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-rw-r--r--layout/generic/nsTextFrameUtils.cpp408
1 files changed, 408 insertions, 0 deletions
diff --git a/layout/generic/nsTextFrameUtils.cpp b/layout/generic/nsTextFrameUtils.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsTextFrameUtils.h"
+
+#include "mozilla/dom/Text.h"
+#include "nsBidiUtils.h"
+#include "nsCharTraits.h"
+#include "nsIContent.h"
+#include "nsStyleStruct.h"
+#include "nsTextFragment.h"
+#include "nsUnicharUtils.h"
+#include "nsUnicodeProperties.h"
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// static
+bool nsTextFrameUtils::IsSpaceCombiningSequenceTail(const char16_t* aChars,
+ int32_t aLength) {
+ return aLength > 0 &&
+ (mozilla::unicode::IsClusterExtenderExcludingJoiners(aChars[0]) ||
+ (IsBidiControl(aChars[0]) &&
+ IsSpaceCombiningSequenceTail(aChars + 1, aLength - 1)));
+}
+
+static bool IsDiscardable(char16_t ch, nsTextFrameUtils::Flags* aFlags) {
+ // Unlike IS_DISCARDABLE, we don't discard \r. \r will be ignored by
+ // gfxTextRun and discarding it would force us to copy text in many cases of
+ // preformatted text containing \r\n.
+ if (ch == CH_SHY) {
+ *aFlags |= nsTextFrameUtils::Flags::HasShy;
+ return true;
+ }
+ return IsBidiControl(ch);
+}
+
+static bool IsDiscardable(uint8_t ch, nsTextFrameUtils::Flags* aFlags) {
+ if (ch == CH_SHY) {
+ *aFlags |= nsTextFrameUtils::Flags::HasShy;
+ return true;
+ }
+ return false;
+}
+
+static bool IsSegmentBreak(char16_t aCh) { return aCh == '\n'; }
+
+static bool IsSpaceOrTab(char16_t aCh) { return aCh == ' ' || aCh == '\t'; }
+
+static bool IsSpaceOrTabOrSegmentBreak(char16_t aCh) {
+ return IsSpaceOrTab(aCh) || IsSegmentBreak(aCh);
+}
+
+template <typename CharT>
+/* static */
+bool nsTextFrameUtils::IsSkippableCharacterForTransformText(CharT aChar) {
+ return aChar == ' ' || aChar == '\t' || aChar == '\n' || aChar == CH_SHY ||
+ (aChar > 0xFF && IsBidiControl(aChar));
+}
+
+#ifdef DEBUG
+template <typename CharT>
+static void AssertSkippedExpectedChars(const CharT* aText,
+ const gfxSkipChars& aSkipChars,
+ int32_t aSkipCharsOffset) {
+ gfxSkipCharsIterator it(aSkipChars);
+ it.AdvanceOriginal(aSkipCharsOffset);
+ while (it.GetOriginalOffset() < it.GetOriginalEnd()) {
+ CharT ch = aText[it.GetOriginalOffset() - aSkipCharsOffset];
+ MOZ_ASSERT(!it.IsOriginalCharSkipped() ||
+ nsTextFrameUtils::IsSkippableCharacterForTransformText(ch),
+ "skipped unexpected character; need to update "
+ "IsSkippableCharacterForTransformText?");
+ it.AdvanceOriginal(1);
+ }
+}
+#endif
+
+template <class CharT>
+static CharT* TransformWhiteSpaces(
+ const CharT* aText, uint32_t aLength, uint32_t aBegin, uint32_t aEnd,
+ bool aHasSegmentBreak, bool& aInWhitespace, CharT* aOutput,
+ nsTextFrameUtils::Flags& aFlags,
+ nsTextFrameUtils::CompressionMode aCompression, gfxSkipChars* aSkipChars) {
+ MOZ_ASSERT(aCompression == nsTextFrameUtils::COMPRESS_WHITESPACE ||
+ aCompression == nsTextFrameUtils::COMPRESS_WHITESPACE_NEWLINE,
+ "whitespaces should be skippable!!");
+ // Get the context preceding/following this white space range.
+ // For 8-bit text (sizeof CharT == 1), the checks here should get optimized
+ // out, and isSegmentBreakSkippable should be initialized to be 'false'.
+ bool isSegmentBreakSkippable =
+ sizeof(CharT) > 1 &&
+ ((aBegin > 0 && IS_ZERO_WIDTH_SPACE(aText[aBegin - 1])) ||
+ (aEnd < aLength && IS_ZERO_WIDTH_SPACE(aText[aEnd])));
+ if (sizeof(CharT) > 1 && !isSegmentBreakSkippable && aBegin > 0 &&
+ aEnd < aLength) {
+ uint32_t ucs4before;
+ uint32_t ucs4after;
+ if (aBegin > 1 &&
+ NS_IS_SURROGATE_PAIR(aText[aBegin - 2], aText[aBegin - 1])) {
+ ucs4before = SURROGATE_TO_UCS4(aText[aBegin - 2], aText[aBegin - 1]);
+ } else {
+ ucs4before = aText[aBegin - 1];
+ }
+ if (aEnd + 1 < aLength &&
+ NS_IS_SURROGATE_PAIR(aText[aEnd], aText[aEnd + 1])) {
+ ucs4after = SURROGATE_TO_UCS4(aText[aEnd], aText[aEnd + 1]);
+ } else {
+ ucs4after = aText[aEnd];
+ }
+ // Discard newlines between characters that have F, W, or H
+ // EastAsianWidth property and neither side is Hangul.
+ isSegmentBreakSkippable =
+ IsSegmentBreakSkipChar(ucs4before) && IsSegmentBreakSkipChar(ucs4after);
+ }
+
+ for (uint32_t i = aBegin; i < aEnd; ++i) {
+ CharT ch = aText[i];
+ bool keepChar = false;
+ bool keepTransformedWhiteSpace = false;
+ if (IsDiscardable(ch, &aFlags)) {
+ aSkipChars->SkipChar();
+ continue;
+ }
+ if (IsSpaceOrTab(ch)) {
+ if (aHasSegmentBreak) {
+ // If white-space is set to normal, nowrap, or pre-line, white space
+ // characters are considered collapsible and all spaces and tabs
+ // immediately preceding or following a segment break are removed.
+ aSkipChars->SkipChar();
+ continue;
+ }
+
+ if (aInWhitespace) {
+ aSkipChars->SkipChar();
+ continue;
+ } else {
+ keepTransformedWhiteSpace = true;
+ }
+ } else {
+ // Apply Segment Break Transformation Rules (CSS Text 3 - 4.1.2) for
+ // segment break characters.
+ if (aCompression == nsTextFrameUtils::COMPRESS_WHITESPACE ||
+ // XXX: According to CSS Text 3, a lone CR should not always be
+ // kept, but still go through the Segment Break Transformation
+ // Rules. However, this is what current modern browser engines
+ // (webkit/blink/edge) do. So, once we can get some clarity
+ // from the specification issue, we should either remove the
+ // lone CR condition here, or leave it here with this comment
+ // being rephrased.
+ // Please see https://github.com/w3c/csswg-drafts/issues/855.
+ ch == '\r') {
+ keepChar = true;
+ } else {
+ // aCompression == COMPRESS_WHITESPACE_NEWLINE
+
+ // Any collapsible segment break immediately following another
+ // collapsible segment break is removed. Then the remaining segment
+ // break is either transformed into a space (U+0020) or removed
+ // depending on the context before and after the break.
+ if (isSegmentBreakSkippable || aInWhitespace) {
+ aSkipChars->SkipChar();
+ continue;
+ }
+ isSegmentBreakSkippable = true;
+ keepTransformedWhiteSpace = true;
+ }
+ }
+
+ if (keepChar) {
+ *aOutput++ = ch;
+ aSkipChars->KeepChar();
+ aInWhitespace = IsSpaceOrTab(ch);
+ } else if (keepTransformedWhiteSpace) {
+ *aOutput++ = ' ';
+ aSkipChars->KeepChar();
+ aInWhitespace = true;
+ } else {
+ MOZ_ASSERT_UNREACHABLE("Should've skipped the character!!");
+ }
+ }
+ return aOutput;
+}
+
+template <class CharT>
+CharT* nsTextFrameUtils::TransformText(const CharT* aText, uint32_t aLength,
+ CharT* aOutput,
+ CompressionMode aCompression,
+ uint8_t* aIncomingFlags,
+ gfxSkipChars* aSkipChars,
+ Flags* aAnalysisFlags) {
+ Flags flags = Flags();
+#ifdef DEBUG
+ int32_t skipCharsOffset = aSkipChars->GetOriginalCharCount();
+#endif
+
+ bool lastCharArabic = false;
+ if (aCompression == COMPRESS_NONE ||
+ aCompression == COMPRESS_NONE_TRANSFORM_TO_SPACE) {
+ // Skip discardables.
+ uint32_t i;
+ for (i = 0; i < aLength; ++i) {
+ CharT ch = aText[i];
+ if (IsDiscardable(ch, &flags)) {
+ aSkipChars->SkipChar();
+ } else {
+ aSkipChars->KeepChar();
+ if (ch > ' ') {
+ lastCharArabic = IS_ARABIC_CHAR(ch);
+ } else if (aCompression == COMPRESS_NONE_TRANSFORM_TO_SPACE) {
+ if (ch == '\t' || ch == '\n') {
+ ch = ' ';
+ }
+ } else {
+ // aCompression == COMPRESS_NONE
+ if (ch == '\t') {
+ flags |= Flags::HasTab;
+ }
+ }
+ *aOutput++ = ch;
+ }
+ }
+ if (lastCharArabic) {
+ *aIncomingFlags |= INCOMING_ARABICCHAR;
+ } else {
+ *aIncomingFlags &= ~INCOMING_ARABICCHAR;
+ }
+ *aIncomingFlags &= ~INCOMING_WHITESPACE;
+ } else {
+ bool inWhitespace = (*aIncomingFlags & INCOMING_WHITESPACE) != 0;
+ uint32_t i;
+ for (i = 0; i < aLength; ++i) {
+ CharT ch = aText[i];
+ // CSS Text 3 - 4.1. The White Space Processing Rules
+ // White space processing in CSS affects only the document white space
+ // characters: spaces (U+0020), tabs (U+0009), and segment breaks.
+ // Since we need the context of segment breaks and their surrounding
+ // white spaces to proceed the white space processing, a consecutive run
+ // of spaces/tabs/segment breaks is collected in a first pass loop, then
+ // we apply the collapsing and transformation rules to this run in a
+ // second pass loop.
+ if (IsSpaceOrTabOrSegmentBreak(ch)) {
+ bool keepLastSpace = false;
+ bool hasSegmentBreak = IsSegmentBreak(ch);
+ uint32_t countTrailingDiscardables = 0;
+ uint32_t j;
+ for (j = i + 1; j < aLength && (IsSpaceOrTabOrSegmentBreak(aText[j]) ||
+ IsDiscardable(aText[j], &flags));
+ j++) {
+ if (IsSegmentBreak(aText[j])) {
+ hasSegmentBreak = true;
+ }
+ }
+ // Exclude trailing discardables before checking space combining
+ // sequence tail.
+ for (; IsDiscardable(aText[j - 1], &flags); j--) {
+ countTrailingDiscardables++;
+ }
+ // If the last white space is followed by a combining sequence tail,
+ // exclude it from the range of TransformWhiteSpaces.
+ if (sizeof(CharT) > 1 && aText[j - 1] == ' ' && j < aLength &&
+ IsSpaceCombiningSequenceTail(&aText[j], aLength - j)) {
+ keepLastSpace = true;
+ j--;
+ }
+ if (j > i) {
+ aOutput = TransformWhiteSpaces(aText, aLength, i, j, hasSegmentBreak,
+ inWhitespace, aOutput, flags,
+ aCompression, aSkipChars);
+ }
+ // We need to keep KeepChar()/SkipChar() in order, so process the
+ // last white space first, then process the trailing discardables.
+ if (keepLastSpace) {
+ keepLastSpace = false;
+ *aOutput++ = ' ';
+ aSkipChars->KeepChar();
+ lastCharArabic = false;
+ j++;
+ }
+ for (; countTrailingDiscardables > 0; countTrailingDiscardables--) {
+ aSkipChars->SkipChar();
+ j++;
+ }
+ i = j - 1;
+ continue;
+ }
+ // Process characters other than the document white space characters.
+ if (IsDiscardable(ch, &flags)) {
+ aSkipChars->SkipChar();
+ } else {
+ *aOutput++ = ch;
+ aSkipChars->KeepChar();
+ }
+ lastCharArabic = IS_ARABIC_CHAR(ch);
+ inWhitespace = false;
+ }
+
+ if (lastCharArabic) {
+ *aIncomingFlags |= INCOMING_ARABICCHAR;
+ } else {
+ *aIncomingFlags &= ~INCOMING_ARABICCHAR;
+ }
+ if (inWhitespace) {
+ *aIncomingFlags |= INCOMING_WHITESPACE;
+ } else {
+ *aIncomingFlags &= ~INCOMING_WHITESPACE;
+ }
+ }
+
+ *aAnalysisFlags = flags;
+
+#ifdef DEBUG
+ AssertSkippedExpectedChars(aText, *aSkipChars, skipCharsOffset);
+#endif
+ return aOutput;
+}
+
+/*
+ * NOTE: The TransformText and IsSkippableCharacterForTransformText template
+ * functions are part of the public API of nsTextFrameUtils, while
+ * their function bodies are not available in the header. They may stop working
+ * (fail to resolve symbol in link time) once their callsites are moved to a
+ * different translation unit (e.g. a different unified source file).
+ * Explicit instantiating this function template with `uint8_t` and `char16_t`
+ * could prevent us from the potential risk.
+ */
+template uint8_t* nsTextFrameUtils::TransformText(
+ const uint8_t* aText, uint32_t aLength, uint8_t* aOutput,
+ CompressionMode aCompression, uint8_t* aIncomingFlags,
+ gfxSkipChars* aSkipChars, Flags* aAnalysisFlags);
+template char16_t* nsTextFrameUtils::TransformText(
+ const char16_t* aText, uint32_t aLength, char16_t* aOutput,
+ CompressionMode aCompression, uint8_t* aIncomingFlags,
+ gfxSkipChars* aSkipChars, Flags* aAnalysisFlags);
+template bool nsTextFrameUtils::IsSkippableCharacterForTransformText(
+ uint8_t aChar);
+template bool nsTextFrameUtils::IsSkippableCharacterForTransformText(
+ char16_t aChar);
+
+template <typename CharT>
+static uint32_t DoComputeApproximateLengthWithWhitespaceCompression(
+ const CharT* aChars, uint32_t aLength, const nsStyleText* aStyleText) {
+ // This is an approximation so we don't really need anything
+ // too fancy here.
+ uint32_t len;
+ if (aStyleText->WhiteSpaceIsSignificant()) {
+ return aLength;
+ }
+ bool prevWS = true; // more important to ignore blocks with
+ // only whitespace than get inline boundaries
+ // exactly right
+ len = 0;
+ for (uint32_t i = 0; i < aLength; ++i) {
+ CharT c = aChars[i];
+ if (c == ' ' || c == '\n' || c == '\t' || c == '\r') {
+ if (!prevWS) {
+ ++len;
+ }
+ prevWS = true;
+ } else {
+ ++len;
+ prevWS = false;
+ }
+ }
+ return len;
+}
+
+uint32_t nsTextFrameUtils::ComputeApproximateLengthWithWhitespaceCompression(
+ Text* aText, const nsStyleText* aStyleText) {
+ const nsTextFragment* frag = &aText->TextFragment();
+ if (frag->Is2b()) {
+ return DoComputeApproximateLengthWithWhitespaceCompression(
+ frag->Get2b(), frag->GetLength(), aStyleText);
+ }
+ return DoComputeApproximateLengthWithWhitespaceCompression(
+ frag->Get1b(), frag->GetLength(), aStyleText);
+}
+
+uint32_t nsTextFrameUtils::ComputeApproximateLengthWithWhitespaceCompression(
+ const nsAString& aString, const nsStyleText* aStyleText) {
+ return DoComputeApproximateLengthWithWhitespaceCompression(
+ aString.BeginReading(), aString.Length(), aStyleText);
+}
+
+bool nsSkipCharsRunIterator::NextRun() {
+ do {
+ if (mRunLength) {
+ mIterator.AdvanceOriginal(mRunLength);
+ NS_ASSERTION(mRunLength > 0,
+ "No characters in run (initial length too large?)");
+ if (!mSkipped || mLengthIncludesSkipped) {
+ mRemainingLength -= mRunLength;
+ }
+ }
+ if (!mRemainingLength) {
+ return false;
+ }
+ int32_t length;
+ mSkipped = mIterator.IsOriginalCharSkipped(&length);
+ mRunLength = std::min(length, mRemainingLength);
+ } while (!mVisitSkipped && mSkipped);
+
+ return true;
+}