Write transparent pixels more often (SkGifCodec)

third_party/gif/SkGifImageReader.cpp

 /* -*- Mode: C; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
  * The contents of this file are subject to the Mozilla Public License Version
  * 1.1 (the "License"); you may not use this file except in compliance with
  * the License. You may obtain a copy of the License at
  * http://www.mozilla.org/MPL/
  *
  * Software distributed under the License is distributed on an "AS IS" basis,
@@ skipping 128 matching lines @@
             drowStart = 0;
 
         if ((unsigned)drowEnd >= m_frameContext->height())
             drowEnd = m_frameContext->height() - 1;
     }
 
     // Protect against too much image data.
     if ((unsigned)drowStart >= m_frameContext->height())
         return true;
 
+    bool writeTransparentPixels = alwaysWriteTransparentPixels ||
+            (m_frameContext->progressiveDisplay() && m_frameContext->interlaced() && ipass > 1);
     // CALLBACK: Let the client know we have decoded a row.
     if (!m_client->haveDecodedRow(m_frameContext->frameId(), rowBegin,
-        drowStart, drowEnd - drowStart + 1, m_frameContext->progressiveDisplay() && m_frameContext->interlaced() && ipass > 1))
+        drowStart, drowEnd - drowStart + 1, writeTransparentPixels))
         return false;
 
     if (!m_frameContext->interlaced())
         irow++;
     else {
         do {
             switch (ipass) {
             case 1:
                 irow += 8;
                 if (irow >= m_frameContext->height()) {
@@ skipping 735 matching lines @@
     if (m_frameContext->dataSize() >= SK_MAX_DICTIONARY_ENTRY_BITS)
         return false;
     clearCode = 1 << m_frameContext->dataSize();
     avail = clearCode + 2;
     oldcode = -1;
     codesize = m_frameContext->dataSize() + 1;
     codemask = (1 << codesize) - 1;
     datum = bits = 0;
     ipass = m_frameContext->interlaced() ? 1 : 0;
     irow = 0;
+    alwaysWriteTransparentPixels = !m_frameContext->interlaced()
+            && m_frameContext->getRequiredFrame() == SkCodec::kNone;
 
     // We want to know the longest sequence encodable by a dictionary with
     // SK_MAX_DICTIONARY_ENTRIES entries. If we ignore the need to encode the base
     // values themselves at the beginning of the dictionary, as well as the need
     // for a clear code or a termination code, we could use every entry to
     // encode a series of multiple values. If the input value stream looked
     // like "AAAAA..." (a long string of just one value), the first dictionary
     // entry would encode AA, the next AAA, the next AAAA, and so forth. Thus
     // the longest sequence would be SK_MAX_DICTIONARY_ENTRIES + 1 values.
     //
@@ skipping 15 matching lines @@
     rowsRemaining = m_frameContext->height();
 
     // Clearing the whole suffix table lets us be more tolerant of bad data.
     for (int i = 0; i < clearCode; ++i) {
         suffix[i] = i;
         suffixLength[i] = 1;
     }
     return true;
 }