Add initial AppImage packaging support through CPack.

INSTALLER.md

@@ -145,6 +145,16 @@ Overte Interface AppImages are built using [linuxdeploy](https://github.com/linu
    cmake --preset conan-release -DOVERTE_CPU_ARCHITECTURE=-msse3
    ```
 
+3. Create AppImage
+   ```bash
+   cmake --build --preset conan-release --target package
+   ```
+   CPack will build target ALL instead of INTERFACE, which is a limitation of CPack.
+
+4. Lint with [appimagelint](https://github.com/TheAssassin/appimagelint) to check which Linux distributions the AppImage will likely be able to run on.
+
+**Alternatively**, you can also create the AppImage manually:
+
 3. Build Interface
    ```bash
    cmake --build --preset conan-release --target interface
@@ -160,7 +170,6 @@ Overte Interface AppImages are built using [linuxdeploy](https://github.com/linu
    ~/temp/linuxdeploy-x86_64.AppImage --appdir build/AppDir --executable build/interface/interface --output appimage --plugin qt --icon-file interface/icon/interface.svg --desktop-file interface/org.overte.interface.desktop
    ```
 
-7. Lint with [appimagelint](https://github.com/TheAssassin/appimagelint) to check which Linux distributions the AppImage will likely be able to run on.
 
 #### Server
 

cmake/macros/GenerateInstallers.cmake

@@ -5,7 +5,7 @@
 #  Created by Leonardo Murillo on 12/16/2015.
 #  Copyright 2015 High Fidelity, Inc.
 #  Copyright 2021 Vircadia contributors.
-#  Copyright 2022-2024 Overte e.V.
+#  Copyright 2022-2025 Overte e.V.
 #
 #  Distributed under the Apache License, Version 2.0.
 #  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
@@ -111,7 +111,22 @@ macro(GENERATE_INSTALLERS)
       # hide the special Icon? file
       install(CODE "execute_process(COMMAND SetFile -a V \${CMAKE_INSTALL_PREFIX}/${ESCAPED_DMG_SUBFOLDER_NAME}/Icon\\r)")
     endif ()
+  elseif (LINUX)
+    # Produce Interface AppImage using our own scripts.
+    set(CPACK_GENERATOR "External")
 
+    set(CPACK_EXTERNAL_ENABLE_STAGING YES)
+    set(CPACK_EXTERNAL_PACKAGE_SCRIPT "${HF_CMAKE_DIR}/modules/GenerateAppImage.cmake")
+    set(CPACK_CMAKE_SOURCE_DIR "${CMAKE_SOURCE_DIR}")
+
+    # Guard against packaging an AppImage with native optimization.
+    string(FIND "${CMAKE_CXX_FLAGS}" "native" HAS_NATIVE_OPTIMIZATION)
+    if ((NOT HAS_NATIVE_OPTIMIZATION EQUAL -1) AND (NOT APPIMAGE_IGNORE_OPTIMIZATION))
+      message(FATAL_ERROR
+          "Binaries appear to have been built with native optimization. "
+          "The resulting AppImage will not be able to run on most machines. "
+          "Set APPIMAGE_IGNORE_OPTIMIZATION to continue anyway.")
+    endif()
   endif ()
 
   # configure a cpack properties file for custom variables in template

cmake/modules/GenerateAppImage.cmake

@@ -0,0 +1,67 @@
+#
+#  GenerateAppImage.cmake
+#  cmake/modules
+#
+#  This gets called by cmake/macros/GenerateInstaller.cmake and is intended to package Interface AppImages only.
+#
+#  Created by Julian Groß on 2025-04-12.
+#  Copyright 2025 Overte e.V.
+#
+#  Distributed under the Apache License, Version 2.0.
+#  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+#
+
+set(APPIMAGE_DESKTOP_FILE ${CPACK_CMAKE_SOURCE_DIR}/interface/org.overte.interface.desktop)
+set(APPIMAGE_ICON_FILE ${CPACK_CMAKE_SOURCE_DIR}/interface/icon/interface.svg)
+
+find_program(LINUXDEPLOY_EXECUTABLE
+  NAMES linuxdeploy linuxdeploy-${CMAKE_SYSTEM_PROCESSOR}.AppImage
+  PATHS ${CPACK_PACKAGE_DIRECTORY}/linuxdeploy)
+
+if (NOT LINUXDEPLOY_EXECUTABLE)
+  message(STATUS "Downloading linuxdeploy")
+  set(LINUXDEPLOY_EXECUTABLE ${CPACK_PACKAGE_DIRECTORY}/linuxdeploy/linuxdeploy)
+  file(DOWNLOAD
+      https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-${CMAKE_SYSTEM_PROCESSOR}.AppImage
+      ${LINUXDEPLOY_EXECUTABLE}
+      LOG ${CPACK_PACKAGE_DIRECTORY}/linuxdeploy/linuxdeploy-download.log
+      STATUS LINUXDEPLOY_DOWNLOAD)
+  execute_process(COMMAND chmod +x ${LINUXDEPLOY_EXECUTABLE} COMMAND_ECHO STDOUT)
+endif()
+
+find_program(LINUXDEPLOY_PLUGIN_QT_EXECUTABLE
+  NAMES linuxdeploy-plugin-qt linuxdeploy-plugin-qt-${CMAKE_SYSTEM_PROCESSOR}.AppImage
+  PATHS ${CPACK_PACKAGE_DIRECTORY}/linuxdeploy)
+
+if (NOT LINUXDEPLOY_PLUGIN_QT_EXECUTABLE)
+  message(STATUS "Downloading linuxdeploy-plugin-qt")
+  set(LINUXDEPLOY_PLUGIN_QT_EXECUTABLE ${CPACK_PACKAGE_DIRECTORY}/linuxdeploy/linuxdeploy-plugin-qt)
+  file(DOWNLOAD
+      https://github.com/linuxdeploy/linuxdeploy-plugin-qt/releases/download/continuous/linuxdeploy-plugin-qt-${CMAKE_SYSTEM_PROCESSOR}.AppImage
+      ${LINUXDEPLOY_PLUGIN_QT_EXECUTABLE}
+      LOG ${CPACK_PACKAGE_DIRECTORY}/linuxdeploy/linuxdeploy-plugin-qt-download.log
+      STATUS LINUXDEPLOY-PLUGIN-QT_DOWNLOAD)
+  execute_process(COMMAND chmod +x ${LINUXDEPLOY_PLUGIN_QT_EXECUTABLE} COMMAND_ECHO STDOUT)
+endif()
+
+
+file(COPY ${CPACK_CMAKE_SOURCE_DIR}/interface/org.overte.interface.appdata.xml DESTINATION ${CPACK_TEMPORARY_DIRECTORY}/usr/share/metainfo/)
+file(COPY ${CPACK_PACKAGE_DIRECTORY}/interface/plugins DESTINATION ${CPACK_TEMPORARY_DIRECTORY}/usr/bin/)
+file(COPY ${CPACK_PACKAGE_DIRECTORY}/interface/scripts DESTINATION ${CPACK_TEMPORARY_DIRECTORY}/usr/bin/)
+file(COPY ${CPACK_PACKAGE_DIRECTORY}/interface/resources DESTINATION ${CPACK_TEMPORARY_DIRECTORY}/usr/bin/)
+file(COPY ${CPACK_PACKAGE_DIRECTORY}/interface/resources.rcc DESTINATION ${CPACK_TEMPORARY_DIRECTORY}/usr/bin/)
+
+execute_process(
+  COMMAND
+    ${CMAKE_COMMAND} -E env
+      OUTPUT=${CPACK_PACKAGE_FILE_NAME}.AppImage
+      VERSION=${CPACK_PACKAGE_VERSION}
+      QML_SOURCES_PATHS=${CPACK_CMAKE_SOURCE_DIR}/interface/resources/qml/
+    ${LINUXDEPLOY_EXECUTABLE}
+    --appdir=${CPACK_TEMPORARY_DIRECTORY}
+    --executable=${CPACK_PACKAGE_DIRECTORY}/interface/interface
+    --desktop-file=${APPIMAGE_DESKTOP_FILE}
+    --icon-file=${APPIMAGE_ICON_FILE}
+    --plugin qt
+    --output=appimage
+)