fix: window list flicker and icons missing from the icon theme

The Windows tab rebuilt every row once a second, and each rebuild walked
every window icon through its fallback names again, so the rows blinked.
It now re-renders only when the state changed.

Icon lookup only searched the configured theme, so an app the theme
lacks (pcmanfm-qt under candy-icons) lost its icon and showed its label.
It now falls back to hicolor, as the icon theme spec does, in hicolor's
size/category layout.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/deckit/server.py b/deckit/server.py
index e392041..6bea422 100644
--- a/deckit/server.py
+++ b/deckit/server.py
@@ -84,12 +84,15 @@ def icon_path(name: str, theme: str | None = None, bases=ICON_BASES):
     """An app icon from the installed icon theme, so launchers follow the theme."""
     if not ICON.fullmatch(name):
         return None
-    theme = theme or icon_theme()
-    for base in bases:
-        for sub in ("apps/scalable", "apps/64", "apps/48", "apps/32"):
-            path = Path(base) / theme / sub / f"{name}.svg"
-            if path.is_file():
-                return path
+    # hicolor last: the spec's fallback every theme inherits, where apps
+    # install their own icon when the theme has none for them.
+    for th in (theme or icon_theme(), "hicolor"):
+        for base in bases:
+            # Themes lay out category/size (candy-icons) or size/category (hicolor).
+            for sub in ("apps/scalable", "apps/64", "apps/48", "apps/32", "scalable/apps"):
+                path = Path(base) / th / sub / f"{name}.svg"
+                if path.is_file():
+                    return path
     return None