aspect ratio and keep awake

README.md

@@ -56,6 +56,21 @@ When idle for 5 minutes, a fish-tank screensaver protects the CRT from burn-in.
    Add `--windowed` to test in a window instead of fullscreen.
    **Press Esc or Q to quit.**
 
+## Running headless (lid closed)
+
+While it is running, the booth holds systemd keep-awake locks
+(`systemd-inhibit`, block mode: `sleep`, `idle`, and `handle-lid-switch`
+when no desktop environment already holds it). The laptop will not suspend
+or idle-sleep, and — on machines where logind manages the lid — closing
+the lid does nothing, so the laptop can run tucked away behind the CRT.
+The locks are released as soon as the program exits.
+
+If the machine still suspends when the lid closes (some desktop
+environments keep the lid lock for themselves), disable lid suspend on
+that machine: put `HandleLidSwitch=ignore` in
+`/etc/systemd/logind.conf.d/photobooth.conf` (needs root, applies even
+when the booth is not running) or use the desktop's own power settings.
+
 ## Customizing
 
 - **All settings** live in `config.toml` — camera choice, screen text,
@@ -84,9 +99,10 @@ To use a different camera:
   automatically after a successful print. (If the program is restarted
   mid-cycle, photos here are counted so no progress is lost.)
 - `contact_sheets/` — every printed sheet, kept as a backup in case of
-  printer trouble. Delete them manually now and then, or set
-  `delete_contact_sheets = true` in the config to remove each one right
-  after it prints.
+  printer trouble. Sheets are full US-letter pages at 300 DPI, so they
+  also print at the right size from any other app. Delete them manually
+  now and then, or set `delete_contact_sheets = true` in the config to
+  remove each one right after it prints.
 
 ## If printing fails