Add tooltip for tags

lib/components/tag_tooltip.dart

@@ -0,0 +1,28 @@
+import 'package:flutter/material.dart';
+import '../api/gallery.dart';
+
+String _getTag(Tag tag) {
+  final tags = tag.tag.split(":");
+  if (tags.length < 2) return tag.translated ?? tag.tag;
+  final name = tags[1]!;
+  return tag.translated ?? name;
+}
+
+class TagTooltip extends StatelessWidget {
+  const TagTooltip(this.tag, {Key? key}) : super(key: key);
+  final Tag tag;
+
+  @override
+  Widget build(BuildContext context) {
+    final name = _getTag(tag);
+    final t = SelectableText(name);
+    return tag.intro != null && tag.intro!.isNotEmpty ? Tooltip(
+      message: tag.intro!,
+      decoration: BoxDecoration(
+        borderRadius: BorderRadius.circular(4.0),
+        color: Theme.of(context).colorScheme.secondary,
+      ),
+      child: t,
+    ) : t;
+  }
+}

lib/components/tags.dart

@@ -3,6 +3,7 @@ import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 import '../api/gallery.dart';
 import '../globals.dart';
 import '../main.dart';
+import 'tag_tooltip.dart';
 import 'scroll_parent.dart';
 
 class TagsPanel extends StatefulWidget {
@@ -14,13 +15,6 @@ class TagsPanel extends StatefulWidget {
   State<TagsPanel> createState() => _TagsPanel();
 }
 
-String _getTag(Tag tag) {
-  final tags = tag.tag.split(":");
-  if (tags.length < 2) return tag.translated ?? tag.tag;
-  final name = tags[1]!;
-  return tag.translated ?? name;
-}
-
 class _TagsPanel extends State<TagsPanel> {
   List<(String, List<Tag>)>? data;
   @override
@@ -77,8 +71,9 @@ class _TagsPanel extends State<TagsPanel> {
                     borderRadius: const BorderRadius.all(Radius.circular(4.0)),
                     border: Border.all(width: 1, color: cs.primary),
                   ),
-                  child: SelectableText(
-                      stt ? _getTag(ta[index - 1]!) : ta[index - 1]!.tag));
+                  child: stt
+                      ? TagTooltip(ta[index - 1]!)
+                      : SelectableText(ta[index - 1]!.tag));
             }
           }));
         });