Bug 1644337, add an isAnchored property to popups, as popups can be anchored to a rectangle as well as a node. This prevented the arrow from appearing in panels, r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D86099

dom/webidl/XULPopupElement.webidl

@@ -142,6 +142,12 @@ interface XULPopupElement : XULElement
    */
   readonly attribute Node? triggerNode;
 
+  /**
+   * True if the popup is anchored to a point or rectangle. False if it
+   * appears at a fixed screen coordinate.
+   */
+  readonly attribute boolean isAnchored;
+
   /**
    * Retrieve the anchor that was specified to openPopup or for menupopups in a
    * menu, the parent menu.

dom/xul/XULPopupElement.cpp

@@ -188,6 +188,15 @@ nsINode* XULPopupElement::GetTriggerNode() const {
   return nsMenuPopupFrame::GetTriggerContent(menuPopupFrame);
 }
 
+bool XULPopupElement::IsAnchored() const {
+  nsMenuPopupFrame* menuPopupFrame = do_QueryFrame(GetPrimaryFrame());
+  if (!menuPopupFrame) {
+    return false;
+  }
+
+  return menuPopupFrame->IsAnchored();
+}
+
 // FIXME(emilio): should probably be renamed to GetAnchorElement?
 Element* XULPopupElement::GetAnchorNode() const {
   nsMenuPopupFrame* menuPopupFrame = do_QueryFrame(GetPrimaryFrame());

dom/xul/XULPopupElement.h

@@ -72,6 +72,8 @@ class XULPopupElement : public nsXULElement {
 
   nsINode* GetTriggerNode() const;
 
+  bool IsAnchored() const;
+
   Element* GetAnchorNode() const;
 
   already_AddRefed<DOMRect> GetOuterScreenRect();

toolkit/content/widgets/panel.js

@@ -96,12 +96,7 @@
     }
 
     adjustArrowPosition() {
-      if (!this.isArrowPanel) {
-        return;
-      }
-
-      var anchor = this.anchorNode;
-      if (!anchor) {
+      if (!this.isArrowPanel || !this.isAnchored) {
         return;
       }
 
@@ -159,7 +154,7 @@
     on_popupshowing(event) {
       if (this.isArrowPanel && event.target == this) {
         var arrow = this.shadowRoot.querySelector(".panel-arrow");
-        arrow.hidden = this.anchorNode == null;
+        arrow.hidden = !this.isAnchored;
         this.shadowRoot
           .querySelector(".panel-arrowbox")
           .style.removeProperty("transform");