Culling API

src/core/SkPictureRecord.cpp

Index: src/core/SkPictureRecord.cpp
diff --git a/src/core/SkPictureRecord.cpp b/src/core/SkPictureRecord.cpp
index 042e6a39cb9602bf929b8cfaed6e7bbd57c5353a..5b6461084c9c8afe8d463a1933d52d504c7ca1ef 100644
--- a/src/core/SkPictureRecord.cpp
+++ b/src/core/SkPictureRecord.cpp
@@ -76,6 +76,8 @@ static inline uint32_t getPaintOffset(DrawType op, uint32_t opSize) {
         0,  // CLIP_REGION - no paint
         0,  // CLIP_RECT - no paint
         0,  // CLIP_RRECT - no paint
+        0,  // PUSH_CULL - no paint
+        0,  // POP_CULL - no paint
         0,  // CONCAT - no paint
         1,  // DRAW_BITMAP - right after op code
         1,  // DRAW_BITMAP_MATRIX - right after op code
@@ -1530,6 +1532,60 @@ void SkPictureRecord::endCommentGroup() {
     this->validate(initialOffset, size);
 }
 
+// [op/size] [rect] [skip offset]
+static const uint32_t kPushCullOpSize = 2 * kUInt32Size + sizeof(SkRect);
+void SkPictureRecord::onPushCull(const SkRect& cullRect) {
+    // Skip identical cull rects.
+    if (!fCullOffsetStack.isEmpty()) {
+        const SkRect& prevCull = fWriter.readTAt<SkRect>(fCullOffsetStack.top() - sizeof(SkRect));
+        if (prevCull == cullRect) {
+            // Skipped culls are tracked on the stack, but they point to the previous offset.
+            fCullOffsetStack.push(fCullOffsetStack.top());
+            return;
+        }
+    }
+
+    uint32_t size = kPushCullOpSize;
+    size_t initialOffset = this->addDraw(PUSH_CULL, &size);
+    // PUSH_CULL's size should stay constant (used to rewind).
+    SkASSERT(size == kPushCullOpSize);
+
+    addRect(cullRect);
+    fCullOffsetStack.push(fWriter.bytesWritten());
+    addInt(0);
+    this->validate(initialOffset, size);
+}
+
+void SkPictureRecord::onPopCull() {
+    SkASSERT(!fCullOffsetStack.isEmpty());
+
+    uint32_t cullSkipOffset = fCullOffsetStack.top();
+    fCullOffsetStack.pop();
+
+    // Skipped push, do the same for pop.
+    if (!fCullOffsetStack.isEmpty() && cullSkipOffset == fCullOffsetStack.top()) {
+        return;
+    }
+
+    // Collapse empty push/pop pairs.
+    if ((size_t)(cullSkipOffset + kUInt32Size) == fWriter.bytesWritten()) {
+        SkASSERT(fWriter.bytesWritten() >= kPushCullOpSize);
+        SkASSERT(fWriter.readTAt<uint32_t>(
+                     fWriter.bytesWritten() - kPushCullOpSize) >> 24 == PUSH_CULL);
+        fWriter.rewindToOffset(fWriter.bytesWritten() - kPushCullOpSize);
+        return;
+    }
+
+    // op only
+    uint32_t size = kUInt32Size;
+    size_t initialOffset = this->addDraw(POP_CULL, &size);
+
+    // update the cull skip offset to point past this op.
+    fWriter.overwriteTAt<uint32_t>(cullSkipOffset, fWriter.bytesWritten());
+
+    this->validate(initialOffset, size);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 SkSurface* SkPictureRecord::onNewSurface(const SkImageInfo& info) {