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