snap: Multiple improvements (#3697)

* Add avahi-browse interface, fixing Chromecast support ([hopefully] Closes: #3650)
* Use gnome-3-28 platform extension, reducing snap size.
* Set appropriate TMPDIR environment, fixing the indicator icon
* (Should) Actually build in the Launchpad environment (hopefully!)

snap/snapcraft.yaml

@@ -0,0 +1,90 @@
+name: google-play-music-desktop-player
+adopt-info: google-play-music-desktop-player
+summary: Standalone player for Google Play Music
+description: |
+  This Google Play Music player provides desktop integration - with music
+  hotkeys and the sound indicator via an MPRIS interface, the abiliy to use
+  custom colours and load custom themes, a remote-control interface, and
+  lower resource consumption than a full-blown browser tab.
+  .
+  This is *not* an official Google project.
+grade: stable
+base: core18
+confinement: strict
+icon: src/assets/icons/svg/vector_logo.svg
+
+apps:
+  google-play-music-desktop-player:
+    command: desktop-launch google-play-music-desktop-player
+    environment:
+      TMPDIR: $XDG_RUNTIME_DIR
+    desktop: usr/share/applications/google-play-music-desktop-player.desktop
+    extensions:
+      - gnome-3-28
+    plugs:
+      - unity7
+      - alsa
+      - audio-playback
+      - pulseaudio
+      - opengl
+      - browser-support
+      - network
+      - network-bind
+      - gsettings
+      - avahi-observe
+    slots:
+      - mpris-player
+
+slots:
+  mpris-player:
+    interface: mpris
+    name: google_play_music_desktop_player
+
+
+parts:
+  google-play-music-desktop-player:
+    plugin: nodejs
+    source: .
+    source-type: git
+    build-packages:
+      - g++
+      - libavahi-compat-libdnssd-dev
+      - libdbus-1-dev
+      - libx11-dev
+      - libexpat1-dev
+      - libnotify-dev
+      - python3
+      - python
+      - git
+    stage-packages:
+      - libnss3
+      - ca-certificates
+      - libasound2-data
+      - libasound2-plugins
+      - libnotify4
+      - libavahi-compat-libdnssd1
+      - libxss1
+      - libgconf2-4
+      - libxtst6
+      - libdbus-1-3
+      - libx11-xcb1
+      - libappindicator3-1
+      - unity-gtk3-module
+    override-build: |
+        export PATH=$PATH:$SNAPCRAFT_PART_BUILD/../npm/bin
+        export PATH=$PATH:$SNAPCRAFT_PART_BUILD/node_modules/.bin
+        snapcraftctl set-version $(git describe --tags)
+        npm install
+        npm run build
+        npm run make:deb:64
+        cp ${SNAPCRAFT_PART_BUILD}/dist/installers/debian/*.deb ${SNAPCRAFT_STAGE}/dist.deb
+
+  dump-package:
+    plugin: dump
+    source: ../stage/dist.deb
+    source-type: deb
+    override-build: |
+      snapcraftctl build
+      sed -i 's|Icon=google-play-music-desktop-player|Icon=/usr/share/pixmaps/google-play-music-desktop-player.png|g' $SNAPCRAFT_PART_INSTALL/usr/share/applications/google-play-music-desktop-player.desktop
+    after:
+      - google-play-music-desktop-player

snapcraft.yaml

@@ -1,69 +0,0 @@
-name: google-play-music-desktop-player
-version: '4.6.0'
-summary: Standalone player for Google Play Music
-description: |
-  This Google Play Music player provides desktop integration - with music
-  hotkeys and the sound indicator via an MPRIS interface, the abiliy to use
-  custom colours and load custom themes, a remote-control interface, and
-  lower resource consumption than a full-blown browser tab.
-  .
-  This is *not* an official Google project.
-grade: stable
-confinement: strict
-icon: src/assets/icons/svg/vector_logo.svg
-
-apps:
-  google-play-music-desktop-player:
-    command: desktop-launch "$SNAP/google-play-music-desktop-player/Google Play Music Desktop Player"
-    desktop: google-play-music-desktop-player.desktop
-    plugs:
-      - pulseaudio
-      - x11
-      - opengl
-      - browser-support
-      - network
-      - network-bind
-      - process-control
-      - unity7
-      - gsettings
-    slots:
-      - mpris
-
-parts:
-  desktop-file:
-    plugin: dump
-    source: vendor/snap/
-
-  google-play-music-desktop-player:
-    plugin: gulp
-    node-engine: 8.11.1
-    source: .
-    source-type: git
-    gulp-tasks:
-      - package:linux:64
-    build-packages:
-      - g++
-      - libavahi-compat-libdnssd-dev
-      - libdbus-1-dev
-      - libx11-dev
-      - libexpat1-dev
-      - libnotify-dev
-      - python3
-      - python
-    stage-packages:
-      - libnss3
-      - ca-certificates
-      - libasound2-data
-      - libasound2-plugins
-      - libnotify4
-      - libavahi-compat-libdnssd1
-      - libxss1
-      - libgconf2-4
-      - libxtst6
-      - libdbus-1-3
-    after:
-      - desktop-gtk2
-      - indicator-gtk2
-    organize:
-      '../build/dist/Google Play Music Desktop Player-linux-x64': google-play-music-desktop-player
-      ../build/build/assets/img/main.png: main.png

vendor/snap/google-play-music-desktop-player.desktop

@@ -1,13 +0,0 @@
-[Desktop Entry]
-Name=Google Play Music Desktop Player
-Name[fr]=Google Play Musique pour Bureau
-Comment=An electron wrapper for Google Play Music
-Comment[fr]=Une application Electron intégrant Google Play Musique au bureau.
-GenericName=Google Play Music Desktop Player
-GenericName[fr]=Lecteur en streaming de Google - version pour bureau
-Exec=env PULSE_PROP=media.role=music google-play-music-desktop-player %U
-Icon=google-play-music-desktop-player
-Type=Application
-StartupNotify=true
-Categories=AudioVideo;Audio;
-X-PulseAudio-Properties=media.role=music