* nixos/xmonad: xmonad config w/ghc+xmessage
When the "config" option isn't set, we use xmonad-with-packages to
provide xmonad with runtime access to an isolated ghc, ensuring it can
recompile and exec a user's local config (e.g. $HOME/.xmonad/xmonad.hs)
regardless of which ghc (if any) is on PATH.
When the "config" option is set, however, we compile a configured xmonad
executable upfront (during nixos-rebuild), and prior to this commit, it
was not provided with runtime access to an isolated ghc.
As a result, with the "config" option set, it was not possible
to recompile and exec a user's local config unless there was a
compatible version of ghc on PATH with the necessary packages (xmonad,
xmonad-contrib, etc.) in its package database. Adding such a ghc to
environment.systemPackages, e.g.
(haskellPackages.ghcWithPackages (ps: with ps; [xmonad xmonad-contrib]))
is problematic because it adds both ghc and an unconfigured xmonad to
PATH, e.g.
$ ls -l $(which xmonad ghc)
lrwxrwxrwx ... /run/current-system/sw/bin/ghc -> /nix/store/...-ghc-8.10.2-with-packages/bin/ghc
lrwxrwxrwx ... /run/current-system/sw/bin/xmonad -> /nix/store/...-ghc-8.10.2-with-packages/bin/xmonad
Having the unconfigured xmonad on PATH is particularly bad because
restarting xmonad will dump the user into the unconfigured version, and
if no local config exists (e.g. in $HOME/.xmonad/xmonad.hs), they'll be
left in this unconfigured state.
In this commmit, we give the configured xmonad runtime access to ghc
like xmonad-with-packages does for the unconfigured version. The aim
is to allow the user to switch between the nixos module's config and a
local config (e.g. $HOME/.xmonad/xmonad.hs) at will, so they can try out
config changes without performing a nixos-rebuild.
Since the xmonad on PATH is the configured executable, there's no
danger a user could unwittingly restart into the unconfigured version,
and because xmonad will refuse to recompile when no local config
exists, there's no danger a user could unwittingly recompile into an
unconfigured version.
Given that a local config exists, the recompile/restart behavior depends
on two factors:
- which entry point is used
* 'XMonad.xmonad' (default)
* 'XMonad.launch' (recommended in "config" option description)
- what operation is triggered (i.e. via mod+q)
* `spawn "xmonad --recompile && xmonad --restart"` (default)
* `restart "xmonad" True`
* custom function
If the default 'XMonad.xmonad' entrypoint and default mod+q operation
are used, hitting mod+q will compile and exec the local config, which
will remain in use until next time the display manager is restarted.
If the entrypoint is changed to 'XMonad.launch' but mod+q left with its
default operation, hitting mod+q will have no visible effect. The logs
(as seen by running `journalctl --identifier xmonad --follow`) will show
an error,
X Error of failed request: BadAccess (attempt to access private resource denied)
which indicates that the shell was unable to start xmonad because
another window manager is already running (namely, the nixos-configured
xmonad).
https://wiki.haskell.org/Xmonad/Frequently_asked_questions#X_Error_of_failed_request:_BadAccess_.28attempt_to_access_private_resource_denied.29
Changing the mod+q operation to `restart "xmonad" True` (as recommended
in the "config" option's description) will allow a restart of the
nixos-configured xmonad to be triggeredy by hitting mod+q.
Finally, if the entrypoint is 'XMonad.launch', mod+q has been
bound to `restart "xmonad" True` and another key bound to a custom
recompile/restart function (e.g. `compileRestart` as shown in the
"config" option example), the user can switch between the nixos module's
config and their local config, with the custom key switching to the
local config and mod+q switching back.
* nixos/xmonad: refactor let binding
* nixos/xmonad: refactor (eliminate duplicate code)
* nixos/xmonad: install man pages
Prior to this commit, man pages were not installed if the "config"
option was set.
* nixos/xmonad: comment grammar fixups
* nixos/xmonad: writeStateToFile in example config
Calling writeStateToFile prior to recompiling and restarting allows
state (workspaces, etc.) to be preserved across the restart.
* nixos/xmonad: add ivanbrennan to maintainers
* nixos/xmonad: adjust compileRestart example
* nixos/xmonad: add missing import to example config
b90c5cb703