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Side by Side Diff: src/utils/SkCanvasStateUtils.cpp

Issue 23545017: Create a semi-stable API for capturing the state of an SkCanvas and reconstructing that state acros… (Closed) Base URL: https://skia.googlecode.com/svn/trunk
Patch Set: fixing nits Created 7 years, 3 months ago
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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 #include "SkCanvasStateUtils.h"
9 #include "SkCanvas.h"
10 #include "SkDevice.h"
11 #include "SkNWayCanvas.h"
12 #include "SkWriter32.h"
13
14 #define CANVAS_STATE_VERSION 1
15 /*
16 * WARNING: The structs below are part of a stable ABI and as such we explicitly
17 * use unambigious primitives (e.g. int32_t instead of an enum).
18 *
19 * ANY CHANGES TO THE STRUCTS BELOW THAT IMPACT THE ABI SHOULD RESULT IN AN
20 * UPDATE OF THE CANVAS_STATE_VERSION. SUCH CHANGES SHOULD ONLY BE MADE IF
21 * ABSOLUTELY NECESSARY!
22 */
23 enum RasterConfigs {
24 kUnknown_RasterConfig = 0,
25 kRGB_565_RasterConfig = 1,
26 kARGB_8888_RasterConfig = 2
27 };
28 typedef int32_t RasterConfig;
29
30 enum CanvasBackends {
31 kUnknown_CanvasBackend = 0,
32 kRaster_CanvasBackend = 1,
33 kGPU_CanvasBackend = 2,
34 kPDF_CanvasBackend = 3
35 };
36 typedef int32_t CanvasBackend;
37
38 struct ClipRect {
39 int32_t left, top, right, bottom;
40 };
41
42 struct SkMCState {
43 float matrix[9];
44 // NOTE: this only works for non-antialiased clips
45 int32_t clipRectCount;
46 ClipRect* clipRects;
47 };
48
49 // NOTE: If you add more members, bump CanvasState::version.
50 struct SkCanvasLayerState {
51 CanvasBackend type;
52 int32_t x, y;
53 int32_t width;
54 int32_t height;
55
56 SkMCState mcState;
57
58 union {
59 struct {
60 RasterConfig config; // pixel format: a value from RasterConfigs.
61 uint32_t rowBytes; // Number of bytes from start of one line to ne xt.
62 void* pixels; // The pixels, all (height * rowBytes) of them.
63 } raster;
64 struct {
65 int32_t textureID;
66 } gpu;
67 };
68 };
69
70 class SkCanvasState {
71 public:
72 SkCanvasState(SkCanvas* canvas) {
73 SkASSERT(canvas);
74 version = CANVAS_STATE_VERSION;
75 width = canvas->getDeviceSize().width();
76 height = canvas->getDeviceSize().height();
77 layerCount = 0;
78 layers = NULL;
79 originalCanvas = SkRef(canvas);
80
81 mcState.clipRectCount = 0;
82 mcState.clipRects = NULL;
83 }
84
85 ~SkCanvasState() {
86 // loop through the layers and free the data allocated to the clipRects
87 for (int i = 0; i < layerCount; ++i) {
88 sk_free(layers[i].mcState.clipRects);
89 }
90
91 sk_free(mcState.clipRects);
92 sk_free(layers);
93
94 // it is now safe to free the canvas since there should be no remaining
95 // references to the content that is referenced by this canvas (e.g. pix els)
96 originalCanvas->unref();
97 }
98
99 /**
100 * The version this struct was built with. This field must always appear
101 * first in the struct so that when the versions don't match (and the
102 * remaining contents and size are potentially different) we can still
103 * compare the version numbers.
104 */
105 int32_t version;
106
107 int32_t width;
108 int32_t height;
109
110 SkMCState mcState;
111
112 int32_t layerCount;
113 SkCanvasLayerState* layers;
114
115 private:
116 SkCanvas* originalCanvas;
117 };
118
119 ////////////////////////////////////////////////////////////////////////////////
120
121 class ClipValidator : public SkCanvas::ClipVisitor {
122 public:
123 ClipValidator() : fFailed(false) {}
124 bool failed() { return fFailed; }
125
126 // ClipVisitor
127 virtual void clipRect(const SkRect& rect, SkRegion::Op op, bool antialias) S K_OVERRIDE {
128 fFailed |= antialias;
129 }
130
131 virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) SK_OVERRI DE {
132 fFailed |= antialias;
133 }
134
135 private:
136 bool fFailed;
137 };
138
139 static void setup_MC_state(SkMCState* state, const SkMatrix& matrix, const SkReg ion& clip) {
140 // initialize the struct
141 state->clipRectCount = 0;
142
143 // capture the matrix
144 for (int i = 0; i < 9; i++) {
145 state->matrix[i] = matrix.get(i);
146 }
147
148 /*
149 * capture the clip
150 *
151 * storage is allocated on the stack for the first 4 rects. This value was
152 * chosen somewhat arbitrarily, but does allow us to represent simple clips
153 * and some more common complex clips (e.g. a clipRect with a sub-rect
154 * clipped out of its interior) without needing to malloc any additional mem ory.
155 */
156 const int clipBufferSize = 4 * sizeof(ClipRect);
157 char clipBuffer[clipBufferSize];
158 SkWriter32 clipWriter(sizeof(ClipRect), clipBuffer, clipBufferSize);
159
160 if (!clip.isEmpty()) {
161 // only returns the b/w clip so aa clips fail
162 SkRegion::Iterator clip_iterator(clip);
163 for (; !clip_iterator.done(); clip_iterator.next()) {
164 // this assumes the SkIRect is stored in l,t,r,b ordering which
165 // matches the ordering of our ClipRect struct
166 clipWriter.writeIRect(clip_iterator.rect());
167 state->clipRectCount++;
168 }
169 }
170
171 // allocate memory for the clip then and copy them to the struct
172 state->clipRects = (ClipRect*) sk_malloc_throw(clipWriter.size());
173 clipWriter.flatten(state->clipRects);
174 }
175
176
177
178 SkCanvasState* SkCanvasStateUtils::CaptureCanvasState(SkCanvas* canvas) {
179 SkASSERT(canvas);
180
181 // Check the clip can be decomposed into rectangles (i.e. no soft clips).
182 ClipValidator validator;
183 canvas->replayClips(&validator);
184 if (validator.failed()) {
185 SkDEBUGF(("CaptureCanvasState does not support canvases with antialiased clips.\n"));
186 return NULL;
187 }
188
189 SkAutoTDelete<SkCanvasState> canvasState(SkNEW_ARGS(SkCanvasState, (canvas)) );
190
191 // decompose the total matrix and clip
192 setup_MC_state(&canvasState->mcState, canvas->getTotalMatrix(), canvas->getT otalClip());
193
194 /*
195 * decompose the layers
196 *
197 * storage is allocated on the stack for the first 3 layers. It is common in
198 * some view systems (e.g. Android) that a few non-clipped layers are presen t
199 * and we will not need to malloc any additional memory in those cases.
200 */
201 const int layerBufferSize = 3 * sizeof(SkCanvasLayerState);
202 char layerBuffer[layerBufferSize];
203 SkWriter32 layerWriter(sizeof(SkCanvasLayerState), layerBuffer, layerBufferS ize);
204 int layerCount = 0;
205 for (SkCanvas::LayerIter layer(canvas, true/*skipEmptyClips*/); !layer.done( ); layer.next()) {
206
207 // we currently only work for bitmap backed devices
208 const SkBitmap& bitmap = layer.device()->accessBitmap(true/*changePixels */);
209 if (bitmap.empty() || bitmap.isNull() || !bitmap.lockPixelsAreWritable() ) {
210 return NULL;
211 }
212
213 SkCanvasLayerState* layerState =
214 (SkCanvasLayerState*) layerWriter.reserve(sizeof(SkCanvasLayerSt ate));
215 layerState->type = kRaster_CanvasBackend;
216 layerState->x = layer.x();
217 layerState->y = layer.y();
218 layerState->width = bitmap.width();
219 layerState->height = bitmap.height();
220
221 switch (bitmap.config()) {
222 case SkBitmap::kARGB_8888_Config:
223 layerState->raster.config = kARGB_8888_RasterConfig;
224 break;
225 case SkBitmap::kRGB_565_Config:
226 layerState->raster.config = kRGB_565_RasterConfig;
227 break;
228 default:
229 return NULL;
230 }
231 layerState->raster.rowBytes = bitmap.rowBytes();
232 layerState->raster.pixels = bitmap.getPixels();
233
234 setup_MC_state(&layerState->mcState, layer.matrix(), layer.clip());
235 layerCount++;
236 }
237
238 // allocate memory for the layers and then and copy them to the struct
239 SkASSERT(layerWriter.size() == layerCount * sizeof(SkCanvasLayerState));
240 canvasState->layerCount = layerCount;
241 canvasState->layers = (SkCanvasLayerState*) sk_malloc_throw(layerWriter.size ());
242 layerWriter.flatten(canvasState->layers);
243
244 // for now, just ignore any client supplied DrawFilter.
245 if (canvas->getDrawFilter()) {
246 SkDEBUGF(("CaptureCanvasState will ignore the canvases draw filter.\n")) ;
247 }
248
249 return canvasState.detach();
250 }
251
252 ////////////////////////////////////////////////////////////////////////////////
253
254 static void setup_canvas_from_MC_state(const SkMCState& state, SkCanvas* canvas) {
255 // reconstruct the matrix
256 SkMatrix matrix;
257 for (int i = 0; i < 9; i++) {
258 matrix.set(i, state.matrix[i]);
259 }
260
261 // reconstruct the clip
262 SkRegion clip;
263 for (int i = 0; i < state.clipRectCount; ++i) {
264 clip.op(SkIRect::MakeLTRB(state.clipRects[i].left,
265 state.clipRects[i].top,
266 state.clipRects[i].right,
267 state.clipRects[i].bottom),
268 SkRegion::kUnion_Op);
269 }
270
271 canvas->setMatrix(matrix);
272 canvas->setClipRegion(clip);
273 }
274
275 static SkCanvas* create_canvas_from_canvas_layer(const SkCanvasLayerState& layer State) {
276 SkASSERT(kRaster_CanvasBackend == layerState.type);
277
278 SkBitmap bitmap;
279 SkBitmap::Config config =
280 layerState.raster.config == kARGB_8888_RasterConfig ? SkBitmap::kARGB_88 88_Config :
281 layerState.raster.config == kRGB_565_RasterConfig ? SkBitmap::kRGB_565_C onfig :
282 SkBitmap::kNo_Config;
283
284 if (config == SkBitmap::kNo_Config) {
285 return NULL;
286 }
287
288 bitmap.setConfig(config, layerState.width, layerState.height,
289 layerState.raster.rowBytes);
290 bitmap.setPixels(layerState.raster.pixels);
291
292 SkASSERT(!bitmap.empty());
293 SkASSERT(!bitmap.isNull());
294
295 // create a device & canvas
296 SkAutoTUnref<SkDevice> device(SkNEW_ARGS(SkDevice, (bitmap)));
297 SkAutoTUnref<SkCanvas> canvas(SkNEW_ARGS(SkCanvas, (device.get())));
298
299 // setup the matrix and clip
300 setup_canvas_from_MC_state(layerState.mcState, canvas.get());
301
302 return canvas.detach();
303 }
304
305 SkCanvas* SkCanvasStateUtils::CreateFromCanvasState(const SkCanvasState* state) {
306 SkASSERT(state);
307
308 // check that the versions match
309 if (CANVAS_STATE_VERSION != state->version) {
310 SkDebugf("CreateFromCanvasState version does not match the one use to cr eate the input");
311 return NULL;
312 }
313
314 if (state->layerCount < 1) {
315 return NULL;
316 }
317
318 SkAutoTUnref<SkNWayCanvas> canvas(SkNEW_ARGS(SkNWayCanvas, (state->width, st ate->height)));
319
320 // setup the matrix and clip on the n-way canvas
321 setup_canvas_from_MC_state(state->mcState, canvas);
322
323 // Iterate over the layers and add them to the n-way canvas
324 for (int i = 0; i < state->layerCount; ++i) {
325 SkAutoTUnref<SkCanvas> canvasLayer(create_canvas_from_canvas_layer(state ->layers[i]));
326 if (!canvasLayer.get()) {
327 return NULL;
328 }
329 canvas->addCanvas(canvasLayer.get());
330 }
331
332 return canvas.detach();
333 }
334
335 ////////////////////////////////////////////////////////////////////////////////
336
337 void SkCanvasStateUtils::ReleaseCanvasState(SkCanvasState* state) {
338 SkDELETE(state);
339 }
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