From c5a40382a9428fa63dadc4870896a74eb0139fd2 Mon Sep 17 00:00:00 2001
From: Takashi Kawasaki <espresso3389@gmail.com>
Date: Fri, 30 Aug 2024 15:32:28 +0900
Subject: [PATCH] Reduce frequent onTextSelectionChange calls

---
 lib/src/pdf_api.dart                       |  2 +-
 lib/src/widgets/pdf_page_text_overlay.dart | 13 ++++++++--
 lib/src/widgets/pdf_viewer.dart            | 29 ++++++++++------------
 3 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/lib/src/pdf_api.dart b/lib/src/pdf_api.dart
index bf5050c..77788ca 100644
--- a/lib/src/pdf_api.dart
+++ b/lib/src/pdf_api.dart
@@ -625,7 +625,7 @@ class PdfTextRanges {
   bool get isEmpty => ranges.isEmpty;
 
   /// Determine whether the text ranges are *NOT* empty.
-  bool get isNotEmpty => !isEmpty;
+  bool get isNotEmpty => ranges.isNotEmpty;
 
   /// Page number of the text ranges.
   int get pageNumber => pageText.pageNumber;
diff --git a/lib/src/widgets/pdf_page_text_overlay.dart b/lib/src/widgets/pdf_page_text_overlay.dart
index cee2baa..64e0505 100644
--- a/lib/src/widgets/pdf_page_text_overlay.dart
+++ b/lib/src/widgets/pdf_page_text_overlay.dart
@@ -1,3 +1,5 @@
+import 'dart:collection';
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
@@ -28,7 +30,7 @@ class PdfPageTextOverlay extends StatefulWidget {
     super.key,
   });
 
-  final Map<int, Selectable> selectables;
+  final SplayTreeMap<int, PdfPageTextSelectable> selectables;
   final bool enabled;
   final PdfPage page;
   final Rect pageRect;
@@ -197,8 +199,12 @@ class _PdfTextWidget extends LeafRenderObjectWidget {
   }
 }
 
+mixin PdfPageTextSelectable implements Selectable {
+  PdfTextRanges get selectedRanges;
+}
+
 /// The code is based on the code on [Making a widget selectable](https://api.flutter.dev/flutter/widgets/SelectableRegion-class.html#widgets).SelectableRegion.2]
-class _PdfTextRenderBox extends RenderBox with Selectable, SelectionRegistrant {
+class _PdfTextRenderBox extends RenderBox with PdfPageTextSelectable, Selectable, SelectionRegistrant {
   _PdfTextRenderBox(
     this._selectionColor,
     this._textWidget,
@@ -277,6 +283,9 @@ class _PdfTextRenderBox extends RenderBox with Selectable, SelectionRegistrant {
   late PdfTextRanges _selectedRanges =
       PdfTextRanges.createEmpty(_textWidget._state._pageText!);
 
+  @override
+  PdfTextRanges get selectedRanges => _selectedRanges;
+
   void _notifySelectionChange() {
     _textWidget._state._notifySelectionChange(_selectedRanges);
   }
diff --git a/lib/src/widgets/pdf_viewer.dart b/lib/src/widgets/pdf_viewer.dart
index fdb462d..0e7ab54 100644
--- a/lib/src/widgets/pdf_viewer.dart
+++ b/lib/src/widgets/pdf_viewer.dart
@@ -228,10 +228,11 @@ class _PdfViewerState extends State<PdfViewer>
   // Changes to the stream rebuilds the viewer
   final _updateStream = BehaviorSubject<Matrix4>();
 
-  final _selectionHandlers = <int, Selectable>{};
+  final _selectionHandlers = SplayTreeMap<int, PdfPageTextSelectable>();
+  Timer? _selectionChangedThrottleTimer;
 
-  final _textSelections = SplayTreeSet<PdfTextRanges>(
-      (a, b) => a.pageNumber.compareTo(b.pageNumber));
+  Timer? _interactionEndedTimer;
+  bool _isInteractionGoingOn = false;
 
   @override
   void initState() {
@@ -306,6 +307,7 @@ class _PdfViewerState extends State<PdfViewer>
   void _onDocumentChanged() async {
     _layout = null;
 
+    _selectionChangedThrottleTimer?.cancel();
     _stopInteraction();
     _releaseAllImages();
     _canvasLinkPainter.resetAll();
@@ -347,6 +349,7 @@ class _PdfViewerState extends State<PdfViewer>
 
   @override
   void dispose() {
+    _selectionChangedThrottleTimer?.cancel();
     _stopInteraction();
     _cancelAllPendingRenderings();
     _animController.dispose();
@@ -484,9 +487,6 @@ class _PdfViewerState extends State<PdfViewer>
     });
   }
 
-  Timer? _interactionEndedTimer;
-  bool _isInteractionGoingOn = false;
-
   void _startInteraction() {
     _interactionEndedTimer?.cancel();
     _interactionEndedTimer = null;
@@ -866,16 +866,13 @@ class _PdfViewerState extends State<PdfViewer>
   }
 
   void _onSelectionChange(PdfTextRanges selection) {
-    if (selection.isEmpty) {
-      if (!_textSelections.contains(selection)) return;
-      _textSelections.remove(selection);
-    } else {
-      if (_textSelections.contains(selection)) {
-        _textSelections.remove(selection);
-      }
-      _textSelections.add(selection);
-    }
-    widget.params.onTextSelectionChange?.call(_textSelections.toList());
+    _selectionChangedThrottleTimer?.cancel();
+    _selectionChangedThrottleTimer = Timer(const Duration(milliseconds: 300), () {
+      if (!mounted || !_selectionHandlers.containsKey(selection.pageNumber)) return;
+      widget.params.onTextSelectionChange?.call(
+        _selectionHandlers.values.map((s) => s.selectedRanges).where((s) => s.isNotEmpty).toList()
+      );
+    });
   }
 
   Rect _getCacheExtentRect() {