slock

My personal build of slock, suckless's screen locker, version 1.4 (see VERSION in config.mk).

Patches

There's no patches/ directory here, but one patch is merged straight into slock.c: background image support (the suckless "background image" patch, built on Imlib2 and libXrandr). It loads an image with imlib_load_image, then for every monitor XRRGetMonitors reports, blends and scales that image onto a pixmap sized to that monitor (slock.c:377-397). Each monitor gets the same image stretched to fill it, there's no aspect-ratio preservation or cropping.

Changes beyond stock

• background_image in config.def.h points at an absolute path, /home/martin/dev/suckless-btw/slock/slock.png. Anyone else building this needs to change that to wherever they actually keep the image, or to slock.png in this repo if the checkout lives in the same spot.
• colorname[] keeps the stock three-state palette (blue while typing, red on a wrong password, black at rest), but see below, that feedback doesn't actually show once a background image is set.

Known issues

• The comment above FAILED in config.def.h says "Does not curently work with BG IMG", and that's accurate: readpw() in slock.c (around line 194) only swaps XSetWindowBackground to the plain color when locks[screen]->bgmap is unset. Whenever a background image is loaded, every color transition (XSetWindowBackgroundPixmap(dpy, ..., bgmap)) redraws the same static image instead, so typing or getting the password wrong never changes what's on screen.
• make dist copies a file named README with no extension; this repo only has README.md, so that target fails at the cp -R step.

Building

Needs Xlib, Xext, Xrandr, Imlib2, and libcrypt (drop -lcrypt from config.mk on OpenBSD or Darwin, and drop -DHAVE_SHADOW_H on any non-Linux BSD, both are called out in commented-out lines in config.mk).

make

Prints the build options (compiler, CFLAGS, LDFLAGS), copies config.def.h to config.h on the first run, and compiles slock.c plus explicit_bzero.c into an slock binary. Edit config.h, not config.def.h, once it exists, and make sure to point background_image at a real path on your machine before building.

Install system-wide:

sudo make install

This needs root because it sets the setuid bit on the installed binary (chmod u+s), which slock needs to read /etc/shadow for the password hash before it drops privileges. It copies the binary to ${PREFIX}/bin (/usr/local/bin by default) and the man page to ${MANPREFIX}/share/man/man1. Override PREFIX/DESTDIR as usual, e.g. make install PREFIX=/usr.

make clean removes the binary and object files. make uninstall removes what install put down. make dist builds a source tarball (currently broken, see above).

The man page's security section is worth reading before relying on this: to stop the lock being bypassed by switching virtual terminals or killing the X server with Ctrl+Alt+Backspace, add to xorg.conf:

Section "ServerFlags"
    Option "DontVTSwitch" "True"
    Option "DontZap"      "True"
EndSection

Credits

slock is written and maintained by suckless.org; see LICENSE for the full contributor list. The background-image patch traces back to the one published on suckless.org/patches.