feat: allow overriding icon theme via cli.json (#106)

* theme: allow overriding Qt icon theme via cli.json

Papirus colors XDG special folders (Downloads, Pictures, Music, etc.)
differently from regular ones - they end up a different color while
everything else stays neutral. With themes like breeze-dark, all folder
icons share the same style, so everything looks consistent.

Add optional `iconTheme` field to the `theme` section of cli.json.
When set, it replaces the Papirus icon theme in the generated qtengine
config with the specified theme.

Example usage in cli.json:
  "theme": { "iconTheme": "breeze-dark" }

* theme: allow overriding Qt and GTK icon theme via cli.json

Some folders in Dolphin end up with Papirus-style icons while others
use the default theme icons, resulting in two different icon styles
mixed together in the same view. Dolphin's default folder icons take
their color directly from the active color scheme, so they always match
the theme exactly - Papirus has a fixed, limited palette and does not
always match.

Add optional iconThemeDark and iconThemeLight fields to the theme
section of cli.json. When set, they override the Papirus icon theme in
both the generated qtengine config and the GTK dconf setting. A generic
iconTheme field is also supported as a fallback for both modes.

Example usage in cli.json:
  "theme": { "iconThemeDark": "breeze-dark", "iconThemeLight": "breeze" }

---------

Co-authored-by: Foxlike Creature <safonovkirill113@gmail.com>

src/caelestia/utils/theme.py

@@ -302,7 +302,7 @@ def _determine_hue_color(r: int, g: int, b: int, brightness: int, use_pale: bool
 
 
 @log_exception
-def apply_gtk(colours: dict[str, str], mode: str) -> None:
+def apply_gtk(colours: dict[str, str], mode: str, icon_theme: str | None = None) -> None:
     gtk_template = gen_replace(colours, templates_dir / "gtk.css", hash=True)
     thunar_template = gen_replace(colours, templates_dir / "thunar.css", hash=True)
 
@@ -313,18 +313,21 @@ def apply_gtk(colours: dict[str, str], mode: str) -> None:
 
     subprocess.run(["dconf", "write", "/org/gnome/desktop/interface/gtk-theme", "'adw-gtk3-dark'"])
     subprocess.run(["dconf", "write", "/org/gnome/desktop/interface/color-scheme", f"'prefer-{mode}'"])
-    subprocess.run(["dconf", "write", "/org/gnome/desktop/interface/icon-theme", f"'Papirus-{mode.capitalize()}'"])
+    gtk_icon_theme = icon_theme if icon_theme is not None else f"Papirus-{mode.capitalize()}"
+    subprocess.run(["dconf", "write", "/org/gnome/desktop/interface/icon-theme", f"'{gtk_icon_theme}'"])
 
     sync_papirus_colors(colours["primary"])
 
 
 @log_exception
-def apply_qt(colours: dict[str, str], mode: str) -> None:
+def apply_qt(colours: dict[str, str], mode: str, icon_theme: str | None = None) -> None:
     colours = gen_replace(colours, templates_dir / f"qt{mode}.colors", hash=True)
     write_file(config_dir / "qtengine/caelestia.colors", colours)
 
     config = (templates_dir / "qtengine.json").read_text()
     config = config.replace("{{ $mode }}", mode.capitalize())
+    if icon_theme is not None:
+        config = config.replace(f'"iconTheme": "Papirus-{mode.capitalize()}"', f'"iconTheme": "{icon_theme}"')
     write_file(config_dir / "qtengine/config.json", config)
 
 
@@ -438,10 +441,11 @@ def apply_colours(colours: dict[str, str], mode: str) -> None:
                 apply_nvtop(colours)
             if check("enableHtop"):
                 apply_htop(colours)
+            icon_theme = cfg.get(f"iconTheme{mode.capitalize()}") or cfg.get("iconTheme")
             if check("enableGtk"):
-                apply_gtk(colours, mode)
+                apply_gtk(colours, mode, icon_theme)
             if check("enableQt"):
-                apply_qt(colours, mode)
+                apply_qt(colours, mode, icon_theme)
             if check("enableWarp"):
                 apply_warp(colours, mode)
             if check("enableChromium"):