fix(ui): fix centerTitle for ChannelHeader

packages/stream_chat_flutter/lib/src/channel_header.dart

@@ -112,6 +112,7 @@ class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
 
   @override
   Widget build(BuildContext context) {
+    final effectiveCenterTitle = _getEffectiveCenterTitle(Theme.of(context));
     final channel = StreamChannel.of(context).channel;
     final channelHeaderTheme = ChannelHeaderTheme.of(context);
 
@@ -175,9 +176,11 @@ class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
               onTap: onTitleTap,
               child: SizedBox(
                 height: preferredSize.height,
-                width: preferredSize.width,
                 child: Column(
                   mainAxisAlignment: MainAxisAlignment.center,
+                  crossAxisAlignment: effectiveCenterTitle
+                      ? CrossAxisAlignment.center
+                      : CrossAxisAlignment.stretch,
                   children: <Widget>[
                     title ??
                         ChannelName(
@@ -202,4 +205,21 @@ class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
 
   @override
   final Size preferredSize;
+
+  bool _getEffectiveCenterTitle(ThemeData theme) {
+    if (centerTitle != null) return centerTitle!;
+    if (theme.appBarTheme.centerTitle != null) {
+      return theme.appBarTheme.centerTitle!;
+    }
+    switch (theme.platform) {
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.linux:
+      case TargetPlatform.windows:
+        return false;
+      case TargetPlatform.iOS:
+      case TargetPlatform.macOS:
+        return actions == null || actions!.length < 2;
+    }
+  }
 }