lib/web_ui/lib/src/engine/text/font_collection.dart - mirrors/engine - Git at Google

 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';

 import 'package:ui/src/engine/fonts.dart';

 import '../assets.dart';
 import '../dom.dart';
 import '../util.dart';
 import 'layout_service.dart';

 /// This class is responsible for registering and loading fonts.
 ///
 /// Once an asset manager has been set in the framework, call
 /// [downloadAssetFonts] with it to register fonts declared in the
 /// font manifest. If test fonts are enabled, then call
 /// [debugDownloadTestFonts] as well.
 class HtmlFontCollection implements FontCollection {
   FontManager? _assetFontManager;
   FontManager? _testFontManager;

   /// Reads the font manifest using the [assetManager] and downloads all of the
   /// fonts declared within.
   @override
   Future<void> downloadAssetFonts(AssetManager assetManager) async {
     ByteData byteData;

     try {
       byteData = await assetManager.load('FontManifest.json');
     } on AssetManagerException catch (e) {
       if (e.httpStatus == 404) {
         printWarning('Font manifest does not exist at `${e.url}` – ignoring.');
         return;
       } else {
         rethrow;
       }
     }

     final List<dynamic>? fontManifest =
         json.decode(utf8.decode(byteData.buffer.asUint8List())) as List<dynamic>?;
     if (fontManifest == null) {
       throw AssertionError(
           'There was a problem trying to load FontManifest.json');
     }

     _assetFontManager = FontManager();

     for (final Map<String, dynamic> fontFamily
         in fontManifest.cast<Map<String, dynamic>>()) {
       final String? family = fontFamily.tryString('family');
       final List<Map<String, dynamic>> fontAssets = fontFamily.castList<Map<String, dynamic>>('fonts');

       for (final Map<String, dynamic> fontAsset in fontAssets) {
         final String asset = fontAsset.readString('asset');
         final Map<String, String> descriptors = <String, String>{};
         for (final String descriptor in fontAsset.keys) {
           if (descriptor != 'asset') {
             descriptors[descriptor] = '${fontAsset[descriptor]}';
           }
         }
         _assetFontManager!.downloadAsset(
             family!, 'url(${assetManager.getAssetUrl(asset)})', descriptors);
       }
     }
     await _assetFontManager!.downloadAllFonts();
   }

   @override
   Future<void> loadFontFromList(Uint8List list, {String? fontFamily}) {
     if (fontFamily == null) {
       throw AssertionError('Font family must be provided to HtmlFontCollection.');
     }
     return _assetFontManager!._loadFontFaceBytes(fontFamily, list);
   }

   /// Downloads fonts that are used by tests.
   @override
   Future<void> debugDownloadTestFonts() async {
     _testFontManager = FontManager();
     _testFontManager!.downloadAsset(
         ahemFontFamily, 'url($ahemFontUrl)', const <String, String>{});
     _testFontManager!.downloadAsset(robotoFontFamily,
         'url($robotoTestFontUrl)', const <String, String>{});
     _testFontManager!.downloadAsset(robotoVariableFontFamily,
         'url($robotoVariableTestFontUrl)', const <String, String>{});
     await _testFontManager!.downloadAllFonts();
   }

   @override
   void registerDownloadedFonts() {
     _assetFontManager?.registerDownloadedFonts();
     _testFontManager?.registerDownloadedFonts();
   }

   /// Unregister all fonts that have been registered.
   @override
   void clear() {
     _assetFontManager = null;
     _testFontManager = null;
     domDocument.fonts!.clear();
   }
 }

 /// Manages a collection of fonts and ensures they are loaded.
 class FontManager {

   /// Fonts that started the downloading process. Once the fonts have downloaded
   /// without error, they are moved to [_downloadedFonts]. Those fonts
   /// are subsequently registered by [registerDownloadedFonts].
   final List<Future<DomFontFace?>> _fontLoadingFutures = <Future<DomFontFace?>>[];

   final List<DomFontFace> _downloadedFonts = <DomFontFace>[];

   // Regular expression to detect a string with no punctuations.
   // For example font family 'Ahem!' does not fall into this category
   // so the family name will be wrapped in quotes.
   static final RegExp notPunctuation =
       RegExp(r'[a-z0-9\s]+', caseSensitive: false);
   // Regular expression to detect tokens starting with a digit.
   // For example font family 'Goudy Bookletter 1911' falls into this
   // category.
   static final RegExp startWithDigit = RegExp(r'\b\d');

   /// Registers assets to Flutter Web Engine.
   ///
   /// Browsers and browsers versions differ significantly on how a valid font
   /// family name should be formatted. Notable issues are:
   ///
   /// Safari 12 and Firefox crash if you create a [DomFontFace] with a font
   /// family that is not correct CSS syntax. Font family names with invalid
   /// characters are accepted on these browsers, when wrapped it in
   /// quotes.
   ///
   /// Additionally, for Safari 12 to work [DomFontFace] name should be
   /// loaded correctly on the first try.
   ///
   /// A font in Chrome is not usable other than inside a '<p>' tag, if a
   /// [DomFontFace] is loaded wrapped with quotes. Unlike Safari 12 if a
   /// valid version of the font is also loaded afterwards it will show
   /// that font normally.
   ///
   /// In Safari 13 the [DomFontFace] should be loaded with unquoted family
   /// names.
   ///
   /// In order to avoid all these browser compatibility issues this method:
   /// * Detects the family names that might cause a conflict.
   /// * Loads it with the quotes.
   /// * Loads it again without the quotes.
   /// * For all the other family names [DomFontFace] is loaded only once.
   ///
   /// See also:
   ///
   /// * https://developer.mozilla.org/en-US/docs/Web/CSS/font-family#Valid_family_names
   /// * https://drafts.csswg.org/css-fonts-3/#font-family-prop
   void downloadAsset(
     String family,
     String asset,
     Map<String, String> descriptors,
   ) {
     if (startWithDigit.hasMatch(family) ||
         notPunctuation.stringMatch(family) != family) {
       // Load a font family name with special characters once here wrapped in
       // quotes.
       _loadFontFace("'$family'", asset, descriptors);
     }
     // Load all fonts, without quoted family names.
     _loadFontFace(family, asset, descriptors);
   }

   void _loadFontFace(
     String family,
     String asset,
     Map<String, String> descriptors,
   ) {
     Future<DomFontFace?> fontFaceLoad(DomFontFace fontFace) async {
       try {
         final DomFontFace loadedFontFace = await fontFace.load();
         return loadedFontFace;
       } catch (e) {
         printWarning('Error while trying to load font family "$family":\n$e');
         return null;
       }
     }
     // try/catch because `new FontFace` can crash with an improper font family.
     try {
       final DomFontFace fontFace = createDomFontFace(family, asset, descriptors);
       _fontLoadingFutures.add(fontFaceLoad(fontFace));
     } catch (e) {
       printWarning('Error while loading font family "$family":\n$e');
     }
   }

   void registerDownloadedFonts() {
     if (_downloadedFonts.isEmpty) {
       return;
     }
     _downloadedFonts.forEach(domDocument.fonts!.add);
   }


   Future<void> downloadAllFonts() async {
     final List<DomFontFace?> loadedFonts = await Future.wait(_fontLoadingFutures);
     _downloadedFonts.addAll(loadedFonts.whereType<DomFontFace>());
   }

   // Loads a font from bytes, surfacing errors through the future.
   Future<void> _loadFontFaceBytes(String family, Uint8List list) {
     // Since these fonts are loaded by user code, surface the error
     // through the returned future.
     final DomFontFace fontFace = createDomFontFace(family, list);
     return fontFace.load().then((_) {
       domDocument.fonts!.add(fontFace);
       // There might be paragraph measurements for this new font before it is
       // loaded. They were measured using fallback font, so we should clear the
       // cache.
       Spanometer.clearRulersCache();
     }, onError: (dynamic exception) {
       // Failures here will throw an DomException which confusingly
       // does not implement Exception or Error. Rethrow an Exception so it can
       // be caught in user code without depending on dart:html or requiring a
       // catch block without "on".
       throw Exception(exception.toString());
     });
   }
 }
	// Copyright 2013 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:async';
	import 'dart:convert';
	import 'dart:typed_data';

	import 'package:ui/src/engine/fonts.dart';

	import '../assets.dart';
	import '../dom.dart';
	import '../util.dart';
	import 'layout_service.dart';

	/// This class is responsible for registering and loading fonts.
	///
	/// Once an asset manager has been set in the framework, call
	/// [downloadAssetFonts] with it to register fonts declared in the
	/// font manifest. If test fonts are enabled, then call
	/// [debugDownloadTestFonts] as well.
	class HtmlFontCollection implements FontCollection {
	FontManager? _assetFontManager;
	FontManager? _testFontManager;

	/// Reads the font manifest using the [assetManager] and downloads all of the
	/// fonts declared within.
	@override
	Future<void> downloadAssetFonts(AssetManager assetManager) async {
	ByteData byteData;

	try {
	byteData = await assetManager.load('FontManifest.json');
	} on AssetManagerException catch (e) {
	if (e.httpStatus == 404) {
	printWarning('Font manifest does not exist at `${e.url}` – ignoring.');
	return;
	} else {
	rethrow;
	}
	}

	final List<dynamic>? fontManifest =
	json.decode(utf8.decode(byteData.buffer.asUint8List())) as List<dynamic>?;
	if (fontManifest == null) {
	throw AssertionError(
	'There was a problem trying to load FontManifest.json');
	}

	_assetFontManager = FontManager();

	for (final Map<String, dynamic> fontFamily
	in fontManifest.cast<Map<String, dynamic>>()) {
	final String? family = fontFamily.tryString('family');
	final List<Map<String, dynamic>> fontAssets = fontFamily.castList<Map<String, dynamic>>('fonts');

	for (final Map<String, dynamic> fontAsset in fontAssets) {
	final String asset = fontAsset.readString('asset');
	final Map<String, String> descriptors = <String, String>{};
	for (final String descriptor in fontAsset.keys) {
	if (descriptor != 'asset') {
	descriptors[descriptor] = '${fontAsset[descriptor]}';
	}
	}
	_assetFontManager!.downloadAsset(
	family!, 'url(${assetManager.getAssetUrl(asset)})', descriptors);
	}
	}
	await _assetFontManager!.downloadAllFonts();
	}

	@override
	Future<void> loadFontFromList(Uint8List list, {String? fontFamily}) {
	if (fontFamily == null) {
	throw AssertionError('Font family must be provided to HtmlFontCollection.');
	}
	return _assetFontManager!._loadFontFaceBytes(fontFamily, list);
	}

	/// Downloads fonts that are used by tests.
	@override
	Future<void> debugDownloadTestFonts() async {
	_testFontManager = FontManager();
	_testFontManager!.downloadAsset(
	ahemFontFamily, 'url($ahemFontUrl)', const <String, String>{});
	_testFontManager!.downloadAsset(robotoFontFamily,
	'url($robotoTestFontUrl)', const <String, String>{});
	_testFontManager!.downloadAsset(robotoVariableFontFamily,
	'url($robotoVariableTestFontUrl)', const <String, String>{});
	await _testFontManager!.downloadAllFonts();
	}

	@override
	void registerDownloadedFonts() {
	_assetFontManager?.registerDownloadedFonts();
	_testFontManager?.registerDownloadedFonts();
	}

	/// Unregister all fonts that have been registered.
	@override
	void clear() {
	_assetFontManager = null;
	_testFontManager = null;
	domDocument.fonts!.clear();
	}
	}

	/// Manages a collection of fonts and ensures they are loaded.
	class FontManager {

	/// Fonts that started the downloading process. Once the fonts have downloaded
	/// without error, they are moved to [_downloadedFonts]. Those fonts
	/// are subsequently registered by [registerDownloadedFonts].
	final List<Future<DomFontFace?>> _fontLoadingFutures = <Future<DomFontFace?>>[];

	final List<DomFontFace> _downloadedFonts = <DomFontFace>[];

	// Regular expression to detect a string with no punctuations.
	// For example font family 'Ahem!' does not fall into this category
	// so the family name will be wrapped in quotes.
	static final RegExp notPunctuation =
	RegExp(r'[a-z0-9\s]+', caseSensitive: false);
	// Regular expression to detect tokens starting with a digit.
	// For example font family 'Goudy Bookletter 1911' falls into this
	// category.
	static final RegExp startWithDigit = RegExp(r'\b\d');

	/// Registers assets to Flutter Web Engine.
	///
	/// Browsers and browsers versions differ significantly on how a valid font
	/// family name should be formatted. Notable issues are:
	///
	/// Safari 12 and Firefox crash if you create a [DomFontFace] with a font
	/// family that is not correct CSS syntax. Font family names with invalid
	/// characters are accepted on these browsers, when wrapped it in
	/// quotes.
	///
	/// Additionally, for Safari 12 to work [DomFontFace] name should be
	/// loaded correctly on the first try.
	///
	/// A font in Chrome is not usable other than inside a '<p>' tag, if a
	/// [DomFontFace] is loaded wrapped with quotes. Unlike Safari 12 if a
	/// valid version of the font is also loaded afterwards it will show
	/// that font normally.
	///
	/// In Safari 13 the [DomFontFace] should be loaded with unquoted family
	/// names.
	///
	/// In order to avoid all these browser compatibility issues this method:
	/// * Detects the family names that might cause a conflict.
	/// * Loads it with the quotes.
	/// * Loads it again without the quotes.
	/// * For all the other family names [DomFontFace] is loaded only once.
	///
	/// See also:
	///
	/// * https://developer.mozilla.org/en-US/docs/Web/CSS/font-family#Valid_family_names
	/// * https://drafts.csswg.org/css-fonts-3/#font-family-prop
	void downloadAsset(
	String family,
	String asset,
	Map<String, String> descriptors,
	) {
	if (startWithDigit.hasMatch(family) \|\|
	notPunctuation.stringMatch(family) != family) {
	// Load a font family name with special characters once here wrapped in
	// quotes.
	_loadFontFace("'$family'", asset, descriptors);
	}
	// Load all fonts, without quoted family names.
	_loadFontFace(family, asset, descriptors);
	}

	void _loadFontFace(
	String family,
	String asset,
	Map<String, String> descriptors,
	) {
	Future<DomFontFace?> fontFaceLoad(DomFontFace fontFace) async {
	try {
	final DomFontFace loadedFontFace = await fontFace.load();
	return loadedFontFace;
	} catch (e) {
	printWarning('Error while trying to load font family "$family":\n$e');
	return null;
	}
	}
	// try/catch because `new FontFace` can crash with an improper font family.
	try {
	final DomFontFace fontFace = createDomFontFace(family, asset, descriptors);
	_fontLoadingFutures.add(fontFaceLoad(fontFace));
	} catch (e) {
	printWarning('Error while loading font family "$family":\n$e');
	}
	}

	void registerDownloadedFonts() {
	if (_downloadedFonts.isEmpty) {
	return;
	}
	_downloadedFonts.forEach(domDocument.fonts!.add);
	}


	Future<void> downloadAllFonts() async {
	final List<DomFontFace?> loadedFonts = await Future.wait(_fontLoadingFutures);
	_downloadedFonts.addAll(loadedFonts.whereType<DomFontFace>());
	}

	// Loads a font from bytes, surfacing errors through the future.
	Future<void> _loadFontFaceBytes(String family, Uint8List list) {
	// Since these fonts are loaded by user code, surface the error
	// through the returned future.
	final DomFontFace fontFace = createDomFontFace(family, list);
	return fontFace.load().then((_) {
	domDocument.fonts!.add(fontFace);
	// There might be paragraph measurements for this new font before it is
	// loaded. They were measured using fallback font, so we should clear the
	// cache.
	Spanometer.clearRulersCache();
	}, onError: (dynamic exception) {
	// Failures here will throw an DomException which confusingly
	// does not implement Exception or Error. Rethrow an Exception so it can
	// be caught in user code without depending on dart:html or requiring a
	// catch block without "on".
	throw Exception(exception.toString());
	});
	}
	}