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/*
 * interface for rendering objects that wrap rendering objects that should
 * be scrollable
 */

#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;

class nsIScrollableFrame : public nsIScrollableViewProvider {
public:

  NS_DECL_QUERYFRAME_TARGET(nsIScrollableFrame)

  /**
   * 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;
  virtual nsMargin GetDesiredScrollbarSizes(nsPresContext* aPresContext,
                                            nsIRenderingContext* aRC) = 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 indicate smooth or async scrolling
   * @return error status
   */
  virtual void ScrollTo(nsPoint aScrollPosition, PRUint32 aFlags = 0)=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;

  /**
   * Allows the docshell to request that the scroll frame post an event
   * after being restored from history.
   */
  NS_IMETHOD PostScrolledAreaEventForCurrentArea() = 0;

};

#endif
