perf: only parse pdf once, and dispose it properly

Author: adil192

lib/components/canvas/_asset_cache.dart

@@ -5,6 +5,7 @@ import 'package:collection/collection.dart';
 import 'package:flutter/painting.dart';
 import 'package:logging/logging.dart';
 import 'package:saber/components/canvas/image/editor_image.dart';
+import 'package:saber/components/canvas/image/pdf_document_cache.dart';
 
 /// A cache for assets that are loaded from disk.
 ///
@@ -18,6 +19,8 @@ class AssetCache {
 
   final log = Logger('AssetCache');
 
+  final pdfDocumentCache = PdfDocumentCache();
+
   /// Maps a file path to its value.
   final Map<String, Object> _cache = {};
 
@@ -73,6 +76,7 @@ class AssetCache {
   void dispose() {
     _images.clear();
     _cache.clear();
+    pdfDocumentCache.dispose();
   }
 }
 

lib/components/canvas/image/pdf_document_cache.dart

@@ -0,0 +1,32 @@
+import 'dart:async';
+import 'dart:typed_data';
+
+import 'package:pdfrx/pdfrx.dart';
+
+class PdfDocumentCache {
+  final Map<String, FutureOr<PdfDocument>> _cache = {};
+
+  /// Loads a PDF document from [filePath].
+  /// If the bytes are provided, they are used instead of reading from disk.
+  FutureOr<PdfDocument> load(String filePath, {Uint8List? pdfBytes}) {
+    return _cache[filePath] ??= _loadCacheMiss(filePath, pdfBytes: pdfBytes);
+  }
+
+  Future<PdfDocument> _loadCacheMiss(
+    String filePath, {
+    Uint8List? pdfBytes,
+  }) async {
+    final document = pdfBytes == null
+        ? PdfDocument.openFile(filePath)
+        : PdfDocument.openData(pdfBytes);
+    _cache[filePath] = document;
+    return document;
+  }
+
+  void dispose() {
+    for (final documentFuture in _cache.values) {
+      Future.value(documentFuture).then((document) => document.dispose());
+    }
+    _cache.clear();
+  }
+}

lib/components/canvas/image/pdf_editor_image.dart

@@ -126,9 +126,11 @@ class PdfEditorImage extends EditorImage {
       dstRect = dstRect.topLeft & dstSize;
     }
 
-    _pdfDocument.value ??= pdfFile != null
-        ? await PdfDocument.openFile(pdfFile!.path)
-        : await PdfDocument.openData(pdfBytes!);
+    assert(id != -1, 'id must be set before firstLoad is called');
+    _pdfDocument.value ??= await assetCache.pdfDocumentCache.load(
+      pdfFile?.path ?? 'inline_pdf_$id.pdf',
+      pdfBytes: pdfBytes,
+    );
   }
 
   @override
@@ -199,4 +201,11 @@ class PdfEditorImage extends EditorImage {
     naturalSize: naturalSize,
     isThumbnail: isThumbnail,
   );
+
+  @override
+  void dispose() {
+    pdfBytes = null;
+    _pdfDocument.dispose();
+    super.dispose();
+  }
 }

lib/data/editor/page.dart

@@ -288,6 +288,9 @@ class EditorPage extends ChangeNotifier implements HasSize {
     quill.dispose();
     _pencilShader?.dispose();
     isRendered = false;
+    for (final image in images) {
+      image.dispose();
+    }
     backgroundImage?.dispose();
     super.dispose();
   }