feat(icons): read the icon theme from gsettings

The icon theme name was hardcoded in three places (bin/wb-icon,
modules/extras/taskbar.jsonc and install.sh), so switching themes in the
appearance drawer was silently reverted as far as this bar was concerned.

wb-icon now reads org.gnome.desktop.interface icon-theme and gains two modes
for install.sh: --path NAME prints one icon's absolute path, --theme prints
the resolved theme name.

Icons are resolved per name rather than by substituting a directory prefix,
because themes disagree about both subdirectory and file extension: the Suru
themes keep web-browser at categories/22/*.svg, elementary-xfce at
apps/22/*.png. Only a real GTK lookup knows the path.

styles/modules.css therefore carries @ICON:name@ placeholders and
modules/extras/taskbar.jsonc carries @ICON_THEME@, both filled at install
time. taskbar.jsonc is generated rather than symlinked for that reason, and
install.sh removes the old symlink first so the redirect cannot overwrite the
committed source.

A theme missing one of the twenty names fails the install at the --selftest
step rather than drawing empty pills.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 52 insertions, 5 deletions

diff --git a/bin/wb-icon b/bin/wb-icon
index 9e011b9..1d76369 100755
--- a/bin/wb-icon
+++ b/bin/wb-icon
@@ -10,6 +10,7 @@
 #
 #     wb-icon volume     # reads wpctl, prints the matching icon
 #     wb-icon mic
+#     wb-icon --path NAME # absolute path of one icon, for install.sh
 #     wb-icon --selftest # every name this bar asks for must resolve
 #
 # Icons keep their own colours: this desktop's icon theme draws them with
@@ -24,9 +25,29 @@ import gi
 gi.require_version("Gtk", "3.0")
 from gi.repository import Gtk  # noqa: E402  (must follow require_version)
 
-# The icon theme to draw from. Kept in one place because changing it is a
-# single edit, and because --selftest needs the same value the modules use.
-THEME = "Material-Black-Plum-Suru"
+# The icon theme to draw from: whatever the desktop is set to. The appearance
+# drawer switches it through gsettings, so reading that key is what keeps this
+# bar following a switch instead of silently pointing at the old theme.
+#
+# The fallback only matters when gsettings is unreadable; GTK falls back to
+# hicolor on its own if the named theme is missing.
+FALLBACK_THEME = "Adwaita"
+
+
+def icon_theme():
+    """The desktop's icon theme name, per gsettings."""
+    try:
+        out = subprocess.run(
+            ["gsettings", "get", "org.gnome.desktop.interface", "icon-theme"],
+            capture_output=True, text=True, timeout=2,
+        ).stdout.strip()
+    except (OSError, subprocess.SubprocessError):
+        return FALLBACK_THEME
+    # gsettings quotes its answer: 'Material-Black-Plum-Suru'
+    return out.strip("'\"") or FALLBACK_THEME
+
+
+THEME = icon_theme()
 
 SIZE = 22
 
@@ -47,7 +68,13 @@ ICONS = {
 
 
 def lookup(name):
-    """Absolute path of an icon in THEME, or None."""
+    """Absolute path of an icon in THEME, or None.
+
+    GTK resolves the theme's own layout, so this works across icon themes
+    that disagree about subdirectory and file extension: the Suru themes keep
+    web-browser under categories/22/*.svg, elementary-xfce under apps/22/*.png.
+    Nothing outside this function may assume a path shape.
+    """
     theme = Gtk.IconTheme.new()
     theme.set_custom_theme(THEME)
     info = theme.lookup_icon(name, SIZE, 0)
@@ -138,7 +165,8 @@ def selftest():
 
 def main(argv):
     if len(argv) < 2 or argv[1] in ("-h", "--help"):
-        print(__doc__ or "usage: wb-icon <volume|mic|idle|--selftest> [state]")
+        print(__doc__ or
+              "usage: wb-icon <volume|mic|--path NAME|--theme|--selftest>")
         return 0
 
     what = argv[1]
@@ -146,6 +174,25 @@ def main(argv):
     if what == "--selftest":
         return selftest()
 
+    # install.sh bakes icon paths into the generated stylesheet, because CSS
+    # cannot look an icon up by name. It asks here so that the theme is
+    # resolved in exactly one place.
+    if what == "--path":
+        if len(argv) < 3:
+            print("wb-icon: --path needs an icon name", file=sys.stderr)
+            return 2
+        path = lookup(argv[2])
+        if not path:
+            print(f"wb-icon: no icon named {argv[2]!r} in {THEME}",
+                  file=sys.stderr)
+            return 1
+        print(path)
+        return 0
+
+    if what == "--theme":
+        print(THEME)
+        return 0
+
     if what == "volume":
         pct, muted = wpctl("@DEFAULT_AUDIO_SINK@")
         if pct is None: