feat: Implement mouse select chat list items

lib/components/list_items/chat_list_item.dart

@@ -1,4 +1,5 @@
 import 'package:bot_toast/bot_toast.dart';
+import 'package:circular_check_box/circular_check_box.dart';
 import 'package:famedlysdk/famedlysdk.dart';
 import 'package:fluffychat/utils/matrix_locals.dart';
 import 'package:fluffychat/views/chat.dart';
@@ -13,6 +14,7 @@ import '../avatar.dart';
 import '../dialogs/send_file_dialog.dart';
 import '../dialogs/simple_dialogs.dart';
 import '../matrix.dart';
+import '../mouse_over_builder.dart';
 import '../theme_switcher.dart';
 
 class ChatListItem extends StatelessWidget {
@@ -128,7 +130,20 @@ class ChatListItem extends StatelessWidget {
         color: chatListItemColor(context, activeChat, selected),
         child: ListTile(
           onLongPress: onLongPress,
-          leading: Avatar(room.avatar, room.displayname),
+          leading: MouseOverBuilder(
+            builder: (context, hover) =>
+                onLongPress != null && (hover || selected)
+                    ? Container(
+                        width: Avatar.defaultSize,
+                        height: Avatar.defaultSize,
+                        alignment: Alignment.center,
+                        child: CircularCheckBox(
+                          value: selected,
+                          onChanged: (_) => onLongPress(),
+                        ),
+                      )
+                    : Avatar(room.avatar, room.displayname),
+          ),
           title: Row(
             children: <Widget>[
               Expanded(

lib/components/mouse_over_builder.dart

@@ -0,0 +1,28 @@
+import 'package:flutter/material.dart';
+
+class MouseOverBuilder extends StatefulWidget {
+  final Function(BuildContext, bool) builder;
+
+  const MouseOverBuilder({Key key, this.builder}) : super(key: key);
+  @override
+  _MouseOverBuilderState createState() => _MouseOverBuilderState();
+}
+
+class _MouseOverBuilderState extends State<MouseOverBuilder> {
+  bool _hover = false;
+
+  void _toggleHover(bool hover) {
+    if (_hover != hover) {
+      setState(() => _hover = hover);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return MouseRegion(
+      onEnter: (_) => _toggleHover(true),
+      onExit: (_) => _toggleHover(false),
+      child: widget.builder != null ? widget.builder(context, _hover) : null,
+    );
+  }
+}