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 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 /*

  * rendering object for the point that anchors out-of-flow rendering

  * objects such as floats and absolutely positioned elements

  */

 /*

  * Destruction of a placeholder and its out-of-flow must observe the

  * following constraints:

  *

  * - The mapping from the out-of-flow to the placeholder must be

  *   removed from the frame manager before the placeholder is destroyed.

  * - The mapping from the out-of-flow to the placeholder must be

  *   removed from the frame manager before the out-of-flow is destroyed.

  * - The placeholder must be removed from the frame tree, or have the

  *   mapping from it to its out-of-flow cleared, before the out-of-flow

  *   is destroyed (so that the placeholder will not point to a destroyed

  *   frame while it's in the frame tree).

  *

  * Furthermore, some code assumes that placeholders point to something

  * useful, so placeholders without an associated out-of-flow should not

  * remain in the tree.

  *

  * The placeholder's Destroy() implementation handles the destruction of

  * the placeholder and its out-of-flow. To avoid crashes, frame removal

  * and destruction code that works with placeholders must not assume

  * that the placeholder points to its out-of-flow.

  */

 #ifndef nsPlaceholderFrame_h___

 #define nsPlaceholderFrame_h___

 #include "mozilla/Attributes.h"

 #include "nsFrame.h"

 #include "nsGkAtoms.h"

 nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell,

                                  nsStyleContext* aContext,

                                  nsFrameState aTypeBit);

 #define PLACEHOLDER_TYPE_MASK    (PLACEHOLDER_FOR_FLOAT | \

                                   PLACEHOLDER_FOR_ABSPOS | \

                                   PLACEHOLDER_FOR_FIXEDPOS | \

                                   PLACEHOLDER_FOR_POPUP)

 /**

  * Implementation of a frame that's used as a placeholder for a frame that

  * has been moved out of the flow.

  */

 class nsPlaceholderFrame MOZ_FINAL : public nsFrame {

 public:

   NS_DECL_FRAMEARENA_HELPERS

 #ifdef DEBUG

   NS_DECL_QUERYFRAME_TARGET(nsPlaceholderFrame)

   NS_DECL_QUERYFRAME

 #endif

   /**

    * Create a new placeholder frame.  aTypeBit must be one of the

    * PLACEHOLDER_FOR_* constants above.

    */

   friend nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell,

                                           nsStyleContext* aContext,

                                           nsFrameState aTypeBit);

   nsPlaceholderFrame(nsStyleContext* aContext, nsFrameState aTypeBit)

     : nsFrame(aContext)

   {

     NS_PRECONDITION(aTypeBit == PLACEHOLDER_FOR_FLOAT ||

                     aTypeBit == PLACEHOLDER_FOR_ABSPOS ||

                     aTypeBit == PLACEHOLDER_FOR_FIXEDPOS ||

                     aTypeBit == PLACEHOLDER_FOR_POPUP,

                     "Unexpected type bit");

     AddStateBits(aTypeBit);

   }

   // Get/Set the associated out of flow frame

   nsIFrame*  GetOutOfFlowFrame() const { return mOutOfFlowFrame; }

   void       SetOutOfFlowFrame(nsIFrame* aFrame) {

                NS_ASSERTION(!aFrame || !aFrame->GetPrevContinuation(),

                             "OOF must be first continuation");

                mOutOfFlowFrame = aFrame;

              }

   // nsIFrame overrides

   // We need to override GetMinSize and GetPrefSize because XUL uses

   // placeholders not within lines.

   virtual void AddInlineMinWidth(nsRenderingContext* aRenderingContext,

                                  InlineMinWidthData* aData) MOZ_OVERRIDE;

   virtual void AddInlinePrefWidth(nsRenderingContext* aRenderingContext,

                                   InlinePrefWidthData* aData) MOZ_OVERRIDE;

   virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   virtual nsresult Reflow(nsPresContext* aPresContext,

                           nsHTMLReflowMetrics& aDesiredSize,

                           const nsHTMLReflowState& aReflowState,

                           nsReflowStatus& aStatus) MOZ_OVERRIDE;

   virtual void DestroyFrom(nsIFrame* aDestructRoot) MOZ_OVERRIDE;

 #if defined(DEBUG) || (defined(MOZ_REFLOW_PERF_DSP) && defined(MOZ_REFLOW_PERF))

   virtual void BuildDisplayList(nsDisplayListBuilder*   aBuilder,

                                 const nsRect&           aDirtyRect,

                                 const nsDisplayListSet& aLists) MOZ_OVERRIDE;

 #endif // DEBUG || (MOZ_REFLOW_PERF_DSP && MOZ_REFLOW_PERF)

 #ifdef DEBUG_FRAME_DUMP

   void List(FILE* out = stderr, const char* aPrefix = "", uint32_t aFlags = 0) const MOZ_OVERRIDE;

   virtual nsresult GetFrameName(nsAString& aResult) const MOZ_OVERRIDE;

 #endif // DEBUG

   /**

    * Get the "type" of the frame

    *

    * @see nsGkAtoms::placeholderFrame

    */

   virtual nsIAtom* GetType() const MOZ_OVERRIDE;

   virtual bool IsEmpty() MOZ_OVERRIDE { return true; }

   virtual bool IsSelfEmpty() MOZ_OVERRIDE { return true; }

   virtual bool CanContinueTextRun() const MOZ_OVERRIDE;

 #ifdef ACCESSIBILITY

   virtual mozilla::a11y::AccType AccessibleType() MOZ_OVERRIDE

   {

     nsIFrame* realFrame = GetRealFrameForPlaceholder(this);

     return realFrame ? realFrame->AccessibleType() :

                        nsFrame::AccessibleType();

   }

 #endif

   virtual nsIFrame* GetParentStyleContextFrame() const MOZ_OVERRIDE;

   /**

    * @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() == nsGkAtoms::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() == nsGkAtoms::placeholderFrame,

                     "Must have placeholder frame as input");

     nsIFrame* outOfFlow =

       static_cast<nsPlaceholderFrame*>(aFrame)->GetOutOfFlowFrame();

     NS_ASSERTION(outOfFlow, "Null out-of-flow for placeholder?");

     return outOfFlow;

   }

 protected:

   nsIFrame* mOutOfFlowFrame;

 };

 #endif /* nsPlaceholderFrame_h___ */