gecko-dev/layout/generic/nsFrame.h
2005-11-20 22:05:24 +00:00

597 lines
25 KiB
C++

/* -*- 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
*
* 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):
* Pierre Phaneuf <pp@ludusdesign.com>
*
* 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 ***** */
#ifndef nsFrame_h___
#define nsFrame_h___
#include "nsBox.h"
#include "nsRect.h"
#include "nsString.h"
#include "prlog.h"
#ifdef NS_DEBUG
#include "nsIFrameDebug.h"
#endif
#include "nsIPresShell.h"
#include "nsHTMLReflowCommand.h"
#include "nsIFrameSelection.h"
#include "nsHTMLReflowState.h"
#include "nsHTMLReflowMetrics.h"
/**
* nsFrame logging constants. We redefine the nspr
* PRLogModuleInfo.level field to be a bitfield. Each bit controls a
* specific type of logging. Each logging operation has associated
* inline methods defined below.
*/
#define NS_FRAME_TRACE_CALLS 0x1
#define NS_FRAME_TRACE_PUSH_PULL 0x2
#define NS_FRAME_TRACE_CHILD_REFLOW 0x4
#define NS_FRAME_TRACE_NEW_FRAMES 0x8
#define NS_FRAME_LOG_TEST(_lm,_bit) (PRIntn((_lm)->level) & (_bit))
#ifdef NS_DEBUG
#define NS_FRAME_LOG(_bit,_args) \
PR_BEGIN_MACRO \
if (NS_FRAME_LOG_TEST(nsIFrameDebug::GetLogModuleInfo(),_bit)) { \
PR_LogPrint _args; \
} \
PR_END_MACRO
#else
#define NS_FRAME_LOG(_bit,_args)
#endif
// XXX Need to rework this so that logging is free when it's off
#ifdef NS_DEBUG
#define NS_FRAME_TRACE_IN(_method) Trace(_method, PR_TRUE)
#define NS_FRAME_TRACE_OUT(_method) Trace(_method, PR_FALSE)
// XXX remove me
#define NS_FRAME_TRACE_MSG(_bit,_args) \
PR_BEGIN_MACRO \
if (NS_FRAME_LOG_TEST(nsIFrameDebug::GetLogModuleInfo(),_bit)) { \
TraceMsg _args; \
} \
PR_END_MACRO
#define NS_FRAME_TRACE(_bit,_args) \
PR_BEGIN_MACRO \
if (NS_FRAME_LOG_TEST(nsIFrameDebug::GetLogModuleInfo(),_bit)) { \
TraceMsg _args; \
} \
PR_END_MACRO
#define NS_FRAME_TRACE_REFLOW_IN(_method) Trace(_method, PR_TRUE)
#define NS_FRAME_TRACE_REFLOW_OUT(_method, _status) \
Trace(_method, PR_FALSE, _status)
#else
#define NS_FRAME_TRACE(_bits,_args)
#define NS_FRAME_TRACE_IN(_method)
#define NS_FRAME_TRACE_OUT(_method)
#define NS_FRAME_TRACE_MSG(_bits,_args)
#define NS_FRAME_TRACE_REFLOW_IN(_method)
#define NS_FRAME_TRACE_REFLOW_OUT(_method, _status)
#endif
// handy utilities
void SetFontFromStyle(nsIRenderingContext* aRC, nsStyleContext* aSC);
//----------------------------------------------------------------------
struct nsBoxLayoutMetrics;
/**
* Implementation of a simple frame that's not splittable and has no
* child frames.
*
* Sets the NS_FRAME_SYNCHRONIZE_FRAME_AND_VIEW bit, so the default
* behavior is to keep the frame and view position and size in sync.
*/
class nsFrame : public nsBox
#ifdef NS_DEBUG
, public nsIFrameDebug
#endif
{
public:
/**
* Create a new "empty" frame that maps a given piece of content into a
* 0,0 area.
*/
friend nsIFrame* NS_NewEmptyFrame(nsIPresShell* aShell);
// Overloaded new operator. Initializes the memory to 0 and relies on an arena
// (which comes from the presShell) to perform the allocation.
void* operator new(size_t sz, nsIPresShell* aPresShell) CPP_THROW_NEW;
// Overridden to prevent the global delete from being called, since the memory
// came out of an arena instead of the global delete operator's heap.
// XXX Would like to make this private some day, but our UNIX compilers can't
// deal with it.
void operator delete(void* aPtr, size_t sz);
// We compute and store the HTML content's overflow area. So don't
// try to compute it in the box code.
virtual PRBool ComputesOwnOverflowArea() { return PR_TRUE; }
private:
// The normal operator new is disallowed on nsFrames.
void* operator new(size_t sz) CPP_THROW_NEW { return nsnull; };
public:
// nsISupports
NS_IMETHOD QueryInterface(const nsIID& aIID, void** aInstancePtr);
// nsIFrame
NS_IMETHOD Init(nsPresContext* aPresContext,
nsIContent* aContent,
nsIFrame* aParent,
nsStyleContext* aContext,
nsIFrame* asPrevInFlow);
NS_IMETHOD SetInitialChildList(nsPresContext* aPresContext,
nsIAtom* aListName,
nsIFrame* aChildList);
NS_IMETHOD AppendFrames(nsIAtom* aListName,
nsIFrame* aFrameList);
NS_IMETHOD InsertFrames(nsIAtom* aListName,
nsIFrame* aPrevFrame,
nsIFrame* aFrameList);
NS_IMETHOD RemoveFrame(nsIAtom* aListName,
nsIFrame* aOldFrame);
NS_IMETHOD ReplaceFrame(nsIAtom* aListName,
nsIFrame* aOldFrame,
nsIFrame* aNewFrame);
NS_IMETHOD Destroy(nsPresContext* aPresContext);
NS_IMETHOD CalcBorderPadding(nsMargin& aBorderPadding) const;
virtual nsStyleContext* GetAdditionalStyleContext(PRInt32 aIndex) const;
virtual void SetAdditionalStyleContext(PRInt32 aIndex,
nsStyleContext* aStyleContext);
NS_IMETHOD SetParent(const nsIFrame* aParent);
virtual nsIAtom* GetAdditionalChildListName(PRInt32 aIndex) const;
virtual nsIFrame* GetFirstChild(nsIAtom* aListName) const;
NS_IMETHOD Paint(nsPresContext* aPresContext,
nsIRenderingContext& aRenderingContext,
const nsRect& aDirtyRect,
nsFramePaintLayer aWhichLayer,
PRUint32 aFlags = 0);
NS_IMETHOD HandleEvent(nsPresContext* aPresContext,
nsGUIEvent* aEvent,
nsEventStatus* aEventStatus);
NS_IMETHOD GetContentForEvent(nsPresContext* aPresContext,
nsEvent* aEvent,
nsIContent** aContent);
NS_IMETHOD GetCursor(const nsPoint& aPoint,
nsIFrame::Cursor& aCursor);
virtual nsIFrame* GetFrameForPoint(const nsPoint& aPoint,
nsFramePaintLayer aWhichLayer);
NS_IMETHOD GetPointFromOffset(nsPresContext* inPresContext,
nsIRenderingContext* inRendContext,
PRInt32 inOffset,
nsPoint* outPoint);
NS_IMETHOD GetChildFrameContainingOffset(PRInt32 inContentOffset,
PRBool inHint,
PRInt32* outFrameContentOffset,
nsIFrame* *outChildFrame);
static nsresult GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
nsPeekOffsetStruct *aPos,
nsIFrame *aBlockFrame,
PRInt32 aLineStart,
PRInt8 aOutSideLimit
);
NS_IMETHOD CharacterDataChanged(nsPresContext* aPresContext,
nsIContent* aChild,
PRBool aAppend);
NS_IMETHOD AttributeChanged(PRInt32 aNameSpaceID,
nsIAtom* aAttribute,
PRInt32 aModType);
NS_IMETHOD IsSplittable(nsSplittableType& aIsSplittable) const;
virtual nsIFrame* GetPrevInFlow() const;
NS_IMETHOD SetPrevInFlow(nsIFrame*);
virtual nsIFrame* GetNextInFlow() const;
NS_IMETHOD SetNextInFlow(nsIFrame*);
NS_IMETHOD GetOffsetFromView(nsPoint& aOffset, nsIView** aView) const;
NS_IMETHOD GetOriginToViewOffset(nsPoint& aOffset, nsIView **aView) const;
virtual nsIAtom* GetType() const;
virtual PRBool IsContainingBlock() const;
#ifdef NS_DEBUG
NS_IMETHOD List(FILE* out, PRInt32 aIndent) const;
NS_IMETHOD GetFrameName(nsAString& aResult) const;
NS_IMETHOD_(nsFrameState) GetDebugStateBits() const;
NS_IMETHOD DumpRegressionData(nsPresContext* aPresContext, FILE* out, PRInt32 aIndent, PRBool aIncludeStyleData);
NS_IMETHOD VerifyTree() const;
#endif
NS_IMETHOD SetSelected(nsPresContext* aPresContext, nsIDOMRange *aRange,PRBool aSelected, nsSpread aSpread);
NS_IMETHOD GetSelected(PRBool *aSelected) const;
NS_IMETHOD IsSelectable(PRBool* aIsSelectable, PRUint8* aSelectStyle) const;
NS_IMETHOD GetSelectionController(nsPresContext *aPresContext, nsISelectionController **aSelCon);
NS_IMETHOD PeekOffset(nsPresContext* aPresContext, nsPeekOffsetStruct *aPos) ;
NS_IMETHOD CheckVisibility(nsPresContext* aContext, PRInt32 aStartIndex, PRInt32 aEndIndex, PRBool aRecurse, PRBool *aFinished, PRBool *_retval);
NS_IMETHOD PeekOffsetParagraph(nsPresContext* aPresContext,
nsPeekOffsetStruct *aPos);
NS_IMETHOD GetOffsets(PRInt32 &aStart, PRInt32 &aEnd) const;
NS_IMETHOD ReflowDirtyChild(nsIPresShell* aPresShell, nsIFrame* aChild);
#ifdef ACCESSIBILITY
NS_IMETHOD GetAccessible(nsIAccessible** aAccessible);
#endif
NS_IMETHOD GetParentStyleContextFrame(nsPresContext* aPresContext,
nsIFrame** aProviderFrame,
PRBool* aIsChild);
// Check Style Visibility and mState for Selection (when printing)
NS_IMETHOD IsVisibleForPainting(nsPresContext * aPresContext,
nsIRenderingContext& aRenderingContext,
PRBool aCheckVis,
PRBool* aIsVisible);
virtual PRBool IsEmpty();
virtual PRBool IsSelfEmpty();
// nsIHTMLReflow
NS_IMETHOD WillReflow(nsPresContext* aPresContext);
NS_IMETHOD Reflow(nsPresContext* aPresContext,
nsHTMLReflowMetrics& aDesiredSize,
const nsHTMLReflowState& aReflowState,
nsReflowStatus& aStatus);
NS_IMETHOD DidReflow(nsPresContext* aPresContext,
const nsHTMLReflowState* aReflowState,
nsDidReflowStatus aStatus);
NS_IMETHOD CanContinueTextRun(PRBool& aContinueTextRun) const;
NS_IMETHOD AdjustFrameSize(nscoord aExtraSpace, nscoord& aUsedSpace);
NS_IMETHOD TrimTrailingWhiteSpace(nsPresContext* aPresContext,
nsIRenderingContext& aRC,
nscoord& aDeltaWidth,
PRBool& aLastCharIsJustifiable);
// Selection Methods
// XXX Doc me... (in nsIFrame.h puhleeze)
// XXX If these are selection specific, then the name should imply selection
// rather than generic event processing, e.g., SelectionHandlePress...
NS_IMETHOD HandlePress(nsPresContext* aPresContext,
nsGUIEvent * aEvent,
nsEventStatus* aEventStatus);
NS_IMETHOD HandleMultiplePress(nsPresContext* aPresContext,
nsGUIEvent * aEvent,
nsEventStatus* aEventStatus);
NS_IMETHOD HandleDrag(nsPresContext* aPresContext,
nsGUIEvent * aEvent,
nsEventStatus* aEventStatus);
NS_IMETHOD HandleRelease(nsPresContext* aPresContext,
nsGUIEvent * aEvent,
nsEventStatus* aEventStatus);
NS_IMETHOD GetContentAndOffsetsFromPoint(nsPresContext* aCX,
const nsPoint& aPoint,
nsIContent ** aNewContent,
PRInt32& aContentOffset,
PRInt32& aContentOffsetEnd,
PRBool& aBeginFrameContent);
NS_IMETHOD PeekBackwardAndForward(nsSelectionAmount aAmountBack,
nsSelectionAmount aAmountForward,
PRInt32 aStartPos,
nsPresContext* aPresContext,
PRBool aJumpLines);
// Box layout methods
NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
NS_IMETHOD GetFlex(nsBoxLayoutState& aBoxLayoutState, nscoord& aFlex);
NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
NS_IMETHOD SetIncludeOverflow(PRBool aInclude);
NS_IMETHOD GetOverflow(nsSize& aOverflow);
NS_IMETHOD NeedsRecalc();
//--------------------------------------------------
// Additional methods
/**
* Helper method to invalidate portions of a standard container frame if the
* reflow state indicates that the size has changed (specifically border,
* background and outline).
* We assume that the difference between the old frame area and the new
* frame area is invalidated by some other means.
* @param aPresContext the presentation context
* @param aDesiredSize the new size of the frame
* @param aReflowState the reflow that was just done on this frame
*/
void CheckInvalidateSizeChange(nsPresContext* aPresContext,
nsHTMLReflowMetrics& aDesiredSize,
const nsHTMLReflowState& aReflowState);
// Helper function that tests if the frame tree is too deep; if it
// is it marks the frame as "unflowable" and zeros out the metrics
// and returns PR_TRUE. Otherwise, the frame is unmarked
// "unflowable" and the metrics are not touched and PR_FALSE is
// returned.
PRBool IsFrameTreeTooDeep(const nsHTMLReflowState& aReflowState,
nsHTMLReflowMetrics& aMetrics);
// Do the work for getting the parent style context frame so that
// other frame's |GetParentStyleContextFrame| methods can call this
// method on *another* frame. (This function handles out-of-flow
// frames by using the frame manager's placeholder map and it also
// handles block-within-inline and generated content wrappers.)
nsresult DoGetParentStyleContextFrame(nsPresContext* aPresContext,
nsIFrame** aProviderFrame,
PRBool* aIsChild);
// incorporate the child overflow area into the parent overflow area
// if the child does not have a overflow use the child area
void ConsiderChildOverflow(nsRect& aOverflowArea,
nsIFrame* aChildFrame);
//Mouse Capturing code used by the frames to tell the view to capture all the following events
NS_IMETHOD CaptureMouse(nsPresContext* aPresContext, PRBool aGrabMouseEvents);
PRBool IsMouseCaptured(nsPresContext* aPresContext);
virtual const nsStyleStruct* GetStyleDataExternal(nsStyleStructID aSID) const;
#ifdef NS_DEBUG
/**
* Tracing method that writes a method enter/exit routine to the
* nspr log using the nsIFrame log module. The tracing is only
* done when the NS_FRAME_TRACE_CALLS bit is set in the log module's
* level field.
*/
void Trace(const char* aMethod, PRBool aEnter);
void Trace(const char* aMethod, PRBool aEnter, nsReflowStatus aStatus);
void TraceMsg(const char* fmt, ...);
// Helper function that verifies that each frame in the list has the
// NS_FRAME_IS_DIRTY bit set
static void VerifyDirtyBitSet(nsIFrame* aFrameList);
// Helper function to return the index in parent of the frame's content
// object. Returns -1 on error or if the frame doesn't have a content object
static PRInt32 ContentIndexInContainer(const nsIFrame* aFrame);
void ListTag(FILE* out) const {
ListTag(out, (nsIFrame*)this);
}
static void ListTag(FILE* out, nsIFrame* aFrame) {
nsAutoString tmp;
nsIFrameDebug* frameDebug;
if (NS_SUCCEEDED(aFrame->QueryInterface(NS_GET_IID(nsIFrameDebug), (void**)&frameDebug))) {
frameDebug->GetFrameName(tmp);
}
fputs(NS_LossyConvertUCS2toASCII(tmp).get(), out);
fprintf(out, "@%p", NS_STATIC_CAST(void*, aFrame));
}
static void IndentBy(FILE* out, PRInt32 aIndent) {
while (--aIndent >= 0) fputs(" ", out);
}
static void XMLQuote(nsString& aString);
/**
* Dump out the "base classes" regression data. This should dump
* out the interior data, not the "frame" XML container. And it
* should call the base classes same named method before doing
* anything specific in a derived class. This means that derived
* classes need not override DumpRegressionData unless they need
* some custom behavior that requires changing how the outer "frame"
* XML container is dumped.
*/
virtual void DumpBaseRegressionData(nsPresContext* aPresContext, FILE* out, PRInt32 aIndent, PRBool aIncludeStyleData);
nsresult MakeFrameName(const nsAString& aKind, nsAString& aResult) const;
// Display Reflow Debugging
static void* DisplayReflowEnter(nsPresContext* aPresContext,
nsIFrame* aFrame,
const nsHTMLReflowState& aReflowState);
static void DisplayReflowExit(nsPresContext* aPresContext,
nsIFrame* aFrame,
nsHTMLReflowMetrics& aMetrics,
PRUint32 aStatus,
void* aFrameTreeNode);
static void DisplayReflowStartup();
static void DisplayReflowShutdown();
#endif
protected:
// Protected constructor and destructor
nsFrame();
virtual ~nsFrame();
/**
* To be called by |Paint| of this class or derived classes to paint
* the background, border, and outline, when in the correct layer to
* do so.
*/
void PaintSelf(nsPresContext* aPresContext,
nsIRenderingContext& aRenderingContext,
const nsRect& aDirtyRect,
PRIntn aSkipSides = 0,
PRBool aUsePrintBackgroundSettings = PR_TRUE);
PRInt16 DisplaySelection(nsPresContext* aPresContext, PRBool isOkToTurnOn = PR_FALSE);
//this will modify aPos and return the next frame etc.
NS_IMETHOD GetFrameFromDirection(nsPresContext* aPresContext, nsPeekOffsetStruct *aPos);
// Style post processing hook
NS_IMETHOD DidSetStyleContext(nsPresContext* aPresContext);
// Helper routine for determining whether to print selection
nsresult GetSelectionForVisCheck(nsPresContext * aPresContext, nsISelection** aSelection);
//return the line number of the aFrame
static PRInt32 GetLineNumber(nsIFrame *aFrame);
public:
//given a frame five me the first/last leaf available
//XXX Robert O'Callahan wants to move these elsewhere
static void GetLastLeaf(nsPresContext* aPresContext, nsIFrame **aFrame);
static void GetFirstLeaf(nsPresContext* aPresContext, nsIFrame **aFrame);
protected:
// Test if we are selecting a table object:
// Most table/cell selection requires that Ctrl (Cmd on Mac) key is down
// during a mouse click or drag. Exception is using Shift+click when
// already in "table/cell selection mode" to extend a block selection
// Get the parent content node and offset of the frame
// of the enclosing cell or table (if not inside a cell)
// aTarget tells us what table element to select (currently only cell and table supported)
// (enums for this are defined in nsIFrame.h)
NS_IMETHOD GetDataForTableSelection(nsIFrameSelection *aFrameSelection,
nsIPresShell *aPresShell, nsMouseEvent *aMouseEvent,
nsIContent **aParentContent, PRInt32 *aContentOffset,
PRInt32 *aTarget);
virtual PRBool ParentDisablesSelection() const;
// Set the overflow clip rect into the rendering-context. Used for block-level
// elements and replaced elements that have 'overflow' set to 'hidden'. This
// member function assumes that the caller has checked that the clip property
// applies to its situation.
void SetOverflowClipRect(nsIRenderingContext& aRenderingContext);
// Fills aCursor with the appropriate information from ui
static void FillCursorInformationFromStyle(const nsStyleUserInterface* ui,
nsIFrame::Cursor& aCursor);
NS_IMETHOD DoLayout(nsBoxLayoutState& aBoxLayoutState);
#ifdef DEBUG_LAYOUT
virtual void GetBoxName(nsAutoString& aName);
#endif
virtual PRBool HasStyleChange();
virtual void SetStyleChangeFlag(PRBool aDirty);
virtual PRBool GetWasCollapsed(nsBoxLayoutState& aState);
virtual void SetWasCollapsed(nsBoxLayoutState& aState, PRBool aWas);
void InitBoxMetrics(PRBool aClear);
nsBoxLayoutMetrics* BoxMetrics() const;
private:
nsresult BoxReflow(nsBoxLayoutState& aState,
nsPresContext* aPresContext,
nsHTMLReflowMetrics& aDesiredSize,
const nsHTMLReflowState& aReflowState,
nsReflowStatus& aStatus,
nscoord aX,
nscoord aY,
nscoord aWidth,
nscoord aHeight,
PRBool aMoveFrame = PR_TRUE);
void HandleIncrementalReflow(nsBoxLayoutState& aState,
const nsHTMLReflowState& aReflowState,
nsReflowReason& aReason,
nsReflowPath** aReflowPath,
PRBool& aRedrawNow,
PRBool& aNeedReflow,
PRBool& aRedrawAfterReflow,
PRBool& aMoveFrame);
PRBool CanSetMaxElementWidth(nsBoxLayoutState& aState,
nsReflowReason& aReason,
nsReflowPath **aReflowPath);
NS_IMETHODIMP RefreshSizeCache(nsBoxLayoutState& aState);
protected:
NS_IMETHOD_(nsrefcnt) AddRef(void);
NS_IMETHOD_(nsrefcnt) Release(void);
};
// Start Display Reflow Debugging
#ifdef DEBUG
struct DR_cookie {
DR_cookie(nsPresContext* aPresContext,
nsIFrame* aFrame,
const nsHTMLReflowState& aReflowState,
nsHTMLReflowMetrics& aMetrics,
nsReflowStatus& aStatus);
~DR_cookie();
void Change() const;
nsPresContext* mPresContext;
nsIFrame* mFrame;
const nsHTMLReflowState& mReflowState;
nsHTMLReflowMetrics& mMetrics;
nsReflowStatus& mStatus;
void* mValue;
};
#define DISPLAY_REFLOW(dr_pres_context, dr_frame, dr_rf_state, dr_rf_metrics, dr_rf_status) \
DR_cookie dr_cookie(dr_pres_context, dr_frame, dr_rf_state, dr_rf_metrics, dr_rf_status);
#define DISPLAY_REFLOW_CHANGE() \
dr_cookie.Change();
#else
#define DISPLAY_REFLOW(dr_pres_context, dr_frame, dr_rf_state, dr_rf_metrics, dr_rf_status)
#define DISPLAY_REFLOW_CHANGE()
#endif
// End Display Reflow Debugging
// similar to NS_ENSURE_TRUE but with no return value
#define ENSURE_TRUE(x) \
PR_BEGIN_MACRO \
if (!(x)) { \
NS_WARNING("ENSURE_TRUE(" #x ") failed"); \
return; \
} \
PR_END_MACRO
#endif /* nsFrame_h___ */