feat(palette): add GTK3 and GTK4 as palette consumers

70 new targets: the two stylesheets, the metatheme descriptor and 67 widget
assets. The assets are discovered from disk rather than listed, because they
arrive as a set from upstream and a hand-written list would miss one added by
a future refresh.

Substitution does the _RGB@ form before the bare @ROLE@: @FG@ is a prefix of
@FG_RGB@, so the other order would eat the start of the triple placeholder
and leave a literal "_RGB@" in the CSS.

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

1 files changed, 43 insertions, 0 deletions

diff --git a/bin/udt-palette b/bin/udt-palette
index f92a6b7..bee7dc5 100755
--- a/bin/udt-palette
+++ b/bin/udt-palette
@@ -368,6 +368,37 @@ def gen_kvantum(res, scheme, palette, template):
     return out
 
 
+def gen_gtk(res, scheme, palette, template):
+    """GTK3/GTK4: substitute the palette into the upstream stylesheet.
+
+    Derived from catppuccin/gtk v1.0.3, which is archived upstream. The whole
+    file is substituted rather than just its @define-color block, because the
+    8400 lines above that block hardcode palette colours too.
+
+    Two forms per role: the hex, and the bare `r, g, b` triple that the theme
+    writes inside rgba(). Neutral greys and upstream's derived tints are left
+    exactly as drawn, the same rule the Kvantum SVG follows.
+    """
+    out = template
+    for role in GTK_ROLES:
+        # _RGB@ first: @FG@ is a prefix of @FG_RGB@, so the bare form would
+        # otherwise eat the start of the triple placeholder and leave "_RGB@".
+        out = out.replace(f"@{role.upper()}_RGB@", rgb_triple(res[role]))
+        out = out.replace(f"@{role.upper()}@", hex6(res[role]))
+    # Spelled for the upstream colour it replaces rather than for its role,
+    # which keeps the template readable against the theme it came from.
+    out = out.replace("@MAUVE@", hex6(res["highlight"]))
+    return out
+
+
+def gen_gtk_asset(res, scheme, palette, template):
+    """One GTK widget asset. Only three palette colours appear in the SVGs."""
+    out = template
+    for role in ("bg", "bg_alt", "accent"):
+        out = out.replace(f"@{role.upper()}@", hex6(res[role]))
+    return out
+
+
 def gen_homepage(res, scheme, palette):
     """gethomepage: a custom.css overriding its ten-step colour ramp.
 
@@ -595,6 +626,18 @@ TARGETS = [
      "templates/sublime/udt.sublime-color-scheme.in"),
     ("templates/sublime/udt.sublime-theme", gen_sublime_theme,
      "templates/sublime/udt.sublime-theme.in"),
+    ("templates/gtk/gtk3.css", gen_gtk, "templates/gtk/gtk3.css.in"),
+    ("templates/gtk/gtk4.css", gen_gtk, "templates/gtk/gtk4.css.in"),
+    ("templates/gtk/index.theme", gen_gtk, "templates/gtk/index.theme.in"),
+]
+
+# The GTK widget assets, one target each. Discovered rather than listed: there
+# are 67 of them and they arrive as a set from upstream, so a hand-written list
+# would silently miss one added by a future theme refresh.
+TARGETS += [
+    (f"templates/gtk/assets/{p.name[:-3]}", gen_gtk_asset,
+     f"templates/gtk/assets/{p.name}")
+    for p in sorted((REPO / "templates" / "gtk" / "assets").glob("*.svg.in"))
 ]