fix(app): study faces centred in the card

The read-only view passed its alignment to the text alone, which the
editor lays out only as wide as itself, so a centred face stayed at the
start. It now aligns top-level paragraphs and headings that have no
alignment of their own; lists, quotes and the rest keep the start, and
an alignment chosen in the format bar wins.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/src/core/editor/editor_blocks.dart

@@ -88,31 +88,21 @@ class const EditorBlocksScope({
 /// English.
 Map<String, BlockComponentBuilder> buildersWithUnknown(
   EditorBlocks blocks,
-  AppLocalizations l10n, {
-  TextAlign? textAlign,
-}) => {
+  AppLocalizations l10n,
+) => {
   for (final MapEntry(key: type, value: builder) in blocks.builders.entries)
-    type: _withPlaceholder(builder, l10n, textAlign),
+    type: _withPlaceholder(builder, l10n),
   errorBlockComponentBuilderKey: _UnknownBlockBuilder(),
 };
 
 /// [builder] alike, but saying what its block is in [l10n]'s language while
-/// empty, for the editor's own text blocks, and aligning their text as
-/// [textAlign] says where the text doesn't say otherwise; others as they
-/// are.
+/// empty, for the editor's own text blocks; others as they are.
 BlockComponentBuilder _withPlaceholder(
   BlockComponentBuilder builder,
   AppLocalizations l10n,
-  TextAlign? textAlign,
 ) {
   BlockComponentConfiguration saying(String Function(Node node) text) =>
-      builder.configuration.copyWith(
-        placeholderText: text,
-        textAlign: switch (textAlign) {
-          final align? => (_) => align,
-          null => null,
-        },
-      );
+      builder.configuration.copyWith(placeholderText: text);
   return switch (builder) {
     final ParagraphBlockComponentBuilder paragraph =>
       ParagraphBlockComponentBuilder(

halkyon_learn_flutter/lib/src/core/editor/rich_content_view.dart

@@ -24,7 +24,9 @@ class const RichContentView({
   /// The text's style; the theme's `bodyLarge` without.
   final TextStyle? textStyle,
 
-  /// How the text aligns where it doesn't say itself; at the start without.
+  /// How paragraphs and headings align where the editor gave them no
+  /// alignment of their own; at the start without. Lists, quotes and the
+  /// other blocks keep the start: centred, a list's markers drift apart.
   final TextAlign? textAlign,
   super.key,
 }) extends StatefulWidget {
@@ -33,16 +35,17 @@ class const RichContentView({
 }
 
 class _RichContentViewState() extends State<RichContentView> {
-  late EditorState _editorState = _readOnly(widget.content);
+  late EditorState _editorState = _readOnly(widget.content, widget.textAlign);
 
   @override
   void didUpdateWidget(RichContentView oldWidget) {
     super.didUpdateWidget(oldWidget);
-    if (widget.content != oldWidget.content) {
+    if (widget.content != oldWidget.content ||
+        widget.textAlign != oldWidget.textAlign) {
       // The old editor is still attached until this frame is built.
       final previous = _editorState;
       WidgetsBinding.instance.addPostFrameCallback((_) => previous.dispose());
-      _editorState = _readOnly(widget.content);
+      _editorState = _readOnly(widget.content, widget.textAlign);
     }
   }
 
@@ -68,7 +71,6 @@ class _RichContentViewState() extends State<RichContentView> {
       blockComponentBuilders: buildersWithUnknown(
         blocksOf(context),
         AppLocalizations.of(context),
-        textAlign: widget.textAlign,
       ),
       editable: false,
       disableSelectionService: true,
@@ -78,5 +80,25 @@ class _RichContentViewState() extends State<RichContentView> {
   );
 }
 
-EditorState _readOnly(RichContent content) =>
-    EditorState(document: content.toDocument())..editable = false;
+/// [content] to show, its top-level paragraphs and headings aligned as
+/// [textAlign] says where they don't say themselves. The editor lays a text
+/// block's text out only as wide as it is, so aligning the text alone moves
+/// nothing: the block's own `align` places it. The document is never saved.
+EditorState _readOnly(RichContent content, TextAlign? textAlign) {
+  final document = content.toDocument();
+  final align = switch (textAlign) {
+    TextAlign.center => 'center',
+    TextAlign.right => 'right',
+    _ => null,
+  };
+  if (align != null) {
+    for (final node in document.root.children) {
+      if ((node.type == ParagraphBlockKeys.type ||
+              node.type == HeadingBlockKeys.type) &&
+          node.attributes[blockComponentAlign] == null) {
+        node.updateAttributes({blockComponentAlign: align});
+      }
+    }
+  }
+  return EditorState(document: document)..editable = false;
+}

halkyon_learn_flutter/test/core/editor/rich_content_view_test.dart

@@ -74,4 +74,83 @@ void main() {
     expect(tapped, 1);
     expect(tester.testTextInput.hasAnyClients, isFalse);
   }, variant: TargetPlatformVariant.all());
+
+  group('asked to centre', () {
+    Map<String, Object?> block(
+      String type,
+      String text, [
+      Map<String, Object?> data = const {},
+    ]) => {
+      'type': type,
+      'data': {
+        ...data,
+        'delta': [
+          {'insert': text},
+        ],
+      },
+    };
+
+    Future<void> showCentred(
+      WidgetTester tester,
+      List<Map<String, Object?>> blocks,
+    ) async {
+      tester.view.physicalSize = const Size(400, 800);
+      tester.view.devicePixelRatio = 1;
+      addTearDown(tester.view.reset);
+      await tester.pumpWidget(
+        MaterialApp(
+          localizationsDelegates: AppLocalizations.localizationsDelegates,
+          home: Scaffold(
+            body: ListView(
+              children: [
+                RichContentView(
+                  content: RichContent({
+                    'document': {'type': 'page', 'children': blocks},
+                  }),
+                  textAlign: TextAlign.center,
+                ),
+              ],
+            ),
+          ),
+        ),
+      );
+      await tester.pump(const Duration(seconds: 1));
+    }
+
+    double centreOf(WidgetTester tester, String text) =>
+        tester.getCenter(find.text(text, findRichText: true)).dx;
+    double leftOf(WidgetTester tester, String text) =>
+        tester.getTopLeft(find.text(text, findRichText: true)).dx;
+
+    testWidgets('centres paragraphs and headings', (tester) async {
+      await showCentred(tester, [
+        block('heading', 'Greetings', {'level': 2}),
+        block('paragraph', 'hola'),
+      ]);
+
+      expect(centreOf(tester, 'Greetings'), moreOrLessEquals(200, epsilon: 1));
+      expect(centreOf(tester, 'hola'), moreOrLessEquals(200, epsilon: 1));
+    });
+
+    testWidgets('leaves a list at the start: centred, its markers would '
+        'drift apart', (tester) async {
+      await showCentred(tester, [
+        block('bulleted_list', 'hola'),
+        block('bulleted_list', 'buenos días'),
+      ]);
+
+      expect(leftOf(tester, 'hola'), lessThan(60));
+      expect(leftOf(tester, 'buenos días'), leftOf(tester, 'hola'));
+    });
+
+    testWidgets('keeps the alignment a paragraph was given in the editor', (
+      tester,
+    ) async {
+      await showCentred(tester, [
+        block('paragraph', 'hola', {'align': 'left'}),
+      ]);
+
+      expect(leftOf(tester, 'hola'), lessThan(40));
+    });
+  });
 }

halkyon_learn_flutter/test/feature/study/widget/study_screen_test.dart

@@ -138,6 +138,28 @@ void main() {
     expect(find.textContaining('cat', findRichText: true), findsNothing);
   });
 
+  testWidgets('the faces are centred in the card, and a tap on their text '
+      'shows and hides the answer too', (tester) async {
+    await cards.create(
+      'japanese',
+      CardContent(front: paragraph('猫'), back: paragraph('cat')),
+    );
+    await study(tester, width: 400);
+    final card = tester.getRect(find.byType(StudyCardSurface));
+    double centreOf(String text) =>
+        tester.getCenter(find.text(text, findRichText: true)).dx;
+
+    expect(centreOf('猫'), moreOrLessEquals(card.center.dx, epsilon: 1));
+
+    await tester.tap(find.text('猫', findRichText: true));
+    await tester.pumpAndSettle();
+    expect(centreOf('cat'), moreOrLessEquals(card.center.dx, epsilon: 1));
+
+    await tester.tap(find.text('cat', findRichText: true));
+    await tester.pumpAndSettle();
+    expect(find.textContaining('cat', findRichText: true), findsNothing);
+  });
+
   testWidgets('on a phone, a card swiped right is rated Good, one let go '
       'early springs back', (tester) async {
     await cards.create(