Package development

Gluon packages are OpenWrt packages and follow the same rules described at https://openwrt.org/docs/guide-developer/packages.

Gluon package makefiles

As many packages share the same or a similar structure, Gluon provides a package/gluon.mk that can be included for common definitions. This file replaces OpenWrt’s $(INCLUDE_DIR)/package.mk; it is usually included as include ../gluon.mk from Gluon core packages, or as include $(TOPDIR)/../package/gluon.mk from feeds.

Provided macros

  • GluonBuildI18N (arguments: <source directory>)

    Converts the .po files for all enabled languages from the given source directory to the binary .lmo format and stores them in $(PKG_BUILD_DIR)/i18n.

  • GluonInstallI18N

    Install .lmo files from $(PKG_BUILD_DIR)/i18n to /lib/gluon/web/i18n in the package install directory.

  • GluonSrcDiet (arguments: <source directory>, <destination directory>)

    Copies a directory tree, processing all files in it using LuaSrcDiet. The directory tree should only contain Lua files.

  • GluonCheckSite (arguments: <source file>)

    Intended to be used in a package postinst script. It will use the passed Lua snippet to verify package-specific site configuration.

  • BuildPackageGluon (replaces BuildPackage)

    Extends the Package/<name> definition with common defaults, sets the package install script to the common Gluon/Build/Install, and automatically creates a postinst script using GluonCheckSite if a check_site.lua is found in the package directory.

Default build steps

These defaults greatly reduce the boilerplate in each package, but they can also be confusing because of the many implicit behaviors depending on files in the package directory. If any part of Gluon/Build/Compile or Gluon/Build/Install does not work as intended for a package, the compile and install steps can always be replaced or extended.

Build/Compile is set to Gluon/Build/Compile by default, which will

  • run OpenWrt standard default commands (Build/Compile/Default) if a src/Makefile or src/CMakeLists.txt is found
  • run GluonSrcDiet on all files in the luasrc directory
  • run GluonBuildI18N if a i18n directory is found

Package/<name> defaults to Gluon/Build/Install for packages defined using BuildPackageGluon, which will

  • copy all files from $(PKG_INSTALL_DIR) into the package if $(PKG_INSTALL) is 1
  • copy all files from files into the package
  • copy all Lua files built from luasrc into the package
  • installs $(PKG_BUILD_DIR)/respondd.so to /usr/lib/respondd/$(PKG_NAME).so if src/respondd.c exists
  • installs compiled i18n .lmo files

Feature flags

Feature flags provide a convenient way to define package selections without making it necessary to list each package explicitly. The list of features to enable for a Gluon build is set by the GLUON_FEATURES variable in site.mk.

The main feature flag definition file is package/features, but each package feed can provide additional definitions in a file called features at the root of the feed repository.

Each flag $flag will include the package the name gluon-$flag by default. The feature definition file can modify the package selection by adding or removing packages when certain combinations of flags are set.

Feature definitions use Lua syntax. The function feature has two arguments:

  • A logical expression composed of feature flag names (each prefixed with an underscore before the opening quotation mark), logical operators (and, or, not) and parantheses
  • A table with settings that are applied when the logical expression is satisfied:
    • Setting nodefault to true suppresses the default of including the gluon-$flag package. This setting is only applicable when the logical expression is a single, non-negated flag name.
    • The packages field adds or removes packages to install. A package is removed when the package name is prefixed with a - (after the opening quotation mark).

Example:

feature(_'web-wizard', {
  nodefault = true,
  packages = {
    'gluon-config-mode-hostname',
    'gluon-config-mode-geo-location',
    'gluon-config-mode-contact-info',
    'gluon-config-mode-outdoor',
  },
})

feature(_'web-wizard' and (_'mesh-vpn-fastd' or _'mesh-vpn-tunneldigger'), {
  packages = {
    'gluon-config-mode-mesh-vpn',
  },
})

feature(_'no-radvd', {
  nodefault = true,
  packages = {
    '-gluon-radvd',
  },
})

This will

  • disable the inclusion of the (non-existent) packages gluon-web-wizard and gluon-no-radvd when their corresponding feature flags appear in GLUON_FEATURES
  • enable four additional config mode packages when the web-wizard feature is enabled
  • enable gluon-config-mode-mesh-vpn when both web-wizard and one of mesh-vpn-fastd and mesh-vpn-tunneldigger are enabled
  • disable the gluon-radvd package when gluon-no-radvd is enabled