdf_is_dict(ctx, obj))
			return default_value;
		/* FIXME: Should look at Zoom (and return hidden if out of
		 * max/min range) */
		/* FIXME: Could provide hooks to the caller to check if
		 * User is appropriate - if not return hidden. */
		obj2 = pdf_dict_gets(ctx, obj, usage);
		es = pdf_dict_gets(ctx, obj2, event_state);
		if (pdf_name_eq(ctx, es, PDF_NAME(OFF)))
		{
			return 1;
		}
		if (pdf_name_eq(ctx, es, PDF_NAME(ON)))
		{
			return 0;
		}
		return default_value;
	}
	else if (pdf_name_eq(ctx, type, PDF_NAME(OCMD)))
	{
		/* An Optional Content Membership Dictionary */
		pdf_obj *name;
		int combine, on = 0;

		obj = pdf_dict_get(ctx, ocg, PDF_NAME(VE));
		if (pdf_is_array(ctx, obj)) {
			/* FIXME: Calculate visibility from array */
			return 0;
		}
		name = pdf_dict_get(ctx, ocg, PDF_NAME(P));
		/* Set combine; Bit 0 set => AND, Bit 1 set => true means
		 * Off, otherwise true means On */
		if (pdf_name_eq(ctx, name, PDF_NAME(AllOn)))
		{
			combine = 1;
		}
		else if (pdf_name_eq(ctx, name, PDF_NAME(AnyOff)))
		{
			combine = 2;
		}
		else if (pdf_name_eq(ctx, name, PDF_NAME(AllOff)))
		{
			combine = 3;
		}
		else /* Assume it's the default (AnyOn) */
		{
			combine = 0;
		}

		if (pdf_mark_obj(ctx, ocg))
			return 0; /* Should never happen */
		fz_try(ctx)
		{
			obj = pdf_dict_get(ctx, ocg, PDF_NAME(OCGs));
			on = combine & 1;
			if (pdf_is_array(ctx, obj)) {
				int i, len;
				len = pdf_array_len(ctx, obj);
				for (i = 0; i < len; i++)
				{
					int hidden = pdf_is_hidden_ocg(ctx, desc, rdb, usage, pdf_array_get(ctx, obj, i));
					if ((combine & 1) == 0)
						hidden = !hidden;
					if (combine & 2)
						on &= hidden;
					else
						on |= hidden;
				}
			}
			else
			{
				on = pdf_is_hidden_ocg(ctx, desc, rdb, usage, obj);
				if ((combine & 1) == 0)
					on = !on;
			}
		}
		fz_always(ctx)
		{
			pdf_unmark_obj(ctx, ocg);
		}
		fz_catch(ctx)
		{
			fz_rethrow(ctx);
		}
		return !on;
	}
	/* No idea what sort of object this is - be visible */
	return 0;
}

void
pdf_read_ocg(fz_context *ctx, pdf_document *doc)
{
	pdf_obj *obj, *ocg, *configs;
	int len, i, num_configs;
	pdf_ocg_descriptor *desc;

	fz_var(desc);

	obj = pdf_dict_get(ctx, pdf_dict_get(ctx, pdf_trailer(ctx, doc), PDF_NAME(Root)), PDF_NAME(OCProperties));
	if (!obj)
		return;

	configs = pdf_dict_get(ctx, obj, PDF_NAME(Configs));
	if (configs == NULL)
		num_configs = 1;
	else if (!pdf_is_array(ctx, configs))
		fz_throw(ctx, FZ_ERROR_GENERIC, "Invalid Configs value");
	else
		num_configs = pdf_array_len(ctx, configs);

	ocg = pdf_dict_get(ctx, obj, PDF_NAME(OCGs));
	if (!ocg || !pdf_is_array(ctx, ocg))
		/* Not ever supposed to happen, but live with it. */
		return;
	len = pdf_array_len(ctx, ocg);

	desc = fz_malloc_struct(ctx, pdf_ocg_descriptor);
	desc->ocgs = NULL;

	fz_try(ctx)
	{
		desc->num_configs = num_configs;
		desc->len = len;
		desc->ocgs = fz_calloc(ctx, len, sizeof(*desc->ocgs));
		desc->intent = NULL;
		for (i=0; i < len; i++)
		{
			pdf_obj *o = pdf_array_get(ctx, ocg, i);
			desc->ocgs[i].obj = pdf_keep_obj(ctx, o);
			desc->ocgs[i].state = 1;
		}
		doc->ocg = desc;
	}
	fz_catch(ctx)
	{
		fz_free(ctx, desc->ocgs);
		fz_free(ctx, desc);
		fz_rethrow(ctx);
	}

	pdf_select_layer_config(ctx, doc, 0);
}

void
pdf_set_layer_config_as_default(fz_context *ctx, pdf_document *doc)
{
	pdf_obj *ocprops, *d, *order, *on, *configs, *rbgroups;
	int k;

	if (doc == NULL || doc->ocg == NULL)
		return;

	ocprops = pdf_dict_getp(ctx, pdf_trailer(ctx, doc), "Root/OCProperties");
	if (!ocprops)
		return;

	/* All files with OCGs are required to have a D entry */
	d = pdf_dict_get(ctx, ocprops, PDF_NAME(D));
	if (d == NULL)
		return;

	pdf_dict_put(ctx, d, PDF_NAME(BaseState), PDF_NAME(OFF));

	/* We are about to delete RBGroups and Order, from D. These are
	 * both the underlying defaults for other configs, so copy the
	 * current values out to any config that doesn't have one
	 * already. */
	order = pdf_dict_get(ctx, d, PDF_NAME(Order));
	rbgroups = pdf_dict_get(ctx, d, PDF_NAME(RBGroups));
	configs = pdf_dict_get(ctx, ocprops, PDF_NAME(Configs));
	if (configs)
	{
		int len = pdf_array_len(ctx, configs);
		for (k=0; k < len; k++)
		{
			pdf_obj *config = pdf_array_get(ctx, configs, k);

			if (order && !pdf_dict_get(ctx, config, PDF_NAME(Order)))
				pdf_dict_put(ctx, config, PDF_NAME(Order), order);
			if (rbgroups && !pdf_dict_get(ctx, config, PDF_NAME(RBGroups)))
				pdf_dict_put(ctx, config, PDF_NAME(RBGroups), rbgroups);
		}
	}

	/* Offer all the layers in the UI */
	order = pdf_new_array(ctx, doc, 4);
	on = pdf_new_array(ctx, doc, 4);
	for (k = 0; k < doc->ocg->len; k++)
	{
		pdf_ocg_entry *s = &doc->ocg->ocgs[k];

		pdf_array_push(ctx, order, s->obj);
		if (s->state)
			pdf_array_push(ctx, on, s->obj);
	}
	pdf_dict_put(ctx, d, PDF_NAME(Order), order);
	pdf_dict_put(ctx, d, PDF_NAME(ON), on);
	pdf_dict_del(ctx, d, PDF_NAME(OFF));
	pdf_dict_del(ctx, d, PDF_NAME(AS));
	pdf_dict_put(ctx, d, PDF_NAME(Intent), PDF_NAME(View));
	pdf_dict_del(ctx, d, PDF_NAME(Name));
	pdf_dict_del(ctx, d, PDF_NAME(Creator));
	pdf_dict_del(ctx, d, PDF_NAME(RBGroups));
	pdf_dict_del(ctx, d, PDF_NAME(Locked));

	pdf_dict_del(ctx, ocprops, PDF_NAME(Configs));
}