extensions: add 'graphics' extension

This extension provides a shortcut for snaps that make use of the 'mesa-core22' snap
of graphics libraries & resources.  It configures the conventional 'graphics-core22'
content plug and provides the 'graphics-core22-wrapper' helper script for setting-up
the environment.  It also provides the 'wayland-launch' helper script for Wayland programs.

extensions/graphics/wayland/bin/setup.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+set -e
+
+snap_connect_harder() {
+  # Note the available slot providers
+  if ! snap connections %SNAP% | grep --quiet "^content.*%SNAP%:$1.*$"; then
+    available_providers="$(snap interface "$1" | sed -e '1,/slots:/d')"
+  else
+    available_providers="$(snap interface content | sed -e '1,/slots:/d' | grep "$1")"
+  fi
+
+  # For wayland try some well known providers
+  if [ "wayland" = "$1" ]; then
+    for PROVIDER in ubuntu-frame mir-kiosk; do
+       if echo "$available_providers" | grep --quiet "\- ${PROVIDER}"; then
+         sudo snap connect "%SNAP%:$1" "${PROVIDER}:$1"
+         return 0
+       fi
+    done
+  fi
+
+  echo "Warning: Failed to connect '$1'. Please connect manually, available providers are:\n$available_providers"
+}
+
+for PLUG in %PLUGS%; do
+  if ! snap connections %SNAP% | grep --quiet "^.*%SNAP%:${PLUG}.*${PLUG}.*$"; then
+    sudo snap connect "%SNAP%:${PLUG}" 2> /dev/null || snap_connect_harder ${PLUG}
+  fi
+done
+

extensions/graphics/wayland/bin/wayland-launch

@@ -0,0 +1,49 @@
+#!/bin/sh
+set -e
+
+for PLUG in %PLUGS%; do
+  if ! snapctl is-connected ${PLUG}
+  then
+    echo "WARNING: ${PLUG} interface not connected! Please run: /snap/%SNAP%/current/bin/setup.sh"
+  fi
+done
+
+if ! command -v inotifywait > /dev/null
+then
+    echo "ERROR: inotifywait could not be found, mir-kiosk-snap-launch expects:"
+    echo " . . :     stage-packages:"
+    echo " . . :        - inotify-tools"
+    exit 1
+fi
+
+wait_for()
+{
+  until
+    until
+      inotifywait --event create "$(dirname "$1")"&
+      inotify_pid=$!
+      [ -e "$1" ] || sleep 2 && [ -e "$1" ]
+    do
+      wait "${inotify_pid}"
+    done
+    kill "${inotify_pid}"
+    [ -O "$1" ]
+  do
+    sleep 1
+  done
+}
+
+real_xdg_runtime_dir=$(dirname "${XDG_RUNTIME_DIR}")
+real_wayland=${real_xdg_runtime_dir}/${WAYLAND_DISPLAY:-wayland-0}
+
+# On core systems may need to wait for real XDG_RUNTIME_DIR
+wait_for "${real_xdg_runtime_dir}"
+wait_for "${real_wayland}"
+
+mkdir -p "$XDG_RUNTIME_DIR" -m 700
+ln -sf "${real_wayland}" "$XDG_RUNTIME_DIR"
+ln -sf "${real_wayland}.lock" "$XDG_RUNTIME_DIR"
+unset DISPLAY
+
+exec "$@"
+

snapcraft/extensions/graphics.py

@@ -0,0 +1,150 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright 2023 Canonical Ltd.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Extension that automates the use of mesa-core22 (and eventually later) and related helper utilities."""
+from typing import Any, Dict, Optional, Tuple
+
+from overrides import overrides
+
+from .extension import Extension, get_extensions_data_dir
+
+_MESA_SNAP = {"core22": "mesa-core22"}
+_GRAPHICS_NAME = {"core22": "graphics-core22"}
+_BASE_TO_VER = {"core22": "22"}
+_EXT_NAME = "graphics"
+
+
+class Graphics(Extension):
+    """An extension that provides graphics libraries for snaps that don't need to integrate with a full desktop environment.
+
+    This extension is intended to be used with Wayland-ready application snaps that will execute on an
+    Ubuntu Core 22 (and eventually later) systems with ubuntu-frame,
+    however it is not exclusively fixated on Ubuntu Core systems - Desktop should work fine
+    (though you may want to consider one of the gnome/kde extensions instead).
+
+    This extension defines a single plug "graphics-core{base version number}" which is a content
+    interface to the "mesa-core{base version number}" snap that provides the graphics libraries and
+    other important resources.  It also configures apps to use the "opengl" and "wayland" plugs,
+    which are essential for graphical output.
+
+    To assist in the execution of Wayland applications, this extension provides a helper
+    "wayland-launch" script that can be added to the app's command-chain.
+    """
+
+    @staticmethod
+    @overrides
+    def get_supported_bases() -> Tuple[str, ...]:
+        return ("core22",)
+
+    @staticmethod
+    @overrides
+    def get_supported_confinement() -> Tuple[str, ...]:
+        return "strict", "devmode"
+
+    @staticmethod
+    @overrides
+    def is_experimental(base: Optional[str]) -> bool:
+        return False
+
+    @overrides
+    def get_root_snippet(self) -> Dict[str, Any]:
+        base = self.yaml_data["base"]
+        return {
+            "plugs": {
+                _GRAPHICS_NAME[base]: {
+                    "interface": "content",
+                    "target": "$SNAP/graphics",
+                    "default-provider": _MESA_SNAP[base],
+                },
+            },
+            "layout": {
+                "/usr/share/drirc.d": {
+                    "bind": "$SNAP/graphics/drirc.d",
+                },
+                "/usr/share/libdrm": {
+                    "bind": "$SNAP/graphics/libdrm",
+                },
+                "/usr/share/X11": {
+                    "bind": "$SNAP/graphics/X11",
+                },
+            },
+        }
+
+    @overrides
+    def get_app_snippet(self) -> Dict[str, Any]:
+        base = self.yaml_data["base"]
+        return {
+            "command-chain": [
+                f"bin/graphics-core{_BASE_TO_VER[base]}-wrapper",
+            ],
+            "plugs": ["opengl", "wayland"],
+        }
+
+    @overrides
+    def get_part_snippet(self, *, plugin_name: str) -> Dict[str, Any]:
+        return {
+            "build-packages": [
+                "libdrm-dev",
+                "libegl-dev",
+                "libgbm-dev",
+                "libgl-dev",
+                "libgles-dev",
+                "libglx-dev",
+                "libnvidia-egl-wayland-dev",
+                "libva-dev",
+                "libvdpau-dev",
+                "libvulkan-dev",
+                "libwayland-dev",
+                "libwayland-egl-backend-dev",
+                "libx11-xcb-dev",
+                "libxau-dev",
+                "libxcb-dri2-0-dev",
+                "libxcb-dri3-dev",
+                "libxcb-present-dev",
+                "libxcb-sync-dev",
+                "libxcb-xfixes0-dev",
+                "libxcb1-dev",
+                "libxdamage-dev",
+                "libxdmcp-dev",
+                "libxshmfence-dev",
+            ],
+        }
+
+    @overrides
+    def get_parts_snippet(self) -> Dict[str, Any]:
+        base = self.yaml_data["base"]
+        return {
+            f"{_EXT_NAME}/{_GRAPHICS_NAME[base]}": {
+                "source": f"https://github.com/MirServer/{_GRAPHICS_NAME[base]}.git",
+                "plugin": "dump",
+                "override-prime": "craftctl default\n${CRAFT_PART_SRC}"
+                                  f"/bin/{_GRAPHICS_NAME[base]}-cleanup {_MESA_SNAP[base]}",
+                "prime": [f"bin/{_GRAPHICS_NAME[base]}-wrapper"],
+                # This should be the last part to prime, so the clean-up can execute properly
+                "after": list(self.yaml_data["parts"].keys()),
+            },
+            f"{_EXT_NAME}/wayland-launch": {
+                "source": str(get_extensions_data_dir() / _EXT_NAME / "wayland"),
+                "plugin": "dump",
+                "stage-packages": ["inotify-tools"],
+                "override-build": f'PLUGS="opengl wayland {_GRAPHICS_NAME[base]}"\n'
+                                  'sed --in-place "s/%PLUGS%/$PLUGS/g" $CRAFT_PART_BUILD/bin/wayland-launch\n'
+                                  'sed --in-place "s/%PLUGS%/$PLUGS/g" $CRAFT_PART_BUILD/bin/setup.sh\n'
+                                  'sed --in-place "s/%SNAP%/$CRAFT_PROJECT_NAME/g" $CRAFT_PART_BUILD/bin/wayland-launch\n'
+                                  'sed --in-place "s/%SNAP%/$CRAFT_PROJECT_NAME/g" $CRAFT_PART_BUILD/bin/setup.sh\n'
+                                  'craftctl default',
+            },
+        }

snapcraft/extensions/registry.py

@@ -21,6 +21,7 @@
 from snapcraft import errors
 
 from .gnome import GNOME
+from .graphics import Graphics
 from .kde_neon import KDENeon
 from .ros2_humble import ROS2HumbleExtension
 
@@ -30,6 +31,7 @@
     ExtensionType = Type[Extension]
 
 _EXTENSIONS: Dict[str, "ExtensionType"] = {
+    "graphics": Graphics,
     "gnome": GNOME,
     "ros2-humble": ROS2HumbleExtension,
     "kde-neon": KDENeon,