fix: Respect symbolic toolbar icons as fallback

CHANGES

@@ -52,6 +52,7 @@ Version 1.6.0-dev (development of upcoming release)
 * Removed: UI translation in Bosnian, Thai, and Occidental/Interlingue (#1914)
 * Removed: LICENSE file in favor of LICENSES directory and LICENSES.md file
 * Removed: SSH Cipher configuration in Manage profiles dialog (#2143)
+# Fixed: Consider symbolic icons as fallbacks (#2345, #2289)
 * Fixed: Warn users and prevent backups to exFAT volumes due to lack of hardlink support (#2337)
 * Fixed: Show proper message to users when root mode fails due to inactive or missing polkit agent (#2328, Derek Veit @DerekVeit)
 * Fixed: Crash in Compare snapshots dialog (aka Snapshots dialog) when comparing/diff two backups (#2327 Michael Neese @madic-creates)

qt/icon.py

@@ -28,6 +28,11 @@
     'oxygen',
 )
 ICON_NAME_TO_CHECK = 'document-save'
+# A workaround especially for GNOME systems not offering regular icons
+# specified by the Free Desktop Icon Naming Specs.
+# See this thread for more discussion:
+# https://lists.debian.org/debian-gtk-gnome/2026/01/msg00000.html
+ICON_NAME_TO_CHECK_SYMBOLIC = f'{ICON_NAME_TO_CHECK}-symbolic'
 
 for theme in themes_to_try:
     # Check if the current theme does provide the BiT "logo" icon
@@ -36,7 +41,9 @@
     # Note: "hicolor" does currently (2022) use different icon names
     # (not fully compliant to the freedesktop.org spec)
     # and is not recommended as main theme (it is meant as fallback only).
-    if not QIcon.fromTheme(ICON_NAME_TO_CHECK).isNull():
+    if not QIcon.fromTheme(ICON_NAME_TO_CHECK,
+                           QIcon.fromTheme(ICON_NAME_TO_CHECK_SYMBOLIC)
+                           ).isNull():
         logger.debug(
             f'Icon "{ICON_NAME_TO_CHECK}" found in theme: {QIcon.themeName()}'
         )
@@ -47,11 +54,13 @@
     logger.debug(f'Probing theme: "{theme}" '
                  f'(activated as "{QIcon.themeName()}")')
 
-if QIcon.fromTheme(ICON_NAME_TO_CHECK).isNull():
+if QIcon.fromTheme(ICON_NAME_TO_CHECK,
+                   QIcon.fromTheme(ICON_NAME_TO_CHECK_SYMBOLIC)
+                   ).isNull():
     logger.error(
         f'Icon theme missing or not supported. Icon "{ICON_NAME_TO_CHECK}" '
-        'not found. An icon theme should be installed. '
-        'For example: tango-icon-theme, oxygen-icon-theme'
+        f' and "{ICON_NAME_TO_CHECK_SYMBOLIC}" not found. An icon theme should'
+        ' be installed. For example: tango-icon-theme, oxygen-icon-theme'
     )
 
 # Dev note: Please prefer choosing icons from the freedesktop.org spec
@@ -64,6 +73,23 @@
 # the second argument of QIcon.fromTheme() to provide a fallback
 # icon from the freedesktop.org spec.
 
+
+def load_icon(name: str) -> QIcon | None:
+    return QIcon.fromTheme(
+        name,
+        QIcon.fromTheme(f'{name}-symbolic')
+    )
+
+
+def load_icon_alt(names: list[str]) -> QIcon | None:
+    for name in names:
+        ico = load_icon(name)
+
+        if not ico.isNull():
+            return ico
+
+    return None
+
 # BackInTime Logo
 # TODO If we knew for sure that the global var "qapp" exists then
 #      we could use a built-in "standard" Qt icon as fallback if the theme
@@ -76,76 +102,73 @@
 BIT_LOGO_SYMBOLIC_NAME = 'backintime-symbolic'
 
 # Main toolbar
-TAKE_SNAPSHOT       = QIcon.fromTheme('document-save')
-PAUSE               = QIcon.fromTheme('media-playback-pause')
-RESUME              = QIcon.fromTheme('media-playback-start')
-STOP                = QIcon.fromTheme('media-playback-stop')
-REFRESH = QIcon.fromTheme('view-refresh')
+TAKE_SNAPSHOT = load_icon('document-save')
+PAUSE = load_icon('media-playback-pause')
+RESUME = load_icon('media-playback-start')
+STOP = load_icon('media-playback-stop')
+REFRESH = load_icon('view-refresh')
 REFRESH_SNAPSHOT = REFRESH
-SNAPSHOT_NAME       = QIcon.fromTheme('stock_edit',
-                      QIcon.fromTheme('gtk-edit',
-                      QIcon.fromTheme('edit-rename',
-                      QIcon.fromTheme('accessories-text-editor'))))
+SNAPSHOT_NAME = load_icon_alt([
+    'stock_edit',
+    'gtk-edit',
+    'edit-rename',
+    'accessories-text-editor'
+])
+
 EDIT_USER_CALLBACK = SNAPSHOT_NAME
-REMOVE_SNAPSHOT     = QIcon.fromTheme('edit-delete')
-VIEW_SNAPSHOT_LOG   = QIcon.fromTheme('text-plain',
-                      QIcon.fromTheme('text-x-generic'))
-VIEW_LAST_LOG       = QIcon.fromTheme('document-open-recent')
-SETTINGS            = QIcon.fromTheme('gtk-preferences',
-                      QIcon.fromTheme('configure',
-                      # Free Desktop Icon Naming Specification
-                      QIcon.fromTheme('preferences-system')))
-SHUTDOWN            = QIcon.fromTheme('system-shutdown')
-EXIT                = QIcon.fromTheme('gtk-close',
-                      QIcon.fromTheme('application-exit'))
+REMOVE_SNAPSHOT = load_icon('edit-delete')
+VIEW_SNAPSHOT_LOG  = load_icon_alt(['text-plain', 'text-x-generic'])
+VIEW_LAST_LOG = load_icon('document-open-recent')
+SETTINGS = load_icon_alt([
+    'gtk-preferences',
+    'configure',
+    # Free Desktop Icon Naming Specification
+    'preferences-system'
+])
+SHUTDOWN = load_icon('system-shutdown')
+EXIT = load_icon_alt(['gtk-close', 'application-exit'])
 
 # Help menu
-HELP                = QIcon.fromTheme('help-browser',
-                                      QIcon.fromTheme('help-contents'))
-WEBSITE             = QIcon.fromTheme('go-home')
-CHANGELOG           = QIcon.fromTheme('format-justify-fill')
-FAQ                 = QIcon.fromTheme('help-faq',
-                      QIcon.fromTheme('help-hint'))
-QUESTION            = QIcon.fromTheme('stock_dialog-question',
-                      QIcon.fromTheme('help-feedback'))
-BUG                 = QIcon.fromTheme('stock_dialog-error',
-                      QIcon.fromTheme('tools-report-bug'))
-ABOUT               = QIcon.fromTheme('help-about')
+HELP = load_icon_alt(['help-browser', 'help-contents'])
+WEBSITE = load_icon('go-home')
+CHANGELOG = load_icon('format-justify-fill')
+FAQ = load_icon_alt(['help-faq', 'help-hint'])
+QUESTION = load_icon_alt(['stock_dialog-question', 'help-feedback'])
+BUG = load_icon_alt(['stock_dialog-error', 'tools-report-bug'])
+ABOUT = load_icon('help-about')
 
 # Files toolbar
-UP                  = QIcon.fromTheme('go-up')
-                    # currently only in Breeze (see #1159)
-SHOW_HIDDEN         = QIcon.fromTheme('view-hidden',
-                      # icon installed with BIT #507
-                      QIcon.fromTheme('show-hidden',
-                      QIcon.fromTheme('list-add')))
-RESTORE             = QIcon.fromTheme('edit-undo')
-RESTORE_TO          = QIcon.fromTheme('document-revert')
-SNAPSHOTS           = QIcon.fromTheme('file-manager',
-                      QIcon.fromTheme('view-list-details',
-                      QIcon.fromTheme('system-file-manager')))
-
-# Snapshot dialog
-DIFF_OPTIONS        = SETTINGS
-DELETE_FILE         = REMOVE_SNAPSHOT
-SELECT_ALL          = QIcon.fromTheme('edit-select-all')
+UP = load_icon('go-up')
+SHOW_HIDDEN = load_icon_alt([
+    'view-hidden',  # currently only in Breeze (see #1159)
+    'show-hidden',   # icon installed with BIT #507
+    'list-add'
+])
+RESTORE = load_icon('edit-undo')
+RESTORE_TO = load_icon('document-revert')
+SNAPSHOTS = load_icon_alt([
+    'file-manager',
+    'view-list-details',
+    'system-file-manager'
+])
+
+# Compare backups dialog (aka Snapshot dialog)
+DIFF_OPTIONS = SETTINGS
+DELETE_FILE = REMOVE_SNAPSHOT
+SELECT_ALL = load_icon('edit-select-all')
 
 # Restore dialog
-RESTORE_DIALOG      = VIEW_SNAPSHOT_LOG
+RESTORE_DIALOG = VIEW_SNAPSHOT_LOG
 
 # Settings dialog
-SETTINGS_DIALOG     = SETTINGS
-PROFILE_EDIT        = SNAPSHOT_NAME
-ADD                 = QIcon.fromTheme('list-add')
-REMOVE              = QIcon.fromTheme('list-remove')
-FOLDER              = QIcon.fromTheme('folder')
-FILE                = QIcon.fromTheme('text-plain',
-                      QIcon.fromTheme('text-x-generic'))
-EXCLUDE             = QIcon.fromTheme('edit-delete')
-# "emblem-default" is a green mark and doesn't make sense in this case.
-DEFAULT_EXCLUDE     = QIcon.fromTheme('emblem-important')
-INVALID_EXCLUDE     = QIcon.fromTheme('emblem-ohno',
-                      QIcon.fromTheme('face-surprise'))
-
-ENCRYPT = QIcon.fromTheme('lock', QIcon.fromTheme('security-high'))
-LANGUAGE = QIcon.fromTheme('preferences-desktop-locale')
+SETTINGS_DIALOG = SETTINGS
+PROFILE_EDIT = SNAPSHOT_NAME
+ADD = load_icon('list-add')
+REMOVE = load_icon('list-remove')
+FOLDER = load_icon('folder')
+FILE = load_icon_alt(['text-plain', 'text-x-generic'])
+EXCLUDE = load_icon('edit-delete')
+DEFAULT_EXCLUDE = load_icon('emblem-important')
+INVALID_EXCLUDE = load_icon_alt(['emblem-ohno', 'face-surprise'])
+ENCRYPT = load_icon_alt(['lock', 'security-high'])
+LANGUAGE = load_icon('preferences-desktop-locale')