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      1 
      2 /*
      3  * Copyright 2012 Google Inc.
      4  *
      5  * Use of this source code is governed by a BSD-style license that can be
      6  * found in the LICENSE file.
      7  */
      8 
      9 #ifndef SkPictureStateTree_DEFINED
     10 #define SkPictureStateTree_DEFINED
     11 
     12 #include "SkTDArray.h"
     13 #include "SkChunkAlloc.h"
     14 #include "SkDeque.h"
     15 #include "SkMatrix.h"
     16 #include "SkRefCnt.h"
     17 
     18 class SkCanvas;
     19 
     20 /**
     21  * Provides an interface that, given a sequence of draws into an SkPicture with corresponding
     22  * offsets, allows for playback of an arbitrary subset of the draws (note that Z-order is only
     23  * guaranteed if the draws are explicitly sorted).
     24  */
     25 class SkPictureStateTree : public SkRefCnt {
     26 private:
     27     struct Node;
     28 public:
     29     SK_DECLARE_INST_COUNT(SkPictureStateTree)
     30 
     31     /**
     32      * A draw call, stores offset into command buffer, a pointer to the matrix, and a pointer to
     33      * the node in the tree that corresponds to its clip/layer state
     34      */
     35     struct Draw {
     36         SkMatrix* fMatrix;
     37         Node* fNode;
     38         uint32_t fOffset;
     39         bool operator<(const Draw& other) const { return fOffset < other.fOffset; }
     40     };
     41 
     42     class Iterator;
     43 
     44     SkPictureStateTree();
     45     ~SkPictureStateTree();
     46 
     47     /**
     48      * Creates and returns a struct representing a draw at the given offset.
     49      */
     50     Draw* appendDraw(size_t offset);
     51 
     52     /**
     53      * Given a list of draws, and a canvas, initialize an iterator that produces the correct
     54      * sequence of offsets into the command buffer to carry out those calls with correct
     55      * matrix/clip state. This handles saves/restores, and does all necessary matrix setup.
     56      */
     57     void initIterator(SkPictureStateTree::Iterator* iter,
     58                       const SkTDArray<void*>& draws,
     59                       SkCanvas* canvas);
     60 
     61     void appendSave();
     62     void appendSaveLayer(size_t offset);
     63     void appendRestore();
     64     void appendTransform(const SkMatrix& trans);
     65     void appendClip(size_t offset);
     66 
     67     /**
     68      * Call this immediately after an appendRestore call that is associated
     69      * a save or saveLayer that was removed from the command stream
     70      * due to a command pattern optimization in SkPicture.
     71      */
     72     void saveCollapsed();
     73 
     74     /**
     75      * Playback helper
     76      */
     77     class Iterator {
     78     public:
     79         /** Returns the next op offset needed to create the drawing state
     80             required by the queued up draw operation or the offset of the queued
     81             up draw operation itself. In the latter case, the next draw operation
     82             will move into the queued up slot.
     83             It retuns kDrawComplete when done.
     84             TODO: this might be better named nextOp
     85         */
     86         uint32_t nextDraw();
     87         static const uint32_t kDrawComplete = SK_MaxU32;
     88         Iterator() : fValid(false) { }
     89         bool isValid() const { return fValid; }
     90 
     91     private:
     92         void init(const SkTDArray<void*>& draws, SkCanvas* canvas, Node* root);
     93 
     94         void setCurrentMatrix(const SkMatrix*);
     95 
     96         // The draws this iterator is associated with
     97         const SkTDArray<void*>* fDraws;
     98 
     99         // canvas this is playing into (so we can insert saves/restores as necessary)
    100         SkCanvas* fCanvas;
    101 
    102         // current state node
    103         Node* fCurrentNode;
    104 
    105         // List of nodes whose state we need to apply to reach TargetNode
    106         SkTDArray<Node*> fNodes;
    107 
    108         // The matrix of the canvas we're playing back into
    109         SkMatrix fPlaybackMatrix;
    110 
    111         // Cache of current matrix, so we can avoid redundantly setting it
    112         const SkMatrix* fCurrentMatrix;
    113 
    114         // current position in the array of draws
    115         int fPlaybackIndex;
    116         // Whether or not we need to do a save next iteration
    117         bool fSave;
    118 
    119         // Whether or not this is a valid iterator (the default public constructor sets this false)
    120         bool fValid;
    121 
    122         uint32_t finish();
    123 
    124         friend class SkPictureStateTree;
    125     };
    126 
    127 private:
    128 
    129     void appendNode(size_t offset);
    130 
    131     SkChunkAlloc fAlloc;
    132     // Needed by saveCollapsed() because nodes do not currently store
    133     // references to their children.  If they did, we could just retrieve the
    134     // last added child.
    135     Node* fLastRestoredNode;
    136 
    137     // The currently active state
    138     Draw fCurrentState;
    139     // A stack of states for tracking save/restores
    140     SkDeque fStateStack;
    141 
    142     // Represents a notable piece of state that requires an offset into the command buffer,
    143     // corresponding to a clip/saveLayer/etc call, to apply.
    144     struct Node {
    145         Node* fParent;
    146         uint32_t fOffset;
    147         uint16_t fLevel;
    148         uint16_t fFlags;
    149         SkMatrix* fMatrix;
    150         enum Flags {
    151             kSave_Flag      = 0x1,
    152             kSaveLayer_Flag = 0x2
    153         };
    154     };
    155 
    156     Node fRoot;
    157     SkMatrix fRootMatrix;
    158 
    159     typedef SkRefCnt INHERITED;
    160 };
    161 
    162 #endif
    163