Blink-side contiguous allocation of display items.

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 10 matching lines @@
 #include "platform/graphics/LoggingCanvas.h"
 #include "wtf/text/StringBuilder.h"
 #include <stdio.h>
 #endif
 
 namespace blink {
 
 const DisplayItems& DisplayItemList::displayItems() const
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
-    ASSERT(m_newDisplayItems.isEmpty());
+    ASSERT(m_newDisplayItems.empty());
     return m_currentDisplayItems;
 }
 
 bool DisplayItemList::lastDisplayItemIsNoopBegin() const
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
-    if (m_newDisplayItems.isEmpty())
+    if (m_newDisplayItems.empty())
         return false;
 
-    const auto& lastDisplayItem = m_newDisplayItems.last();
+    const auto& lastDisplayItem = *m_newDisplayItems.back();
     return lastDisplayItem.isBegin() && !lastDisplayItem.drawsContent();
 }
 
 void DisplayItemList::removeLastDisplayItem()
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
-    if (m_newDisplayItems.isEmpty())
+    if (m_newDisplayItems.empty())
         return;
 
 #if ENABLE(ASSERT)
     // Also remove the index pointing to the removed display item.
-    DisplayItemIndicesByClientMap::iterator it = m_newDisplayItemIndicesByClient.find(m_newDisplayItems.last().client());
+    DisplayItemIndicesByClientMap::iterator it = m_newDisplayItemIndicesByClient.find(m_newDisplayItems.back()->client());
     if (it != m_newDisplayItemIndicesByClient.end()) {
         Vector<size_t>& indices = it->value;
         if (!indices.isEmpty() && indices.last() == (m_newDisplayItems.size() - 1))
             indices.removeLast();
     }
 #endif
     m_newDisplayItems.removeLast();
 }
 
-void DisplayItemList::add(WTF::PassOwnPtr<DisplayItem> displayItem)
+void DisplayItemList::processNewItem(DisplayItem* displayItem)
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
     ASSERT(!m_constructionDisabled);
     ASSERT(!skippingCache() || !displayItem->isCached());
 
     if (DisplayItem::isCachedType(displayItem->type()))
         ++m_numCachedItems;
 
 #if ENABLE(ASSERT)
     // Verify noop begin/end pairs have been removed.
-    if (!m_newDisplayItems.isEmpty() && m_newDisplayItems.last().isBegin() && !m_newDisplayItems.last().drawsContent())
-        ASSERT(!displayItem->isEndAndPairedWith(m_newDisplayItems.last().type()));
+    if (m_newDisplayItems.size() >= 2 && displayItem->isEnd()) {
+        const auto& beginDisplayItem = *m_newDisplayItems.elementAt(m_newDisplayItems.size() - 2);
+        if (beginDisplayItem.isBegin() && !beginDisplayItem.drawsContent())
+            ASSERT(!displayItem->isEndAndPairedWith(beginDisplayItem.type()));
+    }
 #endif
 
     if (!m_scopeStack.isEmpty())
         displayItem->setScope(m_scopeStack.last().id, m_scopeStack.last().client);
 
 #if ENABLE(ASSERT)
     size_t index = findMatchingItemFromIndex(displayItem->id(), displayItem->type(), m_newDisplayItemIndicesByClient, m_newDisplayItems);
     if (index != kNotFound) {
 #ifndef NDEBUG
         showDebugData();
         WTFLogAlways("DisplayItem %s has duplicated id with previous %s (index=%d)\n",
-            displayItem->asDebugString().utf8().data(), m_newDisplayItems[index].asDebugString().utf8().data(), static_cast<int>(index));
+            displayItem->asDebugString().utf8().data(), m_newDisplayItems.elementAt(index)->asDebugString().utf8().data(), static_cast<int>(index));
 #endif
         ASSERT_NOT_REACHED();
     }
-    addItemToIndex(displayItem->client(), displayItem->type(), m_newDisplayItems.size(), m_newDisplayItemIndicesByClient);
+    addItemToIndex(displayItem->client(), displayItem->type(), m_newDisplayItems.size() - 1, m_newDisplayItemIndicesByClient);
 #endif // ENABLE(ASSERT)
 
     ASSERT(!displayItem->skippedCache()); // Only DisplayItemList can set the flag.
     if (skippingCache())
         displayItem->setSkippedCache();
-
-    m_newDisplayItems.append(displayItem);
 }
 
 void DisplayItemList::beginScope(DisplayItemClient client)
 {
     ClientScopeIdMap::iterator it = m_clientScopeIdMap.find(client);
     int scopeId;
     if (it == m_clientScopeIdMap.end()) {
         m_clientScopeIdMap.add(client, 0);
         scopeId = 0;
     } else {
         scopeId = ++it->value;
     }
     m_scopeStack.append(Scope(client, scopeId));
     beginSkippingCache();
 }
 
 void DisplayItemList::endScope(DisplayItemClient client)
 {
     m_scopeStack.removeLast();
     endSkippingCache();
 }
 
 void DisplayItemList::invalidate(DisplayItemClient client)
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
     // Can only be called during layout/paintInvalidation, not during painting.
-    ASSERT(m_newDisplayItems.isEmpty());
+    ASSERT(m_newDisplayItems.empty());
     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());
+    ASSERT(m_newDisplayItems.empty());
     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);
 }
 
 size_t DisplayItemList::findMatchingItemFromIndex(const DisplayItem::Id& id, DisplayItem::Type matchingType, 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) {
-        DisplayItems::ItemHandle existingItem = list[index];
-        ASSERT(existingItem.isGone() || existingItem.client() == id.client);
-        if (!existingItem.isGone() && existingItem.id().equalToExceptForType(id, matchingType))
+        const DisplayItem& existingItem = *list.elementAt(index);

[danakj, 2015/06/30 18:49:01]

This is using elementAt() in non-assert code AFAICT, and in a loop :(

Is it possible to restructure code such that you hold pointers instead of
indicies or something? Pointers into a ListContainer are stable (as opposed to
pointers into a vector which are not)

[jbroman, 2015/06/30 18:59:17]

I'd suggest attempting this in a followup CL. I eliminated a bunch of these
instances when I refactored DisplayItems previously, but I'd left these then
because changing them involved changing a bunch of the caching code.

If this CL is already a perf win, then why not land the additional perf win
separately, if it's straightforward?

[pdr., 2015/06/30 22:16:06]

I added a TODO here and filed crbug.com/505965.

+        ASSERT(existingItem.ignoreFromDisplayList() || existingItem.client() == id.client);
+        if (!existingItem.ignoreFromDisplayList() && existingItem.id().equalToExceptForType(id, matchingType))
             return index;
     }
 
     return kNotFound;
 }
 
 void DisplayItemList::addItemToIndex(DisplayItemClient client, DisplayItem::Type type, size_t index, DisplayItemIndicesByClientMap& displayItemIndicesByClient)
 {
     // Only need to index DrawingDisplayItems and FIXME: BeginSubtreeDisplayItems.
     if (!DisplayItem::isDrawingType(type))
@@ skipping 15 matching lines @@
         return m_currentDisplayItems.iteratorAt(foundIndex);
 
     return findOutOfOrderCachedItemForward(currentIt, id, matchingType, displayItemIndicesByClient);
 }
 
 // Find forward for the item and index all skipped indexable items.
 DisplayItems::Iterator DisplayItemList::findOutOfOrderCachedItemForward(DisplayItems::Iterator currentIt, const DisplayItem::Id& id, DisplayItem::Type matchingType, DisplayItemIndicesByClientMap& displayItemIndicesByClient)
 {
     DisplayItems::Iterator currentEnd = m_currentDisplayItems.end();
     for (; currentIt != currentEnd; ++currentIt) {
-        DisplayItems::ItemHandle item = *currentIt;
-        if (!item.isGone()
+        const DisplayItem& item = **currentIt;
+        if (!item.ignoreFromDisplayList()
             && DisplayItem::isDrawingType(item.type())
             && m_validlyCachedClients.contains(item.client())) {
             if (item.id().equalToExceptForType(id, matchingType))
                 return currentIt;
 
-            size_t currentDisplayItemsIndex = m_currentDisplayItems.indexForIterator(currentIt);
-            addItemToIndex(item.client(), item.type(), currentDisplayItemsIndex, displayItemIndicesByClient);
+            addItemToIndex(item.client(), item.type(), currentIt.index(), displayItemIndicesByClient);
         }
     }
     return currentEnd;
 }
 
 // Update the existing display items by removing invalidated entries, updating
 // repainted ones, and appending new items.
 // - For CachedDisplayItem, copy the corresponding cached DrawingDisplayItem;
 // - FIXME: Re-enable SubtreeCachedDisplayItem:
 //   For SubtreeCachedDisplayItem, copy the cached display items between the
@@ skipping 10 matching lines @@
 
     // These data structures are used during painting only.
     m_clientScopeIdMap.clear();
     ASSERT(m_scopeStack.isEmpty());
     m_scopeStack.clear();
     ASSERT(!skippingCache());
 #if ENABLE(ASSERT)
     m_newDisplayItemIndicesByClient.clear();
 #endif
 
-    if (m_currentDisplayItems.isEmpty()) {
+    if (m_currentDisplayItems.empty()) {
 #if ENABLE(ASSERT)
-        for (auto& item : m_newDisplayItems) {
-            ASSERT(!DisplayItem::isCachedType(item.type())
-                && !DisplayItem::isSubtreeCachedType(item.type()));
+        for (const auto& item : m_newDisplayItems) {
+            ASSERT(!DisplayItem::isCachedType(item->type())
+                && !DisplayItem::isSubtreeCachedType(item->type()));
         }
 #endif
         m_currentDisplayItems.swap(m_newDisplayItems);
         m_validlyCachedClientsDirty = true;
         m_numCachedItems = 0;
         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.
     DisplayItemIndicesByClientMap displayItemIndicesByClient;
 
 #if ENABLE(ASSERT)
     if (RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled()) {
         // Under-invalidation checking requires a full index of m_currentDisplayItems.
         size_t i = 0;
         for (const auto& item : m_currentDisplayItems) {
-            addItemToIndex(item.client(), item.type(), i, displayItemIndicesByClient);
+            addItemToIndex(item->client(), item->type(), i, displayItemIndicesByClient);
             ++i;
         }
     }
 #endif // ENABLE(ASSERT)
 
-    DisplayItems updatedList;
+    DisplayItems updatedList(kMaximumDisplayItemSize, std::max(m_currentDisplayItems.size(), m_newDisplayItems.size()));
     DisplayItems::Iterator currentIt = m_currentDisplayItems.begin();
     DisplayItems::Iterator currentEnd = m_currentDisplayItems.end();
     for (DisplayItems::Iterator newIt = m_newDisplayItems.begin(); newIt != m_newDisplayItems.end(); ++newIt) {
-        DisplayItems::ItemHandle newDisplayItem = *newIt;
+        const DisplayItem& newDisplayItem = **newIt;
         DisplayItem::Type matchingType = newDisplayItem.type();
         if (DisplayItem::isCachedType(newDisplayItem.type()))
             matchingType = DisplayItem::cachedTypeToDrawingType(matchingType);
         bool isSynchronized = currentIt != currentEnd
-            && !currentIt->isGone()
+            && !currentIt->ignoreFromDisplayList()
             && currentIt->id().equalToExceptForType(newDisplayItem.id(), matchingType);
 
         if (DisplayItem::isCachedType(newDisplayItem.type())) {
             ASSERT(!RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled());
             ASSERT(clientCacheIsValid(newDisplayItem.client()));
             if (isSynchronized) {
-                updatedList.appendByMoving(currentIt);
+                updatedList.appendByMoving(*currentIt);
             } else {
                 DisplayItems::Iterator foundIt = findOutOfOrderCachedItem(currentIt, newDisplayItem.id(), matchingType, displayItemIndicesByClient);
                 isSynchronized = (foundIt == currentIt);
 
 #ifndef NDEBUG
                 if (foundIt == currentEnd) {
                     showDebugData();
                     WTFLogAlways("CachedDisplayItem %s not found in m_currentDisplayItems\n",
                         newDisplayItem.asDebugString().utf8().data());
                     ASSERT_NOT_REACHED();
                 }
 #endif
                 // If foundIt == currentEnd, it means that 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.
                 if (foundIt == currentEnd)
                     continue;
 
                 currentIt = foundIt;
 
-                updatedList.appendByMoving(foundIt);
+                updatedList.appendByMoving(*foundIt);
             }
         } else {
 #if ENABLE(ASSERT)
             if (RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled())
                 checkCachedDisplayItemIsUnchanged(newDisplayItem, displayItemIndicesByClient);
             else
                 ASSERT(!DisplayItem::isDrawingType(newDisplayItem.type()) || newDisplayItem.skippedCache() || !clientCacheIsValid(newDisplayItem.client()));
 #endif // ENABLE(ASSERT)
-            updatedList.appendByMoving(newIt);
+            updatedList.appendByMoving(*newIt);
         }
 
         if (isSynchronized)
             ++currentIt;
     }
 
 #if ENABLE(ASSERT)
     if (RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled())
         checkNoRemainingCachedDisplayItems();
 #endif // ENABLE(ASSERT)
 
     m_newDisplayItems.clear();
     m_validlyCachedClientsDirty = true;
-    m_currentDisplayItems.clear();
     m_currentDisplayItems.swap(updatedList);
     m_numCachedItems = 0;
 }
 
 void DisplayItemList::updateValidlyCachedClientsIfNeeded() const
 {
     if (!m_validlyCachedClientsDirty)
         return;
 
     m_validlyCachedClients.clear();
     m_validlyCachedClientsDirty = false;
 
     DisplayItemClient lastClient = nullptr;
     for (const auto& displayItem : m_currentDisplayItems) {
-        if (displayItem.client() == lastClient)
+        if (displayItem->client() == lastClient)
             continue;
-        lastClient = displayItem.client();
-        if (!displayItem.skippedCache())
+        lastClient = displayItem->client();
+        if (!displayItem->skippedCache())
             m_validlyCachedClients.add(lastClient);
     }
 }
 
 void DisplayItemList::commitNewDisplayItemsAndAppendToWebDisplayItemList(WebDisplayItemList* list)
 {
     commitNewDisplayItems();
-    for (auto& item : m_currentDisplayItems)
-        item.appendToWebDisplayItemList(list);
+    for (const auto& item : m_currentDisplayItems)
+        item->appendToWebDisplayItemList(list);
 }
 
 #if ENABLE(ASSERT)
 
-static void showUnderInvalidationError(const char* reason, const DisplayItems::ItemHandle& displayItem)
+static void showUnderInvalidationError(const char* reason, const DisplayItem& displayItem)
 {
 #ifndef NDEBUG
     WTFLogAlways("%s: %s\nSee http://crbug.com/450725.", reason, displayItem.asDebugString().utf8().data());
 #else
     WTFLogAlways("%s. Run debug build to get more details\nSee http://crbug.com/450725.", reason);
 #endif // NDEBUG
 }
 
 static bool bitmapIsAllZero(const SkBitmap& bitmap)
 {
     bitmap.lockPixels();
     bool result = true;
     for (int x = 0; result && x < bitmap.width(); ++x) {
         for (int y = 0; result && y < bitmap.height(); ++y) {
             if (SkColorSetA(bitmap.getColor(x, y), 0) != SK_ColorTRANSPARENT)
                 result = false;
         }
     }
     bitmap.unlockPixels();
     return result;
 }
 
-void DisplayItemList::checkCachedDisplayItemIsUnchanged(const DisplayItems::ItemHandle& displayItem, DisplayItemIndicesByClientMap& displayItemIndicesByClient)
+void DisplayItemList::checkCachedDisplayItemIsUnchanged(const DisplayItem& displayItem, DisplayItemIndicesByClientMap& displayItemIndicesByClient)
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled());
 
     if (!DisplayItem::isDrawingType(displayItem.type()) || displayItem.skippedCache() || !clientCacheIsValid(displayItem.client()))
         return;
 
     // If checking under-invalidation, we always generate new display item even if the client is not invalidated.
     // Checks if the new picture is the same as the cached old picture. If the new picture is different but
     // the client is not invalidated, issue error about under-invalidation.
     size_t index = findMatchingItemFromIndex(displayItem.id(), displayItem.type(), displayItemIndicesByClient, m_currentDisplayItems);
     if (index == kNotFound) {
         showUnderInvalidationError("ERROR: under-invalidation: no cached display item", displayItem);
         ASSERT_NOT_REACHED();
         return;
     }
 
     DisplayItems::Iterator foundItem = m_currentDisplayItems.iteratorAt(index);
-    RefPtr<const SkPicture> newPicture = displayItem.picture();
-    RefPtr<const SkPicture> oldPicture = foundItem->picture();
-    // Remove the display item from cache so that we can check if there are any remaining cached display items after merging.
-    m_currentDisplayItems.setGone(foundItem);
+    RefPtr<const SkPicture> newPicture = static_cast<const DrawingDisplayItem&>(displayItem).picture();
+    RefPtr<const SkPicture> oldPicture = static_cast<const DrawingDisplayItem*>(*foundItem)->picture();
+    // Mark the display item as ignored so that we can check if there are any remaining cached display items after merging.
+    foundItem->setIgnoredFromDisplayList();
 
     if (!newPicture && !oldPicture)
         return;
     if (newPicture && oldPicture) {
-        switch (displayItem.underInvalidationCheckingMode()) {
+        switch (static_cast<const DrawingDisplayItem&>(displayItem).underInvalidationCheckingMode()) {
         case DrawingDisplayItem::CheckPicture:
             if (newPicture->approximateOpCount() == oldPicture->approximateOpCount()) {
                 SkDynamicMemoryWStream newPictureSerialized;
                 newPicture->serialize(&newPictureSerialized);
                 SkDynamicMemoryWStream oldPictureSerialized;
                 oldPicture->serialize(&oldPictureSerialized);
 
                 if (newPictureSerialized.bytesWritten() == oldPictureSerialized.bytesWritten()) {
                     RefPtr<SkData> oldData = adoptRef(oldPictureSerialized.copyToData());
                     RefPtr<SkData> newData = adoptRef(newPictureSerialized.copyToData());
@@ skipping 30 matching lines @@
 #endif // NDEBUG
 
     ASSERT_NOT_REACHED();
 }
 
 void DisplayItemList::checkNoRemainingCachedDisplayItems()
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled());
 
     for (const auto& displayItem : m_currentDisplayItems) {
-        if (displayItem.isGone() || !DisplayItem::isDrawingType(displayItem.type()) || !clientCacheIsValid(displayItem.client()))
+        if (displayItem->ignoreFromDisplayList() || !DisplayItem::isDrawingType(displayItem->type()) || !clientCacheIsValid(displayItem->client()))
             continue;
-        showUnderInvalidationError("May be under-invalidation: no new display item", displayItem);
+        showUnderInvalidationError("May be under-invalidation: no new display item", *displayItem);
     }
 }
 
 #endif // ENABLE(ASSERT)
 
 #ifndef NDEBUG
 
 WTF::String DisplayItemList::displayItemsAsDebugString(const DisplayItems& list) const
 {
     StringBuilder stringBuilder;
     size_t i = 0;
     for (auto it = list.begin(); it != list.end(); ++it, ++i) {
-        DisplayItems::ItemHandle displayItem = list[i];
+        const DisplayItem& displayItem = *list.elementAt(i);
         if (i)
             stringBuilder.append(",\n");
-        if (displayItem.isGone()) {
+        if (displayItem.ignoreFromDisplayList()) {
             stringBuilder.append("null");
             continue;
         }
         stringBuilder.append(String::format("{index: %d, ", (int)i));
         displayItem.dumpPropertiesAsDebugString(stringBuilder);
         stringBuilder.append(", cacheIsValid: ");
         stringBuilder.append(clientCacheIsValid(displayItem.client()) ? "true" : "false");
         stringBuilder.append('}');
     }
     return stringBuilder.toString();
 }
 
 void DisplayItemList::showDebugData() const
 {
     WTFLogAlways("current display items: [%s]\n", displayItemsAsDebugString(m_currentDisplayItems).utf8().data());
     WTFLogAlways("new display items: [%s]\n", displayItemsAsDebugString(m_newDisplayItems).utf8().data());
 }
 
 #endif // ifndef NDEBUG
 
-void DisplayItemList::replay(GraphicsContext& context) const
+void DisplayItemList::replay(GraphicsContext& context)
 {
     TRACE_EVENT0("blink,benchmark", "DisplayItemList::replay");
-    ASSERT(m_newDisplayItems.isEmpty());
-    for (auto& displayItem : m_currentDisplayItems)
-        displayItem.replay(context);
+    ASSERT(m_newDisplayItems.empty());
+    for (auto displayItem : m_currentDisplayItems)
+        displayItem->replay(context);
 }
 
 } // namespace blink