Add support for toplevel capture #334

emersion · 2025-07-19T20:07:41Z

~~Resizing doesn't work yet (but that's orthogonal to capture sources)~~
wlroots doesn't support capturing toplevel cursors yet
Sway doesn't include child toplevels in the parent toplevel capture

Some work has been stolen from #329

src/screencast/screencast.c

pmkap · 2025-07-20T16:35:44Z

I'm getting a segfault

(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00006392783a23d0 in xdpw_buffer_destroy (buffer=0x63928faee9d0)
    at ../src/screencast/screencast_common.c:209
#2  0x00006392783ac94f in pwr_handle_stream_remove_buffer (data=0x63928f9e6c20, 
    buffer=0x63928faab888) at ../src/screencast/pipewire_screencast.c:559
#3  0x00007067fe5d5d0b in clear_buffers (stream=stream@entry=0x63928faab440)
    at ../pipewire/src/pipewire/stream.c:832
#4  0x00007067fe5d61a8 in impl_port_set_param (object=0x63928faab440, 
    direction=<optimized out>, port_id=<optimized out>, id=4, 
    flags=<optimized out>, param=<optimized out>)
    at ../pipewire/src/pipewire/stream.c:915
#5  0x00007067fe5cd48f in spa_node_port_set_param (object=<optimized out>, 
    direction=<optimized out>, port_id=<optimized out>, id=4, flags=0, 
    param=0x63928f9d7900) at ../pipewire/spa/include/spa/node/node.h:718
#6  pw_impl_port_set_param (port=port@entry=0x63928fab4f20, id=id@entry=4, 
    flags=flags@entry=0, param=param@entry=0x63928f9d7900)
    at ../pipewire/src/pipewire/impl-port.c:1827
#7  0x00007067fd0a7fd8 in client_node_port_set_param (_data=0x63928fa768f8, 
    direction=SPA_DIRECTION_OUTPUT, port_id=0, id=4, flags=0, param=0x63928f9d7900)
    at ../pipewire/src/modules/module-client-node/remote-node.c:564
#8  0x00007067fd0bb740 in client_node_demarshal_port_set_param (
    data=<optimized out>, msg=<optimized out>)
    at ../pipewire/src/modules/module-client-node/protocol-native.c:496
#9  0x00007067fd0d662e in process_remote (impl=impl@entry=0x63928f9cd680)
    at ../pipewire/src/modules/module-protocol-native.c:1095
#10 0x00007067fd0d6cd8 in on_remote_data (data=0x63928f9cd680, fd=16, mask=5)
    at ../pipewire/src/modules/module-protocol-native.c:1129
#11 0x00007067fe759d46 in loop_iterate (object=<optimized out>, 
--Type <RET> for more, q to quit, c to continue without paging--
    timeout=<optimized out>) at ../pipewire/spa/plugins/support/loop.c:726
#12 0x000063927839badf in spa_loop_control_iterate_fast (object=0x63928f9a8300, 
    timeout=0) at /usr/include/spa-0.2/spa/support/loop.h:312
#13 0x000063927839bb48 in pw_loop_iterate (object=0x63928f9a8190, timeout=0)
    at /usr/include/pipewire-0.3/pipewire/loop.h:89
#14 0x000063927839c4e7 in main (argc=1, argv=0x7ffe30d43aa8)
    at ../src/core/main.c:262
(gdb) frame 1
#1  0x00006392783a23d0 in xdpw_buffer_destroy (buffer=0x63928faee9d0)
    at ../src/screencast/screencast_common.c:209
209			gbm_bo_destroy(buffer->bo);
(gdb) p buffer->bo
$4 = (struct gbm_bo *) 0x63928fa92d60

buffer->bo is not NULL

I'm trying to reproduce and find out more.

My compositor implementation that I'm testing: https://codeberg.org/pkap/river/src/branch/toplevel-capture

src/screencast/chooser.c

emersion · 2025-07-21T12:15:49Z

I'm getting a segfault

How do you trigger the segfault? It sounds unrelated to toplevel capture (ie, I think it would affect output capture as well).

pmkap · 2025-07-21T15:14:15Z

@emersion

How do you trigger the segfault? It sounds unrelated to toplevel capture (ie, I think it would affect output capture as well).

It happens when I resize the shared toplevel. When I build with meson setup build -Db_sanitize=address && ninja -C build, this crash does not occur and everything works perfectly, even the resizing. (just some [ERROR] - ext: frame capture failed: buffer constraint mismatch, but it works)

edit: here's more stacktrace

#0  0x00007ed79943c1e1 in dri2_destroy_image () at ../mesa-25.1.5/src/gallium/frontends/dri/dri_helpers.c:332
#1  0x00007ed79bf1754c in gbm_dri_bo_destroy () at ../mesa-25.1.5/src/gbm/backends/dri/gbm_dri.c:633
#2  0x00005a6390cad43b in xdpw_buffer_destroy (buffer=0x5a63b497a180) at ../src/screencast/screencast_common.c:209
#3  0x00005a6390cb79ba in pwr_handle_stream_remove_buffer (data=0x5a63b48d12b0, buffer=0x5a63b4995cb8)
    at ../src/screencast/pipewire_screencast.c:559

Molytho · 2025-07-21T15:27:49Z

What is the expected behavior when a streamed window is closed. I quickly dipped into the portal spec and could not find anything.
In my opinion the screencast session should probably be closed (sending the closed signal) which is not done at the moment as far as I can tell.

emersion · 2025-07-24T12:50:01Z

Updated to fix the crash on resize and send the Closed signal.

src/screencast/chooser.c

kennylevinsen

One small cleanup nit (which is inherited from my original PR I believe), but otherwise LGTM!

src/screencast/wlr_screencast.c

Co-authored-by: Simon Ser <[email protected]>

This is set regardless of the target type.

This is a footgun.

xdpw acts as a permission dialog. Don't assume the user wants to share the first output when none of the choosers work.

Stolen from Sway, useful for the next commit.

Co-authored-by: Simon Ser <[email protected]>

We don't need to keep the gbm_bo around once it's exported as FDs.

kennylevinsen

LGTM. :)

emersion · 2025-07-31T13:44:01Z

Thank you!

I had to use `sway-git`, `wlroots-git`, and `xdg-desktop-portal-wlr-git` to be able to select specific windows to share, instead of only being able to select which output to share. Ref: emersion/xdg-desktop-portal-wlr#107 Ref: https://emersion.fr/blog/2025/status-update-79/ Ref: emersion/xdg-desktop-portal-wlr#334 Tested: https://mozilla.github.io/webrtc-landing/gum_test.html

emersion force-pushed the toplevel-capture branch from 1056c53 to 795c18b Compare July 19, 2025 20:09

emersion mentioned this pull request Jul 19, 2025

Toplevel capture #329

Closed

2 tasks

pmkap reviewed Jul 20, 2025

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src/screencast/screencast.c Show resolved Hide resolved

kennylevinsen reviewed Jul 21, 2025

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src/screencast/chooser.c Show resolved Hide resolved

pmkap reviewed Jul 25, 2025

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emersion force-pushed the toplevel-capture branch from b8bdd20 to c3876c2 Compare July 31, 2025 10:20

kennylevinsen approved these changes Jul 31, 2025

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src/screencast/wlr_screencast.c Outdated Show resolved Hide resolved

kennylevinsen and others added 14 commits July 31, 2025 15:06

Track toplevels

dd281f4

Co-authored-by: Simon Ser <[email protected]>

Add xdpw_screencast_target.type

2b6cedc

Move xdpw_screencast_target.with_cursor out of union

62c4028

This is set regardless of the target type.

Drop union from xdpw_screencast_target

7ad1dae

This is a footgun.

Drop unnecessary wl_list_for_each_reverse_safe()

69eb2d1

Don't share first output by default

ffb0402

xdpw acts as a permission dialog. Don't assume the user wants to share the first output when none of the choosers work.

Generalize xdpw_output_chooser for non-outputs

1bde179

Add format_str()

0e19b64

Stolen from Sway, useful for the next commit.

Select and capture toplevels

eafe42f

Co-authored-by: Simon Ser <[email protected]>

Print error when chooser selects unknown target

061134a

Handle chooser cancellation

4fc0864

Don't print getline() error on EOF for chooser

9734408

Drop xdpw_buffer.bo

625beec

We don't need to keep the gbm_bo around once it's exported as FDs.

Send session Closed signal

ba3f6e2

emersion force-pushed the toplevel-capture branch from c3876c2 to ba3f6e2 Compare July 31, 2025 13:07

kennylevinsen approved these changes Jul 31, 2025

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kennylevinsen merged commit e471c3d into master Jul 31, 2025
3 checks passed

kennylevinsen deleted the toplevel-capture branch July 31, 2025 13:43

karras mentioned this pull request Aug 1, 2025

Screensharing Screen/Application picker/selector WayfireWM/wayfire#2652

Closed

wineee mentioned this pull request Dec 3, 2025

[wayland] Add image-copy-capture and image-capture-source support qtile/qtile#5681

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