gecko-dev/layout/generic/nsPlaceholderFrame.h

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#ifndef nsPlaceholderFrame_h___
#define nsPlaceholderFrame_h___

#include "nsSplittableFrame.h"
#include "nsLayoutAtoms.h"

nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell);

/**
 * Implementation of a frame that's used as a placeholder for a frame that
 * has been moved out of the flow
 */
class nsPlaceholderFrame : public nsSplittableFrame {
public:
  /**
   * Create a new placeholder frame
   */
  friend nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell);
  nsPlaceholderFrame();
  virtual ~nsPlaceholderFrame();

  // Get/Set the associated out of flow frame
  nsIFrame*  GetOutOfFlowFrame() const {return mOutOfFlowFrame;}
  void       SetOutOfFlowFrame(nsIFrame* aFrame) {mOutOfFlowFrame = aFrame;}

  // nsIHTMLReflow overrides
  NS_IMETHOD Reflow(nsPresContext* aPresContext,
                    nsHTMLReflowMetrics& aDesiredSize,
                    const nsHTMLReflowState& aReflowState,
                    nsReflowStatus& aStatus);

  virtual void Destroy();

  // nsIFrame overrides
#ifdef DEBUG
  NS_IMETHOD BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                              const nsRect&           aDirtyRect,
                              const nsDisplayListSet& aLists);
  NS_IMETHOD List(FILE* out, PRInt32 aIndent) const;
#endif

  /**
   * Get the "type" of the frame
   *
   * @see nsLayoutAtoms::placeholderFrame
   */
  virtual nsIAtom* GetType() const;

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

  virtual PRBool IsEmpty() { return PR_TRUE; }
  virtual PRBool IsSelfEmpty() { return PR_TRUE; }

#ifdef ACCESSIBILITY
  NS_IMETHOD  GetAccessible(nsIAccessible** aAccessible)
  {
    nsIFrame *realFrame = GetRealFrameForPlaceholder(this);
    return realFrame ? realFrame->GetAccessible(aAccessible) :
                       nsSplittableFrame::GetAccessible(aAccessible);
  }
#endif

  /**
   * @return the out-of-flow for aFrame if aFrame is a placeholder; otherwise
   * aFrame
   */
  static nsIFrame* GetRealFrameFor(nsIFrame* aFrame) {
    NS_PRECONDITION(aFrame, "Must have a frame to work with");
    if (aFrame->GetType() == nsLayoutAtoms::placeholderFrame) {
      return GetRealFrameForPlaceholder(aFrame);
    }
    return aFrame;
  }

  /**
   * @return the out-of-flow for aFrame, which is known to be a placeholder
   */
  static nsIFrame* GetRealFrameForPlaceholder(nsIFrame* aFrame) {
    NS_PRECONDITION(aFrame->GetType() == nsLayoutAtoms::placeholderFrame,
                    "Must have placeholder frame as input");
    nsIFrame* outOfFlow =
      NS_STATIC_CAST(nsPlaceholderFrame*, aFrame)->GetOutOfFlowFrame();
    NS_ASSERTION(outOfFlow, "Null out-of-flow for placeholder?");
    return outOfFlow;
  }

protected:
  nsIFrame* mOutOfFlowFrame;
};

#endif /* nsPlaceholderFrame_h___ */