Bug 1402203 - Add a new layout phase for displaylist building. r=mstange

layout/base/moz.build

@@ -37,6 +37,7 @@ EXPORTS += [
     'FrameProperties.h',
     'LayoutLogging.h',
     'MobileViewportManager.h',
+    'nsAutoLayoutPhase.h',
     'nsBidi.h',
     'nsBidiPresUtils.h',
     'nsCaret.h',

layout/base/nsAutoLayoutPhase.cpp

@@ -33,14 +33,27 @@ nsAutoLayoutPhase::Enter()
     case eLayoutPhase_Paint:
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_Paint] == 0,
                  "recurring into paint");
+      MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_DisplayListBuilding] == 0,
+                 "recurring into paint from display list building");
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_Reflow] == 0,
                  "painting in the middle of reflow");
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_FrameC] == 0,
                  "painting in the middle of frame construction");
       break;
+    case eLayoutPhase_DisplayListBuilding:
+      // It's fine and expected to be in a paint here.
+      MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_DisplayListBuilding] == 0,
+                 "recurring into display list building");
+      MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_Reflow] == 0,
+                 "display list building in the middle of reflow");
+      MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_FrameC] == 0,
+                 "display list building in the middle of frame construction");
+      break;
     case eLayoutPhase_Reflow:
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_Paint] == 0,
                  "reflowing in the middle of a paint");
+      MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_DisplayListBuilding] == 0,
+                 "reflowing in the middle of a display list building");
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_Reflow] == 0,
                  "recurring into reflow");
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_FrameC] == 0,
@@ -49,6 +62,8 @@ nsAutoLayoutPhase::Enter()
     case eLayoutPhase_FrameC:
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_Paint] == 0,
                  "constructing frames in the middle of a paint");
+      MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_DisplayListBuilding] == 0,
+                 "constructing frames in the middle of a display list building");
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_Reflow] == 0,
                  "constructing frames in the middle of reflow");
       MOZ_ASSERT(mPresContext->mLayoutPhaseCount[eLayoutPhase_FrameC] == 0,

layout/base/nsPresContext.h

@@ -108,6 +108,7 @@ struct nsAutoLayoutPhase;
 
 enum nsLayoutPhase {
   eLayoutPhase_Paint,
+  eLayoutPhase_DisplayListBuilding, // sometimes a subset of the paint phase
   eLayoutPhase_Reflow,
   eLayoutPhase_FrameC,
   eLayoutPhase_COUNT

layout/painting/nsDisplayList.cpp

@@ -1218,6 +1218,10 @@ nsDisplayListBuilder::EnterPresShell(nsIFrame* aReferenceFrame,
   state->mCaretFrame = nullptr;
   state->mFirstFrameMarkedForDisplay = mFramesMarkedForDisplay.Length();
 
+#ifdef DEBUG
+  state->mAutoLayoutPhase.emplace(aReferenceFrame->PresContext(), eLayoutPhase_DisplayListBuilding);
+#endif
+
   state->mPresShell->UpdateCanvasBackground();
 
   if (mIsPaintingToWindow) {

layout/painting/nsDisplayList.h

@@ -37,6 +37,7 @@
 #include "mozilla/gfx/UserData.h"
 #include "mozilla/layers/LayerAttributes.h"
 #include "nsCSSRenderingBorders.h"
+#include "nsAutoLayoutPhase.h"
 #include "nsDisplayItemTypes.h"
 
 #include <stdint.h>
@@ -1474,6 +1475,9 @@ private:
 
   struct PresShellState {
     nsIPresShell* mPresShell;
+#ifdef DEBUG
+    mozilla::Maybe<nsAutoLayoutPhase> mAutoLayoutPhase;
+#endif
     nsIFrame*     mCaretFrame;
     nsRect        mCaretRect;
     mozilla::Maybe<OutOfFlowDisplayData> mFixedBackgroundDisplayData;