aboutsummaryrefslogtreecommitdiffstats
path: root/libavdevice/xcbgrab.c
blob: 702e66c71f870928828b070547c0b6e39909234b (plain) (blame)
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
/*
 * XCB input grabber
 * Copyright (C) 2014 Luca Barbato <lu_zero@gentoo.org>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "config.h"

#include <stdlib.h>
#include <xcb/xcb.h>

#if CONFIG_LIBXCB_XFIXES
#include <xcb/xfixes.h>
#endif

#if CONFIG_LIBXCB_SHM
#include <sys/shm.h>
#include <xcb/shm.h>
#endif

#if CONFIG_LIBXCB_SHAPE
#include <xcb/shape.h>
#endif

#include "libavutil/internal.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"
#include "libavutil/parseutils.h"
#include "libavutil/time.h"

#include "libavformat/avformat.h"
#include "libavformat/internal.h"

typedef struct XCBGrabContext {
    const AVClass *class;

    uint8_t *buffer;

    xcb_connection_t *conn;
    xcb_screen_t *screen;
    xcb_window_t window;
#if CONFIG_LIBXCB_SHM
    xcb_shm_seg_t segment;
#endif
    int64_t time_frame;
    AVRational time_base;

    int x, y;
    int width, height;
    int frame_size;
    int bpp;

    int draw_mouse;
    int follow_mouse;
    int show_region;
    int region_border;
    int centered;

    const char *video_size;
    const char *framerate;

    int has_shm;
} XCBGrabContext;

#define FOLLOW_CENTER -1

#define OFFSET(x) offsetof(XCBGrabContext, x)
#define D AV_OPT_FLAG_DECODING_PARAM
static const AVOption options[] = {
    { "x", "Initial x coordinate.", OFFSET(x), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
    { "y", "Initial y coordinate.", OFFSET(y), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
    { "grab_x", "Initial x coordinate.", OFFSET(x), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
    { "grab_y", "Initial y coordinate.", OFFSET(y), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
    { "video_size", "A string describing frame size, such as 640x480 or hd720.", OFFSET(video_size), AV_OPT_TYPE_STRING, {.str = "vga" }, 0, 0, D },
    { "framerate", "", OFFSET(framerate), AV_OPT_TYPE_STRING, {.str = "ntsc" }, 0, 0, D },
    { "draw_mouse", "Draw the mouse pointer.", OFFSET(draw_mouse), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, D },
    { "follow_mouse", "Move the grabbing region when the mouse pointer reaches within specified amount of pixels to the edge of region.",
      OFFSET(follow_mouse), AV_OPT_TYPE_INT, { .i64 = 0 },  FOLLOW_CENTER, INT_MAX, D, "follow_mouse" },
    { "centered", "Keep the mouse pointer at the center of grabbing region when following.", 0, AV_OPT_TYPE_CONST, { .i64 = -1 }, INT_MIN, INT_MAX, D, "follow_mouse" },
    { "show_region", "Show the grabbing region.", OFFSET(show_region), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, D },
    { "region_border", "Set the region border thickness.", OFFSET(region_border), AV_OPT_TYPE_INT, { .i64 = 3 }, 1, 128, D },
    { NULL },
};

static const AVClass xcbgrab_class = {
    .class_name = "xcbgrab indev",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
    .category   = AV_CLASS_CATEGORY_DEVICE_VIDEO_INPUT,
};

static int xcbgrab_reposition(AVFormatContext *s,
                              xcb_query_pointer_reply_t *p,
                              xcb_get_geometry_reply_t *geo)
{
    XCBGrabContext *c = s->priv_data;
    int x = c->x, y = c->y;
    int w = c->width, h = c->height, f = c->follow_mouse;
    int p_x, p_y;

    if (!p || !geo)
        return AVERROR(EIO);

    p_x = p->win_x;
    p_y = p->win_y;

    if (f == FOLLOW_CENTER) {
        x = p_x - w / 2;
        y = p_y - h / 2;
    } else {
        int left   = x + f;
        int right  = x + w - f;
        int top    = y + f;
        int bottom = y + h + f;
        if (p_x > right) {
            x += p_x - right;
        } else if (p_x < left) {
            x -= left - p_x;
        }
        if (p_y > bottom) {
            y += p_y - bottom;
        } else if (p_y < top) {
            y -= top - p_y;
        }
    }

    c->x = FFMIN(FFMAX(0, x), geo->width  - w);
    c->y = FFMIN(FFMAX(0, y), geo->height - h);

    return 0;
}

static int xcbgrab_frame(AVFormatContext *s, AVPacket *pkt)
{
    XCBGrabContext *c = s->priv_data;
    xcb_get_image_cookie_t iq;
    xcb_get_image_reply_t *img;
    xcb_drawable_t drawable = c->screen->root;
    xcb_generic_error_t *e = NULL;
    uint8_t *data;
    int length, ret;

    iq  = xcb_get_image(c->conn, XCB_IMAGE_FORMAT_Z_PIXMAP, drawable,
                        c->x, c->y, c->width, c->height, ~0);

    img = xcb_get_image_reply(c->conn, iq, &e);

    if (e) {
        av_log(s, AV_LOG_ERROR,
               "Cannot get the image data "
               "event_error: response_type:%u error_code:%u "
               "sequence:%u resource_id:%u minor_code:%u major_code:%u.\n",
               e->response_type, e->error_code,
               e->sequence, e->resource_id, e->minor_code, e->major_code);
        return AVERROR(EACCES);
    }

    if (!img)
        return AVERROR(EAGAIN);

    data   = xcb_get_image_data(img);
    length = xcb_get_image_data_length(img);

    ret = av_new_packet(pkt, length);

    if (!ret)
        memcpy(pkt->data, data, length);

    free(img);

    return ret;
}

static void wait_frame(AVFormatContext *s, AVPacket *pkt)
{
    XCBGrabContext *c = s->priv_data;
    int64_t curtime, delay;
    int64_t frame_time = av_rescale_q(1, c->time_base, AV_TIME_BASE_Q);

    c->time_frame += frame_time;

    for (;;) {
        curtime = av_gettime();
        delay   = c->time_frame - curtime;
        if (delay <= 0)
            break;
        av_usleep(delay);
    }

    pkt->pts = curtime;
}

#if CONFIG_LIBXCB_SHM
static int check_shm(xcb_connection_t *conn)
{
    xcb_shm_query_version_cookie_t cookie = xcb_shm_query_version(conn);
    xcb_shm_query_version_reply_t *reply;

    reply = xcb_shm_query_version_reply(conn, cookie, NULL);
    if (reply) {
        free(reply);
        return 1;
    }

    return 0;
}

static int allocate_shm(AVFormatContext *s)
{
    XCBGrabContext *c = s->priv_data;
    int size = c->frame_size + AV_INPUT_BUFFER_PADDING_SIZE;
    uint8_t *data;
    int id;

    if (c->buffer)
        return 0;
    id = shmget(IPC_PRIVATE, size, IPC_CREAT | 0777);
    if (id == -1) {
        char errbuf[1024];
        int err = AVERROR(errno);
        av_strerror(err, errbuf, sizeof(errbuf));
        av_log(s, AV_LOG_ERROR, "Cannot get %d bytes of shared memory: %s.\n",
               size, errbuf);
        return err;
    }
    xcb_shm_attach(c->conn, c->segment, id, 0);
    data = shmat(id, NULL, 0);
    shmctl(id, IPC_RMID, 0);
    if ((intptr_t)data == -1 || !data)
        return AVERROR(errno);
    c->buffer = data;
    return 0;
}

static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt)
{
    XCBGrabContext *c = s->priv_data;
    xcb_shm_get_image_cookie_t iq;
    xcb_shm_get_image_reply_t *img;
    xcb_drawable_t drawable = c->screen->root;
    xcb_generic_error_t *e = NULL;
    int ret;

    ret = allocate_shm(s);
    if (ret < 0)
        return ret;

    iq = xcb_shm_get_image(c->conn, drawable,
                           c->x, c->y, c->width, c->height, ~0,
                           XCB_IMAGE_FORMAT_Z_PIXMAP, c->segment, 0);
    img = xcb_shm_get_image_reply(c->conn, iq, &e);

    xcb_flush(c->conn);

    if (e) {
        av_log(s, AV_LOG_ERROR,
               "Cannot get the image data "
               "event_error: response_type:%u error_code:%u "
               "sequence:%u resource_id:%u minor_code:%u major_code:%u.\n",
               e->response_type, e->error_code,
               e->sequence, e->resource_id, e->minor_code, e->major_code);

        return AVERROR(EACCES);
    }

    free(img);

    pkt->data = c->buffer;
    pkt->size = c->frame_size;

    return 0;
}
#endif /* CONFIG_LIBXCB_SHM */

#if CONFIG_LIBXCB_XFIXES
static int check_xfixes(xcb_connection_t *conn)
{
    xcb_xfixes_query_version_cookie_t cookie;
    xcb_xfixes_query_version_reply_t *reply;

    cookie = xcb_xfixes_query_version(conn, XCB_XFIXES_MAJOR_VERSION,
                                      XCB_XFIXES_MINOR_VERSION);
    reply  = xcb_xfixes_query_version_reply(conn, cookie, NULL);

    if (reply) {
        free(reply);
        return 1;
    }
    return 0;
}

#define BLEND(target, source, alpha) \
    (target) + ((source) * (255 - (alpha)) + 255 / 2) / 255

static void xcbgrab_draw_mouse(AVFormatContext *s, AVPacket *pkt,
                               xcb_query_pointer_reply_t *p,
                               xcb_get_geometry_reply_t *geo)
{
    XCBGrabContext *gr = s->priv_data;
    uint32_t *cursor;
    uint8_t *image = pkt->data;
    int stride     = gr->bpp / 8;
    xcb_xfixes_get_cursor_image_cookie_t cc;
    xcb_xfixes_get_cursor_image_reply_t *ci;
    int cx, cy, x, y, w, h, c_off, i_off;

    cc = xcb_xfixes_get_cursor_image(gr->conn);
    ci = xcb_xfixes_get_cursor_image_reply(gr->conn, cc, NULL);
    if (!ci)
        return;

    cursor = xcb_xfixes_get_cursor_image_cursor_image(ci);
    if (!cursor)
        return;

    cx = ci->x - ci->xhot;
    cy = ci->y - ci->yhot;

    x = FFMAX(cx, gr->x);
    y = FFMAX(cy, gr->y);

    w = FFMIN(cx + ci->width,  gr->x + gr->width)  - x;
    h = FFMIN(cy + ci->height, gr->y + gr->height) - y;

    c_off = x - cx;
    i_off = x - gr->x;

    cursor += (y - cy) * ci->width;
    image  += (y - gr->y) * gr->width * stride;

    for (y = 0; y < h; y++) {
        cursor += c_off;
        image  += i_off * stride;
        for (x = 0; x < w; x++, cursor++, image += stride) {
            int r, g, b, a;

            r =  *cursor        & 0xff;
            g = (*cursor >>  8) & 0xff;
            b = (*cursor >> 16) & 0xff;
            a = (*cursor >> 24) & 0xff;

            if (!a)
                continue;

            if (a == 255) {
                image[0] = r;
                image[1] = g;
                image[2] = b;
            } else {
                image[0] = BLEND(r, image[0], a);
                image[1] = BLEND(g, image[1], a);
                image[2] = BLEND(b, image[2], a);
            }

        }
        cursor +=  ci->width - w - c_off;
        image  += (gr->width - w - i_off) * stride;
    }

    free(ci);
}
#endif /* CONFIG_LIBXCB_XFIXES */

static void xcbgrab_update_region(AVFormatContext *s)
{
    XCBGrabContext *c     = s->priv_data;
    const uint32_t args[] = { c->x - c->region_border,
                              c->y - c->region_border };

    xcb_configure_window(c->conn,
                         c->window,
                         XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y,
                         args);
}

static int xcbgrab_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    XCBGrabContext *c = s->priv_data;
    xcb_query_pointer_cookie_t pc;
    xcb_get_geometry_cookie_t gc;
    xcb_query_pointer_reply_t *p  = NULL;
    xcb_get_geometry_reply_t *geo = NULL;
    int ret = 0;

    wait_frame(s, pkt);

    if (c->follow_mouse || c->draw_mouse) {
        pc  = xcb_query_pointer(c->conn, c->screen->root);
        gc  = xcb_get_geometry(c->conn, c->screen->root);
        p   = xcb_query_pointer_reply(c->conn, pc, NULL);
        geo = xcb_get_geometry_reply(c->conn, gc, NULL);
    }

    if (c->follow_mouse && p->same_screen)
        xcbgrab_reposition(s, p, geo);

    if (c->show_region)
        xcbgrab_update_region(s);

#if CONFIG_LIBXCB_SHM
    if (c->has_shm && xcbgrab_frame_shm(s, pkt) < 0)
        c->has_shm = 0;
#endif
    if (!c->has_shm)
        ret = xcbgrab_frame(s, pkt);

#if CONFIG_LIBXCB_XFIXES
    if (ret >= 0 && c->draw_mouse && p->same_screen)
        xcbgrab_draw_mouse(s, pkt, p, geo);
#endif

    free(p);
    free(geo);

    return ret;
}

static av_cold int xcbgrab_read_close(AVFormatContext *s)
{
    XCBGrabContext *ctx = s->priv_data;

#if CONFIG_LIBXCB_SHM
    if (ctx->buffer) {
        shmdt(ctx->buffer);
    }
#endif

    xcb_disconnect(ctx->conn);

    return 0;
}

static xcb_screen_t *get_screen(const xcb_setup_t *setup, int screen_num)
{
    xcb_screen_iterator_t it = xcb_setup_roots_iterator(setup);
    xcb_screen_t *screen     = NULL;

    for (; it.rem > 0; xcb_screen_next (&it)) {
        if (!screen_num) {
            screen = it.data;
            break;
        }

        screen_num--;
    }

    return screen;
}

static int pixfmt_from_pixmap_format(AVFormatContext *s, int depth,
                                     int *pix_fmt)
{
    XCBGrabContext *c        = s->priv_data;
    const xcb_setup_t *setup = xcb_get_setup(c->conn);
    const xcb_format_t *fmt  = xcb_setup_pixmap_formats(setup);
    int length               = xcb_setup_pixmap_formats_length(setup);

    *pix_fmt = 0;

    while (length--) {
        if (fmt->depth == depth) {
            switch (depth) {
            case 32:
                if (fmt->bits_per_pixel == 32)
                    *pix_fmt = AV_PIX_FMT_0RGB;
                break;
            case 24:
                if (fmt->bits_per_pixel == 32)
                    *pix_fmt = AV_PIX_FMT_0RGB32;
                else if (fmt->bits_per_pixel == 24)
                    *pix_fmt = AV_PIX_FMT_RGB24;
                break;
            case 16:
                if (fmt->bits_per_pixel == 16)
                    *pix_fmt = AV_PIX_FMT_RGB565;
                break;
            case 15:
                if (fmt->bits_per_pixel == 16)
                    *pix_fmt = AV_PIX_FMT_RGB555;
                break;
            case 8:
                if (fmt->bits_per_pixel == 8)
                    *pix_fmt = AV_PIX_FMT_RGB8;
                break;
            }
        }

        if (*pix_fmt) {
            c->bpp        = fmt->bits_per_pixel;
            c->frame_size = c->width * c->height * fmt->bits_per_pixel / 8;
            return 0;
        }

        fmt++;
    }
    av_log(s, AV_LOG_ERROR, "Pixmap format not mappable.\n");

    return AVERROR_PATCHWELCOME;
}

static int create_stream(AVFormatContext *s)
{
    XCBGrabContext *c = s->priv_data;
    AVStream *st      = avformat_new_stream(s, NULL);
    xcb_get_geometry_cookie_t gc;
    xcb_get_geometry_reply_t *geo;
    int ret;

    if (!st)
        return AVERROR(ENOMEM);

    ret = av_parse_video_size(&c->width, &c->height, c->video_size);
    if (ret < 0)
        return ret;

    ret = av_parse_video_rate(&st->avg_frame_rate, c->framerate);
    if (ret < 0)
        return ret;

    avpriv_set_pts_info(st, 64, 1, 1000000);

    gc  = xcb_get_geometry(c->conn, c->screen->root);
    geo = xcb_get_geometry_reply(c->conn, gc, NULL);

    if (c->x + c->width > geo->width ||
        c->y + c->height > geo->height) {
        av_log(s, AV_LOG_ERROR,
               "Capture area %dx%d at position %d.%d "
               "outside the screen size %dx%d\n",
               c->width, c->height,
               c->x, c->y,
               geo->width, geo->height);
        return AVERROR(EINVAL);
    }

    c->time_base  = (AVRational){ st->avg_frame_rate.den,
                                  st->avg_frame_rate.num };
    c->time_frame = av_gettime();

    st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
    st->codecpar->codec_id   = AV_CODEC_ID_RAWVIDEO;
    st->codecpar->width      = c->width;
    st->codecpar->height     = c->height;

    ret = pixfmt_from_pixmap_format(s, geo->depth, &st->codecpar->format);

    free(geo);

    return ret;
}

static void draw_rectangle(AVFormatContext *s)
{
    XCBGrabContext *c = s->priv_data;
    xcb_gcontext_t gc = xcb_generate_id(c->conn);
    uint32_t mask     = XCB_GC_FOREGROUND |
                        XCB_GC_BACKGROUND |
                        XCB_GC_LINE_WIDTH |
                        XCB_GC_LINE_STYLE |
                        XCB_GC_FILL_STYLE;
    uint32_t values[] = { c->screen->black_pixel,
                          c->screen->white_pixel,
                          c->region_border,
                          XCB_LINE_STYLE_DOUBLE_DASH,
                          XCB_FILL_STYLE_SOLID };
    xcb_rectangle_t r = { 1, 1,
                          c->width  + c->region_border * 2 - 3,
                          c->height + c->region_border * 2 - 3 };

    xcb_create_gc(c->conn, gc, c->window, mask, values);

    xcb_poly_rectangle(c->conn, c->window, gc, 1, &r);
}

static void setup_window(AVFormatContext *s)
{
    XCBGrabContext *c = s->priv_data;
    uint32_t mask     = XCB_CW_OVERRIDE_REDIRECT | XCB_CW_EVENT_MASK;
    uint32_t values[] = { 1,
                          XCB_EVENT_MASK_EXPOSURE |
                          XCB_EVENT_MASK_STRUCTURE_NOTIFY };
    av_unused xcb_rectangle_t rect = { 0, 0, c->width, c->height };

    c->window = xcb_generate_id(c->conn);

    xcb_create_window(c->conn, XCB_COPY_FROM_PARENT,
                      c->window,
                      c->screen->root,
                      c->x - c->region_border,
                      c->y - c->region_border,
                      c->width + c->region_border * 2,
                      c->height + c->region_border * 2,
                      0,
                      XCB_WINDOW_CLASS_INPUT_OUTPUT,
                      XCB_COPY_FROM_PARENT,
                      mask, values);

#if CONFIG_LIBXCB_SHAPE
    xcb_shape_rectangles(c->conn, XCB_SHAPE_SO_SUBTRACT,
                         XCB_SHAPE_SK_BOUNDING, XCB_CLIP_ORDERING_UNSORTED,
                         c->window,
                         c->region_border, c->region_border,
                         1, &rect);
#endif

    xcb_map_window(c->conn, c->window);

    draw_rectangle(s);
}

static av_cold int xcbgrab_read_header(AVFormatContext *s)
{
    XCBGrabContext *c = s->priv_data;
    int screen_num, ret;
    const xcb_setup_t *setup;
    char *display_name = av_strdup(s->filename);

    if (!display_name)
        return AVERROR(ENOMEM);

    if (!sscanf(s->filename, "%[^+]+%d,%d", display_name, &c->x, &c->y)) {
        *display_name = 0;
        sscanf(s->filename, "+%d,%d", &c->x, &c->y);
    }

    c->conn = xcb_connect(display_name[0] ? display_name : NULL, &screen_num);
    av_freep(&display_name);

    if ((ret = xcb_connection_has_error(c->conn))) {
        av_log(s, AV_LOG_ERROR, "Cannot open display %s, error %d.\n",
               s->filename[0] ? s->filename : "default", ret);
        return AVERROR(EIO);
    }

    setup = xcb_get_setup(c->conn);

    c->screen = get_screen(setup, screen_num);
    if (!c->screen) {
        av_log(s, AV_LOG_ERROR, "The screen %d does not exist.\n",
               screen_num);
        xcbgrab_read_close(s);
        return AVERROR(EIO);
    }

    ret = create_stream(s);

    if (ret < 0) {
        xcbgrab_read_close(s);
        return ret;
    }

#if CONFIG_LIBXCB_SHM
    if ((c->has_shm = check_shm(c->conn)))
        c->segment = xcb_generate_id(c->conn);
#endif

#if CONFIG_LIBXCB_XFIXES
    if (c->draw_mouse) {
        if (!(c->draw_mouse = check_xfixes(c->conn))) {
            av_log(s, AV_LOG_WARNING,
                   "XFixes not available, cannot draw the mouse.\n");
        }
        if (c->bpp < 24) {
            avpriv_report_missing_feature(s, "%d bits per pixel screen",
                                          c->bpp);
            c->draw_mouse = 0;
        }
    }
#endif

    if (c->show_region)
        setup_window(s);

    return 0;
}

AVInputFormat ff_x11grab_xcb_demuxer = {
    .name           = "x11grab",
    .long_name      = NULL_IF_CONFIG_SMALL("X11 screen capture, using XCB"),
    .priv_data_size = sizeof(XCBGrabContext),
    .read_header    = xcbgrab_read_header,
    .read_packet    = xcbgrab_read_packet,
    .read_close     = xcbgrab_read_close,
    .flags          = AVFMT_NOFILE,
    .priv_class     = &xcbgrab_class,
};