| |
| /* |
| * Copyright 2011 The Android Open Source Project |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| |
| #ifndef SkDrawLooper_DEFINED |
| #define SkDrawLooper_DEFINED |
| |
| #include "SkBlurTypes.h" |
| #include "SkFlattenable.h" |
| #include "SkPoint.h" |
| #include "SkColor.h" |
| |
| class SkArenaAlloc; |
| class SkCanvas; |
| class SkColorSpaceXformer; |
| class SkPaint; |
| struct SkRect; |
| class SkString; |
| |
| /** \class SkDrawLooper |
| Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are, |
| and something is drawn to a canvas with that paint, the looper subclass will |
| be called, allowing it to modify the canvas and/or paint for that draw call. |
| More than that, via the next() method, the looper can modify the draw to be |
| invoked multiple times (hence the name loop-er), allow it to perform effects |
| like shadows or frame/fills, that require more than one pass. |
| */ |
| class SK_API SkDrawLooper : public SkFlattenable { |
| public: |
| /** |
| * Holds state during a draw. Users call next() until it returns false. |
| * |
| * Subclasses of SkDrawLooper should create a subclass of this object to |
| * hold state specific to their subclass. |
| */ |
| class SK_API Context : ::SkNoncopyable { |
| public: |
| Context() {} |
| virtual ~Context() {} |
| |
| /** |
| * Called in a loop on objects returned by SkDrawLooper::createContext(). |
| * Each time true is returned, the object is drawn (possibly with a modified |
| * canvas and/or paint). When false is finally returned, drawing for the object |
| * stops. |
| * |
| * On each call, the paint will be in its original state, but the |
| * canvas will be as it was following the previous call to next() or |
| * createContext(). |
| * |
| * The implementation must ensure that, when next() finally returns |
| * false, the canvas has been restored to the state it was |
| * initially, before createContext() was first called. |
| */ |
| virtual bool next(SkCanvas* canvas, SkPaint* paint) = 0; |
| }; |
| |
| /** |
| * Called right before something is being drawn. Returns a Context |
| * whose next() method should be called until it returns false. |
| */ |
| virtual Context* makeContext(SkCanvas*, SkArenaAlloc*) const = 0; |
| |
| /** |
| * The fast bounds functions are used to enable the paint to be culled early |
| * in the drawing pipeline. If a subclass can support this feature it must |
| * return true for the canComputeFastBounds() function. If that function |
| * returns false then computeFastBounds behavior is undefined otherwise it |
| * is expected to have the following behavior. Given the parent paint and |
| * the parent's bounding rect the subclass must fill in and return the |
| * storage rect, where the storage rect is with the union of the src rect |
| * and the looper's bounding rect. |
| */ |
| bool canComputeFastBounds(const SkPaint& paint) const; |
| void computeFastBounds(const SkPaint& paint, const SkRect& src, SkRect* dst) const; |
| |
| struct BlurShadowRec { |
| SkScalar fSigma; |
| SkVector fOffset; |
| SkColor fColor; |
| SkBlurStyle fStyle; |
| SkBlurQuality fQuality; |
| }; |
| /** |
| * If this looper can be interpreted as having two layers, such that |
| * 1. The first layer (bottom most) just has a blur and translate |
| * 2. The second layer has no modifications to either paint or canvas |
| * 3. No other layers. |
| * then return true, and if not null, fill out the BlurShadowRec). |
| * |
| * If any of the above are not met, return false and ignore the BlurShadowRec parameter. |
| */ |
| virtual bool asABlurShadow(BlurShadowRec*) const; |
| |
| SK_TO_STRING_PUREVIRT() |
| SK_DEFINE_FLATTENABLE_TYPE(SkDrawLooper) |
| |
| protected: |
| sk_sp<SkDrawLooper> makeColorSpace(SkColorSpaceXformer* xformer) const { |
| return this->onMakeColorSpace(xformer); |
| } |
| virtual sk_sp<SkDrawLooper> onMakeColorSpace(SkColorSpaceXformer*) const = 0; |
| |
| SkDrawLooper() {} |
| |
| private: |
| friend class SkColorSpaceXformer; |
| |
| typedef SkFlattenable INHERITED; |
| }; |
| |
| #endif |