gecko-dev/layout/generic/nsPlaceholderFrame.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
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*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
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*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/*
* 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).
*
* Therefore the safe order of teardown is to:
*
* 1) Unregister the placeholder from the frame manager.
* 2) Destroy the placeholder
* 3) Destroy the out of flow
*
* In certain cases it may be possible to replace step (2) with:
*
* 2') Null out the mOutOfFlowFrame pointer in the placeholder
*
* and add
*
* 4) Destroy the placeholder
*
* but this is somewhat dangerous, since lots of code assumes that
* placeholders point to something useful.
*/
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#ifndef nsPlaceholderFrame_h___
#define nsPlaceholderFrame_h___
#include "nsSplittableFrame.h"
#include "nsGkAtoms.h"
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nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
/**
* 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 {
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public:
/**
* Create a new placeholder frame
*/
friend nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
nsPlaceholderFrame(nsStyleContext* aContext) : nsSplittableFrame(aContext) {}
virtual ~nsPlaceholderFrame();
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// Get/Set the associated out of flow frame
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nsIFrame* GetOutOfFlowFrame() const {return mOutOfFlowFrame;}
void SetOutOfFlowFrame(nsIFrame* aFrame) {mOutOfFlowFrame = aFrame;}
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// nsIHTMLReflow overrides
// We need to override GetMinWidth and GetPrefWidth because XUL uses
// placeholders not within lines.
virtual nscoord GetMinWidth(nsIRenderingContext *aRenderingContext);
virtual nscoord GetPrefWidth(nsIRenderingContext *aRenderingContext);
virtual void AddInlineMinWidth(nsIRenderingContext *aRenderingContext,
InlineMinWidthData *aData);
virtual void AddInlinePrefWidth(nsIRenderingContext *aRenderingContext,
InlinePrefWidthData *aData);
NS_IMETHOD Reflow(nsPresContext* aPresContext,
nsHTMLReflowMetrics& aDesiredSize,
const nsHTMLReflowState& aReflowState,
nsReflowStatus& aStatus);
virtual void Destroy();
virtual nsSplittableType GetSplittableType() const;
// nsIFrame overrides
#if defined(DEBUG) || (defined(MOZ_REFLOW_PERF_DSP) && defined(MOZ_REFLOW_PERF))
NS_IMETHOD BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsRect& aDirtyRect,
const nsDisplayListSet& aLists);
#endif // DEBUG || (MOZ_REFLOW_PERF_DSP && MOZ_REFLOW_PERF)
#ifdef DEBUG
NS_IMETHOD List(FILE* out, PRInt32 aIndent) const;
#endif // DEBUG
/**
* Get the "type" of the frame
*
* @see nsGkAtoms::placeholderFrame
*/
virtual nsIAtom* GetType() const;
#ifdef DEBUG
NS_IMETHOD GetFrameName(nsAString& aResult) const;
#endif
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virtual PRBool IsEmpty() { return PR_TRUE; }
virtual PRBool IsSelfEmpty() { return PR_TRUE; }
virtual PRBool CanContinueTextRun() const;
#ifdef ACCESSIBILITY
NS_IMETHOD GetAccessible(nsIAccessible** aAccessible)
{
nsIFrame *realFrame = GetRealFrameForPlaceholder(this);
return realFrame ? realFrame->GetAccessible(aAccessible) :
nsSplittableFrame::GetAccessible(aAccessible);
}
#endif
NS_IMETHOD GetParentStyleContextFrame(nsPresContext* aPresContext,
nsIFrame** aProviderFrame,
PRBool* aIsChild);
/**
* @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;
}
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protected:
nsIFrame* mOutOfFlowFrame;
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};
#endif /* nsPlaceholderFrame_h___ */