From 00783adf915a07209220f3c8c84b7695b56c52bd Mon Sep 17 00:00:00 2001
From: AtlasAutocode <AtlasAutocode@gmail.com>
Date: Fri, 7 Jun 2024 15:20:06 -0600
Subject: [PATCH] Subscript and Superscript

---
 .../quill_controller_configurations.dart      |  8 ++-
 lib/src/widgets/editor/editor.dart            |  1 +
 lib/src/widgets/quill/text_line.dart          | 60 +++++++++++++++++--
 3 files changed, 64 insertions(+), 5 deletions(-)

diff --git a/lib/src/models/config/quill_controller_configurations.dart b/lib/src/models/config/quill_controller_configurations.dart
index ae38841a..95126178 100644
--- a/lib/src/models/config/quill_controller_configurations.dart
+++ b/lib/src/models/config/quill_controller_configurations.dart
@@ -1,8 +1,14 @@
 class QuillControllerConfigurations {
-  const QuillControllerConfigurations({this.onClipboardPaste});
+  const QuillControllerConfigurations(
+      {this.onClipboardPaste, this.requireScriptFontFeatures = false});
 
   /// Callback when the user pastes and data has not already been processed
   ///
   /// Return true if the paste operation was handled
   final Future<bool> Function()? onClipboardPaste;
+
+  /// Render subscript and superscript text using Open Type FontFeatures
+  ///
+  /// Default is false to use built-in script rendering that is independent of font capabilities
+  final bool requireScriptFontFeatures;
 }
diff --git a/lib/src/widgets/editor/editor.dart b/lib/src/widgets/editor/editor.dart
index a5635967..0fba7806 100644
--- a/lib/src/widgets/editor/editor.dart
+++ b/lib/src/widgets/editor/editor.dart
@@ -173,6 +173,7 @@ class QuillEditorState extends State<QuillEditor>
   void initState() {
     super.initState();
     widget.configurations.controller.editorFocusNode ??= widget.focusNode;
+    widget.configurations.controller.editorFocusNode?.requestFocus();
     _editorKey = configurations.editorKey ?? GlobalKey<EditorState>();
     _selectionGestureDetectorBuilder =
         _QuillEditorSelectionGestureDetectorBuilder(
diff --git a/lib/src/widgets/quill/text_line.dart b/lib/src/widgets/quill/text_line.dart
index e03e5ae8..0375273d 100644
--- a/lib/src/widgets/quill/text_line.dart
+++ b/lib/src/widgets/quill/text_line.dart
@@ -322,19 +322,71 @@ class _TextLineState extends State<TextLine> {
     return textStyle;
   }
 
-  TextSpan _getTextSpanFromNode(
+  /// Processes subscript and superscript attributed text.
+  ///
+  /// Reduces text fontSize and shifts down or up. Increases fontWeight to maintain balance with normal text.
+  /// Outputs characters individually to allow correct caret positioning and text selection.
+  InlineSpan _scriptSpan(String text, bool superScript, TextStyle style,
+      DefaultStyles defaultStyles) {
+    assert(text.isNotEmpty);
+    //
+    final lineStyle = style.fontSize == null || style.fontWeight == null
+        ? _getLineStyle(defaultStyles)
+        : null;
+    final fontWeight = FontWeight.lerp(
+        style.fontWeight ?? lineStyle?.fontWeight ?? FontWeight.normal,
+        FontWeight.w900,
+        0.25);
+    final fontSize = style.fontSize ?? lineStyle?.fontSize ?? 16;
+    final y = (superScript ? -0.4 : 0.14) * fontSize;
+    final charStyle = style.copyWith(
+        fontFeatures: <FontFeature>[],
+        fontWeight: fontWeight,
+        fontSize: fontSize * 0.7);
+    //
+    final offset = Offset(0, y);
+    final children = <WidgetSpan>[];
+    for (final c in text.characters) {
+      children.add(WidgetSpan(
+          child: Transform.translate(
+              offset: offset,
+              child: Text(
+                c,
+                style: charStyle,
+              ))));
+    }
+    //
+    if (children.length > 1) {
+      return TextSpan(children: children);
+    }
+    return children[0];
+  }
+
+  InlineSpan _getTextSpanFromNode(
       DefaultStyles defaultStyles, Node node, Style lineStyle) {
     final textNode = node as leaf.QuillText;
     final nodeStyle = textNode.style;
     final isLink = nodeStyle.containsKey(Attribute.link.key) &&
         nodeStyle.attributes[Attribute.link.key]!.value != null;
 
-    final recognizer = _getRecognizer(node, isLink);
+    final style = _getInlineTextStyle(
+        textNode, defaultStyles, nodeStyle, lineStyle, isLink);
+
+    if (widget.controller.configurations.requireScriptFontFeatures == false &&
+        textNode.value.isNotEmpty) {
+      if (nodeStyle.containsKey(Attribute.script.key)) {
+        final attr = nodeStyle.attributes[Attribute.script.key];
+        if (attr == Attribute.superscript || attr == Attribute.subscript) {
+          return _scriptSpan(textNode.value, attr == Attribute.superscript,
+              style, defaultStyles);
+        }
+      }
+    }
 
+    final recognizer = _getRecognizer(node, isLink);
     return TextSpan(
       text: textNode.value,
-      style: _getInlineTextStyle(
-          textNode, defaultStyles, nodeStyle, lineStyle, isLink),
+      style: style,
       recognizer: recognizer,
       mouseCursor: (recognizer != null) ? SystemMouseCursors.click : null,
     );