add inherit-from-root-transform flag (for fixed-positioning)

git-svn-id: http://skia.googlecode.com/svn/trunk@532 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 53 insertions, 23 deletions

diff --git a/include/utils/SkLayer.h b/include/utils/SkLayer.h
index c8dea484dd..c42261f808 100644
--- a/include/utils/SkLayer.h
+++ b/include/utils/SkLayer.h
@@ -34,6 +34,7 @@ public:
     SkLayer(const SkLayer&);
     virtual ~SkLayer();
 
+    bool isInheritFromRootTransform() const;
     SkScalar getOpacity() const { return m_opacity; }
     const SkSize& getSize() const { return m_size; }
     const SkPoint& getPosition() const { return m_position; }
@@ -44,6 +45,7 @@ public:
     SkScalar getWidth() const { return m_size.width(); }
     SkScalar getHeight() const { return m_size.height(); }
 
+    void setInheritFromRootTransform(bool);
     void setOpacity(SkScalar opacity) { m_opacity = opacity; }
     void setSize(SkScalar w, SkScalar h) { m_size.set(w, h); }
     void setPosition(SkScalar x, SkScalar y) { m_position.set(x, y); }
@@ -68,10 +70,10 @@ public:
      */
     SkLayer* addChild(SkLayer* child);
 
-    /** Remove this layer from our child list, and unref() it and return true.
-        If it is not in our child list, do nothing and return false.
+    /** Remove this layer from its parent's list (or do nothing if it has no
+        parent.) If it had a parent, then unref() is called.
      */
-    bool removeChild(SkLayer* child);
+    void detachFromParent();
 
     /** Remove, and unref(), all of the layers in our child list.
      */
@@ -112,6 +114,10 @@ protected:
     virtual void onDraw(SkCanvas*, SkScalar opacity);
 
 private:
+    enum Flags {
+        kInheritFromRootTransform_Flag = 0x01
+    };
+
     SkLayer*    fParent;
     SkScalar    m_opacity;
     SkSize      m_size;
@@ -119,6 +125,7 @@ private:
     SkPoint     m_anchorPoint;
     SkMatrix    fMatrix;
     SkMatrix    fChildrenMatrix;
+    uint32_t    fFlags;
 
     SkTDArray<SkLayer*> m_children;
 };
diff --git a/src/utils/SkLayer.cpp b/src/utils/SkLayer.cpp
index 888afec99e..5c68261bc8 100644
--- a/src/utils/SkLayer.cpp
+++ b/src/utils/SkLayer.cpp
@@ -19,6 +19,7 @@ SkLayer::SkLayer() {
 
     fMatrix.reset();
     fChildrenMatrix.reset();
+    fFlags = 0;
 
 #ifdef DEBUG_TRACK_NEW_DELETE
     gLayerAllocCount += 1;
@@ -35,6 +36,7 @@ SkLayer::SkLayer(const SkLayer& src) {
 
     fMatrix = src.fMatrix;
     fChildrenMatrix = src.fChildrenMatrix;
+    fFlags = src.fFlags;
 
 #ifdef DEBUG_TRACK_NEW_DELETE
     gLayerAllocCount += 1;
@@ -53,6 +55,18 @@ SkLayer::~SkLayer() {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+bool SkLayer::isInheritFromRootTransform() const {
+    return (fFlags & kInheritFromRootTransform_Flag) != 0;
+}
+
+void SkLayer::setInheritFromRootTransform(bool doInherit) {
+    if (doInherit) {
+        fFlags |= kInheritFromRootTransform_Flag;
+    } else {
+        fFlags &= ~kInheritFromRootTransform_Flag;
+    }
+}
+
 void SkLayer::setMatrix(const SkMatrix& matrix) {
     fMatrix = matrix;
 }
@@ -69,16 +83,16 @@ int SkLayer::countChildren() const {
 
 SkLayer* SkLayer::getChild(int index) const {
     if ((unsigned)index < (unsigned)m_children.count()) {
+        SkASSERT(m_children[index]->fParent == this);
         return m_children[index];
     }
     return NULL;
 }
 
 SkLayer* SkLayer::addChild(SkLayer* child) {
+    SkASSERT(this != child);
     child->ref();
-    if (child->fParent) {
-        child->fParent->removeChild(child);
-    }
+    child->detachFromParent();
     SkASSERT(child->fParent == NULL);
     child->fParent = this;
 
@@ -86,20 +100,24 @@ SkLayer* SkLayer::addChild(SkLayer* child) {
     return child;
 }
 
-bool SkLayer::removeChild(SkLayer* child) {
-    int index = m_children.find(child);
-    if (index >= 0) {
-        SkASSERT(child->fParent == this);
-        child->fParent = NULL;
-        child->unref();
-        m_children.remove(index);
-        return true;
+void SkLayer::detachFromParent() {
+    if (fParent) {
+        int index = fParent->m_children.find(this);
+        SkASSERT(index >= 0);
+        fParent->m_children.remove(index);
+        fParent = NULL;
+        this->unref();  // this call might delete us
     }
-    return false;
 }
 
 void SkLayer::removeChildren() {
-    m_children.unrefAll();
+    int count = m_children.count();
+    for (int i = 0; i < count; i++) {
+        SkLayer* child = m_children[i];
+        SkASSERT(child->fParent == this);
+        child->fParent = NULL;  // in case it has more than one owner
+        child->unref();
+    }
     m_children.reset();
 }
 
@@ -126,6 +144,11 @@ void SkLayer::getLocalTransform(SkMatrix* matrix) const {
 void SkLayer::localToGlobal(SkMatrix* matrix) const {
     this->getLocalTransform(matrix);
 
+    if (this->isInheritFromRootTransform()) {
+        matrix->postConcat(this->getRootLayer()->getMatrix());
+        return;
+    }
+
     const SkLayer* layer = this;
     while (layer->fParent != NULL) {
         layer = layer->fParent;
@@ -165,13 +188,13 @@ void SkLayer::draw(SkCanvas* canvas, SkScalar opacity) {
 
     // apply our local transform
     {
-        canvas->translate(m_position.fX, m_position.fY);
-        
-        SkScalar tx = SkScalarMul(m_anchorPoint.fX, m_size.width());
-        SkScalar ty = SkScalarMul(m_anchorPoint.fY, m_size.height());
-        canvas->translate(tx, ty);
-        canvas->concat(this->getMatrix());
-        canvas->translate(-tx, -ty);
+        SkMatrix tmp;
+        this->getLocalTransform(&tmp);
+        if (this->isInheritFromRootTransform()) {
+            // should we also apply the root's childrenMatrix?
+            canvas->setMatrix(getRootLayer()->getMatrix());
+        }
+        canvas->concat(tmp);
     }
 
     this->onDraw(canvas, opacity);