flutter_flutter/sky/engine/platform/fonts/FontFallbackList.cpp

/*
 * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "flutter/sky/engine/platform/fonts/FontFallbackList.h"

#include "flutter/common/settings.h"
#include "flutter/sky/engine/platform/fonts/FontCache.h"
#include "flutter/sky/engine/platform/fonts/FontDescription.h"
#include "flutter/sky/engine/platform/fonts/FontFamily.h"
#include "flutter/sky/engine/platform/fonts/SegmentedFontData.h"
#include "flutter/sky/engine/wtf/unicode/CharacterNames.h"

namespace blink {

FontFallbackList::FontFallbackList()
    : m_pageZero(0),
      m_cachedPrimarySimpleFontData(0),
      m_fontSelector(nullptr),
      m_fontSelectorVersion(0),
      m_familyIndex(0),
      m_generation(FontCache::fontCache()->generation()),
      m_pitch(UnknownPitch),
      m_hasLoadingFallback(false) {}

void FontFallbackList::invalidate(PassRefPtr<FontSelector> fontSelector) {
  releaseFontData();
  m_fontList.clear();
  m_pageZero = 0;
  m_pages.clear();
  m_cachedPrimarySimpleFontData = 0;
  m_familyIndex = 0;
  m_pitch = UnknownPitch;
  m_hasLoadingFallback = false;
  m_fontSelector = fontSelector;
  m_fontSelectorVersion = m_fontSelector ? m_fontSelector->version() : 0;
  m_generation = FontCache::fontCache()->generation();
  m_widthCache.clear();
}

void FontFallbackList::releaseFontData() {
  unsigned numFonts = m_fontList.size();
  for (unsigned i = 0; i < numFonts; ++i) {
    if (!m_fontList[i]->isCustomFont()) {
      ASSERT(!m_fontList[i]->isSegmented());
      FontCache::fontCache()->releaseFontData(toSimpleFontData(m_fontList[i]));
    }
  }
}

void FontFallbackList::determinePitch(
    const FontDescription& fontDescription) const {
  for (unsigned fontIndex = 0;; ++fontIndex) {
    const FontData* fontData = fontDataAt(fontDescription, fontIndex);
    if (!fontData) {
      // All fonts are custom fonts and are loading. Fallback should be variable
      // pitch.
      m_pitch = VariablePitch;
      break;
    }

    const SimpleFontData* simpleFontData;
    if (fontData->isSegmented()) {
      const SegmentedFontData* segmentedFontData =
          toSegmentedFontData(fontData);
      if (segmentedFontData->numRanges() != 1 ||
          !segmentedFontData->rangeAt(0).isEntireRange()) {
        m_pitch = VariablePitch;
        break;
      }
      simpleFontData = segmentedFontData->rangeAt(0).fontData().get();
    } else {
      simpleFontData = toSimpleFontData(fontData);
    }
    if (!fontData->isLoadingFallback()) {
      m_pitch = simpleFontData->pitch();
      break;
    }
  }
}

bool FontFallbackList::loadingCustomFonts() const {
  if (!m_hasLoadingFallback)
    return false;

  unsigned numFonts = m_fontList.size();
  for (unsigned i = 0; i < numFonts; ++i) {
    if (m_fontList[i]->isLoading())
      return true;
  }
  return false;
}

bool FontFallbackList::shouldSkipDrawing() const {
  if (!m_hasLoadingFallback)
    return false;

  unsigned numFonts = m_fontList.size();
  for (unsigned i = 0; i < numFonts; ++i) {
    if (m_fontList[i]->shouldSkipDrawing())
      return true;
  }
  return false;
}

const SimpleFontData* FontFallbackList::determinePrimarySimpleFontData(
    const FontDescription& fontDescription) const {
  bool shouldLoadCustomFont = true;

  for (unsigned fontIndex = 0;; ++fontIndex) {
    const FontData* fontData = fontDataAt(fontDescription, fontIndex);
    if (!fontData) {
      // All fonts are custom fonts and are loading. Return the first FontData.
      fontData = fontDataAt(fontDescription, 0);
      if (fontData)
        return fontData->fontDataForCharacter(space);

      SimpleFontData* lastResortFallback =
          FontCache::fontCache()
              ->getLastResortFallbackFont(fontDescription)
              .get();
      ASSERT(lastResortFallback);
      return lastResortFallback;
    }

    if (fontData->isSegmented() &&
        !toSegmentedFontData(fontData)->containsCharacter(space))
      continue;

    const SimpleFontData* fontDataForSpace =
        fontData->fontDataForCharacter(space);
    ASSERT(fontDataForSpace);

    // When a custom font is loading, we should use the correct fallback font to
    // layout the text. Here skip the temporary font for the loading custom font
    // which may not act as the correct fallback font.
    if (!fontDataForSpace->isLoadingFallback())
      return fontDataForSpace;

    if (fontData->isSegmented()) {
      const SegmentedFontData* segmented = toSegmentedFontData(fontData);
      for (unsigned i = 0; i < segmented->numRanges(); i++) {
        const SimpleFontData* rangeFontData =
            segmented->rangeAt(i).fontData().get();
        if (!rangeFontData->isLoadingFallback())
          return rangeFontData;
      }
      if (fontData->isLoading())
        shouldLoadCustomFont = false;
    }

    // Begin to load the first custom font if needed.
    if (shouldLoadCustomFont) {
      shouldLoadCustomFont = false;
      fontDataForSpace->customFontData()->beginLoadIfNeeded();
    }
  }
}

PassRefPtr<FontData> FontFallbackList::getFontData(
    const FontDescription& fontDescription,
    int& familyIndex) const {
  RefPtr<FontData> result;

  int startIndex = familyIndex;
  const FontFamily* startFamily = &fontDescription.family();
  for (int i = 0; startFamily && i < startIndex; i++)
    startFamily = startFamily->next();
  const FontFamily* currFamily = startFamily;
  while (currFamily && !result) {
    familyIndex++;
    if (currFamily->family().length() || Settings::Get().use_test_fonts) {
      if (m_fontSelector)
        result =
            m_fontSelector->getFontData(fontDescription, currFamily->family());

      if (!result)
        result = FontCache::fontCache()->getFontData(fontDescription,
                                                     currFamily->family());
    }
    currFamily = currFamily->next();
  }

  if (!currFamily)
    familyIndex = cAllFamiliesScanned;

  if (result || startIndex)
    return result.release();

  // Still no result. Hand back our last resort fallback font.
  return FontCache::fontCache()->getLastResortFallbackFont(fontDescription);
}

const FontData* FontFallbackList::fontDataAt(
    const FontDescription& fontDescription,
    unsigned realizedFontIndex) const {
  if (realizedFontIndex < m_fontList.size())
    return m_fontList[realizedFontIndex]
        .get();  // This fallback font is already in our list.

  // Make sure we're not passing in some crazy value here.
  ASSERT(realizedFontIndex == m_fontList.size());

  if (m_familyIndex == cAllFamiliesScanned)
    return 0;

  // Ask the font cache for the font data.
  // We are obtaining this font for the first time.  We keep track of the
  // families we've looked at before in |m_familyIndex|, so that we never scan
  // the same spot in the list twice.  getFontData will adjust our
  // |m_familyIndex| as it scans for the right font to make.
  ASSERT(FontCache::fontCache()->generation() == m_generation);
  RefPtr<FontData> result = getFontData(fontDescription, m_familyIndex);
  if (result) {
    m_fontList.append(result);
    if (result->isLoadingFallback())
      m_hasLoadingFallback = true;
  }
  return result.get();
}

}  // namespace blink