Use path intersection instead of saveLayer+mesh to mask projected ripples

bug:14297149

SaveLayer's performance cost is high, and proportional to the surface
being projected onto. Since ripples (even unbounded ones) are now
always projected to the arbitrary background content behind them, this
cost is especially important to avoid.

This removes the last semi-secret, saveLayer from the projected
ripple implementation.

Also fixes the HW test app to correctly demonstrate this projection
masking behavior.

Additionaly, alters PathTessellator to gracefully handle
counter-clockwise paths, and simplifies the work done by
ShadowTessellator to ensure all of its paths are counterclockwise.

Change-Id: Ibe9e12812bd10a774e20b1d444a140c368cbba8c

1 files changed, 42 insertions, 0 deletions

diff --git a/libs/hwui/Snapshot.cpp b/libs/hwui/Snapshot.cpp
index 9e7faee69fba..beb2e1d0481c 100644
--- a/libs/hwui/Snapshot.cpp
+++ b/libs/hwui/Snapshot.cpp
@@ -36,6 +36,7 @@ Snapshot::Snapshot()
         , empty(false)
         , alpha(1.0f)
         , roundRectClipState(nullptr)
+        , projectionPathMask(nullptr)
         , mClipArea(&mClipAreaRoot) {
     transform = &mTransformRoot;
     region = nullptr;
@@ -54,6 +55,7 @@ Snapshot::Snapshot(const sp<Snapshot>& s, int saveFlags)
         , empty(false)
         , alpha(s->alpha)
         , roundRectClipState(s->roundRectClipState)
+        , projectionPathMask(s->projectionPathMask)
         , mClipArea(nullptr)
         , mViewportData(s->mViewportData)
         , mRelativeLightCenter(s->mRelativeLightCenter) {
@@ -141,6 +143,34 @@ void Snapshot::resetTransform(float x, float y, float z) {
     transform->loadTranslate(x, y, z);
 }
 
+void Snapshot::buildScreenSpaceTransform(Matrix4* outTransform) const {
+    // build (reverse ordered) list of the stack of snapshots, terminated with a NULL
+    Vector<const Snapshot*> snapshotList;
+    snapshotList.push(nullptr);
+    const Snapshot* current = this;
+    do {
+        snapshotList.push(current);
+        current = current->previous.get();
+    } while (current);
+
+    // traverse the list, adding in each transform that contributes to the total transform
+    outTransform->loadIdentity();
+    for (size_t i = snapshotList.size() - 1; i > 0; i--) {
+        // iterate down the stack
+        const Snapshot* current = snapshotList[i];
+        const Snapshot* next = snapshotList[i - 1];
+        if (current->flags & kFlagIsFboLayer) {
+            // if we've hit a layer, translate by the layer's draw offset
+            outTransform->translate(current->layer->layer.left, current->layer->layer.top);
+        }
+        if (!next || (next->flags & kFlagIsFboLayer)) {
+            // if this snapshot is last, or if this snapshot is last before an
+            // FBO layer (which reset the transform), apply it
+            outTransform->multiply(*(current->transform));
+        }
+    }
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Clipping round rect
 ///////////////////////////////////////////////////////////////////////////////
@@ -191,6 +221,18 @@ void Snapshot::setClippingRoundRect(LinearAllocator& allocator, const Rect& boun
     roundRectClipState = state;
 }
 
+void Snapshot::setProjectionPathMask(LinearAllocator& allocator, const SkPath* path) {
+    if (path) {
+        ProjectionPathMask* mask = new (allocator) ProjectionPathMask;
+        mask->projectionMask = path;
+        buildScreenSpaceTransform(&(mask->projectionMaskTransform));
+
+        projectionPathMask = mask;
+    } else {
+        projectionPathMask = nullptr;
+    }
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Queries
 ///////////////////////////////////////////////////////////////////////////////