Add support for multiple frames in SkCodec

tests/CodecTest.cpp

Index: tests/CodecTest.cpp
diff --git a/tests/CodecTest.cpp b/tests/CodecTest.cpp
index bae8344bad631d5e6e4102ad561f2d911b455b03..7fecec1bf1d8d93acf3ab155c4d8ddb41511f64a 100644
--- a/tests/CodecTest.cpp
+++ b/tests/CodecTest.cpp
@@ -289,7 +289,10 @@ static void check(skiatest::Reporter* r,
 
     if (supportsNewScanlineDecoding && !isIncomplete) {
         test_incremental_decode(r, codec, info, codecDigest);
-        test_in_stripes(r, codec, info, codecDigest);
+        // FIXME: This is broken for gif.

[scroggo_chromium, 2016/10/13 20:38:16]

Incremental decoding with GIF works for the case where we are sampling, when
SkSampledCodec provides a subset that cuts off lines that would be sampled out
anyway. But the API does not distinguish between that and arbitrary subsets,
which is currently broken for GIF. We do not actually need to support this use
case, since we only need true subsetting for png and jpeg (and webp), for
BitmapRegionDecoder. But a bad client could easily make us do the wrong thing
here.

A proper fix might be for SkSampledCodec to not repurpose the subset to mean
ignore these lines that fall outside the sampled area, which I think msarett@
pushed for anyway.

+        if (SkStrEndsWith(path, "png") || SkStrEndsWith(path, "PNG")) {
+            test_in_stripes(r, codec, info, codecDigest);
+        }
     }
 
     // Need to call startScanlineDecode() first.
@@ -469,11 +472,10 @@ DEF_TEST(Codec, r) {
     check(r, "google_chrome.ico", SkISize::Make(256, 256), false, false, false, true);
 
     // GIF
-    // FIXME: We are not ready to test incomplete GIFs
-    check(r, "box.gif", SkISize::Make(200, 55), true, false, false);
-    check(r, "color_wheel.gif", SkISize::Make(128, 128), true, false, false);
+    check(r, "box.gif", SkISize::Make(200, 55), false, false, true, true);
+    check(r, "color_wheel.gif", SkISize::Make(128, 128), false, false, true, true);
     // randPixels.gif is too small to test incomplete
-    check(r, "randPixels.gif", SkISize::Make(8, 8), true, false, false);
+    check(r, "randPixels.gif", SkISize::Make(8, 8), false, false, false, true);
 
     // JPG
     check(r, "CMYK.jpg", SkISize::Make(642, 516), true, false, true);
@@ -1215,6 +1217,69 @@ DEF_TEST(Codec_F16ConversionPossible, r) {
     test_conversion_possible(r, "yellow_rose.png", false, true);
 }
 
+static void decode_frame(skiatest::Reporter* r, SkCodec* codec, size_t frame) {
+    SkBitmap bm;
+    auto info = codec->getInfo().makeColorType(kN32_SkColorType);
+    bm.allocPixels(info);
+
+    SkCodec::Options opts;
+    SkCodec::MultiFrameOptions multiOpts;
+    multiOpts.fIndex = frame;
+    opts.fFrameOptions = &multiOpts;
+    REPORTER_ASSERT(r, SkCodec::kSuccess == codec->getPixels(info,
+            bm.getPixels(), bm.rowBytes(), &opts, nullptr, nullptr));
+}
+
+// For an animated image, we should only read enough to decode the requested
+// frame if the client never calls getFrameInfo.
+DEF_TEST(Codec_skipFullParse, r) {
+    auto path = "test640x479.gif";
+    SkStream* stream(GetResourceAsStream(path));
+    if (!stream) {
+        return;
+    }
+
+    // Note that we cheat and hold on to the stream pointer, but SkCodec will
+    // take ownership. We will not refer to the stream after the SkCodec
+    // deletes it.
+    std::unique_ptr<SkCodec> codec(SkCodec::NewFromStream(stream));
+    if (!codec) {
+        ERRORF(r, "Failed to create codec for %s", path);
+        return;
+    }
+
+    REPORTER_ASSERT(r, stream->hasPosition());
+    const size_t sizePosition = stream->getPosition();
+    REPORTER_ASSERT(r, stream->hasLength() && sizePosition < stream->getLength());
+
+    // This should read more of the stream, but not the whole stream.
+    decode_frame(r, codec.get(), 0);
+    const size_t positionAfterFirstFrame = stream->getPosition();
+    REPORTER_ASSERT(r, positionAfterFirstFrame > sizePosition
+                       && positionAfterFirstFrame < stream->getLength());
+
+    // Again, this should read more of the stream.
+    decode_frame(r, codec.get(), 2);
+    const size_t positionAfterThirdFrame = stream->getPosition();
+    REPORTER_ASSERT(r, positionAfterThirdFrame > positionAfterFirstFrame
+                       && positionAfterThirdFrame < stream->getLength());
+
+    // This does not need to read any more of the stream, since it has already
+    // parsed the second frame.
+    decode_frame(r, codec.get(), 1);
+    REPORTER_ASSERT(r, stream->getPosition() == positionAfterThirdFrame);
+
+    // This should read the rest of the frames.
+    decode_frame(r, codec.get(), 3);
+    const size_t finalPosition = stream->getPosition();
+    REPORTER_ASSERT(r, finalPosition > positionAfterThirdFrame);
+
+    // There may be more data in the stream.
+    auto frameInfo = codec->getFrameInfo();
+    REPORTER_ASSERT(r, frameInfo.size() == 4);
+    REPORTER_ASSERT(r, stream->getPosition() >= finalPosition);
+}
+
 // Only rewinds up to a limit.
 class LimitedRewindingStream : public SkStream {
 public:
@@ -1266,7 +1331,6 @@ DEF_TEST(Codec_fallBack, r) {
 
     // Formats that currently do not support incremental decoding
     auto files = {
-            "box.gif",
             "CMYK.jpg",
             "color_wheel.ico",
             "mandrill.wbmp",