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feresaria/docs/screen-sharing.md
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Samuel Onoja b2363a18b0 Share native theme components and fix dialog backdrop blur
Centralize native palettes, presets, typography, controls, menus, calendar rendering, and icon assets in ferese-theme. Reuse the shared components across the shell, settings, lock screen, authentication prompt, and screen-sharing chooser.

Attach themed dialogs to compositor-owned materials, correct backdrop capture and sampling across output transforms, smooth patterned backgrounds, and prevent clipped picker buttons with the configured shell font.
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Screen sharing and recording

Ferese includes a ScreenCast portal backend, xdg-desktop-portal-ferese. Applications use the standard desktop portal to request a display, then receive video through PipeWire. A recorder or conferencing application handles encoding, saving files, or sending video; those tasks do not run inside the compositor.

Record from the top bar

  1. Click the screen-recording icon in the top bar to open the display picker.
  2. Choose a monitor in the native picker and click Share.
  3. The icon changes to a stop square and shows elapsed time. Click it to stop.

The recorder finishes the video before sending a notification with its saved path. Videos are saved as VP8 WebM files under Videos/Ferese (using your configured XDG Videos folder). Audio is off. The icon uses the same theme accent, hover effect, and corner radius as the other bar controls.

Encoding runs in a separate native ferese-record process using GStreamer. The shell remains responsive while a file is recorded or finalized. If saving fails, an error appears in the notification center; an unfinished .webm.part file may remain at the path shown in the error.

Start sharing

Use a Wayland screen-sharing or recording source in your application. Ferese opens a display picker. Select a display and press Share. Nothing is selected by default. Applications that request multiple displays can share up to four. The picker uses your Ferese theme colors, font, and shell corner radius. Its background uses the same compositor material as popovers and authentication prompts: opaque in solid mode, or blurred and translucent using the shared Appearance → Shell opacity and blur settings. Text and icons remain opaque.

Other applications keep a screen sharing window with a Stop sharing button. Ferese’s built-in recorder uses the top-bar stop control instead, leaving your windows accessible after display selection. The command-line recorder keeps the sharing window when it is not launched by the shell. Press Stop sharing or close the sharing window to revoke an ordinary application’s session. Closing the requesting application, locking Ferese, disconnecting the selected display, or changing its capture size also ends sharing. A new request needs fresh consent; selections are not saved. Everything visible on a shared display, including notifications, is included.

Installation

The standard installer builds and installs the backend, its D-Bus activation entry, and a Ferese-specific portal preference file. Install pipewire, a PipeWire session manager such as wireplumber, xdg-desktop-portal, and xdg-desktop-portal-gtk using your distribution's package manager. The GTK backend supplies other portal interfaces such as file selection. The built-in recorder also needs GStreamer’s PipeWire, base, and good plugins (pipewiresrc, videoconvert, vp8enc, and webmmux). The installation guide includes these packages.

Log into a new Ferese session after installation. The session launcher imports its Wayland display into the D-Bus activation environment. Nested previews leave the host activation environment alone.

Existing custom window rules can float the picker and sharing indicator:

window-rule app-id="dev.ferese.ScreenShare" floating=#true

The packaged example configuration already includes this rule. Existing user configuration is preserved during installation.

Current capabilities

  • Monitor capture, one PipeWire stream per selected display, at up to 30 fps.
  • Hidden or embedded pointer, as requested by the application.
  • Bounded frame storage and reusable shared-memory buffers.
  • Cancellation during selection, an explicit stop control, and process cleanup.
  • ScreenCast backend version 3, without persistent or automatic consent.

Window-only sharing, region selection, and audio capture in Ferese’s recorder are not implemented yet. Other recording applications can handle audio separately. Video currently uses CPU copies through the compositor's shared-memory screencopy path, not DMA-BUF zero-copy. High-resolution or multiple-display recording can therefore use significant CPU and memory bandwidth. A paused stream checks capture availability once per second so locking also ends sessions without an active consumer.

Development checks

Build the backend after installing the native dependencies in the installation guide:

cargo build --release --locked -p xdg-desktop-portal-ferese
cargo test --locked -p xdg-desktop-portal-ferese
# Exercise real video encoding and playback (requires the plugins above):
cargo test --locked -p xdg-desktop-portal-ferese --bin ferese-record encoder_finishes_a_real_webm -- --ignored

The opt-in integration test opens a temporary nested compositor and uses a private D-Bus session. It requires built Ferese and locker binaries, Python GI/GStreamer with pipewiresrc, dbus-daemon, xdg-desktop-portal, and bwrap. It checks capture delivery and timestamps, cancellation, frontend loss, and lock revocation:

FERESE_TEST_PORTAL=1 \
FERESE_TEST_PORTAL_BINARY=target/release/xdg-desktop-portal-ferese \
python3 scripts/tests/test_portal_isolated.py

Add FERESE_TEST_PORTAL_CONSENT=1 to exercise the native picker and restricted PipeWire connection. Select the temporary display and click Share when prompted. Tests capture only the nested preview and leave host PAM policies and D-Bus activation unchanged.

Troubleshooting

Confirm that XDG_CURRENT_DESKTOP contains Ferese, PipeWire is running, and FERESE_ENABLE_SCREENCOPY was not set to 0 before launching the session.

The installed preference is /usr/share/xdg-desktop-portal/ferese-portals.conf. A user override under ~/.config/xdg-desktop-portal/ can take precedence. Its ScreenCast preference should name ferese:

[preferred]
default=gtk;
org.freedesktop.impl.portal.ScreenCast=ferese;

If capture dimensions change, stop and start sharing again. Ferese ends the old session instead of feeding incorrectly sized frames to the application.

For development, xdg-desktop-portal-ferese --sources lists displays available on the current WAYLAND_DISPLAY. This command does not start a stream.