feat(text-editor): add configurable leadingDistribution to TextEditorStyle

Add a new leadingDistribution property to TextEditorStyle that controls
how extra leading is distributed above and below text glyphs.

Default: TextLeadingDistribution.proportional (preserves existing behavior).

When set to TextLeadingDistribution.even, glyphs are vertically centered
within their line height bounds, fixing visual misalignment of text inside
rounded background rects at line heights > 1.0.

Changes:
- TextEditorStyle: new leadingDistribution property with copyWith support
- RoundedBackgroundTextField: both builders read from config instead of
  hardcoding proportional
- RoundedBackgroundText: new leadingDistribution parameter on both
  constructors, wired to parent TextSpan and debugFillProperties
- LayerWidgetTextItem: passes config value to RoundedBackgroundText
  so saved layers match the editing style

Author: faizahmaddae

lib/core/models/styles/text_editor_style.dart

@@ -1,4 +1,6 @@
 // Flutter imports:
+import 'dart:ui' as ui;
+
 import 'package:flutter/material.dart';
 
 import '../../constants/editor_style_constants.dart';
@@ -53,6 +55,7 @@ class TextEditorStyle {
   /// style properties.
   const TextEditorStyle({
     this.textHeight = 0.0,
+    this.leadingDistribution = ui.TextLeadingDistribution.proportional,
     this.fontSizeBottomSheetTitle,
     this.textFieldMargin = const EdgeInsets.only(
       bottom: kBottomNavigationBarHeight,
@@ -126,6 +129,19 @@ class TextEditorStyle {
   /// on various platforms. Set to null to use the default line height.
   final double? textHeight;
 
+  /// Controls how extra leading from the [TextStyle.height] multiplier is
+  /// distributed above and below the text glyph.
+  ///
+  /// [TextLeadingDistribution.proportional] distributes leading proportional
+  /// to the font's ascent / descent ratio (~75% above, ~25% below for most
+  /// Latin fonts). This is the default and matches Flutter's standard
+  /// rendering.
+  ///
+  /// [TextLeadingDistribution.even] splits the extra leading 50 / 50, which
+  /// visually centres glyphs inside their rounded background rects when
+  /// [TextStyle.height] is greater than 1.0.
+  final ui.TextLeadingDistribution leadingDistribution;
+
   /// Creates a copy of this `TextEditorStyle` object with the given fields
   /// replaced with new values.
   ///
@@ -134,6 +150,7 @@ class TextEditorStyle {
   /// others unchanged.
   TextEditorStyle copyWith({
     double? textHeight,
+    ui.TextLeadingDistribution? leadingDistribution,
     Color? appBarBackground,
     Color? appBarColor,
     Color? bottomBarBackground,
@@ -152,6 +169,7 @@ class TextEditorStyle {
   }) {
     return TextEditorStyle(
       textHeight: textHeight ?? this.textHeight,
+      leadingDistribution: leadingDistribution ?? this.leadingDistribution,
       fontScaleBottomSheetBackground:
           fontScaleBottomSheetBackground ?? this.fontScaleBottomSheetBackground,
       appBarBackground: appBarBackground ?? this.appBarBackground,

lib/features/text_editor/widgets/rounded_background_text/rounded_background_text.dart

@@ -26,6 +26,7 @@ class RoundedBackgroundText extends StatelessWidget {
     required this.maxTextWidth,
     this.cursorWidth = 0,
     this.enableHitBoxCorrection = false,
+    this.leadingDistribution = TextLeadingDistribution.proportional,
   }) : text = TextSpan(text: text, style: style);
 
   /// Creates a [RoundedBackgroundText] widget with rich text using
@@ -42,6 +43,7 @@ class RoundedBackgroundText extends StatelessWidget {
     required this.maxTextWidth,
     this.cursorWidth = 0,
     this.enableHitBoxCorrection = false,
+    this.leadingDistribution = TextLeadingDistribution.proportional,
   });
 
   /// A flag to enable or disable hitBox correction for the text.
@@ -64,6 +66,13 @@ class RoundedBackgroundText extends StatelessWidget {
   /// The width of the text cursor when displayed.
   final double cursorWidth;
 
+  /// Controls how extra leading is distributed above and below the text.
+  ///
+  /// Defaults to [TextLeadingDistribution.proportional].
+  /// Set to [TextLeadingDistribution.even] to visually centre glyphs inside
+  /// their rounded background rects when [TextStyle.height] > 1.0.
+  final TextLeadingDistribution leadingDistribution;
+
   /// Callback function triggered with the result of a hit test.
   final Function(bool hasHit)? onHitTestResult;
 
@@ -76,8 +85,8 @@ class RoundedBackgroundText extends StatelessWidget {
     final painter = TextPainter(
       text: TextSpan(
         children: [text],
-        style: const TextStyle(
-          leadingDistribution: TextLeadingDistribution.proportional,
+        style: TextStyle(
+          leadingDistribution: leadingDistribution,
         ).merge(style),
       ),
       textDirection: Directionality.maybeOf(context) ?? TextDirection.ltr,
@@ -140,6 +149,13 @@ class RoundedBackgroundText extends StatelessWidget {
           value: onHitTestResult != null,
           ifTrue: 'callback set',
         ),
+      )
+      ..add(
+        EnumProperty<TextLeadingDistribution>(
+          'leadingDistribution',
+          leadingDistribution,
+          defaultValue: TextLeadingDistribution.proportional,
+        ),
       );
   }
 }

lib/features/text_editor/widgets/rounded_background_text/rounded_background_text_field.dart

@@ -140,7 +140,7 @@ class _RoundedBackgroundTextFieldState
   Widget _buildBackgroundText() {
     final style = widget.style.copyWith(
       color: Colors.transparent,
-      leadingDistribution: TextLeadingDistribution.proportional,
+      leadingDistribution: widget.configs.style.leadingDistribution,
     );
 
     return Positioned(
@@ -183,7 +183,7 @@ class _RoundedBackgroundTextFieldState
         scrollPadding: EdgeInsets.zero,
         style: widget.style.copyWith(
           fontSize: fontSize,
-          leadingDistribution: TextLeadingDistribution.proportional,
+          leadingDistribution: widget.configs.style.leadingDistribution,
           height: widget.configs.style.textHeight,
         ),
         decoration: InputDecoration.collapsed(

lib/shared/widgets/layer/widgets/layer_widget_text_item.dart

@@ -77,6 +77,7 @@ class LayerWidgetTextItem extends StatelessWidget {
       backgroundColor: layer.background,
       textAlign: layer.align,
       style: finalStyle,
+      leadingDistribution: textEditorConfigs.style.leadingDistribution,
     );
   }