doc: add options to change what /usr and /etc paths are shown

Add options to change the 'prefix' and 'sysconfdir' values shown in
documentation, e.g. on config file man pages.

Update CI to set them, so that its produced output doesn't show
/builds/pipewire/... on man pages

.gitlab-ci.yml

@@ -265,6 +265,8 @@ build_on_fedora:
   variables:
     MESON_OPTIONS: >-
         -Ddocs=enabled
+        -Ddoc-prefix-value=/usr
+        -Ddoc-sysconfdir-value=/etc
         -Dinstalled_tests=enabled
         -Dsystemd-system-service=enabled
         -Dbluez5-backend-hsphfpd=enabled

doc/meson.build

@@ -7,14 +7,33 @@ doxyfile_conf.set('top_srcdir', meson.project_source_root())
 doxyfile_conf.set('top_builddir', meson.project_build_root())
 doxyfile_conf.set('output_directory', meson.current_build_dir())
 
+doc_prefix_value = get_option('doc-prefix-value')
+doc_sysconfdir_value = get_option('doc-sysconfdir-value')
+
+if doc_prefix_value == '' and doc_sysconfdir_value == ''
+   doc_spa_plugindir = spa_plugindir
+   doc_pipewire_configdir = pipewire_configdir
+   doc_pipewire_confdatadir = pipewire_confdatadir
+else
+   if doc_prefix_value == ''
+     doc_prefix_value = get_option('prefix')
+   endif
+   if doc_sysconfdir_value == ''
+     doc_sysconfdir_value = get_option('sysconfdir')
+   endif
+   doc_spa_plugindir = doc_prefix_value / get_option('libdir') / spa_name
+   doc_pipewire_configdir = doc_prefix_value / doc_sysconfdir_value / 'pipewire'
+   doc_pipewire_confdatadir = doc_prefix_value / get_option('datadir') / 'pipewire'
+endif
+
 doxygen_env = environment()
 doxygen_env.set('PACKAGE_NAME', meson.project_name())
 doxygen_env.set('PACKAGE_VERSION', meson.project_version())
 doxygen_env.set('PACKAGE_URL', 'https://pipewire.org')
 doxygen_env.set('PACKAGE_BUGREPORT', 'https://gitlab.freedesktop.org/pipewire/pipewire/issues')
-doxygen_env.set('PIPEWIRE_CONFIG_DIR', pipewire_configdir)
-doxygen_env.set('PIPEWIRE_CONFDATADIR', pipewire_confdatadir)
-doxygen_env.set('SPA_PLUGINDIR', spa_plugindir)
+doxygen_env.set('PIPEWIRE_CONFIG_DIR', doc_pipewire_configdir)
+doxygen_env.set('PIPEWIRE_CONFDATADIR', doc_pipewire_confdatadir)
+doxygen_env.set('SPA_PLUGINDIR', doc_spa_plugindir)
 doxygen_env.set('BUILD_DIR', meson.current_build_dir())
 
 dot_found = find_program('dot', required: false).found()

meson_options.txt

@@ -350,3 +350,11 @@ option('snap',
        description : 'Enable Snap permissions support.',
        type : 'feature',
        value : 'auto')
+option('doc-prefix-value',
+       description : 'Installation prefix to show in documentation instead of the actual value.',
+       type : 'string',
+       value : '')
+option('doc-sysconfdir-value',
+       description : 'Sysconf data directory to show in documentation instead of the actual value.',
+       type : 'string',
+       value : '')