1 /* 2 * Copyright 2013 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 SkCanvasStateUtils_DEFINED 9 #define SkCanvasStateUtils_DEFINED 10 11 #include "include/core/SkTypes.h" 12 13 #include <memory> 14 15 class SkCanvas; 16 class SkCanvasState; 17 18 /** 19 * A set of functions that are useful for copying the state of an SkCanvas 20 * across a library boundary where the Skia library on the other side of the 21 * boundary may be newer. The expected usage is outline below... 22 * 23 * Lib Boundary 24 * CaptureCanvasState(...) ||| 25 * SkCanvas --> SkCanvasState ||| 26 * ||| CreateFromCanvasState(...) 27 * ||| SkCanvasState --> SkCanvas` 28 * ||| Draw into SkCanvas` 29 * ||| Unref SkCanvas` 30 * ReleaseCanvasState(...) ||| 31 * 32 */ 33 class SK_API SkCanvasStateUtils { 34 public: 35 /** 36 * Captures the current state of the canvas into an opaque ptr that is safe 37 * to pass to a different instance of Skia (which may be the same version, 38 * or may be newer). The function will return NULL in the event that one of the 39 * following conditions are true. 40 * 1) the canvas device type is not supported (currently only raster is supported) 41 * 2) the canvas clip type is not supported (currently only non-AA clips are supported) 42 * 43 * It is recommended that the original canvas also not be used until all 44 * canvases that have been created using its captured state have been dereferenced. 45 * 46 * Finally, it is important to note that any draw filters attached to the 47 * canvas are NOT currently captured. 48 * 49 * @param canvas The canvas you wish to capture the current state of. 50 * @return NULL or an opaque ptr that can be passed to CreateFromCanvasState 51 * to reconstruct the canvas. The caller is responsible for calling 52 * ReleaseCanvasState to free the memory associated with this state. 53 */ 54 static SkCanvasState* CaptureCanvasState(SkCanvas* canvas); 55 56 /** 57 * Create a new SkCanvas from the captured state of another SkCanvas. The 58 * function will return NULL in the event that one of the 59 * following conditions are true. 60 * 1) the captured state is in an unrecognized format 61 * 2) the captured canvas device type is not supported 62 * 63 * @param state Opaque object created by CaptureCanvasState. 64 * @return NULL or an SkCanvas* whose devices and matrix/clip state are 65 * identical to the captured canvas. The caller is responsible for 66 * calling unref on the SkCanvas. 67 */ 68 static std::unique_ptr<SkCanvas> MakeFromCanvasState(const SkCanvasState* state); 69 70 /** 71 * Free the memory associated with the captured canvas state. The state 72 * should not be released until all SkCanvas objects created using that 73 * state have been dereferenced. Must be called from the same library 74 * instance that created the state via CaptureCanvasState. 75 * 76 * @param state The captured state you wish to dispose of. 77 */ 78 static void ReleaseCanvasState(SkCanvasState* state); 79 }; 80 81 #endif 82