gecko-dev/layout/generic/nsPlaceholderFrame.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* 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/
*
* 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.
*
* 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
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/*
* 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 "nsFrame.h"
#include "nsGkAtoms.h"
nsIFrame* NS_NewPlaceholderFrame(nsIPresShell* aPresShell,
nsStyleContext* aContext,
nsFrameState aTypeBit);
// Frame state bits that are used to keep track of what this is a
// placeholder for.
#define PLACEHOLDER_FOR_FLOAT NS_FRAME_STATE_BIT(20)
#define PLACEHOLDER_FOR_ABSPOS NS_FRAME_STATE_BIT(21)
#define PLACEHOLDER_FOR_FIXEDPOS NS_FRAME_STATE_BIT(22)
#define PLACEHOLDER_FOR_POPUP NS_FRAME_STATE_BIT(23)
#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 : public nsFrame {
public:
NS_DECL_FRAMEARENA_HELPERS
/**
* 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);
}
virtual ~nsPlaceholderFrame();
// 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;
}
// nsIHTMLReflow overrides
// We need to override GetMinWidth and GetPrefWidth because XUL uses
// placeholders not within lines.
virtual nscoord GetMinWidth(nsRenderingContext *aRenderingContext);
virtual nscoord GetPrefWidth(nsRenderingContext *aRenderingContext);
virtual void AddInlineMinWidth(nsRenderingContext *aRenderingContext,
InlineMinWidthData *aData);
virtual void AddInlinePrefWidth(nsRenderingContext *aRenderingContext,
InlinePrefWidthData *aData);
virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState);
NS_IMETHOD Reflow(nsPresContext* aPresContext,
nsHTMLReflowMetrics& aDesiredSize,
const nsHTMLReflowState& aReflowState,
nsReflowStatus& aStatus);
virtual void DestroyFrom(nsIFrame* aDestructRoot);
// 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
virtual bool IsEmpty() { return true; }
virtual bool IsSelfEmpty() { return true; }
virtual bool CanContinueTextRun() const;
#ifdef ACCESSIBILITY
virtual already_AddRefed<nsAccessible> CreateAccessible()
{
nsIFrame* realFrame = GetRealFrameForPlaceholder(this);
return realFrame ? realFrame->CreateAccessible() :
nsFrame::CreateAccessible();
}
#endif
virtual nsIFrame* GetParentStyleContextFrame();
/**
* @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___ */