Add SkCanvasStack and update the Canvas utilities to use it.
BUG=
R=reed@google.com
Review URL: https://codereview.chromium.org/23865004
git-svn-id: http://skia.googlecode.com/svn/trunk@11081 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/utils/SkCanvasStack.cpp b/src/utils/SkCanvasStack.cpp
new file mode 100644
index 0000000..db5a8b2
--- /dev/null
+++ b/src/utils/SkCanvasStack.cpp
@@ -0,0 +1,108 @@
+
+/*
+ * 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 "SkCanvasStack.h"
+
+SkCanvasStack::SkCanvasStack(int width, int height)
+ : INHERITED(width, height) {}
+
+SkCanvasStack::~SkCanvasStack() {
+ this->removeAll();
+}
+
+void SkCanvasStack::pushCanvas(SkCanvas* canvas, const SkIPoint& origin) {
+ if (canvas) {
+ // compute the bounds of this canvas
+ const SkIRect canvasBounds = SkIRect::MakeSize(canvas->getDeviceSize());
+
+ // push the canvas onto the stack
+ this->INHERITED::addCanvas(canvas);
+
+ // push the canvas data onto the stack
+ CanvasData* data = &fCanvasData.push_back();
+ data->origin = origin;
+ data->requiredClip.setRect(canvasBounds);
+
+ // subtract this region from the canvas objects already on the stack.
+ // This ensures they do not draw into the space occupied by the layers
+ // above them.
+ for (int i = fList.count() - 1; i > 0; --i) {
+ SkIRect localBounds = canvasBounds;
+ localBounds.offset(origin - fCanvasData[i-1].origin);
+
+ fCanvasData[i-1].requiredClip.op(localBounds, SkRegion::kDifference_Op);
+ fList[i-i]->clipRegion(fCanvasData[i-1].requiredClip);
+ }
+ }
+ SkASSERT(fList.count() == fCanvasData.count());
+}
+
+void SkCanvasStack::removeAll() {
+ fCanvasData.reset();
+ this->INHERITED::removeAll();
+}
+
+/**
+ * Traverse all canvases (e.g. layers) the stack and ensure that they are clipped
+ * to their bounds and that the area covered by any canvas higher in the stack is
+ * also clipped out.
+ */
+void SkCanvasStack::clipToZOrderedBounds() {
+ SkASSERT(fList.count() == fCanvasData.count());
+ for (int i = 0; i < fList.count(); ++i) {
+ fList[i]->clipRegion(fCanvasData[i].requiredClip, SkRegion::kIntersect_Op);
+ }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * We need to handle setMatrix specially as it overwrites the matrix in each
+ * canvas unlike all other matrix operations (i.e. translate, scale, etc) which
+ * just pre-concatenate with the existing matrix.
+ */
+void SkCanvasStack::setMatrix(const SkMatrix& matrix) {
+ SkASSERT(fList.count() == fCanvasData.count());
+ for (int i = 0; i < fList.count(); ++i) {
+
+ SkMatrix tempMatrix = matrix;
+ tempMatrix.postTranslate(SkIntToScalar(-fCanvasData[i].origin.x()),
+ SkIntToScalar(-fCanvasData[i].origin.y()));
+ fList[i]->setMatrix(tempMatrix);
+ }
+ this->SkCanvas::setMatrix(matrix);
+}
+
+bool SkCanvasStack::clipRect(const SkRect& r, SkRegion::Op op, bool aa) {
+ bool result = this->INHERITED::clipRect(r, op, aa);
+ this->clipToZOrderedBounds();
+ return result;
+}
+
+bool SkCanvasStack::clipRRect(const SkRRect& rr, SkRegion::Op op, bool aa) {
+ bool result = this->INHERITED::clipRRect(rr, op, aa);
+ this->clipToZOrderedBounds();
+ return result;
+}
+
+bool SkCanvasStack::clipPath(const SkPath& p, SkRegion::Op op, bool aa) {
+ bool result = this->INHERITED::clipPath(p, op, aa);
+ this->clipToZOrderedBounds();
+ return result;
+}
+
+bool SkCanvasStack::clipRegion(const SkRegion& deviceRgn, SkRegion::Op op) {
+ SkASSERT(fList.count() == fCanvasData.count());
+ for (int i = 0; i < fList.count(); ++i) {
+ SkRegion tempRegion;
+ deviceRgn.translate(-fCanvasData[i].origin.x(),
+ -fCanvasData[i].origin.y(), &tempRegion);
+ tempRegion.op(fCanvasData[i].requiredClip, SkRegion::kIntersect_Op);
+ fList[i]->clipRegion(tempRegion, op);
+ }
+ return this->SkCanvas::clipRegion(deviceRgn, op);
+}