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