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#ifndef nsIScrollFrame_h___
#define nsIScrollFrame_h___

#include "nsISupports.h"
#include "nsCoord.h"
#include "nsIViewManager.h"
#include "nsIScrollableViewProvider.h"
#include "nsPresContext.h"
#include "nsIFrame.h" // to get nsIBox, which is a typedef

class nsBoxLayoutState;

// IID for the nsIScrollableFrame interface
#define NS_ISCROLLABLE_FRAME_IID    \
{ 0xf285c180, 0x8492, 0x48d5, \
{ 0xb1, 0xb5, 0x03, 0x28, 0x21, 0xc9, 0x72, 0x02 } }

class nsIScrollableFrame : public nsIScrollableViewProvider {
public:

  NS_DEFINE_STATIC_IID_ACCESSOR(NS_ISCROLLABLE_FRAME_IID)

  /**
   * Get the frame that we are scrolling within the scrollable frame.
   * @result child frame
   */
  virtual nsIFrame* GetScrolledFrame() const = 0;

  typedef nsPresContext::ScrollbarStyles ScrollbarStyles;

  virtual ScrollbarStyles GetScrollbarStyles() const = 0;

  /**
   * Return the actual sizes of all possible scrollbars. Returns 0 for scrollbar
   * positions that don't have a scrollbar or where the scrollbar is not visible.
   * Do not call this while this frame's descendants are being reflowed, it won't be
   * accurate.
   */
  virtual nsMargin GetActualScrollbarSizes() const = 0;

  /**
   * Return the sizes of all scrollbars assuming that any scrollbars that could
   * be visible due to overflowing content, are.
   */
  virtual nsMargin GetDesiredScrollbarSizes(nsBoxLayoutState* aState) = 0;

  /**
   * Get the position of the scrolled view.
   */
  virtual nsPoint GetScrollPosition() const = 0;

  /**
   * Scroll the view to the given x,y, update's the scrollbar's thumb
   * positions and the view's offset. Clamps the values to be
   * legal. Updates the display based on aUpdateFlags.
   * @param aX left edge to scroll to
   * @param aY top edge to scroll to
   * @param aUpdateFlags passed onto nsIViewManager->UpdateView()
   * @return error status
   */
  virtual void ScrollTo(nsPoint aScrollPosition, PRUint32 aFlags = NS_VMREFRESH_NO_SYNC)=0;

  virtual nsIScrollableView* GetScrollableView() = 0;

  /**
   * Set information about whether the vertical and horizontal scrollbars
   * are currently visible
   */
  virtual void SetScrollbarVisibility(PRBool aVerticalVisible, PRBool aHorizontalVisible) = 0;

  virtual nsIBox* GetScrollbarBox(PRBool aVertical) = 0;

  virtual void CurPosAttributeChanged(nsIContent* aChild, PRInt32 aModType) = 0;

  /**
   * This tells the scroll frame to try scrolling to the scroll
   * position that was restored from the history. This must be called
   * at least once after state has been restored. It is called by the
   * scrolled frame itself during reflow, but sometimes state can be
   * restored after reflows are done...
   */
  virtual void ScrollToRestoredPosition() = 0;
};

#endif
