9d6681cc70
Mostly just formatting fixes with a few grammatical changes.
Two real notable changes:
- Removed references to SkGLCanvas from Tips & FAQ and replaced with
references to `SkDevice` and `SkSurface`.
- Deleted deprecated "Quick Start Guides" folder
Docs-Preview: https://skia.org/?cl=92361
Bug: skia:
Change-Id: Ief790b1c2bae8fe0e39aa8d66c79f80560d18c9e
Reviewed-on: https://skia-review.googlesource.com/92361
Reviewed-by: Heather Miller <hcm@google.com>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
89 lines
2.4 KiB
Markdown
89 lines
2.4 KiB
Markdown
Flattenables
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============
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Many objects in Skia, such as `SkShaders` and other effects on `SkPaint`, need to be
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flattened into a data stream for either transport or as part of the key to the
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font cache. Classes for these objects should derive from `SkFlattenable` or one of
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its subclasses. If you create a new flattenable class, you need to make sure you
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do a few things so that it will work on all platforms:
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1: Override the method `flatten` (the default scope is protected):
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<!--?prettify?-->
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~~~~
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virtual void flatten(SkFlattenableWriteBuffer& buffer) const override {
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this->INHERITED::flatten(buffer);
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// Write any private data that needs to be stored to recreate this object
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}
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~~~~
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2: Override the (protected) constructor that creates an object from an
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`SkFlattenableReadBuffer`:
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<!--?prettify?-->
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~~~~
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SkNewClass(SkFlattenableReadBuffer& buffer)
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: INHERITED(buffer) {
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// Read the data from the buffer in the same order as it was written to the
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// SkFlattenableWriteBuffer and construct the new object
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}
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~~~~
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3: Declare a set of deserialization procs for your object in the class declaration:
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We have a macro for this:
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<!--?prettify?-->
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~~~~
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public:
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SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkNewClass)
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~~~~
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4: If your class is declared in a `.cpp` file or in a private header file, create a
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function to register its group:
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This occurs in cases where the classes are hidden behind a factory, like many effects
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and shaders are. Then in the parent class header file (such as `SkGradientShader`) you
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need to add:
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<!--?prettify?-->
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~~~~
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public:
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SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
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~~~~
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Then in the cpp file you define all the members of the group together:
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<!--?prettify?-->
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~~~~
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SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkGroupClass)
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SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkMemberClass1)
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SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkMemberClass2)
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// etc
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SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
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~~~~
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5: Register your flattenable with the global registrar:
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You need to add one line to `SkFlattenable::InitalizeFlattenables()`. To register the
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flattenable in a Skia build, that function is defined in `SkGlobalInitialization_default.cpp`.
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For Chromium, it is in `SkGlobalInitialization_chromium.cpp`.
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For a single flattenable add
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<!--?prettify?-->
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~~~~
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SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkNewClass)
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~~~~
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For a group, add
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<!--?prettify?-->
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~~~~
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SkGroupClass::InitializeFlattenables();
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~~~~
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