fix(theming): skip theme writes and hooks when wallpaper change produces no diff

Issue: #2400

Author: Ly-sec

Scripts/python/src/theming/lib/renderer.py

@@ -22,7 +22,7 @@
 import sys
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Any, Optional, Union
+from typing import Any, Optional, Tuple, Union
 
 try:
     import tomllib
@@ -970,22 +970,34 @@ def render(self, template_text: str) -> str:
 
         return result
 
-    def render_file(self, input_path: Path, output_path: Path) -> bool:
+    def render_file(self, input_path: Path, output_path: Path) -> Tuple[bool, bool]:
         """Render a template file to an output path.
 
-        Returns True if successful, False if skipped due to errors.
+        Returns (success, wrote) where wrote is False if the file was skipped because
+        content was already identical (avoids mtime bumps and app reloads).
         """
         self._current_file = str(input_path)
         success = False
+        wrote = False
         try:
             template_text = input_path.read_text()
             rendered_text = self.render(template_text)
 
             if self._error_count > 0:
                 print(f"Skipping {output_path}: template has {self._error_count} error(s)", file=sys.stderr)
             else:
-                output_path.parent.mkdir(parents=True, exist_ok=True)
-                output_path.write_text(rendered_text)
+                out = Path(output_path).expanduser()
+                out.parent.mkdir(parents=True, exist_ok=True)
+                skip_write = False
+                if out.is_file():
+                    try:
+                        if out.read_text() == rendered_text:
+                            skip_write = True
+                    except OSError:
+                        pass
+                if not skip_write:
+                    out.write_text(rendered_text)
+                    wrote = True
                 success = True
         except FileNotFoundError:
             self._log_error(f"Template file not found: {input_path}")
@@ -995,7 +1007,7 @@ def render_file(self, input_path: Path, output_path: Path) -> bool:
             self._log_error(f"Unexpected error: {e}")
         finally:
             self._current_file = None
-        return success
+        return success, wrote
 
     # --- Custom Colors ---
 
@@ -1151,7 +1163,13 @@ def process_config_file(self, config_path: Path):
                     rendered_compare_to = self.render(compare_to)
                     self.closest_color = find_closest_color(rendered_compare_to, colors_to_compare)
 
-                self.render_file(Path(input_path).expanduser(), Path(output_path).expanduser())
+                ok, wrote = self.render_file(Path(input_path).expanduser(), Path(output_path).expanduser())
+                if not ok:
+                    continue
+
+                # Hooks reload external apps (e.g. Discord); skip when output unchanged
+                if not wrote:
+                    continue
 
                 # Execute pre_hook if specified
                 pre_hook = template.get("pre_hook")

Services/Theming/AppThemeService.qml

@@ -23,8 +23,11 @@ Singleton {
 
       if (Settings.data.colorSchemes.useWallpaperColors) {
         generateFromWallpaper();
+      } else if (ColorSchemeService.lastPredefinedSchemeData) {
+        // Regenerate templates only; skip applyScheme so colors.json and scheme reload stay untouched
+        // when outputs are unchanged (see template processor skip-identical writes).
+        generateFromPredefinedScheme(ColorSchemeService.lastPredefinedSchemeData);
       } else {
-        // Re-run predefined scheme templates so {{image}} reflects the new wallpaper path
         ColorSchemeService.applyScheme(Settings.data.colorSchemes.predefinedScheme);
       }
     }

Services/Theming/ColorSchemeService.qml

@@ -16,6 +16,9 @@ Singleton {
   property string schemesDirectory: Quickshell.shellDir + "/Assets/ColorScheme"
   property string downloadedSchemesDirectory: Settings.configDir + "colorschemes"
   property string colorsJsonFilePath: Settings.configDir + "colors.json"
+  // Last successfully parsed predefined scheme JSON (full object). Used to refresh app templates
+  // on wallpaper changes without re-running applyScheme (avoids rewriting colors.json when unchanged).
+  property var lastPredefinedSchemeData: null
   readonly property string gtkRefreshScript: Quickshell.shellDir + "/Scripts/python/src/theming/gtk-refresh.py"
 
   // prefer-light/prefer-dark only; GTK template post_hook still runs full gtk-refresh.
@@ -203,6 +206,7 @@ Singleton {
           }
         }
         writeColorsToDisk(variant);
+        lastPredefinedSchemeData = data;
         Logger.i("ColorScheme", "Applying color scheme:", getBasename(path));
 
         // Generate templates for predefined color schemes