use a text span with a recognizer instead of a WidgetSpan

Fixes displaynames not ellipsising properly

lib/helpers/extensions/global_rect.dart

@@ -12,4 +12,12 @@ extension GlobalRect on BuildContext {
       _ => Rect.zero,
     };
   }
+
+  /// [position] on screen as an empty rect, like where text was tapped, to
+  /// open a popover there.
+  Rect globalRectAt(Offset position) {
+    final overlay = Overlay.of(this).context.findRenderObject() as RenderBox;
+
+    return overlay.globalToLocal(position) & .zero;
+  }
 }

lib/helpers/extensions/show_adaptive_popover.dart

@@ -5,20 +5,20 @@ import "package:nexus/helpers/extensions/show_adaptive_sheet.dart";
 import "package:nexus/widgets/popover_layout.dart";
 
 extension ShowAdaptivePopover on BuildContext {
-  /// Shows the widget from [builder] in a popover next to the widget this
-  /// context belongs to on desktop, or a bottom sheet on mobile. Use the
-  /// context passed to [builder] to close it.
-  Future<void> showAdaptivePopover(WidgetBuilder builder) {
+  /// Shows the widget from [builder] in a popover next to [anchor], or the
+  /// widget this context belongs to, on desktop, or a bottom sheet on mobile.
+  /// Use the context passed to [builder] to close it.
+  Future<void> showAdaptivePopover(WidgetBuilder builder, {Rect? anchor}) {
     if (!isDesktop) return showAdaptiveSheet(builder);
 
-    final anchor = globalRect;
+    final rect = anchor ?? globalRect;
 
     return showDialog(
       context: this,
       barrierColor: Colors.transparent,
       useSafeArea: false,
       builder: (context) => CustomSingleChildLayout(
-        delegate: PopoverLayout(anchor),
+        delegate: PopoverLayout(rect),
         child: ConstrainedBox(
           constraints: const .new(maxWidth: 420, maxHeight: 600),
           child: Material(

lib/helpers/extensions/show_user_popover.dart

@@ -3,6 +3,9 @@ import "package:nexus/helpers/extensions/show_adaptive_popover.dart";
 import "package:nexus/widgets/user_bottom_sheet.dart";
 
 extension ShowUserPopover on BuildContext {
-  void showUserPopover(String userId, {String? roomId}) =>
-      showAdaptivePopover((context) => UserBottomSheet(userId, roomId: roomId));
+  void showUserPopover(String userId, {String? roomId, Rect? anchor}) =>
+      showAdaptivePopover(
+        (context) => UserBottomSheet(userId, roomId: roomId),
+        anchor: anchor,
+      );
 }

lib/helpers/hooks/tap_recognizer.dart

@@ -0,0 +1,11 @@
+import "package:flutter/gestures.dart";
+import "package:flutter_hooks/flutter_hooks.dart";
+
+/// A recognizer for a tappable span in text, like a name, disposed with the
+/// widget.
+TapGestureRecognizer useTapRecognizer() {
+  final recognizer = useMemoized(TapGestureRecognizer.new);
+  useEffect(() => recognizer.dispose, [recognizer]);
+
+  return recognizer;
+}