Draw a wallpaper on a machine that has no theme yet

Seeding the config gets the bar and the keybindings up, and then leaves
you looking at a black screen, because the autostart line that sets the
wallpaper named ~/.local/share/wallpapers/hyprcosmic/current directly.
That is a symlink import-theme --assets maintains, so it does not exist
until a theme has been imported -- which on a machine that has just
installed the package it has not.

The same line waited for the daemon with an unbounded loop:

    until awww query >/dev/null 2>&1; do sleep 0.2; done

awww is a Recommends and lives in a COPR, so on a machine that never
enabled that repository nothing ever answered and the loop spun at 5 Hz
for the length of the session.

Both now live in hyprcosmic-wallpaper, which falls back to the
distribution's own images when there is no link yet, gives up on the
daemon after ten seconds, and exits 0 on every path so autostart is never
left supervising a process that cannot finish. Fedora recommends
cosmic-wallpapers so the fallback has something to find; nothing in the
dependency chain pulled it in before.

Verified against all five paths: no awww at all, a daemon that never
answers, a fresh machine with no link, a link pointing at a real file,
and a link left dangling by a deleted theme.

README.md

@@ -195,6 +195,15 @@ Runtime dependencies of the shell itself are not COSMIC's and are not built
 here: `waybar`, `rofi` (wayland build), `awww` (formerly `swww`), and a Nerd
 Font for the glyphs the bar and the launcher draw with.
 
+The wallpaper is `awww`'s job, and the image it draws is
+`~/.local/share/wallpapers/hyprcosmic/current` — a symlink `import-theme
+--assets` maintains. Before you have imported a theme there is no such link, so
+`hyprcosmic-wallpaper` falls back to whatever the distribution ships,
+`/usr/share/backgrounds/cosmic` first; the Fedora package recommends
+`cosmic-wallpapers` so there is something there. With no `awww` installed it
+says so on the session log and leaves the background alone, rather than waiting
+for a daemon that is never coming.
+
 The font is the one thing the packaging cannot do for you on Fedora, which has
 no package that provides a Nerd Font at all: `texlive-inconsolata-nerd-font`
 installs under `texmf-dist` and kitty's `SymbolsNerdFont` under

config/autostart

@@ -60,28 +60,26 @@ awww-daemon
 # get a blank screen below the bar with no error anywhere: the failure is that
 # nobody asked for a wallpaper, so nothing reports one missing.
 #
-# `sh -c` rather than a bare `awww img`, for one reason: awww-daemon above has
+# It sets ~/.local/share/wallpapers/hyprcosmic/current, a symlink
-# only just been forked and is not listening yet, so an immediate `awww img`
+# `hyprcosmic-conf import-theme --assets` maintains beside the wallpapers it
-# loses a race and fails silently. The loop waits for the daemon to answer
+# copies. The link is used rather than a real path so that this and rofi's
-# before setting the image.
+# local.rasi -- which shows the same image in the launcher's sidebar -- cannot
+# drift apart, and so that importing a different theme does not leave either
+# pointing at a file that no longer exists.
 #
-# This does not weaken the no-shell rule in the header. That rule exists so a
+# Until a theme has been imported there is no such link, so on a machine that
-# file naming programs cannot be escalated into arbitrary execution; naming
+# has just installed the package it falls back to whatever the distribution
-# `sh` explicitly is just naming a program, and anyone able to write this file
+# ships, /usr/share/backgrounds/cosmic first. A first login gets a desktop.
-# could already name any binary on the system.
-#
-# `current` is a symlink `cosmic-conf import-theme --assets` maintains beside
-# the wallpapers it copies, pointing at one of them. It is named here rather
-# than a real file so that this line and rofi's local.rasi -- which shows the
-# same image in the launcher's sidebar -- cannot drift apart, and so that
-# importing a different theme does not leave this pointing at a path that no
-# longer exists.
 #
 # Change the wallpaper by repointing the link, not by editing this file:
 #
 #     ln -sfn ~/".local/share/wallpapers/hyprcosmic/<theme>/<image>" \
 #             ~/.local/share/wallpapers/hyprcosmic/current
-sh -c 'until awww query >/dev/null 2>&1; do sleep 0.2; done; exec awww img "$HOME/.local/share/wallpapers/hyprcosmic/current"'
+#
+# A program rather than the `sh -c` this used to be, because waiting for the
+# daemon needs a bound: awww is a Recommends in a COPR, and the old unbounded
+# `until awww query` loop spun for the whole session on a machine without it.
+hyprcosmic-wallpaper
 
 # A terminal, unconditionally, as the way back in.
 #

config/bin/hyprcosmic-wallpaper

@@ -0,0 +1,81 @@
+#!/bin/sh
+# Set the desktop wallpaper once the wallpaper daemon is listening.
+#
+# The hyprcosmic profile does not start cosmic-bg, so nothing else draws a
+# background: without this there is a black screen below the bar, and no error
+# anywhere, because the failure is that nobody asked for a wallpaper.
+#
+# This was three shell fragments on one autostart line. It became a program for
+# two reasons, both of which cost a first login its desktop:
+#
+#   - `current` is a symlink `import-theme --assets` maintains, so it does not
+#     exist until a theme has been imported. Naming it directly meant a machine
+#     that had just installed the package set no wallpaper at all.
+#   - The wait for the daemon was `until awww query; do sleep 0.2; done`, with
+#     nothing to stop it. awww is a Recommends and lives in a COPR, so on a
+#     machine that never enabled that repository the loop spun at 5 Hz for the
+#     length of the session.
+#
+# Both are now bounded and both say so on the session log.
+
+set -eu
+
+link="${XDG_DATA_HOME:-$HOME/.local/share}/wallpapers/hyprcosmic/current"
+
+# Searched in order when the link is not there yet. The first is cosmic-wallpapers,
+# which the Fedora package recommends for exactly this; the other two are where
+# freedesktop and KDE put theirs, so a machine with neither still has a chance.
+fallbacks='/usr/share/backgrounds/cosmic /usr/share/backgrounds /usr/share/wallpapers'
+
+if ! command -v awww >/dev/null 2>&1; then
+	echo "hyprcosmic-wallpaper: awww is not installed; no wallpaper set" >&2
+	exit 0
+fi
+
+# awww-daemon is started immediately above this in autostart and has only just
+# been forked, so an immediate `awww img` loses the race and fails silently.
+# Ten seconds is far longer than the daemon has ever taken and short enough that
+# a daemon which is never coming does not leave a process spinning all session.
+tries=0
+until awww query >/dev/null 2>&1; do
+	tries=$((tries + 1))
+	if [ "$tries" -ge 50 ]; then
+		echo "hyprcosmic-wallpaper: awww-daemon did not answer in 10s; no wallpaper set" >&2
+		exit 0
+	fi
+	sleep 0.2
+done
+
+# -e rather than -L, deliberately: it follows the link, so a `current` left
+# dangling by a deleted theme falls through to the defaults instead of being
+# handed to awww as a path that is not there.
+img=''
+if [ -e "$link" ]; then
+	img=$link
+else
+	for dir in $fallbacks; do
+		[ -d "$dir" ] || continue
+		for candidate in "$dir"/*.jpg "$dir"/*.jpeg "$dir"/*.png; do
+			# The glob is literal when nothing matches, which is why
+			# this tests the file rather than trusting the expansion.
+			[ -f "$candidate" ] || continue
+			img=$candidate
+			break
+		done
+		# An if, not `[ -n "$img" ] && break`: under set -e a trailing
+		# false at the end of the loop body would take the script with it.
+		if [ -n "$img" ]; then
+			break
+		fi
+	done
+	if [ -n "$img" ]; then
+		echo "hyprcosmic-wallpaper: no $link yet, falling back to $img" >&2
+	fi
+fi
+
+if [ -z "$img" ]; then
+	echo "hyprcosmic-wallpaper: no wallpaper found in $link or $fallbacks" >&2
+	exit 0
+fi
+
+exec awww img "$img"

packaging/fedora/hyprcosmic.spec

@@ -81,6 +81,14 @@ Requires:       rofi-wayland
 # unsatisfiable dependency is not.
 Recommends:     awww
 
+# Something for the wallpaper daemon to draw before a theme has been imported.
+# hyprcosmic-wallpaper looks here first when ~/.local/share/wallpapers has no
+# `current` link yet, which on a machine that has just installed this package is
+# always. Nothing in the dependency chain pulls it in otherwise -- neither
+# cosmic-session nor cosmic-comp requires it -- and without it a first login is
+# a bar on a black screen.
+Recommends:     cosmic-wallpapers
+
 # Nerd Font glyphs are most of what the bar and the launcher draw, and Fedora
 # has nothing that provides them. This line used to say `nerd-fonts`, which is
 # not a package in any Fedora repository -- so it could never be satisfied, and

tools/install-assets.sh

@@ -78,6 +78,7 @@ SHARED=(
     "config/bin/hyprcosmic-powermenu:bin/hyprcosmic-powermenu:755"
     "config/bin/hyprcosmic-fan:bin/hyprcosmic-fan:755"
     "config/bin/hyprcosmic-keybinds:bin/hyprcosmic-keybinds:755"
+    "config/bin/hyprcosmic-wallpaper:bin/hyprcosmic-wallpaper:755"
 )
 
 # The session entry point. Kept apart from SHARED because it is versioned in the