Move GrReducedClip to its own files.
R=robertphillips@google.com
Review URL: https://codereview.appspot.com/6891045
git-svn-id: http://skia.googlecode.com/svn/trunk@6686 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrReducedClip.cpp b/src/gpu/GrReducedClip.cpp
new file mode 100644
index 0000000..8ee28dd
--- /dev/null
+++ b/src/gpu/GrReducedClip.cpp
@@ -0,0 +1,328 @@
+
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrReducedClip.h"
+
+typedef SkClipStack::Element Element;
+////////////////////////////////////////////////////////////////////////////////
+
+namespace GrReducedClip {
+
+/*
+There are plenty of optimizations that could be added here. For example we could consider
+checking for cases where an inverse path can be changed to a regular fill with a different op.
+(e.g. [kIntersect, inverse path] -> [kDifference, path]). Maybe flips could be folded into
+earlier operations. Or would inserting flips and reversing earlier ops ever be a win? Perhaps
+for the case where the bounds are kInsideOut_BoundsType. We could restrict earlier operations
+based on later intersect operations, and perhaps remove intersect-rects. We could optionally
+take a rect in case the caller knows a bound on what is to be drawn through this clip.
+*/
+void GrReduceClipStack(const SkClipStack& stack,
+ const SkRect& queryBounds,
+ ElementList* result,
+ InitialState* initialState) {
+ result->reset();
+
+ if (stack.isWideOpen()) {
+ *initialState = kAllIn_InitialState;
+ return;
+ }
+
+ SkClipStack::BoundsType stackBoundsType;
+ SkRect stackBounds;
+ bool iior;
+ stack.getBounds(&stackBounds, &stackBoundsType, &iior);
+
+ if (iior) {
+ SkASSERT(SkClipStack::kNormal_BoundsType == stackBoundsType);
+ SkRect isectRect;
+ if (stackBounds.contains(queryBounds)) {
+ *initialState = kAllIn_InitialState;
+ } else if (isectRect.intersect(stackBounds, queryBounds)) {
+ // iior should only be true if aa/non-aa status matches among all elements.
+ SkClipStack::Iter iter(stack, SkClipStack::Iter::kTop_IterStart);
+ bool doAA = iter.prev()->isAA();
+ SkNEW_INSERT_AT_LLIST_HEAD(result, Element, (isectRect, SkRegion::kReplace_Op, doAA));
+ } else {
+ *initialState = kAllOut_InitialState;
+ }
+ return;
+ } else {
+ if (SkClipStack::kNormal_BoundsType == stackBoundsType) {
+ if (!SkRect::Intersects(stackBounds, queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ return;
+ }
+ } else {
+ if (stackBounds.contains(queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ return;
+ }
+ }
+ }
+
+ // walk backwards until we get to:
+ // a) the beginning
+ // b) an operation that is known to make the bounds all inside/outside
+ // c) a replace operation
+
+ static const InitialState kUnknown_InitialState = static_cast<InitialState>(-1);
+ *initialState = kUnknown_InitialState;
+
+ // During our backwards walk, track whether we've seen ops that either grow or shrink the clip.
+ // TODO: track these per saved clip so that we can consider them on the forward pass.
+ bool embiggens = false;
+ bool emsmallens = false;
+
+ SkClipStack::Iter iter(stack, SkClipStack::Iter::kTop_IterStart);
+ while ((kUnknown_InitialState == *initialState)) {
+ const Element* element = iter.prev();
+ if (NULL == element) {
+ *initialState = kAllIn_InitialState;
+ break;
+ }
+ if (SkClipStack::kEmptyGenID == element->getGenID()) {
+ *initialState = kAllOut_InitialState;
+ break;
+ }
+ if (SkClipStack::kWideOpenGenID == element->getGenID()) {
+ *initialState = kAllIn_InitialState;
+ break;
+ }
+
+ bool skippable = false;
+ bool isFlip = false; // does this op just flip the in/out state of every point in the bounds
+
+ switch (element->getOp()) {
+ case SkRegion::kDifference_Op:
+ // check if the shape subtracted either contains the entire bounds (and makes
+ // the clip empty) or is outside the bounds and therefore can be skipped.
+ if (element->isInverseFilled()) {
+ if (element->contains(queryBounds)) {
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ }
+ } else {
+ if (element->contains(queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ skippable = true;
+ }
+ }
+ if (!skippable) {
+ emsmallens = true;
+ }
+ break;
+ case SkRegion::kIntersect_Op:
+ // check if the shape intersected contains the entire bounds and therefore can
+ // be skipped or it is outside the entire bounds and therefore makes the clip
+ // empty.
+ if (element->isInverseFilled()) {
+ if (element->contains(queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ skippable = true;
+ }
+ } else {
+ if (element->contains(queryBounds)) {
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ }
+ }
+ if (!skippable) {
+ emsmallens = true;
+ }
+ break;
+ case SkRegion::kUnion_Op:
+ // If the union-ed shape contains the entire bounds then after this element
+ // the bounds is entirely inside the clip. If the union-ed shape is outside the
+ // bounds then this op can be skipped.
+ if (element->isInverseFilled()) {
+ if (element->contains(queryBounds)) {
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ *initialState = kAllIn_InitialState;
+ skippable = true;
+ }
+ } else {
+ if (element->contains(queryBounds)) {
+ *initialState = kAllIn_InitialState;
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ skippable = true;
+ }
+ }
+ if (!skippable) {
+ embiggens = true;
+ }
+ break;
+ case SkRegion::kXOR_Op:
+ // If the bounds is entirely inside the shape being xor-ed then the effect is
+ // to flip the inside/outside state of every point in the bounds. We may be
+ // able to take advantage of this in the forward pass. If the xor-ed shape
+ // doesn't intersect the bounds then it can be skipped.
+ if (element->isInverseFilled()) {
+ if (element->contains(queryBounds)) {
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ isFlip = true;
+ }
+ } else {
+ if (element->contains(queryBounds)) {
+ isFlip = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ skippable = true;
+ }
+ }
+ if (!skippable) {
+ emsmallens = embiggens = true;
+ }
+ break;
+ case SkRegion::kReverseDifference_Op:
+ // When the bounds is entirely within the rev-diff shape then this behaves like xor
+ // and reverses every point inside the bounds. If the shape is completely outside
+ // the bounds then we know after this element is applied that the bounds will be
+ // all outside the current clip.B
+ if (element->isInverseFilled()) {
+ if (element->contains(queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ isFlip = true;
+ }
+ } else {
+ if (element->contains(queryBounds)) {
+ isFlip = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ }
+ }
+ if (!skippable) {
+ emsmallens = embiggens = true;
+ }
+ break;
+ case SkRegion::kReplace_Op:
+ // Replace will always terminate our walk. We will either begin the forward walk
+ // at the replace op or detect here than the shape is either completely inside
+ // or completely outside the bounds. In this latter case it can be skipped by
+ // setting the correct value for initialState.
+ if (element->isInverseFilled()) {
+ if (element->contains(queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ *initialState = kAllIn_InitialState;
+ skippable = true;
+ }
+ } else {
+ if (element->contains(queryBounds)) {
+ *initialState = kAllIn_InitialState;
+ skippable = true;
+ } else if (!SkRect::Intersects(element->getBounds(), queryBounds)) {
+ *initialState = kAllOut_InitialState;
+ skippable = true;
+ }
+ }
+ if (!skippable) {
+ *initialState = kAllOut_InitialState;
+ embiggens = emsmallens = true;
+ }
+ break;
+ default:
+ SkDEBUGFAIL("Unexpected op.");
+ break;
+ }
+ if (!skippable) {
+ // if it is a flip, change it to a bounds-filling rect
+ if (isFlip) {
+ SkASSERT(SkRegion::kXOR_Op == element->getOp() ||
+ SkRegion::kReverseDifference_Op == element->getOp());
+ SkNEW_INSERT_AT_LLIST_HEAD(result,
+ Element,
+ (queryBounds, SkRegion::kReverseDifference_Op, false));
+ } else {
+ result->addToHead(*element);
+ }
+ }
+ }
+
+ if ((kAllOut_InitialState == *initialState && !embiggens) ||
+ (kAllIn_InitialState == *initialState && !emsmallens)) {
+ result->reset();
+ } else {
+ int clipsToSkip = 0;
+ Element* element = result->headIter().get();
+ while (NULL != element) {
+ bool skippable = false;
+ switch (element->getOp()) {
+ case SkRegion::kDifference_Op:
+ // subtracting from the empty set yields the empty set.
+ skippable = kAllOut_InitialState == *initialState;
+ break;
+ case SkRegion::kIntersect_Op:
+ // intersecting with the empty set yields the empty set
+ skippable = kAllOut_InitialState == *initialState;
+ break;
+ case SkRegion::kUnion_Op:
+ if (kAllIn_InitialState == *initialState) {
+ // unioning the infinite plane with anything is a no-op.
+ skippable = true;
+ } else {
+ // unioning the empty set with a shape is the shape.
+ element->setOp(SkRegion::kReplace_Op);
+ }
+ break;
+ case SkRegion::kXOR_Op:
+ if (kAllOut_InitialState == *initialState) {
+ // xor could be changed to diff in the kAllIn case, not sure it's a win.
+ element->setOp(SkRegion::kReplace_Op);
+ }
+ break;
+ case SkRegion::kReverseDifference_Op:
+ if (kAllIn_InitialState == *initialState) {
+ // subtracting the whole plane will yield the empty set.
+ skippable = true;
+ *initialState = kAllOut_InitialState;
+ } else {
+ // this picks up flips inserted in the backwards pass.
+ skippable = element->isInverseFilled() ?
+ !SkRect::Intersects(element->getBounds(), queryBounds) :
+ element->contains(queryBounds);
+ if (skippable) {
+ *initialState = kAllIn_InitialState;
+ } else {
+ element->setOp(SkRegion::kReplace_Op);
+ }
+ }
+ break;
+ case SkRegion::kReplace_Op:
+ SkASSERT(!clipsToSkip); // replace should always be the first op
+ skippable = false; // we would have skipped it in the backwards walk if we
+ // could've.
+ break;
+ default:
+ SkDEBUGFAIL("Unexpected op.");
+ break;
+ }
+ if (!skippable) {
+ break;
+ } else {
+ result->popHead();
+ element = result->headIter().get();
+ }
+ }
+ }
+}
+} // namespace GrReducedClip