Bug 1130400. Part 2. Use a reflow callback to set the position of xul…

… popups. r=enndeakin During reflow our frame, or any ancestors, may not yet be placed at their final position. So calculating the screen position of our popup during our reflow could produce incorrect results. Instead post a reflow callback to do it after reflow is finished.
rmottola · Jun 22, 2019 · aa21170 · aa21170
1 parent 2de244c
commit aa21170
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Showing 2 changed files with 58 additions and 1 deletion.
diff --git a/layout/xul/nsMenuPopupFrame.cpp b/layout/xul/nsMenuPopupFrame.cpp
@@ -458,8 +458,11 @@ nsMenuPopupFrame::LayoutPopup(nsBoxLayoutState& aState, nsIFrame* aParentMenu,
     mPrefSize = prefSize;
   }
 
+  bool needCallback = false;
+
   if (shouldPosition) {
     SetPopupPosition(aAnchor, false, aSizedToPopup);
+    needCallback = true;
   }
 
   nsRect bounds(GetRect());
@@ -477,6 +480,7 @@ nsMenuPopupFrame::LayoutPopup(nsBoxLayoutState& aState, nsIFrame* aParentMenu,
       mPrefSize = newsize;
       if (isOpen) {
         SetPopupPosition(aAnchor, false, aSizedToPopup);
+        needCallback = true;
       }
     }
   }
@@ -528,6 +532,27 @@ nsMenuPopupFrame::LayoutPopup(nsBoxLayoutState& aState, nsIFrame* aParentMenu,
     nsCOMPtr<nsIRunnable> event = new nsXULPopupShownEvent(GetContent(), pc);
     NS_DispatchToCurrentThread(event);
   }
+
+  if (needCallback && !mReflowCallbackData.mPosted) {
+    pc->PresShell()->PostReflowCallback(this);
+    mReflowCallbackData.MarkPosted(aAnchor, aSizedToPopup);
+  }
+}
+
+bool
+nsMenuPopupFrame::ReflowFinished()
+{
+  SetPopupPosition(mReflowCallbackData.mAnchor, false, mReflowCallbackData.mSizedToPopup);
+
+  mReflowCallbackData.Clear();
+
+  return false;
+}
+
+void
+nsMenuPopupFrame::ReflowCallbackCanceled()
+{
+  mReflowCallbackData.Clear();
 }
 
 nsIContent*
@@ -1943,6 +1968,11 @@ nsMenuPopupFrame::MoveToAttributePosition()
 void
 nsMenuPopupFrame::DestroyFrom(nsIFrame* aDestructRoot)
 {
+  if (mReflowCallbackData.mPosted) {
+    PresContext()->PresShell()->CancelReflowCallback(this);
+    mReflowCallbackData.Clear();
+  }
+
   nsMenuFrame* menu = do_QueryFrame(GetParent());
   if (menu) {
     // clear the open attribute on the parent menu

diff --git a/layout/xul/nsMenuPopupFrame.h b/layout/xul/nsMenuPopupFrame.h
@@ -152,7 +152,8 @@ class nsXULPopupShownEvent : public nsRunnable, public nsIDOMEventListener
   nsRefPtr<nsPresContext> mPresContext;
 };
 
-class nsMenuPopupFrame final : public nsBoxFrame, public nsMenuParent
+class nsMenuPopupFrame final : public nsBoxFrame, public nsMenuParent,
+                                   public nsIReflowCallback
 {
 public:
   NS_DECL_QUERYFRAME_TARGET(nsMenuPopupFrame)
@@ -399,6 +400,10 @@ class nsMenuPopupFrame final : public nsBoxFrame, public nsMenuParent
     return false;
   }
 
+  // nsIReflowCallback
+  virtual bool ReflowFinished() MOZ_OVERRIDE;
+  virtual void ReflowCallbackCanceled() MOZ_OVERRIDE;
+
 protected:
 
   // returns the popup's level.
@@ -526,6 +531,28 @@ class nsMenuPopupFrame final : public nsBoxFrame, public nsMenuParent
   uint8_t mConsumeRollupEvent;
   FlipType mFlip; // Whether to flip
 
+  struct ReflowCallbackData {
+    ReflowCallbackData() :
+      mPosted(false),
+      mAnchor(nullptr),
+      mSizedToPopup(false)
+    {}
+    void MarkPosted(nsIFrame* aAnchor, bool aSizedToPopup) {
+      mPosted = true;
+      mAnchor = aAnchor;
+      mSizedToPopup = aSizedToPopup;
+    }
+    void Clear() {
+      mPosted = false;
+      mAnchor = nullptr;
+      mSizedToPopup = false;
+    }
+    bool mPosted;
+    nsIFrame* mAnchor;
+    bool mSizedToPopup;
+  };
+  ReflowCallbackData mReflowCallbackData;
+
   bool mIsOpenChanged; // true if the open state changed since the last layout
   bool mIsContextMenu; // true for context menus
   // true if we need to offset the popup to ensure it's not under the mouse