tor-browser

gfxScriptItemizer.cpp (8477B)

---

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

/*
* This file is based on usc_impl.c from ICU 4.2.0.1, slightly adapted
* for use within Mozilla Gecko, separate from a standard ICU build.
*
* The original ICU license of the code follows:
*
* ICU License - ICU 1.8.1 and later
*
* COPYRIGHT AND PERMISSION NOTICE
*
* Copyright (c) 1995-2009 International Business Machines Corporation and
* others
*
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, provided that the above copyright notice(s) and this
* permission notice appear in all copies of the Software and that both the
* above copyright notice(s) and this permission notice appear in supporting
* documentation.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
* IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS INCLUDED IN THIS NOTICE
* BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES,
* OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
* WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
* ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
* SOFTWARE.
*
* Except as contained in this notice, the name of a copyright holder shall
* not be used in advertising or otherwise to promote the sale, use or other
* dealings in this Software without prior written authorization of the
* copyright holder.
*
* All trademarks and registered trademarks mentioned herein are the property
* of their respective owners.
*/

#include "gfxScriptItemizer.h"
#include "mozilla/intl/UnicodeProperties.h"
#include "nsCharTraits.h"
#include "nsUnicodeProperties.h"
#include "harfbuzz/hb.h"

using namespace mozilla::intl;
using namespace mozilla::unicode;

#define MOD(sp) ((sp) % PAREN_STACK_DEPTH)
#define LIMIT_INC(sp) \
 (((sp) < PAREN_STACK_DEPTH) ? (sp) + 1 : PAREN_STACK_DEPTH)
#define INC(sp, count) (MOD((sp) + (count)))
#define INC1(sp) (INC(sp, 1))
#define DEC(sp, count) (MOD((sp) + PAREN_STACK_DEPTH - (count)))
#define DEC1(sp) (DEC(sp, 1))
#define STACK_IS_EMPTY() (pushCount <= 0)
#define STACK_IS_NOT_EMPTY() (!STACK_IS_EMPTY())
#define TOP() (parenStack[parenSP])
#define SYNC_FIXUP() (fixupCount = 0)

void gfxScriptItemizer::push(uint32_t endPairChar, Script newScriptCode) {
 pushCount = LIMIT_INC(pushCount);
 fixupCount = LIMIT_INC(fixupCount);

 parenSP = INC1(parenSP);
 parenStack[parenSP].endPairChar = endPairChar;
 parenStack[parenSP].scriptCode = newScriptCode;
}

void gfxScriptItemizer::pop() {
 if (STACK_IS_EMPTY()) {
   return;
 }

 if (fixupCount > 0) {
   fixupCount -= 1;
 }

 pushCount -= 1;
 parenSP = DEC1(parenSP);

 /* If the stack is now empty, reset the stack
    pointers to their initial values.
  */
 if (STACK_IS_EMPTY()) {
   parenSP = -1;
 }
}

void gfxScriptItemizer::fixup(Script newScriptCode) {
 int32_t fixupSP = DEC(parenSP, fixupCount);

 while (fixupCount-- > 0) {
   fixupSP = INC1(fixupSP);
   parenStack[fixupSP].scriptCode = newScriptCode;
 }
}

static inline bool CanMergeWithContext(Script aScript) {
 return aScript <= Script::INHERITED || aScript == Script::UNKNOWN;
}

// We regard the current char as having the same script as the in-progress run
// if either script is Common/Inherited/Unknown, or if the run script appears
// in the character's ScriptExtensions, or if the char is a cluster extender.
static inline bool SameScript(Script runScript, Script currCharScript,
                             uint32_t aCurrCh) {
 return CanMergeWithContext(runScript) ||
        CanMergeWithContext(currCharScript) || currCharScript == runScript ||
        IsClusterExtender(aCurrCh) ||
        UnicodeProperties::HasScript(aCurrCh, runScript);
}

gfxScriptItemizer::Run gfxScriptItemizer::Next() {
 MOZ_ASSERT(textLength == 0 || (textIs8bit && textPtr._1b) ||
            (!textIs8bit && textPtr._2b));

 /* if we've fallen off the end of the text, we're done */
 if (scriptLimit >= textLength) {
   return Run{};
 }

 SYNC_FIXUP();
 scriptCode = Script::COMMON;
 Script fallbackScript = Script::UNKNOWN;

 for (scriptStart = scriptLimit; scriptLimit < textLength; scriptLimit += 1) {
   uint32_t ch;
   Script sc;
   uint32_t startOfChar = scriptLimit;

   ch = textIs8bit ? textPtr._1b[scriptLimit] : textPtr._2b[scriptLimit];

   /* decode UTF-16 (may be surrogate pair) */
   if (NS_IS_HIGH_SURROGATE(ch) && scriptLimit < textLength - 1) {
     uint32_t low = textPtr._2b[scriptLimit + 1];
     if (NS_IS_LOW_SURROGATE(low)) {
       ch = SURROGATE_TO_UCS4(ch, low);
       scriptLimit += 1;
     }
   }

   // Initialize gc to UNASSIGNED; we'll only set it to the true GC
   // if the character has script=COMMON, otherwise we don't care.
   uint8_t gc = HB_UNICODE_GENERAL_CATEGORY_UNASSIGNED;

   sc = UnicodeProperties::GetScriptCode(ch);
   if (sc == Script::COMMON) {
     /*
      * Paired character handling:
      *
      * if it's an open character, push it onto the stack.
      * if it's a close character, find the matching open on the
      * stack, and use that script code. Any non-matching open
      * characters above it on the stack will be popped.
      *
      * We only do this if the script is COMMON; for chars with
      * specific script assignments, we just use them as-is.
      */
     gc = GetGeneralCategory(ch);
     if (gc == HB_UNICODE_GENERAL_CATEGORY_OPEN_PUNCTUATION) {
       uint32_t endPairChar = UnicodeProperties::CharMirror(ch);
       if (endPairChar != ch) {
         push(endPairChar, scriptCode);
       }
     } else if (gc == HB_UNICODE_GENERAL_CATEGORY_CLOSE_PUNCTUATION &&
                UnicodeProperties::IsMirrored(ch)) {
       while (STACK_IS_NOT_EMPTY() && TOP().endPairChar != ch) {
         pop();
       }

       if (STACK_IS_NOT_EMPTY()) {
         sc = TOP().scriptCode;
       }
     }
   }

   // Both Hiragana and Katakana are shaped as OpenType 'kana'. Merge them
   // here to avoid script-run breaks and allow kerning to apply between the
   // two alphabets.
   if (sc == Script::HIRAGANA) {
     sc = Script::KATAKANA;
   }

   if (SameScript(scriptCode, sc, ch)) {
     if (scriptCode == Script::COMMON) {
       // If we have not yet resolved a specific scriptCode for the run,
       // check whether this character provides it.
       if (!CanMergeWithContext(sc)) {
         // Use this character's script.
         scriptCode = sc;
         fixup(scriptCode);
       } else if (fallbackScript == Script::UNKNOWN) {
         // See if the character has a ScriptExtensions property we can
         // store for use in the event the run remains unresolved.
         UnicodeProperties::ScriptExtensionVector extensions;
         auto extResult = UnicodeProperties::GetExtensions(ch, extensions);
         if (extResult.isOk()) {
           Script ext = Script(extensions[0]);
           if (!CanMergeWithContext(ext)) {
             fallbackScript = ext;
           }
         }
       }
     }

     /*
      * if this character is a close paired character,
      * pop the matching open character from the stack
      */
     if (gc == HB_UNICODE_GENERAL_CATEGORY_CLOSE_PUNCTUATION &&
         UnicodeProperties::IsMirrored(ch)) {
       pop();
     }
   } else {
     /*
      * reset scriptLimit in case it was advanced during reading a
      * multiple-code-unit character
      */
     scriptLimit = startOfChar;

     break;
   }
 }

 return Run{scriptStart, scriptLimit - scriptStart,
            (scriptCode == Script::COMMON && fallbackScript != Script::UNKNOWN)
                ? fallbackScript
                : scriptCode};
}