feat: GNOME Shell extension for lock screen / GDM camera overlay by HackOverflow404 · Pull Request #1120 · boltgolt/howdy

HackOverflow404 · 2026-06-11T07:46:48Z

What and why

When Howdy authenticates at the lock screen or GDM login screen, there is no visual feedback; the user stares at a static screen with no indication that the camera is active, whether their face is in frame, or if anything is happening at all. On the desktop (sudo/polkit), compare.py already opens an OpenCV window, but that approach doesn't work on the lock screen because Mutter blocks X11 windows from appearing above the lock shield.

This PR adds a GNOME Shell extension that shows the live annotated camera feed above the lock screen and GDM greeter while authentication is running.

How it works

compare.py writes two files to /tmp while the auth is in progress:

File	Purpose
`/tmp/howdy-active`	Sentinel: exists while auth is running, deleted on exit
`/tmp/howdy-frame.jpg`	Latest annotated frame, atomically replaced via `os.replace`

The GNOME Shell extension (howdy-screen@howdy) polls /tmp/howdy-active at 250 ms intervals. When it appears, and the session is locked, or at the greeter, a small overlay panel is shown, and the JPEG is reloaded ~10×/s using GdkPixbuf + St.ImageContent.

Why file-based IPC: compare.py runs as root inside a PAM transaction. The extension runs as the user (or gdm). A Unix socket would work, but requires privilege management. Files in /tmp are simpler, atomic, and work across all session modes.

Why St.ImageContent and not St.Icon: StTextureCache caches gicons by URI with no file-change monitor, causing the feed to freeze on the first frame. GdkPixbuf + St.ImageContent bypasses the cache entirely.

Why session-modes: ["unlock-dialog", "gdm"]: Without unlock-dialog in metadata.json, GNOME Shell disables the extension the instant the screen locks. This is the key insight that makes the lock-screen case work.

Changes

`howdy/src/compare.py`

render_frame_to_window() - new function that draws face annotations and writes the JPEG. Runs on every non-black frame; the OpenCV window (cv2.imshow) is gated separately by do_imshow so JPEG frames are produced even at the Wayland GDM greeter, where no X display exists.
get_compositor() - scans the authenticating user's /proc environment to detect the running Wayland compositor (sway, Hyprland, KDE, GNOME, or generic X11/Wayland). Used by raise_window_once() to pick the right tool.
raise_window_once() - dispatches to swaymsg (sway), hyprctl (Hyprland), or xdotool (X11 / KDE / GNOME / unknown). Falls back to xdotool if the compositor-specific tool is not installed. Safe to call multiple times.
Signal files (/tmp/howdy-active, /tmp/howdy-frame.jpg) are cleaned up in exit() so the overlay closes as soon as auth ends.
Dark frames are no longer skipped before rendering; they are displayed with a "Too dark" annotation, so the user sees live camera output regardless.

`howdy/src/config.ini`

Three new options in [video] (all default to false, zero behaviour change for existing installs):

overlay = false      # write JPEG frames for the GNOME Shell extension
show_window = false  # OpenCV popup during sudo/polkit in logged-in sessions
mirror = false       # horizontally flip the feed (does not affect recognition)

`howdy-gnome-extension/` (new directory)

howdy-screen@howdy/extension.js - the GNOME Shell extension (GNOME 45+)
howdy-screen@howdy/metadata.json
install.sh - deploys to ~/.local/share/ (user session + lock screen) and /usr/share/ + a gdm dconf keyfile (greeter). Re-run after edits to redeploy.
README.md - full setup docs including Wayland compatibility table, GNOME version requirements, PrivateTmp notes for distro maintainers, and optional dependency info.

Compatibility


GNOME version	45+ (ESM extension format). Ubuntu 22.04 LTS (GNOME 42) is not supported.
Session type	Wayland and X11. The extension is Wayland-native; `show_window` uses XWayland and works on all compositors.
Compositors	sway (`swaymsg`), Hyprland (`hyprctl`), KDE + X11 (`xdotool`), GNOME (`xdotool`; overlay extension preferred)
Optional deps	`xdotool` for X11/KDE/GNOME window raising; `swaymsg`/`hyprctl` ship with their compositors

Security note

/tmp/howdy-frame.jpg is written world-readable (0644, owned by root). The gdm user is not root and must be able to read the file for the greeter overlay to work. This means any local user can read camera frames from that path while authentication is in progress. This is a deliberate design choice. Users who consider this unacceptable can leave overlay = false (the default).

Testing

cd howdy-gnome-extension && ./install.sh
sudo howdy config → set overlay = true in [video]
Lock screen (Super+L) → move face in front of camera, overlay should appear
Log out to GDM greeter → trigger howdy, overlay should appear there too
Set show_window = true → run sudo ls, OpenCV popup should appear

Logs: sudo cat /tmp/howdy-debug.log (written only when overlay=true).

Signed-off-by: MusiKid <musikid@outlook.com>

Add python-opencv as a dependency for ArchLinux

Fix some bugs on GUI

inverted error message

Update datetime since datetime.utcnow() was deprecated since Python 3.12.

…lation Since pam_python depends on python2 and python2 cannot be installed through fedoras repositories the installation will fail. The beta of Howdy has fixed this issue. This problem is also explained in the copr repo. But it requires some searching.

Fix datetime.datetime.utcnow()

Remove use of Environment Python

fix(pam): use environ variable when getenv doesn't work

Fix unwanted unlocks when auth client subprocesses exit with 0

Fix polkit policy

Fix things regarding translations

Connect to signals of the shown window

Update README.md for Fedora 41 users

The current EDITOR handling is a bit lacking. Improvements: - check that the editor exists before trying to spawn a subprocess - add vi as nano alternative - if everything else fails, perhaps the user is using sudo. Suggest using 'sudo -E howdy [...]', as otherwise the command would run in a non-interactive shell (i.e. without sourcing the initialization files), and no environment variable is carried over (including EDITOR) unless explicitly preserved

…ndling feat(config): better EDITOR handling

Update compare.py from boltgolt#968

Release 3.0.0

The OpenCV window from compare.py can't draw above the GNOME lock-screen shield or on the Wayland GDM greeter, so add a GNOME Shell extension (howdy-screen@howdy) that renders the howdy camera feed there instead. Extension (howdy-gnome-extension/): - metadata.json declares session-modes ["user","unlock-dialog","gdm"]; without "unlock-dialog" GNOME disables the extension the moment the screen locks, which is why it never showed on the lock screen. - extension.js loads each frame via GdkPixbuf -> St.ImageContent instead of St.Icon + Gio.FileIcon, whose StTextureCache froze the feed on the first frame. Overlay is gated to non-user session modes so the logged-in case keeps using compare.py's OpenCV window. - install.sh deploys to ~/.local (session + lock screen) and, via sudo, to /usr/share + a gdm dconf keyfile (the greeter runs as user gdm and can't read ~/.local). compare.py: - Decouple JPEG frame-writing (/tmp/howdy-frame.jpg, consumed by the extension) from cv2.imshow via a do_imshow flag and a new "overlay" config option (default on). The greeter has no usable X display for cv2.imshow but still needs the frames. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

The extension skipped reloading a frame unless the JPEG's mtime changed, but it read mtime at whole-second resolution (to_unix()). compare.py writes ~3 frames/sec, so frames sharing a second were treated as unchanged and the overlay refreshed only ~1x/sec. Compare time::modified + time::modified-usec for microsecond resolution so every written frame is picked up. Bump version to 3. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

:

…erlay Feat/lock screen camera overlay

houndci-bot · 2026-06-11T07:46:53Z

+            : Cogl.PixelFormat.RGB_888;
+
+        const content = St.ImageContent.new_with_preferred_size(w, h);
+        const ok = content.set_bytes(


'const' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).

houndci-bot · 2026-06-11T07:46:53Z

+            ? Cogl.PixelFormat.RGBA_8888
+            : Cogl.PixelFormat.RGB_888;
+
+        const content = St.ImageContent.new_with_preferred_size(w, h);


'const' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).

houndci-bot · 2026-06-11T07:46:53Z

+        const w = pixbuf.get_width();
+        const h = pixbuf.get_height();
+        const fmt = pixbuf.get_has_alpha()
+            ? Cogl.PixelFormat.RGBA_8888


Misleading line break before '?'; readers may interpret this as an expression boundary.

houndci-bot · 2026-06-11T07:46:53Z

+
+        const w = pixbuf.get_width();
+        const h = pixbuf.get_height();
+        const fmt = pixbuf.get_has_alpha()


'const' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).

houndci-bot · 2026-06-11T07:46:53Z

+        this._frameTime = stamp;
+
+        const w = pixbuf.get_width();
+        const h = pixbuf.get_height();


'const' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).

houndci-bot · 2026-06-11T07:46:53Z

+            this._pollId = null;
+        }
+        if (this._overlay) {
+            this._overlay.get_parent()?.remove_child(this._overlay);


Expected ':' and instead saw 'remove_child'.
Expected an assignment or function call and instead saw an expression.
Expected an identifier and instead saw '.'.

houndci-bot · 2026-06-11T07:46:53Z

+        this._overlay.set_position(40, 80);
+
+        this._frameTime = 0;
+        this._pollId = GLib.timeout_add(GLib.PRIORITY_DEFAULT, POLL_MS, () => {


'arrow function syntax (=>)' is only available in ES6 (use 'esversion: 6').

houndci-bot · 2026-06-11T07:46:53Z

+
+        // screenShieldGroup sits above the lock-screen shield (and exists in
+        // the gdm greeter too); fall back to uiGroup just in case.
+        const parent = Main.layoutManager.screenShieldGroup ?? Main.layoutManager.uiGroup;


'const' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).
Expected ':' and instead saw 'Main'.
Expected an assignment or function call and instead saw an expression.
Expected an identifier and instead saw '.'.
Expected an identifier and instead saw '?'.
Missing semicolon.

houndci-bot · 2026-06-11T07:46:53Z

+            reactive: false,
+        });
+
+        const label = new St.Label({


'const' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).

houndci-bot · 2026-06-11T07:46:53Z

+    }
+
+    _modeAllowsOverlay() {
+        const mode = Main.sessionMode?.currentMode;


'const' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).
Expected ':' and instead saw 'currentMode'.
Expected an identifier and instead saw '.'.
Expected an identifier and instead saw ';'.
Missing semicolon.

saidsay-so and others added 30 commits December 26, 2020 09:33

[WIP]: Add native PAM module

609b8e9

Signed-off-by: MusiKid <musikid@outlook.com>

Fix the build instructions

beee059

Signed-off-by: MusiKid <musikid@outlook.com>

Remove uinput

50d52ec

Signed-off-by: MusiKid <musikid@outlook.com>

Fix typo in build instructions

322899d

Signed-off-by: MusiKid <musikid@outlook.com>

Add C++11 flag for meson

2287bc1

Signed-off-by: MusiKid <musikid@outlook.com>

Made python3 absolute, added comments

fce326d

More documentation

a2e89f0

Add python-opencv as a dependency for ArchLinux

5d6fecb

Fix a typo for the login confirmation

02a831f

Add more documentation

3abc3d5

Fix typo in comments

1c25bf0

Add instructions for installation

1cb38b0

Merge pull request boltgolt#528 from jinnko/master

95331bd

Add python-opencv as a dependency for ArchLinux

Added gettext and more even more comments

7ee0f36

feat: add workarounds

d078f81

fix: fix native and input workarounds

3a4b482

chore: fix misspell

b8bc325

chore: add workaround key to config.ini

5503cfb

fix: fix possible race condition

0392171

build: add boost locale module

27460c8

Add python-opencv as a dependency for ArchLinux

ab4a492

Split files into separate howdy-gtk and howdy packages

692d674

Rename config option for issue boltgolt#565

67b1c95

Add sponsor to readme

559a665

many lib dir

0e4aaa0

check camera opening (fix is_gray(None))

2e2c1ac

fix camera list not always displayed (gi bug)

4f7c656

Merge pull request boltgolt#605 from EmixamPP/beta

aaaabae

Fix some bugs on GUI

inverted error message

fddcdd1

Merge pull request boltgolt#610 from EmixamPP/beta

354c3d1

inverted error message

dthelegend and others added 29 commits May 20, 2024 20:10

add python_path to meson options

be6357b

Merge branch 'boltgolt:beta' into beta

5720faa

Fix datetime.datetime.utcnow()

03e3efa

Update datetime since datetime.utcnow() was deprecated since Python 3.12.

Update other areas where datetime is invoked

cd80876

Fix unwanted unlocks when auth client subprocesses exit with 0

aef35b5

Merge pull request boltgolt#948 from thecalamityjoe87/testing

7bb7711

Fix datetime.datetime.utcnow()

Merge pull request boltgolt#904 from dthelegend/beta

b52ec0f

Remove use of Environment Python

Merge pull request boltgolt#903 from saidsay-so/ssh_fix

85534ba

fix(pam): use environ variable when getenv doesn't work

Merge pull request boltgolt#973 from PaideiaDilemma/beta

0a68a4b

Fix unwanted unlocks when auth client subprocesses exit with 0

Merge branch 'beta' into fix-polkit

b3e783e

Merge pull request boltgolt#879 from principis/fix-polkit

e87a99b

Fix polkit policy

Merge pull request boltgolt#857 from Gliese852/fix-some-translations

a2eabc9

Fix things regarding translations

Merge pull request boltgolt#853 from Gliese852/fix-wrong-signals

2c5d304

Connect to signals of the shown window

Merge pull request boltgolt#972 from Meincrakker/patch-1

c4521c1

Update README.md for Fedora 41 users

Update compare.py from boltgolt#968

d97289c

Merge pull request boltgolt#1009 from aleeraser/feat/better-EDITOR-ha…

806313d

…ndling feat(config): better EDITOR handling

Merge pull request boltgolt#998 from YKScoding/beta

92698cf

Update compare.py from boltgolt#968

Fix build warnings, update changelog

5394ceb

Merge pull request boltgolt#1023 from boltgolt/beta

d3ab993

Release 3.0.0

Updated compare.py file to add my new feature

eb7c37b

Mirrored overlay feed

71c81f6

Added overlay option to the config

3f765e1

Added show window config to config file

d1b7e88

:

Updates to the read me and the documentation and the comments

86d5b9a

Merge pull request #1 from HackOverflow404/feat/lock-screen-camera-ov…

2d466ae

…erlay Feat/lock screen camera overlay

houndci-bot reviewed Jun 11, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

feat: GNOME Shell extension for lock screen / GDM camera overlay#1120

feat: GNOME Shell extension for lock screen / GDM camera overlay#1120
HackOverflow404 wants to merge 228 commits into
boltgolt:devfrom
HackOverflow404:master

HackOverflow404 commented Jun 11, 2026 •

edited

Loading

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

houndci-bot Jun 11, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

20 participants

Uh oh!

Conversation

HackOverflow404 commented Jun 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

What and why

How it works

Changes

howdy/src/compare.py

howdy/src/config.ini

howdy-gnome-extension/ (new directory)

Compatibility

Security note

Testing

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

20 participants

HackOverflow404 commented Jun 11, 2026 •

edited

Loading

`howdy/src/compare.py`

`howdy/src/config.ini`

`howdy-gnome-extension/` (new directory)