Make SkPngCodec decode progressively.

This is a step towards using SkCodec in Chromium, where progressive
decoding is necessary.

Switch from using png_read_row (which expects all the data to be
available) to png_process_data, which uses callbacks when rows are
available.

Create a new API for SkCodec, which supports progressive decoding and
scanline decoding. Future changes will switch the other clients off of
startScanlineDecode and get/skip-Scanlines to the new API.

Remove SkCodec::kNone_ScanlineOrder, which was only used for interlaced
PNG images. In the new API, interlaced PNG fits kTopDown. Also remove
updateCurrScanline(), which was only used by the old implementation for
interlaced PNG.

DMSrcSink:
- In CodecSrc::kScanline_Mode, use the new method for scanline decoding
for the supported formats (just PNG and PNG-in-ICO for now).

fuzz.cpp:
- Remove reference to kNone_ScanlineOrder

SkCodec:
- Add new APIs:
    - startIncrementalDecode
    - incrementalDecode
- Remove kNone_SkScanlineOrder and updateCurrScanline()

SkPngCodec:
- Implement new APIs
- Switch from sk_read_fn/png_read_row etc to png_process_data
- Expand AutoCleanPng's role to decode the header and create the
  SkPngCodec
- Make the interlaced PNG decoder report how many lines were
  initialized during an incomplete decode
- Make initializeSwizzler return a bool instead of an SkCodec::Result
  (It only returned kSuccess or kInvalidInput anyway)

SkIcoCodec:
- Implement the new APIs; supported for PNG in ICO

SkSampledCodec:
- Call the new method for decoding scanlines, and fall back to the old
  method if the new version is unimplemented
- Remove references to kNone_SkScanlineOrder

tests/CodecPartial:
- Add a test which decodes part of an image, then finishes the decode,
  and compares it to the straightforward method

tests/CodecTest:
- Add a test which decodes all scanlines using the new method
- Repurpose the Codec_stripes test to decode using the new method in
  sections rather than all at once
- In the method check(), add a parameter for whether the image supports
  the new method of scanline decoding, and be explicit about whether an
  image supports incomplete
- Test incomplete PNG decodes. We should have been doing it anyway for
  non-interlaced (except for an image that is too small - one row), but
  the new method supports interlaced incomplete as well
- Make test_invalid_parameters test the new method
- Add a test to ensure that it's safe to fall back to scanline decoding without
  rewinding

BUG=skia:4211

The new version was generally faster than the old version (but not significantly so).

Some raw performance differences can be found at https://docs.google.com/a/google.com/spreadsheets/d/1Gis3aRCEa72qBNDRMgGDg3jD-pMgO-FXldlNF9ejo4o/

Design doc can be found at https://docs.google.com/a/google.com/document/d/11Mn8-ePDKwVEMCjs3nWwSjxcSpJ_Cu8DF57KNtUmgLM/

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1997703003

Review-Url: https://codereview.chromium.org/1997703003

1 files changed, 77 insertions, 4 deletions

diff --git a/src/codec/SkIcoCodec.cpp b/src/codec/SkIcoCodec.cpp
index 0e81b72407..a80b9df3cf 100644
--- a/src/codec/SkIcoCodec.cpp
+++ b/src/codec/SkIcoCodec.cpp
@@ -15,6 +15,7 @@
 #include "SkTDArray.h"
 #include "SkTSort.h"
 
+#ifdef SK_HAS_PNG_LIBRARY
 /*
  * Checks the start of the stream to see if the image is an Ico or Cur
  */
@@ -186,6 +187,7 @@ SkIcoCodec::SkIcoCodec(int width, int height, const SkEncodedInfo& info,
     : INHERITED(width, height, info, nullptr)
     , fEmbeddedCodecs(codecs)
     , fCurrScanlineCodec(nullptr)
+    , fCurrIncrementalCodec(nullptr)
 {}
 
 /*
@@ -289,6 +291,7 @@ SkCodec::Result SkIcoCodec::onStartScanlineDecode(const SkImageInfo& dstInfo,
         result = embeddedCodec->startScanlineDecode(dstInfo, &options, colorTable, colorCount);
         if (kSuccess == result) {
             fCurrScanlineCodec = embeddedCodec;
+            fCurrIncrementalCodec = nullptr;
             return result;
         }
 
@@ -309,13 +312,83 @@ bool SkIcoCodec::onSkipScanlines(int count) {
     return fCurrScanlineCodec->skipScanlines(count);
 }
 
+SkCodec::Result SkIcoCodec::onStartIncrementalDecode(const SkImageInfo& dstInfo,
+        void* pixels, size_t rowBytes, const SkCodec::Options& options,
+        SkPMColor* colorTable, int* colorCount) {
+    int index = 0;
+    while (true) {
+        index = this->chooseCodec(dstInfo.dimensions(), index);
+        if (index < 0) {
+            break;
+        }
+
+        SkCodec* embeddedCodec = fEmbeddedCodecs->operator[](index);
+        switch (embeddedCodec->startIncrementalDecode(dstInfo,
+                pixels, rowBytes, &options, colorTable, colorCount)) {
+            case kSuccess:
+                fCurrIncrementalCodec = embeddedCodec;
+                fCurrScanlineCodec = nullptr;
+                return kSuccess;
+            case kUnimplemented:
+                // FIXME: embeddedCodec is a BMP. If scanline decoding would work,
+                // return kUnimplemented so that SkSampledCodec will fall through
+                // to use the scanline decoder.
+                // Note that calling startScanlineDecode will require an extra
+                // rewind. The embedded codec has an SkMemoryStream, which is
+                // cheap to rewind, though it will do extra work re-reading the
+                // header.
+                // Also note that we pass nullptr for Options. This is because
+                // Options that are valid for incremental decoding may not be
+                // valid for scanline decoding.
+                // Once BMP supports incremental decoding this workaround can go
+                // away.
+                if (embeddedCodec->startScanlineDecode(dstInfo, nullptr,
+                        colorTable, colorCount) == kSuccess) {
+                    return kUnimplemented;
+                }
+                // Move on to the next embedded codec.
+                break;
+            default:
+                break;
+        }
+
+        index++;
+    }
+
+    SkCodecPrintf("Error: No matching candidate image in ico.\n");
+    return kInvalidScale;
+}
+
+SkCodec::Result SkIcoCodec::onIncrementalDecode(int* rowsDecoded) {
+    SkASSERT(fCurrIncrementalCodec);
+    return fCurrIncrementalCodec->incrementalDecode(rowsDecoded);
+}
+
 SkCodec::SkScanlineOrder SkIcoCodec::onGetScanlineOrder() const {
     // FIXME: This function will possibly return the wrong value if it is called
-    //        before startScanlineDecode().
-    return fCurrScanlineCodec ? fCurrScanlineCodec->getScanlineOrder() :
-            INHERITED::onGetScanlineOrder();
+    //        before startScanlineDecode()/startIncrementalDecode().
+    if (fCurrScanlineCodec) {
+        SkASSERT(!fCurrIncrementalCodec);
+        return fCurrScanlineCodec->getScanlineOrder();
+    }
+
+    if (fCurrIncrementalCodec) {
+        return fCurrIncrementalCodec->getScanlineOrder();
+    }
+
+    return INHERITED::onGetScanlineOrder();
 }
 
 SkSampler* SkIcoCodec::getSampler(bool createIfNecessary) {
-    return fCurrScanlineCodec ? fCurrScanlineCodec->getSampler(createIfNecessary) : nullptr;
+    if (fCurrScanlineCodec) {
+        SkASSERT(!fCurrIncrementalCodec);
+        return fCurrScanlineCodec->getSampler(createIfNecessary);
+    }
+
+    if (fCurrIncrementalCodec) {
+        return fCurrIncrementalCodec->getSampler(createIfNecessary);
+    }
+
+    return nullptr;
 }
+#endif // SK_HAS_PNG_LIBRARY