initial commit

Makefile

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+all: install
+
+install:
+	mkdir -p ~/.local/bin
+	cp swaybg-swapper.py ~/.local/bin
+	cp systemd/swaybg-swapper.{service,timer} ~/.config/systemd/user/
+	systemctl --user daemon-reload
+	systemctl --user enable --now swaybg-swapper.timer

backgrounds.example.json

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+{
+  "DP-0": [
+    {
+      "file": "test.png",
+      "transform": "fill",
+      "colour": "#000000"
+    },
+    { "file": "empty.png" }
+  ],
+  "DP-1": [
+    { "file": "foo.png" },
+    {
+      "file": "bar.jpg",
+      "transform": "fit"
+    }
+  ]
+}

swaybg-swapper.py

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+#!/usr/bin/env python
+import json
+import random
+import subprocess
+import time
+
+import os.path
+
+pidof = subprocess.run(["pidof", "swaybg"], capture_output=True)
+pids = None
+if pidof.returncode == 0:
+    pids = pidof.stdout[:-1]
+
+file = "~/.config/sway/backgrounds.json"
+if not os.path.isfile(os.path.expanduser(file)):
+    print("Config file “{}” not found".format(file))
+    exit(1)
+
+with open(os.path.expanduser(file)) as config_file:
+    config = json.load(config_file)
+
+cmd=["swaybg"]
+for item in config:
+    output = config[item]
+    background = output[random.randrange(len(output))]
+    cmd.extend(["-o", item, "-i", os.path.expanduser(background["file"])])
+    if "transform" in background:
+        cmd.extend(["-m", background["transform"]])
+    else:
+        cmd.extend(["-m", "center"])
+    if "colour" in background:
+        cmd.extend(["-c", background["colour"]])
+    else: cmd.extend(["-c", "#000000"])
+
+# avoid ugly flickering by
+# 1. running new `swaybg`
+# 2. waiting!
+# 3. killing old `swaybg`(s)
+subprocess.Popen(cmd)
+time.sleep(1)
+if pids is not None:
+    for pid in pids.split():
+        subprocess.run(["kill", pid])

systemd/swaybg-swapper.service

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+[Unit]
+Description=Background swapper for sway/swaybg
+PartOf=sway-session.target
+
+[Service]
+Type=oneshot
+ExecStart=python %h/.local/bin/swaybg-swapper.py
+Restart=on-failure
+RestartSec=1
+TimeoutStopSec=10
+KillMode=process
+
+[Install]
+WantedBy=sway-session.target

systemd/swaybg-swapper.timer

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+[Unit]
+Description=Executes swaybg-swapper.service
+[Timer]
+OnUnitInactiveSec=60m
+[Install]
+WantedBy=timers.target

timer.example.conf

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+[Timer]
+OnUnitInactiveSec=60m