feat: Implement linux desktop notifications

lib/components/avatar.dart

@@ -1,5 +1,4 @@
 import 'package:famedlysdk/famedlysdk.dart';
-import 'package:fluffychat/utils/platform_infos.dart';
 import 'package:fluffychat/utils/string_color.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
@@ -28,31 +27,49 @@ class Avatar extends StatelessWidget {
       Matrix.of(context).client,
       width: size * MediaQuery.of(context).devicePixelRatio,
       height: size * MediaQuery.of(context).devicePixelRatio,
-      method: ThumbnailMethod.scale,
     );
     final src = thumbnail;
     var fallbackLetters = '@';
     if ((name?.length ?? 0) >= 2) {
-      fallbackLetters = name.substring(0, 2);
+      fallbackLetters = String.fromCharCodes(name.runes, 0, 2);
     } else if ((name?.length ?? 0) == 1) {
       fallbackLetters = name;
     }
+    final textWidget = Center(
+      child: Text(
+        fallbackLetters,
+        style: TextStyle(
+          color: Colors.white,
+          fontSize: 18,
+        ),
+      ),
+    );
     final noPic = mxContent == null || mxContent.toString().isEmpty;
     return InkWell(
       onTap: onTap,
-      child: CircleAvatar(
-        radius: size / 2,
-        backgroundImage: !noPic
-            ? PlatformInfos.isBetaDesktop
-                ? NetworkImage(src)
-                : CachedNetworkImageProvider(src)
-            : null,
-        backgroundColor: noPic
-            ? name?.lightColor ?? Theme.of(context).secondaryHeaderColor
-            : Theme.of(context).secondaryHeaderColor,
-        child: noPic
-            ? Text(fallbackLetters, style: TextStyle(color: Colors.white))
-            : null,
+      child: ClipRRect(
+        borderRadius: BorderRadius.circular(size / 2),
+        child: Container(
+          width: size,
+          height: size,
+          color: noPic
+              ? name?.lightColor ?? Theme.of(context).secondaryHeaderColor
+              : Theme.of(context).secondaryHeaderColor,
+          child: noPic
+              ? textWidget
+              : CachedNetworkImage(
+                  imageUrl: src,
+                  fit: BoxFit.cover,
+                  width: size,
+                  height: size,
+                  placeholder: (c, s) => Stack(
+                    children: [
+                      Center(child: CircularProgressIndicator(strokeWidth: 2)),
+                      textWidget,
+                    ],
+                  ),
+                ),
+        ),
       ),
     );
   }