feat: resolve SDDM power icons from the selected icon theme

The greeter runs as the sddm user and cannot read the login user's
dconf, so udt-accent resolves the four FreeDesktop power icon names in
the icon theme gsettings reports and bakes absolute paths into the
generated sddm-theme.conf. An unresolved key stays empty and the
theme falls back to its bundled SVGs.

1 files changed, 101 insertions, 2 deletions

diff --git a/bin/udt-accent b/bin/udt-accent
index 4dc7db3..53839b1 100755
--- a/bin/udt-accent
+++ b/bin/udt-accent
@@ -59,6 +59,21 @@ SDDM_KEYS = ["base", "mantle", "crust", "surface0", "surface1", "surface2",
              "text", "subtext0", "subtext1", "overlay0", "overlay1", "overlay2",
              "red", "yellow", "green", "teal", "blue", "lavender"]
 
+# The SDDM panel's power icons. The greeter runs as the sddm user and cannot
+# read the login user's dconf, so udt-accent resolves the selected icon theme
+# to absolute paths and bakes them into the INI. An unresolved key stays empty
+# and the theme draws its bundled SVG instead.
+ICON_SCHEMA = "org.gnome.desktop.interface"
+ICON_KEY = "icon-theme"
+ICON_DIRS = [Path.home() / ".local" / "share" / "icons",
+             Path("/usr/share/icons")]
+POWER_ICONS = {
+    "powerIcon": ["system-shutdown"],
+    "rebootIcon": ["system-reboot"],
+    "suspendIcon": ["system-suspend"],
+    "hibernateIcon": ["system-hibernate", "system-suspend-hibernate"],
+}
+
 
 def write_atomic(path, content, mode=None, dir_mode=None):
     """Write a file atomically, so no reader ever sees it half-written.
@@ -308,7 +323,55 @@ def write_sublime(name):
         write_atomic(SUBLIME, new)
 
 
-def sddm_conf(palette, name, image):
+def icon_theme():
+    """The icon theme the appearance drawer selected, or "" if unreadable.
+
+    gsettings runs as the login user, so it reads the user's dconf. Empty on
+    any failure: the theme then keeps its bundled power icons.
+    """
+    try:
+        got = subprocess.run(["gsettings", "get", ICON_SCHEMA, ICON_KEY],
+                             capture_output=True, text=True, check=True)
+    except (OSError, subprocess.CalledProcessError):
+        return ""
+    return got.stdout.strip().strip("'")
+
+
+def find_icon(theme, names, dirs=None):
+    """Absolute path to the first of `names` found in `theme`, else "".
+
+    A theme may ship an icon flat or as a symbolic variant at several sizes.
+    Prefer the symbolic variant, then the largest size directory, so the panel
+    gets a tintable silhouette. `dirs` is injectable for the selftest.
+    """
+    if not theme:
+        return ""
+    dirs = ICON_DIRS if dirs is None else dirs
+    wanted = set(names) | {f"{name}-symbolic" for name in names}
+    matches = []
+    for base in dirs:
+        root = base / theme
+        if not root.is_dir():
+            continue
+        matches = [p for p in root.rglob("*.svg") if p.stem in wanted]
+        if matches:
+            break
+
+    def rank(path):
+        symbolic = path.stem.endswith("-symbolic")
+        sizes = [int(part) for part in path.parts if part.isdigit()]
+        return (symbolic, max(sizes, default=0))
+
+    return str(max(matches, key=rank)) if matches else ""
+
+
+def power_icons():
+    """The four power icon paths, resolved from the selected icon theme."""
+    theme = icon_theme()
+    return {key: find_icon(theme, names) for key, names in POWER_ICONS.items()}
+
+
+def sddm_conf(palette, name, image, icons=None):
     """The SDDM theme config, as an INI fragment.
 
     theme.conf.user overrides theme.conf and is exposed to the theme as the
@@ -323,6 +386,8 @@ def sddm_conf(palette, name, image):
         f"accent={ACCENTS[name]}",
     ]
     lines += [f"{key}={palette.get(key, '#000000')}" for key in SDDM_KEYS]
+    icons = icons or {}
+    lines += [f"{key}={icons.get(key, '')}" for key in POWER_ICONS]
     return "\n".join(lines) + "\n"
 
 
@@ -338,7 +403,7 @@ def write_sddm(name, image):
         print("udt-accent: palette.rasi unreadable, skipping SDDM theme",
               file=sys.stderr)
         return
-    write_atomic(SDDM_OUTPUT, sddm_conf(palette, name, image),
+    write_atomic(SDDM_OUTPUT, sddm_conf(palette, name, image, power_icons()),
                  mode=0o644, dir_mode=0o755)
 
 
@@ -449,6 +514,40 @@ def selftest():
         assert outdir.stat().st_mode & 0o777 == 0o755, \
             oct(outdir.stat().st_mode & 0o777)
 
+    # Power icons: an unknown or empty theme resolves to empty, so the greeter
+    # falls back to its bundled SVGs; a real theme prefers the symbolic variant
+    # and a name list is honoured in order.
+    assert find_icon("", ["system-shutdown"]) == ""
+    assert find_icon("no-such-theme-udt", ["system-shutdown"]) == ""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        root = Path(tmpdir) / "icons"
+        base = root / "probe"
+        (base / "actions" / "16").mkdir(parents=True)
+        (base / "actions" / "symbolic").mkdir(parents=True)
+        (base / "actions" / "16" / "system-shutdown.svg").write_text("<svg/>")
+        (base / "actions" / "symbolic" / "system-shutdown-symbolic.svg").write_text("<svg/>")
+        got = find_icon("probe", ["system-shutdown"], dirs=[root])
+        assert got.endswith("actions/symbolic/system-shutdown-symbolic.svg"), got
+        (base / "actions" / "symbolic" / "system-shutdown-symbolic.svg").unlink()
+        got = find_icon("probe", ["system-shutdown"], dirs=[root])
+        assert got.endswith("actions/16/system-shutdown.svg"), got
+        assert find_icon("probe", ["system-hibernate", "system-suspend-hibernate"],
+                         dirs=[root]) == ""
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        probe_image = Path(tmpdir) / "wall.png"
+        probe_image.write_bytes(b"")
+        palette = {k: "#1e2030" for k in SDDM_KEYS}
+        icons = {"powerIcon": "/tmp/power.svg", "rebootIcon": "",
+                 "suspendIcon": "", "hibernateIcon": ""}
+        text = sddm_conf(palette, FALLBACK, str(probe_image), icons)
+        for key in ("powerIcon", "rebootIcon", "suspendIcon", "hibernateIcon"):
+            assert f"\n{key}=" in "\n" + text, f"sddm conf missing {key}"
+        assert "\npowerIcon=/tmp/power.svg" in "\n" + text
+
+    got = power_icons()
+    assert set(got) == {"powerIcon", "rebootIcon", "suspendIcon", "hibernateIcon"}
+
     print("selftest OK")