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fix infinite loop in findMinimumFontsForCodeunits #24441

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yjbanov merged 1 commit into from
Feb 16, 2021
Merged

fix infinite loop in findMinimumFontsForCodeunits #24441

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111 changes: 61 additions & 50 deletions lib/web_ui/lib/src/engine/canvaskit/font_fallbacks.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -12,19 +12,19 @@ bool _registeredSymbolsAndEmoji = false;

final Set<int> codeUnitsWithNoKnownFont = <int>{};

Future<void> _findFontsForMissingCodeunits(List<int> codeunits) async {
Future<void> findFontsForMissingCodeunits(List<int> codeunits) async {
_ensureNotoFontTreeCreated();

// If all of the code units are known to have no Noto Font which covers them,
// then just give up. We have already logged a warning.
if (codeunits.every((u) => codeUnitsWithNoKnownFont.contains(u))) {
return;
}
Set<_NotoFont> fonts = <_NotoFont>{};
Set<NotoFont> fonts = <NotoFont>{};
Set<int> coveredCodeUnits = <int>{};
Set<int> missingCodeUnits = <int>{};
for (int codeunit in codeunits) {
List<_NotoFont> fontsForUnit = _notoTree!.intersections(codeunit);
List<NotoFont> fontsForUnit = _notoTree!.intersections(codeunit);
fonts.addAll(fontsForUnit);
if (fontsForUnit.isNotEmpty) {
coveredCodeUnits.add(codeunit);
Expand All @@ -33,15 +33,15 @@ Future<void> _findFontsForMissingCodeunits(List<int> codeunits) async {
}
}

fonts = _findMinimumFontsForCodeunits(coveredCodeUnits, fonts);
fonts = findMinimumFontsForCodeunits(coveredCodeUnits, fonts);

for (_NotoFont font in fonts) {
for (NotoFont font in fonts) {
await font.ensureResolved();
}

Set<_ResolvedNotoSubset> resolvedFonts = <_ResolvedNotoSubset>{};
for (int codeunit in coveredCodeUnits) {
for (_NotoFont font in fonts) {
for (NotoFont font in fonts) {
if (font.resolvedFont == null) {
// We failed to resolve the font earlier.
continue;
Expand Down Expand Up @@ -232,18 +232,20 @@ Future<void> _registerSymbolsAndEmoji() async {
/// which finds the font which covers the most codeunits. If multiple CJK
/// fonts match the same number of codeunits, we choose one based on the user's
/// locale.
Set<_NotoFont> _findMinimumFontsForCodeunits(
Iterable<int> codeunits, Set<_NotoFont> fonts) {
Set<NotoFont> findMinimumFontsForCodeunits(
Iterable<int> codeunits, Set<NotoFont> fonts) {
assert(fonts.isNotEmpty || codeunits.isEmpty);
List<int> unmatchedCodeunits = List<int>.from(codeunits);
Set<_NotoFont> minimumFonts = <_NotoFont>{};
List<_NotoFont> bestFonts = <_NotoFont>[];
int maxCodeunitsCovered = 0;
Set<NotoFont> minimumFonts = <NotoFont>{};
List<NotoFont> bestFonts = <NotoFont>[];

String language = html.window.navigator.language;

// This is guaranteed to terminate because [codeunits] is a list of fonts
// which we've already determined are covered by [fonts].
while (unmatchedCodeunits.isNotEmpty) {
int maxCodeunitsCovered = 0;
bestFonts.clear();
for (var font in fonts) {
int codeunitsCovered = 0;
for (int codeunit in unmatchedCodeunits) {
Expand All @@ -259,10 +261,13 @@ Set<_NotoFont> _findMinimumFontsForCodeunits(
bestFonts.add(font);
}
}
assert(bestFonts.isNotEmpty);
assert(
bestFonts.isNotEmpty,
'Did not find any fonts that cover code units: ${unmatchedCodeunits.join(', ')}',
);
// If the list of best fonts are all CJK fonts, choose the best one based
// on locale. Otherwise just choose the first font.
_NotoFont bestFont = bestFonts.first;
NotoFont bestFont = bestFonts.first;
if (bestFonts.length > 1) {
if (bestFonts.every((font) => _cjkFonts.contains(font))) {
if (language == 'zh-Hans' ||
Expand Down Expand Up @@ -301,27 +306,27 @@ void _ensureNotoFontTreeCreated() {
return;
}

Map<_NotoFont, List<CodeunitRange>> ranges =
<_NotoFont, List<CodeunitRange>>{};
Map<NotoFont, List<CodeunitRange>> ranges =
<NotoFont, List<CodeunitRange>>{};

for (_NotoFont font in _notoFonts) {
for (NotoFont font in _notoFonts) {
for (CodeunitRange range in font.unicodeRanges) {
ranges.putIfAbsent(font, () => <CodeunitRange>[]).add(range);
}
}

_notoTree = IntervalTree<_NotoFont>.createFromRanges(ranges);
_notoTree = IntervalTree<NotoFont>.createFromRanges(ranges);
}

class _NotoFont {
class NotoFont {
final String name;
final List<CodeunitRange> unicodeRanges;

Completer<void>? _decodingCompleter;

_ResolvedNotoFont? resolvedFont;

_NotoFont(this.name, this.unicodeRanges);
NotoFont(this.name, this.unicodeRanges);

bool matchesCodeunit(int codeunit) {
for (CodeunitRange range in unicodeRanges) {
Expand Down Expand Up @@ -397,45 +402,45 @@ class _ResolvedNotoSubset {
String toString() => '_ResolvedNotoSubset($family, $url)';
}

_NotoFont _notoSansSC = _NotoFont('Noto Sans SC', <CodeunitRange>[
NotoFont _notoSansSC = NotoFont('Noto Sans SC', <CodeunitRange>[
CodeunitRange(12288, 12591),
CodeunitRange(12800, 13311),
CodeunitRange(19968, 40959),
CodeunitRange(65072, 65135),
CodeunitRange(65280, 65519),
]);

_NotoFont _notoSansTC = _NotoFont('Noto Sans TC', <CodeunitRange>[
NotoFont _notoSansTC = NotoFont('Noto Sans TC', <CodeunitRange>[
CodeunitRange(12288, 12351),
CodeunitRange(12549, 12585),
CodeunitRange(19968, 40959),
]);

_NotoFont _notoSansHK = _NotoFont('Noto Sans HK', <CodeunitRange>[
NotoFont _notoSansHK = NotoFont('Noto Sans HK', <CodeunitRange>[
CodeunitRange(12288, 12351),
CodeunitRange(12549, 12585),
CodeunitRange(19968, 40959),
]);

_NotoFont _notoSansJP = _NotoFont('Noto Sans JP', <CodeunitRange>[
NotoFont _notoSansJP = NotoFont('Noto Sans JP', <CodeunitRange>[
CodeunitRange(12288, 12543),
CodeunitRange(19968, 40959),
CodeunitRange(65280, 65519),
]);

List<_NotoFont> _cjkFonts = <_NotoFont>[
List<NotoFont> _cjkFonts = <NotoFont>[
_notoSansSC,
_notoSansTC,
_notoSansHK,
_notoSansJP,
];

List<_NotoFont> _notoFonts = <_NotoFont>[
List<NotoFont> _notoFonts = <NotoFont>[
_notoSansSC,
_notoSansTC,
_notoSansHK,
_notoSansJP,
_NotoFont('Noto Naskh Arabic UI', <CodeunitRange>[
NotoFont('Noto Naskh Arabic UI', <CodeunitRange>[
CodeunitRange(1536, 1791),
CodeunitRange(8204, 8206),
CodeunitRange(8208, 8209),
Expand All @@ -444,44 +449,44 @@ List<_NotoFont> _notoFonts = <_NotoFont>[
CodeunitRange(64336, 65023),
CodeunitRange(65132, 65276),
]),
_NotoFont('Noto Sans Armenian', <CodeunitRange>[
NotoFont('Noto Sans Armenian', <CodeunitRange>[
CodeunitRange(1328, 1424),
CodeunitRange(64275, 64279),
]),
_NotoFont('Noto Sans Bengali UI', <CodeunitRange>[
NotoFont('Noto Sans Bengali UI', <CodeunitRange>[
CodeunitRange(2404, 2405),
CodeunitRange(2433, 2555),
CodeunitRange(8204, 8205),
CodeunitRange(8377, 8377),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Myanmar UI', <CodeunitRange>[
NotoFont('Noto Sans Myanmar UI', <CodeunitRange>[
CodeunitRange(4096, 4255),
CodeunitRange(8204, 8205),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Egyptian Hieroglyphs', <CodeunitRange>[
NotoFont('Noto Sans Egyptian Hieroglyphs', <CodeunitRange>[
CodeunitRange(77824, 78894),
]),
_NotoFont('Noto Sans Ethiopic', <CodeunitRange>[
NotoFont('Noto Sans Ethiopic', <CodeunitRange>[
CodeunitRange(4608, 5017),
CodeunitRange(11648, 11742),
CodeunitRange(43777, 43822),
]),
_NotoFont('Noto Sans Georgian', <CodeunitRange>[
NotoFont('Noto Sans Georgian', <CodeunitRange>[
CodeunitRange(1417, 1417),
CodeunitRange(4256, 4351),
CodeunitRange(11520, 11567),
]),
_NotoFont('Noto Sans Gujarati UI', <CodeunitRange>[
NotoFont('Noto Sans Gujarati UI', <CodeunitRange>[
CodeunitRange(2404, 2405),
CodeunitRange(2688, 2815),
CodeunitRange(8204, 8205),
CodeunitRange(8377, 8377),
CodeunitRange(9676, 9676),
CodeunitRange(43056, 43065),
]),
_NotoFont('Noto Sans Gurmukhi UI', <CodeunitRange>[
NotoFont('Noto Sans Gurmukhi UI', <CodeunitRange>[
CodeunitRange(2404, 2405),
CodeunitRange(2561, 2677),
CodeunitRange(8204, 8205),
Expand All @@ -490,13 +495,13 @@ List<_NotoFont> _notoFonts = <_NotoFont>[
CodeunitRange(9772, 9772),
CodeunitRange(43056, 43065),
]),
_NotoFont('Noto Sans Hebrew', <CodeunitRange>[
NotoFont('Noto Sans Hebrew', <CodeunitRange>[
CodeunitRange(1424, 1535),
CodeunitRange(8362, 8362),
CodeunitRange(9676, 9676),
CodeunitRange(64285, 64335),
]),
_NotoFont('Noto Sans Devanagari UI', <CodeunitRange>[
NotoFont('Noto Sans Devanagari UI', <CodeunitRange>[
CodeunitRange(2304, 2431),
CodeunitRange(7376, 7414),
CodeunitRange(7416, 7417),
Expand All @@ -507,29 +512,29 @@ List<_NotoFont> _notoFonts = <_NotoFont>[
CodeunitRange(43056, 43065),
CodeunitRange(43232, 43259),
]),
_NotoFont('Noto Sans Kannada UI', <CodeunitRange>[
NotoFont('Noto Sans Kannada UI', <CodeunitRange>[
CodeunitRange(2404, 2405),
CodeunitRange(3202, 3314),
CodeunitRange(8204, 8205),
CodeunitRange(8377, 8377),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Khmer UI', <CodeunitRange>[
NotoFont('Noto Sans Khmer UI', <CodeunitRange>[
CodeunitRange(6016, 6143),
CodeunitRange(8204, 8204),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans KR', <CodeunitRange>[
NotoFont('Noto Sans KR', <CodeunitRange>[
CodeunitRange(12593, 12686),
CodeunitRange(12800, 12828),
CodeunitRange(12896, 12923),
CodeunitRange(44032, 55215),
]),
_NotoFont('Noto Sans Lao UI', <CodeunitRange>[
NotoFont('Noto Sans Lao UI', <CodeunitRange>[
CodeunitRange(3713, 3807),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Malayalam UI', <CodeunitRange>[
NotoFont('Noto Sans Malayalam UI', <CodeunitRange>[
CodeunitRange(775, 775),
CodeunitRange(803, 803),
CodeunitRange(2404, 2405),
Expand All @@ -538,33 +543,33 @@ List<_NotoFont> _notoFonts = <_NotoFont>[
CodeunitRange(8377, 8377),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Sinhala', <CodeunitRange>[
NotoFont('Noto Sans Sinhala', <CodeunitRange>[
CodeunitRange(2404, 2405),
CodeunitRange(3458, 3572),
CodeunitRange(8204, 8205),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Tamil UI', <CodeunitRange>[
NotoFont('Noto Sans Tamil UI', <CodeunitRange>[
CodeunitRange(2404, 2405),
CodeunitRange(2946, 3066),
CodeunitRange(8204, 8205),
CodeunitRange(8377, 8377),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Telugu UI', <CodeunitRange>[
NotoFont('Noto Sans Telugu UI', <CodeunitRange>[
CodeunitRange(2385, 2386),
CodeunitRange(2404, 2405),
CodeunitRange(3072, 3199),
CodeunitRange(7386, 7386),
CodeunitRange(8204, 8205),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans Thai UI', <CodeunitRange>[
NotoFont('Noto Sans Thai UI', <CodeunitRange>[
CodeunitRange(3585, 3675),
CodeunitRange(8204, 8205),
CodeunitRange(9676, 9676),
]),
_NotoFont('Noto Sans', <CodeunitRange>[
NotoFont('Noto Sans', <CodeunitRange>[
CodeunitRange(0, 255),
CodeunitRange(305, 305),
CodeunitRange(338, 339),
Expand Down Expand Up @@ -639,7 +644,7 @@ class FallbackFontDownloadQueue {
downloads.add(Future<void>(() async {
ByteBuffer buffer;
try {
buffer = await downloader.downloadAsBytes(subset.url);
buffer = await downloader.downloadAsBytes(subset.url, debugDescription: subset.family);
} catch (e) {
html.window.console
.warn('Failed to load font ${subset.family} at ${subset.url}');
Expand Down Expand Up @@ -695,7 +700,7 @@ class NotoDownloader {
/// Downloads the [url] and returns it as a [ByteBuffer].
///
/// Override this for testing.
Future<ByteBuffer> downloadAsBytes(String url) {
Future<ByteBuffer> downloadAsBytes(String url, {String? debugDescription}) {
if (assertionsEnabled) {
_debugActiveDownloadCount += 1;
}
Expand All @@ -714,7 +719,7 @@ class NotoDownloader {
/// Downloads the [url] and returns is as a [String].
///
/// Override this for testing.
Future<String> downloadAsString(String url) {
Future<String> downloadAsString(String url, {String? debugDescription}) {
if (assertionsEnabled) {
_debugActiveDownloadCount += 1;
}
Expand All @@ -731,6 +736,12 @@ class NotoDownloader {
}

/// The Noto font interval tree.
IntervalTree<_NotoFont>? _notoTree;
IntervalTree<NotoFont>? _notoTree;

/// Returns the tree of Noto fonts for tests.
IntervalTree<NotoFont> get debugNotoTree {
_ensureNotoFontTreeCreated();
return _notoTree!;
}

FallbackFontDownloadQueue notoDownloadQueue = FallbackFontDownloadQueue();
12 changes: 11 additions & 1 deletion lib/web_ui/lib/src/engine/canvaskit/interval_tree.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ class IntervalTree<T> {
/// have a range which contains the point.
factory IntervalTree.createFromRanges(Map<T, List<CodeunitRange>> rangesMap) {
// Get a list of all the ranges ordered by start index.
List<IntervalTreeNode<T>> intervals = <IntervalTreeNode<T>>[];
final List<IntervalTreeNode<T>> intervals = <IntervalTreeNode<T>>[];
rangesMap.forEach((T key, List<CodeunitRange> rangeList) {
for (CodeunitRange range in rangeList) {
intervals.add(IntervalTreeNode<T>(key, range.start, range.end));
Expand Down Expand Up @@ -93,6 +93,16 @@ class IntervalTreeNode<T> {

IntervalTreeNode(this.value, this.low, this.high) : computedHigh = high;

Iterable<T> enumerateAllElements() sync* {
if (left != null) {
yield* left!.enumerateAllElements();
}
yield value;
if (right != null) {
yield* right!.enumerateAllElements();
}
}

bool contains(int x) {
return low <= x && x <= high;
}
Expand Down
2 changes: 1 addition & 1 deletion lib/web_ui/lib/src/engine/canvaskit/text.dart
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -714,7 +714,7 @@ class CkParagraphBuilder implements ui.ParagraphBuilder {
missingCodeUnits.add(codeUnits[i]);
}
}
_findFontsForMissingCodeunits(missingCodeUnits);
findFontsForMissingCodeunits(missingCodeUnits);
}
}

Expand Down
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