Refactor embed API to accept WidgetSpan configs

packages/fleather/example/lib/main.dart

@@ -143,14 +143,17 @@ class _HomePageState extends State<HomePage> {
     );
   }
 
-  Widget _embedBuilder(BuildContext context, EmbedNode node) {
+  FleatherEmbed _embedBuilder(BuildContext context, EmbedNode node) {
     if (node.value.type == 'icon') {
       final data = node.value.data;
       // Icons.rocket_launch_outlined
-      return Icon(
-        IconData(int.parse(data['codePoint']), fontFamily: data['fontFamily']),
-        color: Color(int.parse(data['color'])),
-        size: 18,
+      return FleatherSpanEmbed(
+        child: Icon(
+          IconData(int.parse(data['codePoint']),
+              fontFamily: data['fontFamily']),
+          color: Color(int.parse(data['color'])),
+          size: 18,
+        ),
       );
     }
 
@@ -176,14 +179,17 @@ class _HomePageState extends State<HomePage> {
         }
       }
       if (image != null) {
-        return Padding(
-          // Caret takes 2 pixels, hence not symmetric padding values.
-          padding: const EdgeInsets.only(left: 4, right: 2, top: 2, bottom: 2),
-          child: Container(
-            width: (node.value.data['width'] as num?)?.toDouble() ?? 300,
-            height: (node.value.data['height'] as num?)?.toDouble() ?? 300,
-            decoration: BoxDecoration(
-              image: DecorationImage(image: image, fit: BoxFit.cover),
+        return FleatherEmbed(
+          child: Padding(
+            // Caret takes 2 pixels, hence not symmetric padding values.
+            padding:
+                const EdgeInsets.only(left: 4, right: 2, top: 2, bottom: 2),
+            child: Container(
+              width: (node.value.data['width'] as num?)?.toDouble() ?? 300,
+              height: (node.value.data['height'] as num?)?.toDouble() ?? 300,
+              decoration: BoxDecoration(
+                image: DecorationImage(image: image, fit: BoxFit.cover),
+              ),
             ),
           ),
         );

packages/fleather/lib/src/widgets/editor.dart

@@ -76,29 +76,50 @@ Widget defaultSpellCheckMenuBuilder(
 }
 
 /// Builder function for embeddable objects in [FleatherEditor].
-typedef FleatherEmbedBuilder = Widget Function(
+typedef FleatherEmbedBuilder = FleatherEmbed Function(
     BuildContext context, EmbedNode node);
 
 /// Default implementation of a builder function for embeddable objects in
 /// Fleather.
 ///
 /// Only supports "horizontal rule" embeds.
-Widget defaultFleatherEmbedBuilder(BuildContext context, EmbedNode node) {
+FleatherEmbed defaultFleatherEmbedBuilder(
+    BuildContext context, EmbedNode node) {
   if (node.value.type == 'hr') {
     final fleatherThemeData = FleatherTheme.of(context)!;
 
-    return Divider(
+    return FleatherEmbed(
+        child: Divider(
       height: fleatherThemeData.horizontalRule.height,
       thickness: fleatherThemeData.horizontalRule.thickness,
       color: fleatherThemeData.horizontalRule.color,
-    );
+    ));
   }
   throw UnimplementedError(
       'Embeddable type "${node.value.type}" is not supported by default embed '
       'builder of FleatherEditor. You must pass your own builder function to '
       'embedBuilder property of FleatherEditor or FleatherField widgets.');
 }
 
+final class FleatherEmbed {
+  final Widget child;
+
+  const FleatherEmbed({required this.child});
+}
+
+final class FleatherSpanEmbed extends FleatherEmbed {
+  final PlaceholderAlignment placeholderAlignment;
+  final TextBaseline? textBaseline;
+  final TextStyle? textStyle;
+
+  const FleatherSpanEmbed({
+    required super.child,
+    this.placeholderAlignment = PlaceholderAlignment.bottom,
+    this.textBaseline,
+    this.textStyle,
+  });
+}
+
 /// Widget for editing rich text documents.
 class FleatherEditor extends StatefulWidget {
   /// Controller object which establishes a link between a rich text document

packages/fleather/lib/src/widgets/text_line.dart

@@ -122,8 +122,9 @@ class _TextLineState extends State<TextLine> {
   Widget build(BuildContext context) {
     assert(debugCheckHasMediaQuery(context));
     if (widget.node.hasBlockEmbed) {
-      final embed = widget.node.children.single as EmbedNode;
-      return EmbedProxy(child: widget.embedBuilder(context, embed));
+      final embedNode = widget.node.children.single as EmbedNode;
+      final embedObject = widget.embedBuilder(context, embedNode);
+      return EmbedProxy(child: embedObject.child);
     }
     final theme = FleatherTheme.of(context)!;
     final text = buildText(context, widget.node, theme);
@@ -174,8 +175,18 @@ class _TextLineState extends State<TextLine> {
 
   InlineSpan _segmentToTextSpan(Node segment, FleatherThemeData theme) {
     if (segment is EmbedNode) {
-      return WidgetSpan(
-          child: EmbedProxy(child: widget.embedBuilder(context, segment)));
+      final embedObject = widget.embedBuilder(context, segment);
+      final embedWidget = EmbedProxy(child: embedObject.child);
+      if (embedObject is FleatherSpanEmbed) {
+        return WidgetSpan(
+          child: embedWidget,
+          alignment: embedObject.placeholderAlignment,
+          baseline: embedObject.textBaseline,
+          style: embedObject.textStyle,
+        );
+      } else {
+        return WidgetSpan(child: embedWidget);
+      }
     }
     final text = segment as TextNode;
     final attrs = text.style;