fix(fastfetch): make fastfetch theme sync non-destructive to preserve layout and modules

quickshell/services/python/theme_sync.py

@@ -1006,10 +1006,35 @@ theme[upload_end]="#ff80bf"
             pass
 
 def sync_fastfetch(bg, surface, current_line, fg, accent, sub_accent):
+    import re
     fastfetch_dir = os.path.expanduser('~/.config/fastfetch')
     os.makedirs(fastfetch_dir, exist_ok=True)
     conf_path = os.path.join(fastfetch_dir, 'config.jsonc')
     
+    if os.path.exists(conf_path):
+        try:
+            with open(conf_path, 'r', encoding='utf-8') as f:
+                content = f.read()
+            
+            modified = False
+            if '"keys"' in content:
+                content, count1 = re.subn(r'"keys"\s*:\s*"[^"]*"', f'"keys": "{accent}"', content)
+                if count1 > 0: modified = True
+            if '"title"' in content:
+                content, count2 = re.subn(r'"title"\s*:\s*"[^"]*"', f'"title": "{sub_accent}"', content)
+                if count2 > 0: modified = True
+
+            if not modified and '"display"' in content:
+                content = re.sub(r'"display"\s*:\s*\{', f'"display": {{\n    "color": {{\n      "keys": "{accent}",\n      "title": "{sub_accent}"\n    }},', content, count=1)
+                modified = True
+
+            if modified:
+                with open(conf_path, 'w', encoding='utf-8') as f:
+                    f.write(content)
+                return
+        except Exception:
+            pass
+
     fastfetch_jsonc = f"""{{
   "$schema": "https://github.com/fastfetch-cli/fastfetch/raw/dev/doc/json_schema.json",
   "display": {{
@@ -1039,7 +1064,7 @@ def sync_fastfetch(bg, surface, current_line, fg, accent, sub_accent):
 }}
 """
     try:
-        with open(conf_path, 'w') as f:
+        with open(conf_path, 'w', encoding='utf-8') as f:
             f.write(fastfetch_jsonc)
     except Exception:
         pass