[flutter_markdown] Replace deprecated API (flutter#6134)

* Internally, removes use of the deprecated framework methods related to `textScaleFactor`, in favor of the newer `textScaler`.
* Plumbs that same change through the public API of this package, deprecating the style sheet's `textScaleFactor` and adding a `textScaler`.
* Updates the min Flutter SDK to 3.16 where the new APIs were added.
* Also updates test code that uses the deprecated `renderViewElement` to use `rootElement` instead.

Fixes flutter#143400
Fixes flutter#143448

Author: stuartmorgan-g

packages/flutter_markdown/CHANGELOG.md

@@ -1,6 +1,10 @@
-## NEXT
+## 0.6.20
 
-* Updates minimum supported SDK version to Flutter 3.13/Dart 3.1.
+* Adds `textScaler` to `MarkdownStyleSheet`, and deprecates `textScaleFactor`.
+  * Clients using `textScaleFactor: someFactor` should replace it with
+    `TextScaler.linear(someFactor)` to preserve behavior.
+* Removes use of deprecated Flutter framework `textScaleFactor` methods.
+* Updates minimum supported SDK version to Flutter 3.16.
 
 ## 0.6.19
 
@@ -44,7 +48,7 @@
 
 * Introduces a new `MarkdownElementBuilder.visitElementAfterWithContext()` method passing the widget `BuildContext` and
   the parent text's `TextStyle`.
-  
+
 ## 0.6.16
 
 * Adds `tableVerticalAlignment` property to allow aligning table cells vertically.

packages/flutter_markdown/example/pubspec.yaml

@@ -3,8 +3,8 @@ description: Demonstrates how to use the flutter_markdown package.
 publish_to: none
 
 environment:
-  sdk: ^3.1.0
-  flutter: ">=3.13.0"
+  sdk: ^3.2.0
+  flutter: ">=3.16.0"
 
 dependencies:
   flutter:

packages/flutter_markdown/lib/src/_functions_io.dart

@@ -64,7 +64,7 @@ final MarkdownStyleSheet Function(BuildContext, MarkdownStyleSheetBaseTheme?)
   }
 
   return result.copyWith(
-    textScaleFactor: MediaQuery.textScaleFactorOf(context),
+    textScaler: MediaQuery.textScalerOf(context),
   );
 };
 

packages/flutter_markdown/lib/src/_functions_web.dart

@@ -66,7 +66,7 @@ final MarkdownStyleSheet Function(BuildContext, MarkdownStyleSheetBaseTheme?)
   }
 
   return result.copyWith(
-    textScaleFactor: MediaQuery.textScaleFactorOf(context),
+    textScaler: MediaQuery.textScalerOf(context),
   );
 };
 

packages/flutter_markdown/lib/src/builder.dart

@@ -867,15 +867,15 @@ class MarkdownBuilder implements md.NodeVisitor {
     if (selectable) {
       return SelectableText.rich(
         text!,
-        textScaleFactor: styleSheet.textScaleFactor,
+        textScaler: styleSheet.textScaler,
         textAlign: textAlign ?? TextAlign.start,
         onTap: onTapText,
         key: k,
       );
     } else {
       return Text.rich(
         text!,
-        textScaleFactor: styleSheet.textScaleFactor,
+        textScaler: styleSheet.textScaler,
         textAlign: textAlign ?? TextAlign.start,
         key: k,
       );

packages/flutter_markdown/lib/src/style_sheet.dart

@@ -59,8 +59,19 @@ class MarkdownStyleSheet {
     this.orderedListAlign = WrapAlignment.start,
     this.blockquoteAlign = WrapAlignment.start,
     this.codeblockAlign = WrapAlignment.start,
-    this.textScaleFactor,
-  }) : _styles = <String, TextStyle?>{
+    @Deprecated('Use textScaler instead.') this.textScaleFactor,
+    TextScaler? textScaler,
+  })  : assert(
+          textScaler == null || textScaleFactor == null,
+          'textScaleFactor is deprecated and cannot be specified when textScaler is specified.',
+        ),
+        textScaler = textScaler ??
+            // Internally, only textScaler is used, so convert the scale factor
+            // to a linear scaler.
+            (textScaleFactor == null
+                ? null
+                : TextScaler.linear(textScaleFactor)),
+        _styles = <String, TextStyle?>{
           'a': a,
           'p': p,
           'li': p,
@@ -380,8 +391,19 @@ class MarkdownStyleSheet {
     WrapAlignment? orderedListAlign,
     WrapAlignment? blockquoteAlign,
     WrapAlignment? codeblockAlign,
-    double? textScaleFactor,
+    @Deprecated('Use textScaler instead.') double? textScaleFactor,
+    TextScaler? textScaler,
   }) {
+    assert(
+      textScaler == null || textScaleFactor == null,
+      'textScaleFactor is deprecated and cannot be specified when textScaler is specified.',
+    );
+    // If either of textScaler or textScaleFactor is non-null, pass null for the
+    // other instead of the previous value, since only one is allowed.
+    final TextScaler? newTextScaler =
+        textScaler ?? (textScaleFactor == null ? this.textScaler : null);
+    final double? nextTextScaleFactor =
+        textScaleFactor ?? (textScaler == null ? this.textScaleFactor : null);
     return MarkdownStyleSheet(
       a: a ?? this.a,
       p: p ?? this.p,
@@ -435,7 +457,8 @@ class MarkdownStyleSheet {
       orderedListAlign: orderedListAlign ?? this.orderedListAlign,
       blockquoteAlign: blockquoteAlign ?? this.blockquoteAlign,
       codeblockAlign: codeblockAlign ?? this.codeblockAlign,
-      textScaleFactor: textScaleFactor ?? this.textScaleFactor,
+      textScaler: newTextScaler,
+      textScaleFactor: nextTextScaleFactor,
     );
   }
 
@@ -497,6 +520,11 @@ class MarkdownStyleSheet {
       blockquoteAlign: other.blockquoteAlign,
       codeblockAlign: other.codeblockAlign,
       textScaleFactor: other.textScaleFactor,
+      // Only one of textScaler and textScaleFactor can be passed. If
+      // other.textScaleFactor is non-null, then the sheet was created with a
+      // textScaleFactor and the textScaler was derived from that, so should be
+      // ignored so that the textScaleFactor continues to be set.
+      textScaler: other.textScaleFactor == null ? other.textScaler : null,
     );
   }
 
@@ -650,7 +678,14 @@ class MarkdownStyleSheet {
   /// The [WrapAlignment] to use for a code block. Defaults to start.
   final WrapAlignment codeblockAlign;
 
-  /// The text scale factor to use in textual elements
+  /// The text scaler to use in textual elements.
+  final TextScaler? textScaler;
+
+  /// The text scale factor to use in textual elements.
+  ///
+  /// This will be non-null only if the sheet was created with the deprecated
+  /// [textScaleFactor] instead of [textScaler].
+  @Deprecated('Use textScaler instead.')
   final double? textScaleFactor;
 
   /// A [Map] from element name to the corresponding [TextStyle] object.
@@ -717,7 +752,7 @@ class MarkdownStyleSheet {
         other.orderedListAlign == orderedListAlign &&
         other.blockquoteAlign == blockquoteAlign &&
         other.codeblockAlign == codeblockAlign &&
-        other.textScaleFactor == textScaleFactor;
+        other.textScaler == textScaler;
   }
 
   @override
@@ -774,6 +809,7 @@ class MarkdownStyleSheet {
       orderedListAlign,
       blockquoteAlign,
       codeblockAlign,
+      textScaler,
       textScaleFactor,
     ]);
   }

packages/flutter_markdown/pubspec.yaml

@@ -4,11 +4,11 @@ description: A Markdown renderer for Flutter. Create rich text output,
   formatted with simple Markdown tags.
 repository: https://github.com/flutter/packages/tree/main/packages/flutter_markdown
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+flutter_markdown%22
-version: 0.6.19
+version: 0.6.20
 
 environment:
-  sdk: ^3.1.0
-  flutter: ">=3.13.0"
+  sdk: ^3.2.0
+  flutter: ">=3.16.0"
 
 dependencies:
   flutter:

packages/flutter_markdown/test/all.dart

@@ -18,7 +18,7 @@ import 'selection_area_compatibility_test.dart' as selection_area_test;
 import 'style_sheet_test.dart' as style_sheet_test;
 import 'table_test.dart' as table_test;
 import 'text_alignment_test.dart' as text_alignment_test;
-import 'text_scale_factor_test.dart' as text_scale_factor;
+import 'text_scaler_test.dart' as text_scaler;
 import 'text_test.dart' as text_test;
 import 'uri_test.dart' as uri_test;
 
@@ -40,6 +40,6 @@ void main() {
   table_test.defineTests();
   text_test.defineTests();
   text_alignment_test.defineTests();
-  text_scale_factor.defineTests();
+  text_scaler.defineTests();
   uri_test.defineTests();
 }

packages/flutter_markdown/test/style_sheet_test.dart

@@ -398,5 +398,65 @@ void defineTests() {
         );
       },
     );
+
+    testWidgets(
+      'deprecated textScaleFactor is converted to linear scaler',
+      (WidgetTester tester) async {
+        const double scaleFactor = 2.0;
+        final MarkdownStyleSheet style = MarkdownStyleSheet(
+          textScaleFactor: scaleFactor,
+        );
+
+        expect(style.textScaler, const TextScaler.linear(scaleFactor));
+        expect(style.textScaleFactor, scaleFactor);
+      },
+    );
+
+    testWidgets(
+      'deprecated textScaleFactor is null when a scaler is provided',
+      (WidgetTester tester) async {
+        const TextScaler scaler = TextScaler.linear(2.0);
+        final MarkdownStyleSheet style = MarkdownStyleSheet(
+          textScaler: scaler,
+        );
+
+        expect(style.textScaler, scaler);
+        expect(style.textScaleFactor, null);
+      },
+    );
+
+    testWidgets(
+      'copyWith textScaler overwrites both textScaler and textScaleFactor',
+      (WidgetTester tester) async {
+        final MarkdownStyleSheet original = MarkdownStyleSheet(
+          textScaleFactor: 2.0,
+        );
+
+        const TextScaler newScaler = TextScaler.linear(3.0);
+        final MarkdownStyleSheet copy = original.copyWith(
+          textScaler: newScaler,
+        );
+
+        expect(copy.textScaler, newScaler);
+        expect(copy.textScaleFactor, null);
+      },
+    );
+
+    testWidgets(
+      'copyWith textScaleFactor overwrites both textScaler and textScaleFactor',
+      (WidgetTester tester) async {
+        final MarkdownStyleSheet original = MarkdownStyleSheet(
+          textScaleFactor: 2.0,
+        );
+
+        const double newScaleFactor = 3.0;
+        final MarkdownStyleSheet copy = original.copyWith(
+          textScaleFactor: newScaleFactor,
+        );
+
+        expect(copy.textScaler, const TextScaler.linear(newScaleFactor));
+        expect(copy.textScaleFactor, newScaleFactor);
+      },
+    );
   });
 }

packages/flutter_markdown/test/text_scale_factor_test.dart renamed to packages/flutter_markdown/test/text_scaler_test.dart

@@ -10,33 +10,35 @@ import 'utils.dart';
 void main() => defineTests();
 
 void defineTests() {
-  group('Text Scale Factor', () {
+  group('Text Scaler', () {
     testWidgets(
-      'should use style textScaleFactor in RichText',
+      'should use style textScaler in RichText',
       (WidgetTester tester) async {
+        const TextScaler scaler = TextScaler.linear(2.0);
         const String data = 'Hello';
         await tester.pumpWidget(
           boilerplate(
             MarkdownBody(
-              styleSheet: MarkdownStyleSheet(textScaleFactor: 2.0),
+              styleSheet: MarkdownStyleSheet(textScaler: scaler),
               data: data,
             ),
           ),
         );
 
         final RichText richText = tester.widget(find.byType(RichText));
-        expect(richText.textScaleFactor, 2.0);
+        expect(richText.textScaler, scaler);
       },
     );
 
     testWidgets(
-      'should use MediaQuery textScaleFactor in RichText',
+      'should use MediaQuery textScaler in RichText',
       (WidgetTester tester) async {
+        const TextScaler scaler = TextScaler.linear(2.0);
         const String data = 'Hello';
         await tester.pumpWidget(
           boilerplate(
             const MediaQuery(
-              data: MediaQueryData(textScaleFactor: 2.0),
+              data: MediaQueryData(textScaler: scaler),
               child: MarkdownBody(
                 data: data,
               ),
@@ -45,18 +47,19 @@ void defineTests() {
         );
 
         final RichText richText = tester.widget(find.byType(RichText));
-        expect(richText.textScaleFactor, 2.0);
+        expect(richText.textScaler, scaler);
       },
     );
 
     testWidgets(
-      'should use MediaQuery textScaleFactor in SelectableText.rich',
+      'should use MediaQuery textScaler in SelectableText.rich',
       (WidgetTester tester) async {
+        const TextScaler scaler = TextScaler.linear(2.0);
         const String data = 'Hello';
         await tester.pumpWidget(
           boilerplate(
             const MediaQuery(
-              data: MediaQueryData(textScaleFactor: 2.0),
+              data: MediaQueryData(textScaler: scaler),
               child: MarkdownBody(
                 data: data,
                 selectable: true,
@@ -67,7 +70,7 @@ void defineTests() {
 
         final SelectableText selectableText =
             tester.widget(find.byType(SelectableText));
-        expect(selectableText.textScaleFactor, 2.0);
+        expect(selectableText.textScaler, scaler);
       },
     );
   });