Implement a paint offset cache for slimming paint v2

Source/platform/graphics/paint/DisplayItemList.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "platform/graphics/paint/DisplayItemList.h"
 
 #include "platform/NotImplemented.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/TraceEvent.h"
@@ skipping 121 matching lines @@
 }
 
 bool DisplayItemList::clientCacheIsValid(DisplayItemClient client) const
 {
     if (skippingCache())
         return false;
     updateValidlyCachedClientsIfNeeded();
     return m_validlyCachedClients.contains(client);
 }
 
+void DisplayItemList::invalidatePaintOffset(DisplayItemClient client)
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+
+    m_validlyCachedClients.remove(client);

[Stephen Chennney, 2015/08/27 17:25:41]

My understanding was that the SkPicture did not need to be re-recorded for paint
offset changes. Am I wrong? Am I right but we're not supporting it yet? Is
something else going on?

[pdr., 2015/08/28 03:31:41]

You're thinking along the right lines for sure, this is just a tricky case.

We're just going to use the cache to catch invalidations we may have missed,
instead of optimizing the pure-translation case for now. This is because
subpixel snapping throws a wrench in translations: we need to re-record the
drawing display item if the snapping would have changed. I'd like to revisit
pixel-aligned paintOffset changes as an optimization in the future though.

I've added this point to our doc under "considerations":
https://docs.google.com/document/d/1oY8P7a7G4W2LYOvT3VyqUNKOOek6S_e-jD2XjM_7g...

+
+#if ENABLE(ASSERT)
+    m_clientsWithPaintOffsetInvalidations.add(client);
+
+    // Ensure no phases slipped in using the old paint offset which would indicate
+    // different phases used different paint offsets, which should not happen.
+    for (const auto& item : m_newDisplayItems)
+        ASSERT(!item.isCached() || item.client() != client);
+#endif
+}
+
+#if ENABLE(ASSERT)
+bool DisplayItemList::paintOffsetWasInvalidated(DisplayItemClient client) const
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+    return m_clientsWithPaintOffsetInvalidations.contains(client);
+}
+#endif
+
 size_t DisplayItemList::findMatchingItemFromIndex(const DisplayItem::Id& id, const DisplayItemIndicesByClientMap& displayItemIndicesByClient, const DisplayItems& list)
 {
     DisplayItemIndicesByClientMap::const_iterator it = displayItemIndicesByClient.find(id.client);
     if (it == displayItemIndicesByClient.end())
         return kNotFound;
 
     const Vector<size_t>& indices = it->value;
     for (size_t index : indices) {
         const DisplayItem& existingItem = list[index];
         ASSERT(!existingItem.isValid() || existingItem.client() == id.client);
@@ skipping 135 matching lines @@
         const DisplayItem& newDisplayItem = *newIt;
         const DisplayItem::Id newDisplayItemId = newDisplayItem.nonCachedId();
         bool newDisplayItemHasCachedType = newDisplayItem.type() != newDisplayItemId.type;
 
         bool isSynchronized = currentIt != currentEnd && newDisplayItemId.matches(*currentIt);
 
         if (newDisplayItemHasCachedType) {
             ASSERT(!RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled());
             ASSERT(newDisplayItem.isCached());
             ASSERT(clientCacheIsValid(newDisplayItem.client()));
+            ASSERT(!RuntimeEnabledFeatures::slimmingPaintV2Enabled() || !paintOffsetWasInvalidated(newDisplayItem.client()));
             if (!isSynchronized) {
                 DisplayItems::iterator foundIt = findOutOfOrderCachedItem(currentIt, newDisplayItemId, outOfOrderIndexContext);
 
                 if (foundIt == currentEnd) {
 #ifndef NDEBUG
                     showDebugData();
                     WTFLogAlways("%s not found in m_currentDisplayItems\n", newDisplayItem.asDebugString().utf8().data());
 #endif
                     ASSERT_NOT_REACHED();
 
@@ skipping 10 matching lines @@
             if (newDisplayItem.isCachedDrawing()) {
                 updatedList.appendByMoving(*currentIt, currentIt->derivedSize());
                 ++currentIt;
             } else {
                 ASSERT(newDisplayItem.isCachedSubtree());
                 copyCachedSubtree(currentIt, updatedList);
                 ASSERT(updatedList.last().isEndSubtree());
             }
         } else {
 #if ENABLE(ASSERT)
-            if (RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled())
+            if (RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled()) {
                 checkCachedDisplayItemIsUnchanged(newDisplayItem, outOfOrderIndexContext.displayItemIndicesByClient);
-            else
-                ASSERT(!newDisplayItem.isDrawing() || newDisplayItem.skippedCache() || !clientCacheIsValid(newDisplayItem.client()));
-#endif // ENABLE(ASSERT)
+            } else {
+                ASSERT(!newDisplayItem.isDrawing()
+                    || newDisplayItem.skippedCache()
+                    || !clientCacheIsValid(newDisplayItem.client())
+                    || (RuntimeEnabledFeatures::slimmingPaintV2Enabled() && paintOffsetWasInvalidated(newDisplayItem.client())));
+            }
+#endif
             updatedList.appendByMoving(*newIt, newIt->derivedSize());
 
             if (isSynchronized)
                 ++currentIt;
         }
     }
 
 #if ENABLE(ASSERT)
     if (RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled())
         checkNoRemainingCachedDisplayItems();
 #endif // ENABLE(ASSERT)
 
     m_newDisplayItems.clear();
     m_validlyCachedClientsDirty = true;
     m_currentDisplayItems.swap(updatedList);
     m_numCachedItems = 0;
+
+#if ENABLE(ASSERT)
+    m_clientsWithPaintOffsetInvalidations.clear();
+#endif
 }
 
 size_t DisplayItemList::approximateUnsharedMemoryUsage() const
 {
     size_t memoryUsage = sizeof(*this);
 
     // Memory outside this class due to m_currentDisplayItems.
     memoryUsage += m_currentDisplayItems.memoryUsageInBytes();
 
     // TODO(jbroman): If display items begin to have significant external memory
@@ skipping 187 matching lines @@
 
 void DisplayItemList::replay(GraphicsContext& context)
 {
     TRACE_EVENT0("blink,benchmark", "DisplayItemList::replay");
     ASSERT(m_newDisplayItems.isEmpty());
     for (DisplayItem& displayItem : m_currentDisplayItems)
         displayItem.replay(context);
 }
 
 } // namespace blink