build,snap,CI: create a snap package

For now it is a single package that just runs the GTK frontend.
Further commits will separate this into different snap packages
for the server, and other frontends.

.github/workflows/auto-ci-builds.yml

@@ -339,3 +339,25 @@ jobs:
     - name: build nix pkg
       run: |
         nix-build --expr 'let pkgs = import <nixpkgs> { }; in pkgs.callPackage ./nix/default.nix { gitBranch = "${{ github.ref_name }}"; }'
+
+  snap_build:
+    needs: build_Mono-6_8_0_105
+    runs-on: ubuntu-22.04
+    steps:
+    - uses: actions/checkout@v1
+    - name: Install snap tools
+      run: |
+        sudo apt update --yes
+        ./build/install-snapcraft.sh
+    - name: Generate snap package
+      run: |
+        sudo ./build/snap-build.sh
+    - name: Test snap package
+      run: |
+        sudo snap install --dangerous *.snap
+        smuxi --version
+    - uses: actions/upload-artifact@v3
+      name: Upload snap package as artifact
+      with:
+        name: snap
+        path: ./*.snap

build/install-snapcraft.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euxo pipefail
+
+sudo apt install -y snapd
+snap version
+
+# we can switch to a newer channel when we're ready to upgrade
+# to use SNAPCRAFT_STORE_CREDENTIALS instead of --with when pushing
+sudo snap install --classic snapcraft
+
+# workaround for GithubActionsCI+snapcraft, see https://forum.snapcraft.io/t/permissions-problem-using-snapcraft-in-azure-pipelines/13258/14?u=knocte
+sudo chown root:root /
+
+snapcraft --version

build/snap-build.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -euxo pipefail
+
+# this is the equivalent of using the 'build-packages' (not stage-packages) section in snapcraft
+# but as we're not using the 'make' plugin, we need to this manually now
+DEBIAN_FRONTEND=noninteractive sudo apt install -y build-essential pkg-config cli-common-dev mono-devel libgtk2.0-cil-dev
+
+# just in case this is a retry-run, we want to clean artifacts from previous try
+rm -rf ./staging
+
+./configure.sh --prefix=./staging "$@"
+make
+make install
+
+snapcraft --destructive-mode

snap/snapcraft.yaml

@@ -0,0 +1,97 @@
+name: smuxi
+base: core22 # the base snap is the execution environment for this snap
+version: '1.2.1' # just for humans, typically '1.2+git' or '1.3.2'
+summary: User-friendly and free IRC client for Linux/Windows/macOS based on GNOME/GTK+ # 79 char long summary
+description: |
+  Smuxi is an irssi-inspired, flexible, user-friendly and
+  cross-platform IRC client for sophisticated users, targeting the GNOME desktop.
+
+  Smuxi is based on the client-server model: The core application (engine) can be
+  placed onto a server which is connected to the Internet around-the-clock; one
+  or more frontends then connect to the core. This way, the connection to IRC can
+  be kept up even when all frontends have been closed. The combination of screen
+  and irssi served as example for this architecture.
+
+  Smuxi also supports the regular single application mode. This behaves like a
+  typical IRC client; it doesn't need separate core management and utilizes a
+  local engine that is used by the local frontend client.
+
+  Smuxi's GNOME homepage: https://wiki.gnome.org/Apps/Smuxi
+license: GPL-2.0
+icon: logo.png
+
+# grade must be 'stable' (without the quotes) to release into candidate/stable channels
+grade: stable
+confinement: strict
+
+layout:
+  /usr/share/.mono:
+    symlink: $SNAP/etc/mono/certstore
+  /usr/lib/cli:
+    symlink: $SNAP/usr/lib/cli
+
+apps:
+  smuxi:
+    command: bin/desktop-launch $SNAP/bin/smuxi-gtk
+    plugs:
+      - network
+      - desktop
+      - desktop-legacy
+      - wayland
+      - unity7
+
+parts:
+  smuxi:
+    plugin: dump
+    source: ./staging
+    stage-packages:
+      - mono-devel
+      - libgtk2.0-cil
+
+  certs:
+    plugin: dump
+    source: /etc/mono
+    organize:
+      certstore: etc/mono/certstore
+
+  gtk2:
+    source: https://github.com/ubuntu/snapcraft-desktop-helpers.git
+    source-subdir: gtk
+    plugin: make
+    make-parameters: ["FLAVOR=gtk2"]
+    build-packages:
+      - libgtk2.0-dev
+    stage-packages:
+      - libxkbcommon0  # XKB_CONFIG_ROOT
+      - dmz-cursor-theme
+      - light-themes
+      - adwaita-icon-theme
+      - gnome-themes-standard
+      - shared-mime-info
+      - libgtk2.0-0
+      - libgdk-pixbuf2.0-0
+      - libglib2.0-bin
+      - libgtk2.0-bin
+      - unity-gtk2-module
+      - libappindicator1
+      - locales-all
+      - ibus-gtk
+      - libibus-1.0-5
+
+plugs:
+  gtk-2-engines:
+    interface: content
+    target: $SNAP/lib/gtk-2.0
+    default-provider: gtk2-common-themes
+  gtk-2-themes:
+    interface: content
+    target: $SNAP/data-dir/themes
+    default-provider: gtk-common-themes
+  icon-themes:
+    interface: content
+    target: $SNAP/data-dir/icons
+    default-provider: gtk-common-themes
+  sound-themes:
+    interface: content
+    target: $SNAP/data-dir/sounds
+    default-provider: gtk-common-themes