Automate reloading display configuration (#122)

This allows Frame to handle display reconfiguration without a restart.

Features:

1. If there is no `display` option set, then when Frame runs it is set to a default
2. When the `display` option is set:
2.1. With Miral < 3.8 Frame is restarted and will load the new display configuration
2.2. With Miral 3.8 Frame is not restarted and will attempt to reload
3. When the display option is unset, the configuration is cleared and Frame restarted

Note: there is (still) no validation of the configuration being set

Fixes: #20

scripts/bin/initialise-display-config

@@ -0,0 +1,28 @@
+#!/bin/sh
+set -eu
+
+wait_for()
+{
+  until
+    until
+      inotifywait --event create "$(dirname "$1")"&
+      inotify_pid=$!
+      [ -e "$1" ] || sleep 2 && [ -e "$1" ]
+    do
+      wait "${inotify_pid}"
+    done
+    kill "${inotify_pid}"
+    [ -O "$1" ]
+  do
+    sleep 1
+  done
+}
+
+display_file="$SNAP_DATA/frame.display"
+
+wait_for "${display_file}"
+
+if [ -z "$(snapctl get display)" ] && ! grep "DO NOT EDIT THIS FILE BY HAND"  "${display_file}"
+then
+  snapctl set display="$(cat "${display_file}")"
+fi

scripts/bin/run-daemon

@@ -1,4 +1,10 @@
 #!/bin/sh
 set -eux
 
+display_file="$SNAP_DATA/frame.display"
+if [ -z "$(snapctl get display)" ]
+then
+  initialise-display-config&
+fi
+
 exec nohup "$@"

snap/hooks/configure

@@ -21,12 +21,13 @@ EOT
     mv "${display_file}"  "${display_file}.save" || true
     mv "${display_temp}" "${display_file}"
     chmod a+r "${display_file}"
-    let config_changes+=1
+    ! [ -e "${SNAP}/miral-lt-3.8" ] || ((config_changes+=1))
   else
     rm "${display_temp}"
   fi
-else
+elif grep "DO NOT EDIT THIS FILE BY HAND"  "${display_file}" &> /dev/null; then
   mv "${display_file}"  "${display_file}.save" || true
+  ((config_changes+=1))
 fi
 
 # config_file
@@ -86,7 +87,7 @@ if ! diff "${config_temp}" "${config_file}" > /dev/null; then
   mv "${config_file}"  "${config_file}.save" || true
   mv "${config_temp}" "${config_file}"
   chmod a+r "${config_file}"
-  let config_changes+=1
+  ((config_changes+=1))
 else
   rm "${config_temp}"
 fi

snap/snapcraft.yaml

@@ -147,6 +147,8 @@ parts:
   scripts:
     plugin: dump
     source: scripts
+    stage-packages:
+      - inotify-tools
 
   anon-shm-preload:
     source: https://github.com/MirServer/anon-shm-preload.git
@@ -168,3 +170,12 @@ parts:
       find . -type f,l -exec rm -f $SNAPCRAFT_PRIME/usr/lib/${SNAPCRAFT_ARCH_TRIPLET}/{} \;
       rm -fr "$SNAPCRAFT_PRIME/usr/lib/${SNAPCRAFT_ARCH_TRIPLET}/dri"
       rm -fr "$SNAPCRAFT_PRIME/usr/share/"{bug,doc,doc-base,drirc.d,glvnd,libdrm,lintian,man}
+      
+      # Back compatibility fix until MirAL 3.8 is released
+      miral_version=`LANG=C apt-cache policy libmiral-dev | sed -rne 's/^\s+Candidate:\s+([0-9]*\.[0-9])\..+$/\1/p'`
+      if [ ${miral_version%.*} -eq 3 ] && [ ${miral_version#*.} -lt 8 ]
+      then
+        touch $SNAPCRAFT_PRIME/miral-lt-3.8
+      else
+        rm -f $SNAPCRAFT_PRIME/miral-lt-3.8
+      fi