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 94 matching lines @@
     m_scopeStack.append(m_nextScope++);
     beginSkippingCache();
 }
 
 void DisplayItemList::endScope()
 {
     m_scopeStack.removeLast();
     endSkippingCache();
 }
 
 void DisplayItemList::invalidate(DisplayItemClient client)

[chrishtr, 2015/08/28 17:10:47]

Don't you also want to invalidate the paint offset here? This will handle
invalidation types that are not changes of paint offset.

 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
     // Can only be called during layout/paintInvalidation, not during painting.
     ASSERT(m_newDisplayItems.isEmpty());
     updateValidlyCachedClientsIfNeeded();
     m_validlyCachedClients.remove(client);
 }
 
 void DisplayItemList::invalidateAll()
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
     // Can only be called during layout/paintInvalidation, not during painting.
     ASSERT(m_newDisplayItems.isEmpty());
     m_currentDisplayItems.clear();
     m_validlyCachedClients.clear();
     m_validlyCachedClientsDirty = false;
 }
 
 bool DisplayItemList::clientCacheIsValid(DisplayItemClient client) const
 {
     if (skippingCache())
         return false;
     updateValidlyCachedClientsIfNeeded();
     return m_validlyCachedClients.contains(client);
 }
 
+void DisplayItemList::invalidatePaintOffset(DisplayItemClient client)
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+
+    updateValidlyCachedClientsIfNeeded();
+    m_validlyCachedClients.remove(client);
+
+#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
+
+void DisplayItemList::recordPaintOffset(DisplayItemClient client, const LayoutPoint& paintOffset)
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+    m_previousPaintOffsets.set(client, paintOffset);
+}
+
+bool DisplayItemList::paintOffsetWasRecorded(DisplayItemClient client, const LayoutPoint& paintOffset) const

[chrishtr, 2015/08/28 17:10:47]

This name doesn't seem quite right. Shouldn't it be paintOffsetIsUnchanged?

+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+    PreviousPaintOffsets::const_iterator it = m_previousPaintOffsets.find(client);
+    if (it == m_previousPaintOffsets.end())
+        return false;
+    return paintOffset == it->value;
+}
+
+void DisplayItemList::removeUnneededPaintOffsetEntries()
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+
+    // This function is only needed temporarily while paint offsets are stored
+    // in a map on the list itself. Because we don't always get notified when
+    // a display item client is removed, we need to infer it to prevent the
+    // paint offset map from growing indefinitely. This is achieved by just
+    // removing any paint offset clients that are no longer in the full list.
+
+    HashSet<DisplayItemClient> paintOffsetClientsToRemove;
+    for (auto& client : m_previousPaintOffsets.keys())
+        paintOffsetClientsToRemove.add(client);
+    for (auto& item : m_currentDisplayItems)
+        paintOffsetClientsToRemove.remove(item.client());
+
+    for (auto& client : paintOffsetClientsToRemove)
+        m_previousPaintOffsets.remove(client);
+}
+
 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 95 matching lines @@
 #endif
 
     if (m_currentDisplayItems.isEmpty()) {
 #if ENABLE(ASSERT)
         for (const auto& item : m_newDisplayItems)
             ASSERT(!item.isCached());
 #endif
         m_currentDisplayItems.swap(m_newDisplayItems);
         m_validlyCachedClientsDirty = true;
         m_numCachedItems = 0;
+        if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
+            removeUnneededPaintOffsetEntries();
         return;
     }
 
     updateValidlyCachedClientsIfNeeded();
 
     // Stores indices to valid DrawingDisplayItems in m_currentDisplayItems that have not been matched
     // by CachedDisplayItems during synchronized matching. The indexed items will be matched
     // by later out-of-order CachedDisplayItems in m_newDisplayItems. This ensures that when
     // out-of-order CachedDisplayItems occur, we only traverse at most once over m_currentDisplayItems
     // looking for potential matches. Thus we can ensure that the algorithm runs in linear time.
@@ skipping 19 matching lines @@
     for (DisplayItems::iterator newIt = m_newDisplayItems.begin(); newIt != m_newDisplayItems.end(); ++newIt) {
         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(clientCacheIsValid(newDisplayItem.client()) || (RuntimeEnabledFeatures::slimmingPaintV2Enabled() && !paintOffsetWasInvalidated(newDisplayItem.client())));
             if (!isSynchronized) {
                 currentIt = findOutOfOrderCachedItem(currentIt, newDisplayItemId, outOfOrderIndexContext);
 
                 if (currentIt == currentEnd) {
 #ifndef NDEBUG
                     showDebugData();
                     WTFLogAlways("%s not found in m_currentDisplayItems\n", newDisplayItem.asDebugString().utf8().data());
 #endif
                     ASSERT_NOT_REACHED();
                     // We did not find the cached display item. This should be impossible, but may occur if there is a bug
                     // in the system, such as under-invalidation, incorrect cache checking or duplicate display ids.
                     // In this case, attempt to recover rather than crashing or bailing on display of the rest of the display list.
                     continue;
                 }
             }
 
             if (newDisplayItem.isCachedDrawing()) {
                 updatedList.appendByMoving(*currentIt, currentIt->derivedSize());
                 ++currentIt;
             } else {
                 ASSERT(newDisplayItem.type() == DisplayItem::CachedSubsequence);
                 copyCachedSubsequence(currentIt, updatedList);
                 ASSERT(updatedList.last().type() == DisplayItem::EndSubsequence);
             }
         } 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 (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
+        removeUnneededPaintOffsetEntries();
+
+#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