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 * Contributor(s):
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/*
 * rendering object that is the root of the frame tree, which contains
 * the document's scrollbars and contains fixed-positioned elements
 */

#ifndef nsViewportFrame_h___
#define nsViewportFrame_h___

#include "nsContainerFrame.h"
#include "nsGkAtoms.h"
#include "nsAbsoluteContainingBlock.h"

class nsPresContext;

/**
  * ViewportFrame is the parent of a single child - the doc root frame or a scroll frame 
  * containing the doc root frame. ViewportFrame stores this child in its primary child 
  * list. It stores fixed positioned items in a secondary child list and its mFixedContainer 
  * delegate handles them. 
  */
class ViewportFrame : public nsContainerFrame {
public:
  NS_DECL_FRAMEARENA_HELPERS

  typedef nsContainerFrame Super;

  ViewportFrame(nsStyleContext* aContext)
    : nsContainerFrame(aContext)
    , mFixedContainer(nsGkAtoms::fixedList)
  {}
  virtual ~ViewportFrame() { } // useful for debugging

  virtual void DestroyFrom(nsIFrame* aDestructRoot);

  NS_IMETHOD Init(nsIContent*      aContent,
                  nsIFrame*        aParent,
                  nsIFrame*        asPrevInFlow);

  NS_IMETHOD SetInitialChildList(nsIAtom*        aListName,
                                 nsFrameList&    aChildList);

  NS_IMETHOD AppendFrames(nsIAtom*        aListName,
                          nsFrameList&    aFrameList);

  NS_IMETHOD InsertFrames(nsIAtom*        aListName,
                          nsIFrame*       aPrevFrame,
                          nsFrameList&    aFrameList);

  NS_IMETHOD RemoveFrame(nsIAtom*        aListName,
                         nsIFrame*       aOldFrame);

  virtual nsIAtom* GetAdditionalChildListName(PRInt32 aIndex) const;

  virtual nsFrameList GetChildList(nsIAtom* aListName) const;

  NS_IMETHOD BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                              const nsRect&           aDirtyRect,
                              const nsDisplayListSet& aLists);

  virtual nscoord GetMinWidth(nsIRenderingContext *aRenderingContext);
  virtual nscoord GetPrefWidth(nsIRenderingContext *aRenderingContext);
  NS_IMETHOD Reflow(nsPresContext*          aPresContext,
                    nsHTMLReflowMetrics&     aDesiredSize,
                    const nsHTMLReflowState& aReflowState,
                    nsReflowStatus&          aStatus);

  /**
   * Get the "type" of the frame
   *
   * @see nsGkAtoms::viewportFrame
   */
  virtual nsIAtom* GetType() const;
  
  virtual PRBool IsContainingBlock() const;

  virtual void InvalidateInternal(const nsRect& aDamageRect,
                                  nscoord aX, nscoord aY, nsIFrame* aForChild,
                                  PRUint32 aFlags);

#ifdef DEBUG
  NS_IMETHOD GetFrameName(nsAString& aResult) const;
#endif

protected:
  nsPoint AdjustReflowStateForScrollbars(nsHTMLReflowState* aReflowState) const;

protected:
  // position: fixed content is really content which is absolutely positioned with
  // respect to the viewport.
  nsAbsoluteContainingBlock mFixedContainer;
};


#endif // nsViewportFrame_h___
