Implement an SkPicture image filter source. This is required for the external-SVG reference feature…

src/effects/SkPictureSource.cpp

+/*
+ * Copyright 2013 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPictureSource.h"
+#include "SkDevice.h"
+#include "SkCanvas.h"
+#include "SkFlattenableBuffers.h"
+#include "SkValidationUtils.h"
+
+SkPictureSource::SkPictureSource(const SkPicture& picture)
+  : INHERITED(0, 0),
+    fPicture(picture),
+    fRect(SkRect::MakeWH(picture.width(), picture.height())) {
+}
+
+SkPictureSource::SkPictureSource(const SkPicture& picture, const SkRect& rect)
+  : INHERITED(0, 0),
+    fPicture(picture),
+    fRect(rect) {
+}
+
+SkPictureSource::SkPictureSource(SkFlattenableReadBuffer& buffer)
+  : INHERITED(0, buffer) {
+    // FIXME: unflatten picture here.
+    buffer.readRect(&fRect);
+}
+
+void SkPictureSource::flatten(SkFlattenableWriteBuffer& buffer) const {
+    this->INHERITED::flatten(buffer);
+    // FIXME: flatten picture here.
+    buffer.writeRect(fRect);
+}
+
+bool SkPictureSource::onFilterImage(Proxy* proxy, const SkBitmap&, const SkMatrix& matrix,
+                                   SkBitmap* result, SkIPoint* offset) {
+    SkRect floatBounds;
+    SkIRect bounds;
+    matrix.mapRect(&floatBounds, fRect);
+    floatBounds.roundOut(&bounds);
+
+    if (bounds.isEmpty()) {
+        return true;
+    }
+
+    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(bounds.width(), bounds.height()));
+    if (NULL == device.get()) {
+        return false;
+    }
+
+    SkCanvas canvas(device.get());
+    SkPaint paint;
+
+    canvas.translate(-bounds.fLeft, -bounds.fTop);
+    canvas.concat(matrix);
+    canvas.drawPicture(fPicture);
+
+    *result = device.get()->accessBitmap(false);
+    offset->fX += bounds.fLeft;
+    offset->fY += bounds.fTop;
+    return true;
+}