Added GetScrollbarVisibility()

view/public/nsIScrollableView.h

@@ -139,6 +139,13 @@ public:
    */
   NS_IMETHOD GetControlInsets(nsMargin &aInsets) const = 0;
 
+  /**
+   * Get information about whether the vertical and horizontal scrollbars
+   * are currently visible
+   */
+  NS_IMETHOD GetScrollbarVisibility(PRBool *aVerticalVisible,
+                                    PRBool *aHorizontalVisible) const = 0;
+
 private:
   NS_IMETHOD_(nsrefcnt) AddRef(void) = 0;
   NS_IMETHOD_(nsrefcnt) Release(void) = 0;

view/src/nsScrollingView.cpp

@@ -1295,6 +1295,14 @@ NS_IMETHODIMP nsScrollingView :: GetControlInsets(nsMargin &aInsets) const
   return NS_OK;
 }
 
+NS_IMETHODIMP nsScrollingView :: GetScrollbarVisibility(PRBool *aVerticalVisible,
+                                                        PRBool *aHorizontalVisible) const
+{
+  *aVerticalVisible = mVScrollBarView && ViewIsShowing(mVScrollBarView);
+  *aHorizontalVisible = mHScrollBarView && ViewIsShowing(mHScrollBarView);
+  return NS_OK;
+}
+
 void nsScrollingView :: AdjustChildWidgets(nsScrollingView *aScrolling, nsIView *aView, nscoord aDx, nscoord aDy, float scale)
 {
   PRInt32           numkids;

view/src/nsScrollingView.h

@@ -60,6 +60,8 @@ public:
   NS_IMETHOD  ScrollTo(nscoord aX, nscoord aY, PRUint32 aUpdateFlags);
   NS_IMETHOD  SetControlInsets(const nsMargin &aInsets);
   NS_IMETHOD  GetControlInsets(nsMargin &aInsets) const;
+  NS_IMETHOD  GetScrollbarVisibility(PRBool *aVerticalVisible,
+                                     PRBool *aHorizontalVisible) const;
 
   //private
   virtual void HandleScrollEvent(nsGUIEvent *aEvent, PRUint32 aEventFlags);