test: implement pageup/down key test for large document

frontend/app_flowy/packages/flowy_editor/lib/src/service/internal_key_event_handlers/page_up_down_handler.dart

@@ -2,25 +2,16 @@ import 'package:flowy_editor/flowy_editor.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
-double? getEditorHeight(EditorState editorState) {
-  final renderObj =
-      editorState.service.scrollServiceKey.currentContext?.findRenderObject();
-  if (renderObj is RenderBox) {
-    return renderObj.size.height;
-  }
-  return null;
-}
-
 FlowyKeyEventHandler pageUpDownHandler = (editorState, event) {
   if (event.logicalKey == LogicalKeyboardKey.pageUp) {
-    final scrollHeight = getEditorHeight(editorState);
+    final scrollHeight = editorState.service.scrollService?.onePageHeight;
     final scrollService = editorState.service.scrollService;
     if (scrollHeight != null && scrollService != null) {
       scrollService.scrollTo(scrollService.dy - scrollHeight);
     }
     return KeyEventResult.handled;
   } else if (event.logicalKey == LogicalKeyboardKey.pageDown) {
-    final scrollHeight = getEditorHeight(editorState);
+    final scrollHeight = editorState.service.scrollService?.onePageHeight;
     final scrollService = editorState.service.scrollService;
     if (scrollHeight != null && scrollService != null) {
       scrollService.scrollTo(scrollService.dy + scrollHeight);

frontend/app_flowy/packages/flowy_editor/lib/src/service/scroll_service.dart

@@ -1,8 +1,15 @@
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
+import 'package:flowy_editor/src/extensions/object_extensions.dart';
 
 abstract class FlowyScrollService {
   double get dy;
+  double? get onePageHeight;
+
+  int? get page;
+
+  double get maxScrollExtent;
+  double get minScrollExtent;
 
   void scrollTo(double dy);
 
@@ -32,6 +39,27 @@ class _FlowyScrollState extends State<FlowyScroll>
   @override
   double get dy => _scrollController.position.pixels;
 
+  @override
+  double? get onePageHeight {
+    final renderBox = context.findRenderObject()?.unwrapOrNull<RenderBox>();
+    return renderBox?.size.height;
+  }
+
+  @override
+  double get maxScrollExtent => _scrollController.position.maxScrollExtent;
+
+  @override
+  double get minScrollExtent => _scrollController.position.minScrollExtent;
+
+  @override
+  int? get page {
+    if (onePageHeight != null) {
+      final scrollExtent = maxScrollExtent - minScrollExtent;
+      return (scrollExtent / onePageHeight!).ceil();
+    }
+    return null;
+  }
+
   @override
   Widget build(BuildContext context) {
     return Listener(

frontend/app_flowy/packages/flowy_editor/test/infra/test_raw_key_event.dart

@@ -61,6 +61,12 @@ extension on LogicalKeyboardKey {
     if (this == LogicalKeyboardKey.delete) {
       return PhysicalKeyboardKey.delete;
     }
+    if (this == LogicalKeyboardKey.pageDown) {
+      return PhysicalKeyboardKey.pageDown;
+    }
+    if (this == LogicalKeyboardKey.pageUp) {
+      return PhysicalKeyboardKey.pageUp;
+    }
     throw UnimplementedError();
   }
 }

frontend/app_flowy/packages/flowy_editor/test/service/internal_key_event_handlers/page_up_down_handler_test.dart

@@ -0,0 +1,75 @@
+import 'package:flowy_editor/flowy_editor.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import '../../infra/test_editor.dart';
+
+void main() async {
+  setUpAll(() {
+    TestWidgetsFlutterBinding.ensureInitialized();
+  });
+
+  group('page_up_down_handler_test.dart', () {
+    testWidgets('Presses PageUp and pageDown key in large document',
+        (tester) async {
+      const text = 'Welcome to Appflowy 😁';
+      final editor = tester.editor;
+      for (var i = 0; i < 1000; i++) {
+        editor.insertTextNode(text);
+      }
+      await editor.startTesting();
+      await editor.updateSelection(
+        Selection.single(path: [0], startOffset: 0),
+      );
+
+      final scrollService = editor.editorState.service.scrollService;
+
+      expect(scrollService != null, true);
+
+      if (scrollService == null) {
+        return;
+      }
+
+      final page = scrollService.page;
+      final onePageHeight = scrollService.onePageHeight;
+      expect(page != null, true);
+      expect(onePageHeight != null, true);
+
+      // Pressing the pageDown key continuously.
+      var currentOffsetY = 0.0;
+      for (int i = 1; i <= page!; i++) {
+        await editor.pressLogicKey(
+          LogicalKeyboardKey.pageDown,
+        );
+        currentOffsetY += onePageHeight!;
+        final dy = scrollService.dy;
+        expect(dy, currentOffsetY);
+      }
+
+      for (int i = 1; i <= 5; i++) {
+        await editor.pressLogicKey(
+          LogicalKeyboardKey.pageDown,
+        );
+        final dy = scrollService.dy;
+        expect(dy == scrollService.maxScrollExtent, true);
+      }
+
+      // Pressing the pageUp key continuously.
+      for (int i = page; i >= 1; i--) {
+        await editor.pressLogicKey(
+          LogicalKeyboardKey.pageUp,
+        );
+        currentOffsetY -= onePageHeight!;
+        final dy = editor.editorState.service.scrollService?.dy;
+        expect(dy, currentOffsetY);
+      }
+
+      for (int i = 1; i <= 5; i++) {
+        await editor.pressLogicKey(
+          LogicalKeyboardKey.pageUp,
+        );
+        final dy = scrollService.dy;
+        expect(dy == scrollService.minScrollExtent, true);
+      }
+    });
+  });
+}