Bug 296315. Remove unimplemented nsIScrollableView::GetScrollbarVisibility, implement nsDocShell::GetScrollbarVisibiilty to use nsIScrollableFrame::GetActualScrollbarSizes, which actually works. r+sr=bzbarsky,a=asa

docshell/base/nsDocShell.cpp

@@ -77,6 +77,7 @@
 #include "nsIScriptObjectPrincipal.h"
 #include "nsDocumentCharsetInfoCID.h"
 #include "nsICanvasFrame.h"
+#include "nsIScrollableFrame.h"
 #include "nsContentPolicyUtils.h" // NS_CheckContentLoadPolicy(...)
 #include "nsICategoryManager.h"
 #include "nsXPCOMCID.h"
@@ -3955,21 +3956,25 @@ nsDocShell::GetScrollbarVisibility(PRBool * verticalVisible,
     nsIScrollableView* scrollView;
     NS_ENSURE_SUCCESS(GetRootScrollableView(&scrollView),
                       NS_ERROR_FAILURE);
-    if (!scrollView) {
+    if (!scrollView)
         return NS_ERROR_FAILURE;
-    }
 
-    PRBool vertVisible;
-    PRBool horizVisible;
-
-    NS_ENSURE_SUCCESS(scrollView->GetScrollbarVisibility(&vertVisible,
-                                                         &horizVisible),
-                      NS_ERROR_FAILURE);
+    // We should now call nsLayoutUtils::GetScrollableFrameFor,
+    // but we can't because of stupid linkage!
+    nsIFrame* scrollFrame =
+        NS_STATIC_CAST(nsIFrame*, scrollView->View()->GetParent()->GetClientData());
+    if (!scrollFrame)
+        return NS_ERROR_FAILURE;
+    nsIScrollableFrame* scrollable = nsnull;
+    CallQueryInterface(scrollFrame, &scrollable);
+    if (!scrollable)
+        return NS_ERROR_FAILURE;
 
+    nsMargin scrollbars = scrollable->GetActualScrollbarSizes();
     if (verticalVisible)
-        *verticalVisible = vertVisible;
+        *verticalVisible = scrollbars.left != 0 || scrollbars.right != 0;
     if (horizontalVisible)
-        *horizontalVisible = horizVisible;
+        *horizontalVisible = scrollbars.top != 0 || scrollbars.bottom != 0;
 
     return NS_OK;
 }

layout/generic/nsIScrollableFrame.h

@@ -43,8 +43,8 @@
 #include "nsIViewManager.h"
 #include "nsIScrollableViewProvider.h"
 #include "nsPresContext.h"
+#include "nsIFrame.h" // to get nsIBox, which is a typedef
 
-class nsIFrame;
 class nsBoxLayoutState;
 
 // IID for the nsIScrollableFrame interface

view/public/nsIScrollableView.h

@@ -108,13 +108,6 @@ public:
    */
   NS_IMETHOD ScrollTo(nscoord aX, nscoord aY, PRUint32 aUpdateFlags) = 0;
 
-  /**
-   * Get information about whether the vertical and horizontal scrollbars
-   * are currently visible
-   */
-  NS_IMETHOD GetScrollbarVisibility(PRBool *aVerticalVisible,
-                                    PRBool *aHorizontalVisible) const = 0;
-
   /**
    * Set the properties describing how scrolling can be performed
    * in this scrollable.

view/src/nsScrollPortView.cpp

@@ -328,13 +328,6 @@ NS_IMETHODIMP nsScrollPortView::ScrollTo(nscoord aDestinationX, nscoord aDestina
   return NS_OK;
 }
 
-NS_IMETHODIMP nsScrollPortView::GetScrollbarVisibility(PRBool *aVerticalVisible,
-                                                       PRBool *aHorizontalVisible) const
-{ 
-  NS_WARNING("Attempt to get scrollbars visibility this is not xp!");
-  return NS_OK;
-}
-
 static void AdjustChildWidgets(nsView *aView,
   nsPoint aWidgetToParentViewOrigin, float aScale, PRBool aInvalidate)
 {

view/src/nsScrollPortView.h

@@ -69,8 +69,6 @@ public:
 
   NS_IMETHOD  GetScrollPosition(nscoord &aX, nscoord &aY) const;
   NS_IMETHOD  ScrollTo(nscoord aX, nscoord aY, PRUint32 aUpdateFlags);
-  NS_IMETHOD  GetScrollbarVisibility(PRBool *aVerticalVisible,
-                                     PRBool *aHorizontalVisible) const;
   NS_IMETHOD  SetScrollProperties(PRUint32 aProperties);
   NS_IMETHOD  GetScrollProperties(PRUint32 *aProperties);
   NS_IMETHOD  SetLineHeight(nscoord aHeight);