Bug 1372118 - Part1. Have a path to create WebRender commands without layers. r=jrmuizel, r=kats, r=mattwoodrow

MozReview-Commit-ID: 7iOW9rEtwur

gfx/layers/wr/WebRenderLayerManager.cpp

@@ -20,6 +20,7 @@
 #include "WebRenderPaintedLayerBlob.h"
 #include "WebRenderTextLayer.h"
 #include "WebRenderDisplayItemLayer.h"
+#include "nsDisplayList.h"
 
 namespace mozilla {
 
@@ -32,6 +33,7 @@ WebRenderLayerManager::WebRenderLayerManager(nsIWidget* aWidget)
   , mLatestTransactionId(0)
   , mNeedsComposite(false)
   , mIsFirstPaint(false)
+  , mEndTransactionWithoutLayers(false)
   , mTarget(nullptr)
   , mPaintSequenceNumber(0)
 {
@@ -173,11 +175,81 @@ PopulateScrollData(WebRenderScrollData& aTarget, Layer* aLayer)
   return descendants + 1;
 }
 
+void
+WebRenderLayerManager::CreateWebRenderCommandsFromDisplayList(nsDisplayList* aDisplayList,
+                                                              nsDisplayListBuilder* aDisplayListBuilder,
+                                                              StackingContextHelper& aSc,
+                                                              wr::DisplayListBuilder& aBuilder)
+{
+  nsDisplayList savedItems;
+  nsDisplayItem* item;
+  while ((item = aDisplayList->RemoveBottom()) != nullptr) {
+    nsDisplayItem::Type itemType = item->GetType();
+
+    // If the item is a event regions item, but is empty (has no regions in it)
+    // then we should just throw it out
+    if (itemType == nsDisplayItem::TYPE_LAYER_EVENT_REGIONS) {
+      nsDisplayLayerEventRegions* eventRegions =
+        static_cast<nsDisplayLayerEventRegions*>(item);
+      if (eventRegions->IsEmpty()) {
+        item->~nsDisplayItem();
+        continue;
+      }
+    }
+
+    // Peek ahead to the next item and try merging with it or swapping with it
+    // if necessary.
+    nsDisplayItem* aboveItem;
+    while ((aboveItem = aDisplayList->GetBottom()) != nullptr) {
+      if (aboveItem->TryMerge(item)) {
+        aDisplayList->RemoveBottom();
+        item->~nsDisplayItem();
+        item = aboveItem;
+        itemType = item->GetType();
+      } else {
+        break;
+      }
+    }
+
+    nsDisplayList* itemSameCoordinateSystemChildren
+      = item->GetSameCoordinateSystemChildren();
+    if (item->ShouldFlattenAway(aDisplayListBuilder)) {
+      aDisplayList->AppendToBottom(itemSameCoordinateSystemChildren);
+      item->~nsDisplayItem();
+      continue;
+    }
+
+    savedItems.AppendToTop(item);
+
+    if (!item->CreateWebRenderCommands(aBuilder, aSc, mParentCommands, this,
+                                       aDisplayListBuilder)) {
+      // TODO: fallback
+    }
+  }
+  aDisplayList->AppendToTop(&savedItems);
+}
+
+void
+WebRenderLayerManager::EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
+                                                  nsDisplayListBuilder* aDisplayListBuilder)
+{
+  MOZ_ASSERT(aDisplayList && aDisplayListBuilder);
+  mEndTransactionWithoutLayers = true;
+  DiscardImages();
+  WrBridge()->RemoveExpiredFontKeys();
+  EndTransactionInternal(nullptr,
+                         nullptr,
+                         EndTransactionFlags::END_DEFAULT,
+                         aDisplayList,
+                         aDisplayListBuilder);
+}
+
 void
 WebRenderLayerManager::EndTransaction(DrawPaintedLayerCallback aCallback,
                                       void* aCallbackData,
                                       EndTransactionFlags aFlags)
 {
+  mEndTransactionWithoutLayers = false;
   DiscardImages();
   WrBridge()->RemoveExpiredFontKeys();
   EndTransactionInternal(aCallback, aCallbackData, aFlags);
@@ -186,7 +258,9 @@ WebRenderLayerManager::EndTransaction(DrawPaintedLayerCallback aCallback,
 bool
 WebRenderLayerManager::EndTransactionInternal(DrawPaintedLayerCallback aCallback,
                                               void* aCallbackData,
-                                              EndTransactionFlags aFlags)
+                                              EndTransactionFlags aFlags,
+                                              nsDisplayList* aDisplayList,
+                                              nsDisplayListBuilder* aDisplayListBuilder)
 {
   AutoProfilerTracing tracing("Paint", "RenderLayers");
   mPaintedLayerCallback = aCallback;
@@ -205,12 +279,29 @@ WebRenderLayerManager::EndTransactionInternal(DrawPaintedLayerCallback aCallback
     return false;
   }
   DiscardCompositorAnimations();
-  mRoot->StartPendingAnimations(mAnimationReadyTime);
 
-  StackingContextHelper sc;
   WrSize contentSize { (float)size.width, (float)size.height };
   wr::DisplayListBuilder builder(WrBridge()->GetPipeline(), contentSize);
-  WebRenderLayer::ToWebRenderLayer(mRoot)->RenderLayer(builder, sc);
+
+  if (mEndTransactionWithoutLayers) {
+    // aDisplayList being null here means this is an empty transaction following a layers-free
+    // transaction, so we reuse the previously built displaylist.
+    if (aDisplayList && aDisplayListBuilder) {
+      StackingContextHelper sc;
+      mParentCommands.Clear();
+      CreateWebRenderCommandsFromDisplayList(aDisplayList, aDisplayListBuilder, sc, builder);
+      builder.Finalize(contentSize, mBuiltDisplayList);
+    }
+
+    builder.PushBuiltDisplayList(mBuiltDisplayList);
+    WrBridge()->AddWebRenderParentCommands(mParentCommands);
+  } else {
+    mRoot->StartPendingAnimations(mAnimationReadyTime);
+    StackingContextHelper sc;
+
+    WebRenderLayer::ToWebRenderLayer(mRoot)->RenderLayer(builder, sc);
+  }
+
   mWidget->AddWindowOverlayWebRenderCommands(WrBridge(), builder);
   WrBridge()->ClearReadLocks();
 

gfx/layers/wr/WebRenderLayerManager.h

@@ -10,10 +10,13 @@
 #include "mozilla/MozPromise.h"
 #include "mozilla/layers/APZTestData.h"
 #include "mozilla/layers/FocusTarget.h"
+#include "mozilla/layers/StackingContextHelper.h"
 #include "mozilla/layers/TransactionIdAllocator.h"
+#include "mozilla/webrender/WebRenderAPI.h"
 #include "mozilla/webrender/WebRenderTypes.h"
 
 class nsIWidget;
+class nsDisplayList;
 
 namespace mozilla {
 namespace layers {
@@ -22,6 +25,7 @@ class CompositorBridgeChild;
 class KnowsCompositor;
 class PCompositorBridgeChild;
 class WebRenderBridgeChild;
+class WebRenderParentCommand;
 
 class WebRenderLayerManager final : public LayerManager
 {
@@ -48,6 +52,13 @@ public:
   virtual bool BeginTransactionWithTarget(gfxContext* aTarget) override;
   virtual bool BeginTransaction() override;
   virtual bool EndEmptyTransaction(EndTransactionFlags aFlags = END_DEFAULT) override;
+  void CreateWebRenderCommandsFromDisplayList(nsDisplayList* aDisplayList,
+                                              nsDisplayListBuilder* aDisplayListBuilder,
+                                              StackingContextHelper& aSc,
+                                              wr::DisplayListBuilder& aBuilder);
+  void EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
+                                  nsDisplayListBuilder* aDisplayListBuilder);
+  bool IsLayersFreeTransaction() { return mEndTransactionWithoutLayers; }
   virtual void EndTransaction(DrawPaintedLayerCallback aCallback,
                               void* aCallbackData,
                               EndTransactionFlags aFlags = END_DEFAULT) override;
@@ -152,8 +163,9 @@ private:
 
   bool EndTransactionInternal(DrawPaintedLayerCallback aCallback,
                               void* aCallbackData,
-                              EndTransactionFlags aFlags);
-
+                              EndTransactionFlags aFlags,
+                              nsDisplayList* aDisplayList = nullptr,
+                              nsDisplayListBuilder* aDisplayListBuilder = nullptr);
 
 private:
   nsIWidget* MOZ_NON_OWNING_REF mWidget;
@@ -174,6 +186,11 @@ private:
 
   LayerRefArray mKeepAlive;
 
+  // These fields are used to save a copy of the display list for
+  // empty transactions in layers-free mode.
+  wr::BuiltDisplayList mBuiltDisplayList;
+  nsTArray<WebRenderParentCommand> mParentCommands;
+
   // Layers that have been mutated. If we have an empty transaction
   // then a display item layer will no longer be valid
   // if it was a mutated layers.
@@ -185,6 +202,7 @@ private:
   bool mNeedsComposite;
   bool mIsFirstPaint;
   FocusTarget mFocusTarget;
+  bool mEndTransactionWithoutLayers;
 
  // When we're doing a transaction in order to draw to a non-default
  // target, the layers transaction is only performed in order to send

gfx/thebes/gfxPrefs.h

@@ -473,6 +473,7 @@ private:
   DECL_GFX_PREF(Once, "gfx.vsync.compositor.unobserve-count",  CompositorUnobserveCount, int32_t, 10);
   DECL_OVERRIDE_PREF(Live, "gfx.webrender.omta.enabled",       WebRenderOMTAEnabled, gfxPrefs::OverrideBase_WebRender());
   DECL_GFX_PREF(Live, "gfx.webrender.profiler.enabled",        WebRenderProfilerEnabled, bool, false);
+  DECL_GFX_PREF(Live, "gfx.webrender.layers-free",             WebRenderLayersFree, bool, false);
   DECL_GFX_PREF(Live, "gfx.webrendest.enabled",                WebRendestEnabled, bool, false);
   // Use vsync events generated by hardware
   DECL_GFX_PREF(Once, "gfx.work-around-driver-bugs",           WorkAroundDriverBugs, bool, true);

layout/painting/nsDisplayList.cpp

@@ -2092,6 +2092,30 @@ already_AddRefed<LayerManager> nsDisplayList::PaintRoot(nsDisplayListBuilder* aB
   nsIPresShell* presShell = presContext->PresShell();
   nsIDocument* document = presShell->GetDocument();
 
+  if (gfxPrefs::WebRenderLayersFree() &&
+      layerManager->GetBackendType() == layers::LayersBackend::LAYERS_WR &&
+      // We don't yet support many display items used in chrome, so
+      // layers-free mode is only for content.
+      !presContext->IsChrome()) {
+    if (doBeginTransaction) {
+      if (aCtx) {
+        if (!layerManager->BeginTransactionWithTarget(aCtx)) {
+          return nullptr;
+        }
+      } else {
+        if (!layerManager->BeginTransaction()) {
+          return nullptr;
+        }
+      }
+    }
+
+    MaybeSetupTransactionIdAllocator(layerManager, presContext);
+    bool temp = aBuilder->SetIsCompositingCheap(layerManager->IsCompositingCheap());
+    static_cast<WebRenderLayerManager*>(layerManager.get())->EndTransactionWithoutLayer(this, aBuilder);
+    aBuilder->SetIsCompositingCheap(temp);
+    return layerManager.forget();
+  }
+
   NotifySubDocInvalidationFunc computeInvalidFunc =
     presContext->MayHavePaintEventListenerInSubDocument() ? nsPresContext::NotifySubDocInvalidation : 0;
 

layout/painting/nsDisplayList.h

@@ -1955,10 +1955,16 @@ public:
     * The layer this item is in is passed in as rects must be relative
     * to their parent.
     */
-   virtual void CreateWebRenderCommands(mozilla::wr::DisplayListBuilder& aBuilder,
+   virtual void CreateWebRenderCommand(mozilla::wr::DisplayListBuilder& aBuilder,
+                                       const StackingContextHelper& aSc,
+                                       nsTArray<WebRenderParentCommand>& aParentCommands,
+                                       WebRenderDisplayItemLayer* aLayer) {}
+   virtual bool CreateWebRenderCommands(mozilla::wr::DisplayListBuilder& aBuilder,
                                         const StackingContextHelper& aSc,
                                         nsTArray<WebRenderParentCommand>& aParentCommands,
-                                        WebRenderDisplayItemLayer* aLayer) {}
+                                        mozilla::layers::WebRenderLayerManager* aManager,
+                                        nsDisplayListBuilder* aDisplayListBuilder) { return false; }
+
   /**
    * Builds a DisplayItemLayer and sets the display item to this.
    */

modules/libpref/init/all.js

@@ -4828,6 +4828,7 @@ pref("layers.force-active", false);
 pref("layers.gralloc.disable", false);
 
 pref("webrender.highlight-painted-layers", false);
+pref("gfx.webrender.layers-free", false);
 
 // Enable/Disable the geolocation API for content
 pref("geo.enabled", true);