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Unified 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, 4 months ago
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Index: src/utils/SkCanvasStateUtils.cpp
diff --git a/src/utils/SkCanvasStateUtils.cpp b/src/utils/SkCanvasStateUtils.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..8abab6b5ae19805c9703b7c9e8833e1c76b88d1a
--- /dev/null
+++ b/src/utils/SkCanvasStateUtils.cpp
@@ -0,0 +1,339 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCanvasStateUtils.h"
+#include "SkCanvas.h"
+#include "SkDevice.h"
+#include "SkNWayCanvas.h"
+#include "SkWriter32.h"
+
+#define CANVAS_STATE_VERSION 1
+/*
+ * WARNING: The structs below are part of a stable ABI and as such we explicitly
+ * use unambigious primitives (e.g. int32_t instead of an enum).
+ *
+ * ANY CHANGES TO THE STRUCTS BELOW THAT IMPACT THE ABI SHOULD RESULT IN AN
+ * UPDATE OF THE CANVAS_STATE_VERSION. SUCH CHANGES SHOULD ONLY BE MADE IF
+ * ABSOLUTELY NECESSARY!
+ */
+enum RasterConfigs {
+ kUnknown_RasterConfig = 0,
+ kRGB_565_RasterConfig = 1,
+ kARGB_8888_RasterConfig = 2
+};
+typedef int32_t RasterConfig;
+
+enum CanvasBackends {
+ kUnknown_CanvasBackend = 0,
+ kRaster_CanvasBackend = 1,
+ kGPU_CanvasBackend = 2,
+ kPDF_CanvasBackend = 3
+};
+typedef int32_t CanvasBackend;
+
+struct ClipRect {
+ int32_t left, top, right, bottom;
+};
+
+struct SkMCState {
+ float matrix[9];
+ // NOTE: this only works for non-antialiased clips
+ int32_t clipRectCount;
+ ClipRect* clipRects;
+};
+
+// NOTE: If you add more members, bump CanvasState::version.
+struct SkCanvasLayerState {
+ CanvasBackend type;
+ int32_t x, y;
+ int32_t width;
+ int32_t height;
+
+ SkMCState mcState;
+
+ union {
+ struct {
+ RasterConfig config; // pixel format: a value from RasterConfigs.
+ uint32_t rowBytes; // Number of bytes from start of one line to next.
+ void* pixels; // The pixels, all (height * rowBytes) of them.
+ } raster;
+ struct {
+ int32_t textureID;
+ } gpu;
+ };
+};
+
+class SkCanvasState {
+public:
+ SkCanvasState(SkCanvas* canvas) {
+ SkASSERT(canvas);
+ version = CANVAS_STATE_VERSION;
+ width = canvas->getDeviceSize().width();
+ height = canvas->getDeviceSize().height();
+ layerCount = 0;
+ layers = NULL;
+ originalCanvas = SkRef(canvas);
+
+ mcState.clipRectCount = 0;
+ mcState.clipRects = NULL;
+ }
+
+ ~SkCanvasState() {
+ // loop through the layers and free the data allocated to the clipRects
+ for (int i = 0; i < layerCount; ++i) {
+ sk_free(layers[i].mcState.clipRects);
+ }
+
+ sk_free(mcState.clipRects);
+ sk_free(layers);
+
+ // it is now safe to free the canvas since there should be no remaining
+ // references to the content that is referenced by this canvas (e.g. pixels)
+ originalCanvas->unref();
+ }
+
+ /**
+ * The version this struct was built with. This field must always appear
+ * first in the struct so that when the versions don't match (and the
+ * remaining contents and size are potentially different) we can still
+ * compare the version numbers.
+ */
+ int32_t version;
+
+ int32_t width;
+ int32_t height;
+
+ SkMCState mcState;
+
+ int32_t layerCount;
+ SkCanvasLayerState* layers;
+
+private:
+ SkCanvas* originalCanvas;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+class ClipValidator : public SkCanvas::ClipVisitor {
+public:
+ ClipValidator() : fFailed(false) {}
+ bool failed() { return fFailed; }
+
+ // ClipVisitor
+ virtual void clipRect(const SkRect& rect, SkRegion::Op op, bool antialias) SK_OVERRIDE {
+ fFailed |= antialias;
+ }
+
+ virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) SK_OVERRIDE {
+ fFailed |= antialias;
+ }
+
+private:
+ bool fFailed;
+};
+
+static void setup_MC_state(SkMCState* state, const SkMatrix& matrix, const SkRegion& clip) {
+ // initialize the struct
+ state->clipRectCount = 0;
+
+ // capture the matrix
+ for (int i = 0; i < 9; i++) {
+ state->matrix[i] = matrix.get(i);
+ }
+
+ /*
+ * capture the clip
+ *
+ * storage is allocated on the stack for the first 4 rects. This value was
+ * chosen somewhat arbitrarily, but does allow us to represent simple clips
+ * and some more common complex clips (e.g. a clipRect with a sub-rect
+ * clipped out of its interior) without needing to malloc any additional memory.
+ */
+ const int clipBufferSize = 4 * sizeof(ClipRect);
+ char clipBuffer[clipBufferSize];
+ SkWriter32 clipWriter(sizeof(ClipRect), clipBuffer, clipBufferSize);
+
+ if (!clip.isEmpty()) {
+ // only returns the b/w clip so aa clips fail
+ SkRegion::Iterator clip_iterator(clip);
+ for (; !clip_iterator.done(); clip_iterator.next()) {
+ // this assumes the SkIRect is stored in l,t,r,b ordering which
+ // matches the ordering of our ClipRect struct
+ clipWriter.writeIRect(clip_iterator.rect());
+ state->clipRectCount++;
+ }
+ }
+
+ // allocate memory for the clip then and copy them to the struct
+ state->clipRects = (ClipRect*) sk_malloc_throw(clipWriter.size());
+ clipWriter.flatten(state->clipRects);
+}
+
+
+
+SkCanvasState* SkCanvasStateUtils::CaptureCanvasState(SkCanvas* canvas) {
+ SkASSERT(canvas);
+
+ // Check the clip can be decomposed into rectangles (i.e. no soft clips).
+ ClipValidator validator;
+ canvas->replayClips(&validator);
+ if (validator.failed()) {
+ SkDEBUGF(("CaptureCanvasState does not support canvases with antialiased clips.\n"));
+ return NULL;
+ }
+
+ SkAutoTDelete<SkCanvasState> canvasState(SkNEW_ARGS(SkCanvasState, (canvas)));
+
+ // decompose the total matrix and clip
+ setup_MC_state(&canvasState->mcState, canvas->getTotalMatrix(), canvas->getTotalClip());
+
+ /*
+ * decompose the layers
+ *
+ * storage is allocated on the stack for the first 3 layers. It is common in
+ * some view systems (e.g. Android) that a few non-clipped layers are present
+ * and we will not need to malloc any additional memory in those cases.
+ */
+ const int layerBufferSize = 3 * sizeof(SkCanvasLayerState);
+ char layerBuffer[layerBufferSize];
+ SkWriter32 layerWriter(sizeof(SkCanvasLayerState), layerBuffer, layerBufferSize);
+ int layerCount = 0;
+ for (SkCanvas::LayerIter layer(canvas, true/*skipEmptyClips*/); !layer.done(); layer.next()) {
+
+ // we currently only work for bitmap backed devices
+ const SkBitmap& bitmap = layer.device()->accessBitmap(true/*changePixels*/);
+ if (bitmap.empty() || bitmap.isNull() || !bitmap.lockPixelsAreWritable()) {
+ return NULL;
+ }
+
+ SkCanvasLayerState* layerState =
+ (SkCanvasLayerState*) layerWriter.reserve(sizeof(SkCanvasLayerState));
+ layerState->type = kRaster_CanvasBackend;
+ layerState->x = layer.x();
+ layerState->y = layer.y();
+ layerState->width = bitmap.width();
+ layerState->height = bitmap.height();
+
+ switch (bitmap.config()) {
+ case SkBitmap::kARGB_8888_Config:
+ layerState->raster.config = kARGB_8888_RasterConfig;
+ break;
+ case SkBitmap::kRGB_565_Config:
+ layerState->raster.config = kRGB_565_RasterConfig;
+ break;
+ default:
+ return NULL;
+ }
+ layerState->raster.rowBytes = bitmap.rowBytes();
+ layerState->raster.pixels = bitmap.getPixels();
+
+ setup_MC_state(&layerState->mcState, layer.matrix(), layer.clip());
+ layerCount++;
+ }
+
+ // allocate memory for the layers and then and copy them to the struct
+ SkASSERT(layerWriter.size() == layerCount * sizeof(SkCanvasLayerState));
+ canvasState->layerCount = layerCount;
+ canvasState->layers = (SkCanvasLayerState*) sk_malloc_throw(layerWriter.size());
+ layerWriter.flatten(canvasState->layers);
+
+ // for now, just ignore any client supplied DrawFilter.
+ if (canvas->getDrawFilter()) {
+ SkDEBUGF(("CaptureCanvasState will ignore the canvases draw filter.\n"));
+ }
+
+ return canvasState.detach();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+static void setup_canvas_from_MC_state(const SkMCState& state, SkCanvas* canvas) {
+ // reconstruct the matrix
+ SkMatrix matrix;
+ for (int i = 0; i < 9; i++) {
+ matrix.set(i, state.matrix[i]);
+ }
+
+ // reconstruct the clip
+ SkRegion clip;
+ for (int i = 0; i < state.clipRectCount; ++i) {
+ clip.op(SkIRect::MakeLTRB(state.clipRects[i].left,
+ state.clipRects[i].top,
+ state.clipRects[i].right,
+ state.clipRects[i].bottom),
+ SkRegion::kUnion_Op);
+ }
+
+ canvas->setMatrix(matrix);
+ canvas->setClipRegion(clip);
+}
+
+static SkCanvas* create_canvas_from_canvas_layer(const SkCanvasLayerState& layerState) {
+ SkASSERT(kRaster_CanvasBackend == layerState.type);
+
+ SkBitmap bitmap;
+ SkBitmap::Config config =
+ layerState.raster.config == kARGB_8888_RasterConfig ? SkBitmap::kARGB_8888_Config :
+ layerState.raster.config == kRGB_565_RasterConfig ? SkBitmap::kRGB_565_Config :
+ SkBitmap::kNo_Config;
+
+ if (config == SkBitmap::kNo_Config) {
+ return NULL;
+ }
+
+ bitmap.setConfig(config, layerState.width, layerState.height,
+ layerState.raster.rowBytes);
+ bitmap.setPixels(layerState.raster.pixels);
+
+ SkASSERT(!bitmap.empty());
+ SkASSERT(!bitmap.isNull());
+
+ // create a device & canvas
+ SkAutoTUnref<SkDevice> device(SkNEW_ARGS(SkDevice, (bitmap)));
+ SkAutoTUnref<SkCanvas> canvas(SkNEW_ARGS(SkCanvas, (device.get())));
+
+ // setup the matrix and clip
+ setup_canvas_from_MC_state(layerState.mcState, canvas.get());
+
+ return canvas.detach();
+}
+
+SkCanvas* SkCanvasStateUtils::CreateFromCanvasState(const SkCanvasState* state) {
+ SkASSERT(state);
+
+ // check that the versions match
+ if (CANVAS_STATE_VERSION != state->version) {
+ SkDebugf("CreateFromCanvasState version does not match the one use to create the input");
+ return NULL;
+ }
+
+ if (state->layerCount < 1) {
+ return NULL;
+ }
+
+ SkAutoTUnref<SkNWayCanvas> canvas(SkNEW_ARGS(SkNWayCanvas, (state->width, state->height)));
+
+ // setup the matrix and clip on the n-way canvas
+ setup_canvas_from_MC_state(state->mcState, canvas);
+
+ // Iterate over the layers and add them to the n-way canvas
+ for (int i = 0; i < state->layerCount; ++i) {
+ SkAutoTUnref<SkCanvas> canvasLayer(create_canvas_from_canvas_layer(state->layers[i]));
+ if (!canvasLayer.get()) {
+ return NULL;
+ }
+ canvas->addCanvas(canvasLayer.get());
+ }
+
+ return canvas.detach();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+void SkCanvasStateUtils::ReleaseCanvasState(SkCanvasState* state) {
+ SkDELETE(state);
+}

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