Individually enable and disable SkCodecs

src/codec/SkCodec.cpp

Index: src/codec/SkCodec.cpp
diff --git a/src/codec/SkCodec.cpp b/src/codec/SkCodec.cpp
index bb7b26529b9af8fe7c106818e5514c47617cdf76..dc45f37aa7399122d4f61304d05e70bf8134c2da 100644
--- a/src/codec/SkCodec.cpp
+++ b/src/codec/SkCodec.cpp
@@ -11,11 +11,13 @@
 #include "SkData.h"
 #include "SkGifCodec.h"
 #include "SkIcoCodec.h"
+#ifdef SK_CODEC_DECODES_JPEG
 #include "SkJpegCodec.h"

[msarett, 2016/02/17 14:34:54]

Don't think I can get rid of this ifdef.  SkJpegUtility_codec.h needs to extend
a few structs that are defined in libjpeg.

[mtklein, 2016/02/17 14:57:31]

Are you sure SkJpegCodec.h needs to include SkJpegUtility_codec.h?

[msarett, 2016/02/17 15:13:47]

Ahh thanks!  Removing this.

+#endif
+#ifdef SK_CODEC_DECODES_PNG

[msarett, 2016/02/17 14:34:54]

Was almost able to get rid of this ifdef by forward declaring png_structs.  The
problem is that the names have changed in different versions of libpng (though
they are always typedefed to png_structp).

[mtklein, 2016/02/17 14:57:31]

:/  Sure can't forward declare typedefs.

You can, however, do something like this:

SkPngCodec.h
---------------

class SkPngCodec {
public:
     static bool IsPng(const char*, size_t);
     static SkCodec* NewFromStream(SkStream*, SkPngChunkReader* = nullptr);
};

SkPngCodec.cpp
-----------------

namespace {
class PngCodec : public SkCodec {
     ....
};
}  // namespace

SkCodec* SkPngCodec::NewFromStream(...) { return new PngCodec(...); }

[msarett, 2016/02/17 15:13:47]

Gotcha that's cool.  I think I prefer this as is though - just to stay
consistent with the rest of the codecs.

 #include "SkPngCodec.h"
-#ifdef SK_CODEC_DECODES_RAW
-#include "SkRawCodec.h"
 #endif
+#include "SkRawCodec.h"
 #include "SkStream.h"
 #include "SkWbmpCodec.h"
 #include "SkWebpCodec.h"
@@ -26,10 +28,18 @@ struct DecoderProc {
 };
 
 static const DecoderProc gDecoderProcs[] = {
+#ifdef SK_CODEC_DECODES_JPEG
     { SkJpegCodec::IsJpeg, SkJpegCodec::NewFromStream },
+#endif
+#ifdef SK_CODEC_DECODES_WEBP
     { SkWebpCodec::IsWebp, SkWebpCodec::NewFromStream },
+#endif
+#ifdef SK_CODEC_DECODES_GIF
     { SkGifCodec::IsGif, SkGifCodec::NewFromStream },
+#endif
+#ifdef SK_CODEC_DECODES_PNG
     { SkIcoCodec::IsIco, SkIcoCodec::NewFromStream },
+#endif
     { SkBmpCodec::IsBmp, SkBmpCodec::NewFromStream },
     { SkWbmpCodec::IsWbmp, SkWbmpCodec::NewFromStream }
 };
@@ -77,9 +87,12 @@ SkCodec* SkCodec::NewFromStream(SkStream* stream,
 
     // PNG is special, since we want to be able to supply an SkPngChunkReader.
     // But this code follows the same pattern as the loop.
+#ifdef SK_CODEC_DECODES_PNG
     if (SkPngCodec::IsPng(buffer, bytesRead)) {
         return SkPngCodec::NewFromStream(streamDeleter.detach(), chunkReader);
-    } else {
+    } else
+#endif
+    {
         for (DecoderProc proc : gDecoderProcs) {
             if (proc.IsFormat(buffer, bytesRead)) {
                 return proc.NewFromStream(streamDeleter.detach());