1 /*
2  * Copyright 2019 Google Inc.
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 #ifndef SkSharingProc_DEFINED
9 #define SkSharingProc_DEFINED
10 
11 #include <unordered_map>
12 #include <vector>
13 
14 #include "include/core/SkData.h"
15 #include "include/core/SkImage.h"
16 #include "include/core/SkSerialProcs.h"
17 
18 /**
19  * This serial proc serializes each image it encounters only once, using their uniqueId as the
20  * property for sameness.
21  *
22  * It's most basic usage involves setting your imageProc to SkSharingSerialContext::serializeImage
23  * and creating an SkSharingSerialContext in an appropriate scope to outlive all the images that
24  * will be encountered before serialization.
25  *
26  * Optionally, collectNonTextureImagesFromPicture can be called with an SkSharingContext and an
27  * SkPicture that may reference not-yet-released texture backed images. It will make non-texture
28  * copies if necessary and store them in the context. If present, they will be used in the
29  * final serialization.
30  *
31  * This is intended to be used on Android with MultiPictureDocument's onEndPage parameter, in a
32  * lambda that captures the context, because MPD cannot make assumptions about the type of proc it
33  * receives and clients (Chrome) build MPD without this source file.
34  */
35 
36 struct SkSharingSerialContext {
37     // --- Data and and function for optional texture collection pass --- //
38 
39     // A map from uniqueID of images referenced by commands to non-texture images
40     // collected at the end of each frame.
41     std::unordered_map<uint32_t, sk_sp<SkImage>> fNonTexMap;
42 
43     // Collects any non-texture images referenced by the picture and stores non-texture copies
44     // in the fNonTexMap of the provided SkSharingContext
45     static void collectNonTextureImagesFromPicture(
46         const SkPicture* pic, SkSharingSerialContext* sharingCtx);
47 
48 
49     // --- Data and serialization function for regular use --- //
50 
51     // A map from the ids from SkImage::uniqueID() to ids used within the file
52     // The keys are ids of original images, not of non-texture copies
53     std::unordered_map<uint32_t, uint32_t> fImageMap;
54 
55     // A serial proc that shares images between subpictures
56     // To use this, create an instance of SkSerialProcs and populate it this way.
57     // The client must retain ownership of the context.
58     // auto ctx = std::make_unique<SkSharingSerialContext>()
59     // SkSerialProcs procs;
60     // procs.fImageProc = SkSharingSerialContext::serializeImage;
61     // procs.fImageCtx = ctx.get();
62     static sk_sp<SkData> serializeImage(SkImage* img, void* ctx);
63 };
64 
65 struct SkSharingDeserialContext {
66     // a list of unique images in the order they were encountered in the file
67     // Subsequent occurrences of an image refer to it by it's index in this list.
68     std::vector<sk_sp<SkImage>> fImages;
69 
70     // A deserial proc that can interpret id's in place of images as references to previous images.
71     // Can also deserialize a SKP where all images are inlined (it's backwards compatible)
72     static sk_sp<SkImage> deserializeImage(const void* data, size_t length, void* ctx);
73 };
74 
75 #endif
76