windows-nt-4.0/private/windows/win4help/winhelp/frlayout.c

/*****************************************************************************
*
*  frlayout.c
*
*  Copyright (C) Microsoft Corporation 1990.
*  All Rights reserved.
*
******************************************************************************
*
* This contains the code which handles laying out, scrolling, and
* discarding FCs.
*
* The layout code is responsible for maintaining the chain of FCMs which
* represent the layout on the screen. Only visible FCs are stored- as soon
* as an FC is scrolled off the screen, it is discarded.
*
* The layout code maintains a number of variables in the DE:
*	 TLP tlp;			 This is stores the current layout position as
*							two numbers: the FCL corresponding to the FC
*							at the top of the screen, and a long
*							which is proportional to the percentage of
*							the FC which is scrolled off the screen.
*	 MLI mli;			 The MLI contains two flags:
*							fLayoutAtTop is true if the layout cannot be
*							   scrolled any further up.
*							fLayoutAtBottom is true if the layout cannot
*							   be scrolled any further down.
*	 xScrolled; 		 The number of pixels the layout has been scrolled
*							to the right.
*	 xScrollMax;		 The maximum amount that the layout can be
*							scrolled to the right.	Note that this number
*							is recalculated everytime the user scrolls.
*							If the user scrolls a wide layout off the
*							screen, it is possible for xScrolled to be
*							greater than xScrollMax.
*
*****************************************************************************/

#include "help.h"

#include "inc\frstuff.h"

INLINE INT STDCALL CbitSigBits(unsigned long);
INLINE static int STDCALL WFindThumb(int, int, VA, DWORD, QDE);
INLINE static VA STDCALL VaFromThumb(int, QDE);
INLINE static BOOL STDCALL FFindMatchRect(QDE, int, OBJRG, LPRECT);
static void STDCALL ShowOrHideWindowQde(QDE qde, BOOL fShow);
static VOID STDCALL ShowDEScrollBar(QDE qde, WORD wWhich, BOOL fShow);

#ifdef DEADCODE
static INT16 STDCALL WMulDiv(UINT16 wNum, DWORD ulNum, DWORD ulDen);
#else
#define WMulDiv MulDiv
#endif

/*----------------------------------------------------------------------------+
 | LayoutDEAtQLA															  |
 |																			  |
 | Layout for an arbitrary object, given its address.						  |
 +----------------------------------------------------------------------------*/

void STDCALL LayoutDEAtQLA(QDE qde, QLA qla)
{
	HFC   hfc;
	VA	  va;
	OBJRG objrg;
	int   wErr;
	int   ifcm;
	POINT dpt;

	ASSERT(qde->wLayoutMagic == wLayMagicValue);

	VAandOBJRGfromQLA(qla, qde, &va, &objrg);

	ASSERT(va.dword != vaNil);
	ASSERT(objrg != objrgNil);

	hfc = HfcNear(qde, va, (TOP *) &qde->top, &wErr);

	if (wErr == wERRS_NO && hfc == NULL)
		wErr = wERRS_NOTOPIC;

	if (wErr != wERRS_NO) {
		Error(wErr, wERRA_RETURN);
		return;
	}

	/* (kevynct)
	 * Fix for RAID bug 300:
	 *
	 * We do layout for jumps to invisible windows, since we need
	 * to set the TLP correctly.  Another solution would be to
	 * create a counterpart to the TLP in the DE, set it here,
	 * then check for a nil de.tlp in LayoutDEAtTLP, and do a
	 * LayoutDEAtQLA in that case.
	 */
#if 0
	if (qde->rct.top >= qde->rct.bottom)
	  {
	  return;
	  }
#endif /* 0 */

	AccessMRD(((QMRD)&qde->mrdFCM));
	AccessMRD(((QMRD)&qde->mrdLSM));
	qde->wStyleDraw = wStyleNil;

	FreeLayout(qde);

	if (QDE_TOPIC(qde)) {

		if (qde->fHorScrollVis)
			ShowDEScrollBar(qde, SB_HORZ, FALSE);

		// Fake the layout into thinking we have a vertical scroll bar

		GetClientRect(qde->hwnd, &qde->rct);
		if (qde->deType == deNote)
			qde->rct.bottom = 9999;
		else {
			qde->rct.right -= GetSystemMetrics(SM_CXVSCROLL);
			qde->fVerScrollVis = TRUE;
		}
	}

	ifcm = IfcmLayout(qde, hfc, 0, TRUE, FALSE);

	qde->xScrolled = 0;
	qde->xScrollMaxSoFar = 0;
	DyFinishLayout(qde, 0, TRUE);
	ReviseScrollBar(qde);

	/*
	 * Scan the frames of the given FC, looking for the given object region.
	 * We special-case object region 0 of the first FC in the scrolling and
	 * non-scrolling regions to allow a jump to the top of a topic layout,
	 * instead of the first frame of that layout.  This test assumes that
	 * the NSR precedes the SR in the topic file: we need to handle the case
	 * where the VA points to the topic FC (for a Help 3.0 file).
	 * We also do not scroll in the case that the topic fits in one window.
	 *
	 * If our LA points to a search match, we try to align the match rect
	 * one-sixth of the way down the topic window.
	 */

	dpt.x = dpt.y = 0;

	{
		RECT  rct;

		if ((qde->fHorScrollVis || qde->fVerScrollVis) &&
					FFindMatchRect(qde, ifcm, objrg, &rct)) {
			QFCM qfcm = QfcmFromIfcm(qde, ifcm);

			dpt.x = -((qde->fHorScrollVis) ? qfcm->xPos + rct.left : 0);
			dpt.y = -((qde->fVerScrollVis) ? qfcm->yPos + rct.top : 0);
			dpt.x += max(0, (qde->rct.right - qde->rct.left) - (rct.right - rct.left))/2;
			dpt.y += max(0, (qde->rct.bottom - qde->rct.top) / 6);
		}
	}

	// The following covers same-topic jumps

	if (objrg != (OBJRG) 0 ||
			(va.dword > qde->top.mtop.vaNSR.dword &&
			va.dword != qde->top.mtop.vaSR.dword)) {
		QFCM  qfcm;
		QFR   qfr;
		int ifr;

		if (qde->fHorScrollVis || qde->fVerScrollVis) {

			 /*
			  * Following used to grab the 1st FC in layout which can be the
			  * wrong one if DyFinishLayout has shifted the layout around to
			  * position FC's on the screen. We want to use ifcm layout that was
			  * set by the first call to IfcmLayout because that FC is the one
			  * with the frame we are trying to jump to. ifcm =
			  * IFooFirstMRD(((QMRD)&qde->mrdFCM));
			  */

			qfcm = (QFCM)QFooInMRD(((QMRD)&qde->mrdFCM), sizeof(FCM), ifcm);
			qfr = (QFR)PtrFromGh(qfcm->hfr);

			for (ifr = 0; ifr < qfcm->cfr; ifr++, qfr++) {
				if (qfr->objrgFront == objrgNil || qfr->objrgLast == objrgNil)
					continue;
				if (qfr->objrgFront <= objrg && qfr->objrgLast >= objrg) {
					dpt.x = -((qde->fHorScrollVis) ? qfcm->xPos + qfr->xPos : 0);
					dpt.y = -((qde->fVerScrollVis) ? qfcm->yPos + qfr->yPos : 0);
					if (-dpt.x < qde->rct.right)
						dpt.x = 0;
					break;
				}
			}
		}
	}

	if (dpt.x != 0 || dpt.y != 0)
		DptScrollLayout(qde, dpt);

	DeAccessMRD(((QMRD)&qde->mrdLSM));
	DeAccessMRD(((QMRD)&qde->mrdFCM));
}

/*-------------------------------------------------------------------------
| LayoutDEAtTLP(qde, tlp, fResize)										  |
|																		  |
| Purpose:	This routine destroys any previous layout and creates a new   |
|			layout at the given TLP.  It does not redraw the layout area: |
|			the caller must take care of doing that.					  |
| Params:	fResize:  This is true if we are just resizing the window. In |
|						 this case only, we try to maintain the current   |
|						 horizontal scrolling.							  |
-------------------------------------------------------------------------*/

void STDCALL LayoutDEAtTLP(QDE qde, TLP tlp, BOOL fResize)
{
	HFC hfc;
	IFCM ifcm;
	QFCM qfcm;
	int dy, xScrolledSav;
	int wErr;

	ASSERT(qde->wLayoutMagic == wLayMagicValue);

	/*
	 * (kevynct) We do this to prevent a TLP layout occurring before a QLA
	 * layout.
	 */

	if (tlp.va.dword == vaNil)
		return;

	/* Fix for bug 57 (kevynct):
	 *
	 * The DE's TOP structure is now updated for every layout
	 * request, followed by the window size check.
	 */

	hfc = HfcNear(qde, tlp.va, (TOP *) &qde->top, &wErr);

	if (wErr == wERRS_NO && hfc == NULL)
		wErr = wERRS_NOTOPIC;

	if (wErr != wERRS_NO) {
		Error(wErr, wERRA_RETURN);
		return;
	}

	if (QDE_TOPIC(qde)) {
		if (qde->fHorScrollVis)
			ShowDEScrollBar(qde, SB_HORZ, FALSE);

		// Fake the layout into thinking we have a vertical scroll bar

		if (qde->deType == deNote)
			qde->rct.bottom = 9999;
		else {
			qde->rct.right -= GetSystemMetrics(SM_CXVSCROLL);
			qde->fVerScrollVis = TRUE;
		}
	}

	if (qde->rct.top >= qde->rct.bottom) {
		qde->tlp = tlp;
		FreeGh(hfc);
		return;
	}

	AccessMRD(((QMRD)&qde->mrdFCM));
	AccessMRD(((QMRD)&qde->mrdLSM));
	qde->wStyleDraw = wStyleNil;

	xScrolledSav = qde->xScrolled;
	FreeLayout(qde);

	ifcm = IfcmLayout(qde, hfc, 0, TRUE, FALSE);

	qfcm = (QFCM)QFooInMRD(((QMRD)&qde->mrdFCM), sizeof(FCM), ifcm);
	if (qfcm->va.dword == tlp.va.dword)
		dy = ((int) - ((int)tlp.lScroll * (int)qfcm->dySize) / 0x10000L);
	else
		dy = 0;

	if (!fResize) {
		qde->xScrolled = 0;

		// Initialize the width to 0 as we are relaying out. -	maha

		qde->xScrollMaxSoFar = 0;
	}
	DyFinishLayout(qde, dy, TRUE);

	if (fResize)
		qde->xScrolled = min(xScrolledSav, qde->xScrollMax);
	ReviseScrollBar(qde);

	DeAccessMRD(((QMRD)&qde->mrdLSM));
	DeAccessMRD(((QMRD)&qde->mrdFCM));
}

/*-------------------------------------------------------------------------
| MoveLayoutToThumb(qde, wThumb, fScrollDir)							  |
|																		  |
| Purpose:	This scrolls the layout to a position within the current	  |
| topic which corresponds to the given thumb value.  It does not redraw   |
| the layout region.													  |
-------------------------------------------------------------------------*/

void STDCALL MoveLayoutToThumb(QDE qde, int wThumb, SCRLDIR scrldir)
{
	VA	va;
	HFC hfc;
	IFCM ifcm;
	QFCM qfcm;
	int  dy;
	int wErr;

	ASSERT(qde->wLayoutMagic == wLayMagicValue);
	if (qde->rct.top >= qde->rct.bottom)
		return;

	AccessMRD(((QMRD)&qde->mrdFCM));
	AccessMRD(((QMRD)&qde->mrdLSM));

	qde->wStyleDraw = wStyleNil;

	if (scrldir == SCROLL_VERT) {
	  FreeLayout(qde);

	  va = VaFromThumb(wThumb, qde);
	  hfc = HfcNear(qde, va, (TOP *) &qde->top, &wErr);
	  if (wErr == wERRS_NO && hfc == NULL)
		wErr = wERRS_NOTOPIC;

	  if (wErr != wERRS_NO) {
		  Error(wErr, wERRA_RETURN);
		  return;
	  }

	  ASSERT(hfc != NULL);
	  ifcm = IfcmLayout(qde, hfc, 0, TRUE, FALSE);

	  qfcm = (QFCM)QFooInMRD(((QMRD)&qde->mrdFCM), sizeof(FCM), ifcm);

	  { LONG lcbLinearDiff, lcbDisk;

		/* Find approximate linear diff.  Not super accurate when compression*/
		/* is on and we cross a block boundary. 	*/

		if( QDE_HHDR(qde).wVersionNo == wVersion3_0 ) {
		  lcbLinearDiff = VAToOffset30(&va) - VAToOffset30(&qfcm->va);
		} else {
		  lcbLinearDiff = VAToOffset(&va) - VAToOffset(&qfcm->va);
		}
		lcbDisk = CbDiskHfc(hfc);
		if( lcbLinearDiff > lcbDisk ) {
		  /* The lcbLineDiff arithmetic was off, so apporiximate to
		   * "a large dy difference".  -Tom
		  */
		  dy = qfcm->dySize;
		}
		else {
		  /* Ptr 1249: appriximate positioning arithmetic interacting w/
		   *   compression can cause lcbLinearDiff to be negative.	In this
		   *   case we punt on the dy adjustment and go for zero.
		   */
		  if( lcbLinearDiff < 0 ) {
			lcbLinearDiff = 0;
		  }
		  dy = WMulDiv(qfcm->dySize, lcbLinearDiff, lcbDisk );
		}
	  }

	  DyFinishLayout(qde, -dy, FALSE);
	  qde->xScrolled = min(qde->xScrolled, qde->xScrollMax);
	  }
	else {
		ASSERT(scrldir == SCROLL_HORZ);
		qde->xScrolled = ((wThumb * qde->xScrollMax) / 0x7FFF);
	}

	ReviseScrollBar(qde);
	DeAccessMRD(((QMRD)&qde->mrdLSM));
	DeAccessMRD(((QMRD)&qde->mrdFCM));
}


/*-------------------------------------------------------------------------
| FreeLayout(qde)														  |
|																		  |
| Purpose:	This discards all layout constructs associated with the DE.   |
-------------------------------------------------------------------------*/

void STDCALL FreeLayout(QDE qde)
{
	IFCM ifcm, ifcmNext;
	QFCM qfcm;

	ASSERT(qde->wLayoutMagic == wLayMagicValue);

	for (ifcm = IFooFirstMRD(((QMRD)&qde->mrdFCM)); ifcm != FOO_NIL;
			ifcm = ifcmNext) {
		ifcmNext = IFooNextMRD(((QMRD)&qde->mrdFCM), sizeof(FCM), ifcm);
		qfcm = (QFCM)QFooInMRD(((QMRD)&qde->mrdFCM), sizeof(FCM), ifcm);
		DiscardIfcm(qde, ifcm);
	}
	qde->imhiSelected = FOO_NIL;
	qde->imhiHit = FOO_NIL;
}

/*-------------------------------------------------------------------------
| ReviseScrollBar(qde)													  |
|																		  |
| Purpose:	This recalculates the thumb positions of the vertical and	  |
|			horizontal scroll bars, and redraws them.					  |
-------------------------------------------------------------------------*/

void STDCALL ReviseScrollBar(QDE qde)
{
	IFCM ifcm;
	QFCM qfcm;
	int wThumb;
	int dxScroll;
	long lBasePos;

	if (!QDE_TOPIC(qde))
		return;

	if (qde->fVerScrollVis) {
		if (qde->mli.fLayoutAtTop)
			SetScrollQde(qde, 0, SCROLL_VERT);
		else if (qde->mli.fLayoutAtBottom)
			SetScrollQde(qde, 0x7FFF, SCROLL_VERT);
		else {
			ifcm = IFooFirstMRD(((QMRD)&qde->mrdFCM));
			qfcm = (QFCM)QFooInMRD(((QMRD)&qde->mrdFCM), sizeof(FCM), ifcm);
			wThumb = WFindThumb(-qfcm->yPos, qfcm->dySize, qfcm->va,
				CbDiskHfc(qfcm->hfc), qde);
			if (wThumb == 0x8000)
				wThumb = 0x7FFF;
			if (wThumb < 0x7FFF)
				wThumb++;
			SetScrollQde(qde, wThumb, (SCRLDIR) SCROLL_VERT);
		}
	}

	// show or hide the horz. scroll bar dependinding on the width remembered..
	dxScroll = qde -> xScrollMaxSoFar - qde->rct.right + qde->rct.left;
	ShowDEScrollBar(qde, SB_HORZ, ((dxScroll > 0 ) ? TRUE : FALSE ));

	if (dxScroll > 0) { 		// Horz scroll bar exists, so position thumb.
		if (qde->xScrolled > qde->xScrollMax) {
			SetScrollQde(qde, 0x7FFF, (SCRLDIR) SCROLL_HORZ);
		}
		else if (qde->xScrollMax == 0) {
			SetScrollQde(qde, 0, (SCRLDIR) SCROLL_HORZ);
		}
		else {
			lBasePos = MulDiv(32767, qde->xScrolled, qde->xScrollMax);
			SetScrollQde(qde, (WORD) lBasePos, (SCRLDIR) SCROLL_HORZ);
		}
	}
}

/*-------------------------------------------------------------------------
| DyFinishLayout(qde, dy, fTrySinglePage)								  |
|																		  |
| Purpose:	This is the workhorse of the layout code.  It is called when  |
|			a valid layout consisting of at least a single FCM exists, and|
|			revises that layout to fill the screen.  In addition, it	  |
|			handles scrolling the layout by up to a screen height.		  |
| Params:	dy-   The amount to add to the positions of the current FCs.  |
|			fTrySinglePage - When laying out, check to see if the current |
|			layout will fit onto a single page. 						  |
| Returns:	The offset actually added to the layout.					  |
| Method:	We use a couple of variables:								  |
|			  -qfcmTop, qfcmBottom: correspond to the first and last	  |
|			   FCMs in the layout.										  |
|			  -yTop: top of the first FCM in the layout.				  |
|			  -yBottom: bottom of the last FCM in the layout.			  |
|			  -yHeight: Height of the layout area.						  |
|			  -fBottomPadded: For aesthetic reasons, there is a blank	  |
|				  space of yHeight / 2 at the bottom of the layout. 	  |
|				  fBottomPadded is true if this space has been added.	  |
|			We proceed in a couple of stages:							  |
|																		  |
|			1) Make sure that the layout fills the layout rectangle.  We  |
|			   loop until the yTop <= 0 and yBottom >= yHeight, or until  |
|			   certain termination conditions occur.  In the loop,		  |
|				 - if yTop > 0, we try to grow the top of the layout.  If |
|				   we are unable to do this, we shift the layout to the   |
|				   top of the layout area (there can never be blank space |
|				   at the top of the layout).							  |
|				 - if yBottom < yHeight, we try to grow the bottom of the |
|				   layout.	If we are unable to do this, we pad the bottom|
|				   of the layout by yHeight / 2 if we haven't done so     |
|				   already.  Failing this, we terminate if the layout is  |
|				   pinned at the top (ie, the whole topic fits on one	  |
|				   page), otherwise we shift the layout so that a full	  |
|				   page of layout is always visible.					  |
|			2) If we padded yBottom, we unpad it.						  |
|			3) We discard any excess FCMs on the top of the bottom of the |
|			   layout.													  |
|			4) We set the positions of all FCMs in the layout, and		  |
|			   recalculate xScrollMax.									  |
-------------------------------------------------------------------------*/

enum {
	wStartPageAttempt,
	wInPageAttempt,
	wEndPageAttempt,
};

#define wNoPageAttempt	   wEndPageAttempt

int STDCALL DyFinishLayout(QDE qde, int dy, BOOL fTrySinglePage)
{
	int dyReturn;
	BOOL fTopStuck;
	BOOL fBottomPadded;
	BOOL fRedoLayout = FALSE;
	HFC hfc;
	IFCM ifcm, ifcmTop, ifcmBottom;
	QFCM qfcm;
	int dyTop, dyBottom, yHeight, yPos, dxAvail;
	int wErr;
	int wPageStatus;
	BOOL fIsScrollDE;

	// Review: Should be a macro?

	fIsScrollDE = (BOOL) QDE_TOPIC(qde);

	if (fTrySinglePage && fIsScrollDE)
		wPageStatus = wStartPageAttempt;
	else
		wPageStatus = wNoPageAttempt;

RedoLayout:
	fTopStuck = FALSE;
	fBottomPadded = FALSE;

	dyReturn = dy;

	ASSERT(IFooFirstMRD(((QMRD)&qde->mrdFCM)) != FOO_NIL);
	yHeight = qde->rct.bottom - qde->rct.top;

	ifcmTop = IFooFirstMRD(((QMRD)&qde->mrdFCM));
	dyTop = QfcmFromIfcm(qde, ifcmTop)->yPos + dy;
	ifcmBottom = IFooLastMRD(((QMRD)&qde->mrdFCM));
	dyBottom = QfcmFromIfcm(qde, ifcmBottom)->yPos +
		QfcmFromIfcm(qde, ifcmBottom)->dySize + dy
		- (qde->rct.bottom - qde->rct.top);

	qde->mli.fLayoutAtTop = qde->mli.fLayoutAtBottom = FALSE;

	// Step 1.	Try to grow the layout to fill the page.

	for (;;) {
		int dyBottomSav;

		// Step 1a: Try to grow up towards top of page from current top

		if (dyTop > 0) {
			/*
			 * Note: we check if we are redoing the layout pass. If so, we
			 * already know that trying to get the previous FC will fail.
			 */

			if (!fRedoLayout)
				hfc = HfcPrevHfc(QfcmFromIfcm(qde, ifcmTop)->hfc, &wErr, qde,
					VaMarkTopQde(qde), VaMarkBottomQde(qde));
			else {
				hfc = NULL;
				wErr = wERRS_FCEndOfTopic;
			}
			if (hfc == NULL) {
				if (wErr != wERRS_FCEndOfTopic)
					Error(wErr, wERRA_DIE);
				qde->mli.fLayoutAtTop = TRUE;
				ASSERT(!fTopStuck);
				dyBottom -= dyTop;
				dyReturn -= dyTop;
				dyTop = 0;
				fTopStuck = TRUE;
				continue;
			}
			ifcmTop = IfcmLayout(qde, hfc, 0, TRUE, FALSE);
			dyTop -= QfcmFromIfcm(qde, ifcmTop)->dySize;
			continue;
		}

		// Step 1b: Try to grow down towards bottom of page from current bottom

		if (dyBottom < 0 || wPageStatus == wInPageAttempt) {
			if (wPageStatus == wInPageAttempt) {

				// We already know that we are at the end

				hfc = NULL;
				wErr = wERRS_FCEndOfTopic;
			}
			else
				hfc = HfcNextHfc(QfcmFromIfcm(qde, ifcmBottom) ->hfc, &wErr, qde,
					VaMarkTopQde(qde), VaMarkBottomQde(qde));

			if (hfc == NULL) {
				if (wErr != wERRS_FCEndOfTopic)
					Error(wErr, wERRA_DIE);

				/* We do several things if we hit the end of a topic.  These are
				 * grouped into the following three "passes".
				 *
				 * Pass 1: We are at the bottom. Does the whole topic
				 * actually fit onto a page?  We shift things to the bottom
				 * of the page and attempt to fill the top again. If we are
				 * successful, fTopStuck will be TRUE when we return,
				 * otherwise FALSE.
				 */

				if (wPageStatus == wStartPageAttempt) {
					dyBottomSav = dyBottom;

					dyTop -= dyBottom;
					dyBottom = 0;
					wPageStatus = wInPageAttempt;
					continue;
				}
				else if (wPageStatus == wInPageAttempt) {
					if (!fTopStuck) {
						dyBottom = dyBottomSav;
						dyTop += dyBottom;
					}
					/*
					 * If fTopStuck, then dyTop and dyBottom have already
					 * been set to their correct values. dyReturn may also
					 * have been modified, but we don't care since it is
					 * going to be recomputed anyway.
					 */

					wPageStatus = wEndPageAttempt;
				}

				/*
				 * Pass 2: If the whole topic does not fit on a page, we
				 * pad the bottom for scrolling.
				 */

				if (!fTopStuck && !fBottomPadded && fIsScrollDE) {
					fBottomPadded = TRUE;
					dyBottom += yHeight / 2;
					continue;
				}

				qde->mli.fLayoutAtBottom = TRUE;
				if (fTopStuck || !fIsScrollDE)
					break;

				/*
				 * Pass 3: Even with padding the last FC was still completely on
				 * the page, so just align the last (still padded) FC with the
				 * bottom of the page and leave.
				 */

				dyTop -= dyBottom;
				dyReturn -= dyBottom;
				dyBottom = 0;
				continue;
			}
			ifcmBottom = IfcmLayout(qde, hfc, 0, FALSE, FALSE);
			dyBottom += QfcmFromIfcm(qde, ifcmBottom)->dySize;
			continue;
		}

		break;
	}

	/*
	 * For printing, if we have scrolled everything off the page, returning
	 * FALSE indicates End-of-Topic.
	 */

	if (qde->deType == dePrint && yHeight + dyBottom < 0)
		return FALSE;

	// Step 2: Unpad dyBottom if necessary.

	if (fBottomPadded)
		dyBottom -= yHeight / 2;

	// Step 3a: trim excess FCMs on top of layout.

	while (dyTop + QfcmFromIfcm(qde, ifcmTop) ->dySize < 0) {
		dyTop += QfcmFromIfcm(qde, ifcmTop) ->dySize;
		DiscardIfcm(qde, (IFCM) IFooFirstMRD(((QMRD) &qde->mrdFCM)));
		ASSERT(IFooFirstMRD(((QMRD) &qde->mrdFCM)) != FOO_NIL);
		ifcmTop = IFooFirstMRD(((QMRD) &qde->mrdFCM));
	}

	// Step 3b: trim excess FCMs on bottom of layout.

	while (dyBottom - QfcmFromIfcm(qde, ifcmBottom) ->dySize > 0) {
		if (IFooFirstMRD(((QMRD)&qde->mrdFCM)) == IFooLastMRD(((QMRD)&qde->mrdFCM)))
			break;
		dyBottom -= QfcmFromIfcm(qde, ifcmBottom)->dySize;
		DiscardIfcm(qde, (IFCM) IFooLastMRD(((QMRD)&qde->mrdFCM)));
		ASSERT(IFooLastMRD(((QMRD)&qde->mrdFCM)) != FOO_NIL);
		ifcmBottom = IFooLastMRD(((QMRD)&qde->mrdFCM));
	}

	// Step 4: revise FCM positions, recalculate xScrollMax.

	qde->xScrollMax = 0;
	dxAvail = qde->rct.right - qde->rct.left;
	yPos = dyTop;
	for (ifcm = IFooFirstMRD(((QMRD) &qde->mrdFCM)); ifcm != FOO_NIL;
			ifcm = IFooNextMRD(((QMRD) &qde->mrdFCM), sizeof(FCM), ifcm)) {
		qfcm = (QFCM) QFooInMRD(((QMRD) &qde->mrdFCM), sizeof(FCM), ifcm);
		qfcm->yPos = yPos;
		yPos += qfcm->dySize;
		qde->xScrollMax = max(qde->xScrollMax,
			qfcm->xPos + qfcm->dxSize - dxAvail);

		// my stuff - Maha

		if (qfcm->xPos + qfcm->dxSize - dxAvail > 0)
			qde->xScrollMaxSoFar = max(qde->xScrollMaxSoFar,
				qfcm->xPos + qfcm->dxSize);
	}

	/*
	 * Check to see if we really needed the vertical scrollbar. I blow off
	 * the case where the layout fit exactly. We will add the scroll bar in
	 * this case, instead of looking ahead and possibly doing the layout
	 * again. We need to have figured out xScrollMaxSoFar by this point in
	 * order to handle all cases correctly.
	 */

	/*
	 * 13-Sep-1993 [ralphw] -- It's pretty goofy for the user to see the
	 * scroll bar added when it isn't needed. So, we do the right thing and
	 * get rid of it when we fit. We can bear the penalty of a relayout.
	 */

  //if (!fRedoLayout && fIsScrollDE &&
  //	  dyBottom < 1) {
  //  dyBottom = -(qde->dyHorScrollHeight + 1);
  //  fTopStuck = TRUE;
  //}

	if (!fRedoLayout && fIsScrollDE && fTopStuck && dyBottom < 0) {
		HFC hfcTop;

		/*
		 * Special case: We are about to take away the vertical scroll bar:
		 * Check to see if we will be adding a horz. scroll bar and obscuring
		 * stuff within that space. If so, do not remove the vertical
		 * scrollbar. This duplicates a test in ReviseScrollBar.
		 */

		ASSERT(qde->dyHorScrollHeight > 0 && qde->dxVerScrollWidth > 0);
		if (-dyBottom > qde->dyHorScrollHeight ||
				qde->xScrollMaxSoFar <= qde->dxVerScrollWidth + RECT_WIDTH(qde->rct)) {
			hfcTop = QfcmFromIfcm(qde, ifcmTop)->hfc;
			ShowDEScrollBar(qde, SB_VERT, FALSE);
			qde->wStyleDraw = wStyleNil;

			/*
			* WARNING: For efficiency, we set the FCM's hfc to NULL, so
			* that FreeLayout will not free it: we want to re-use this HFC
			* instead of copying it.
			*/

			QfcmFromIfcm(qde, ifcmTop)->hfc = NULL;
			FreeLayout(qde);
			IfcmLayout(qde, hfcTop, 0, TRUE, FALSE);
			dy = 0;
			fRedoLayout = TRUE;
			goto RedoLayout;
		}
	}

	qde->tlp.va = QfcmFromIfcm(qde, ifcmTop)->va;

	// (kevynct) Deal with empty FCM

	if (QfcmFromIfcm(qde, ifcmTop) ->dySize == 0)
		qde->tlp.lScroll = 0L;
	else
		qde->tlp.lScroll = (long) (0x10000L * (- dyTop) /
			QfcmFromIfcm(qde, ifcmTop) ->dySize);

	if (VaFirstQde(qde) .dword == QfcmFromIfcm(qde, ifcmTop) ->va.dword &&
			QfcmFromIfcm(qde, ifcmTop) ->yPos == 0)
		qde->mli.fLayoutAtTop = TRUE;

	return dyReturn;
}

/*--------------------------------------------------------------------------
| WFindThumb( dyPos, yLen, vaPt, lcbLen, qde )							   |
|																		   |
| Finds the position of the button in the vertical scroll bar button, given|
| some notion of the current position in the help file. 				   |
|																		   |
| Arguments:															   |
|																		   |
|	dyPos		The position within the full context in pixels. 		   |
|	yLen		The length of the full context in pixels.				   |
|	vaPt		The virtual address of the current full context.		   |
|	lcbLen		The length of the full context in bytes.				   |
|	qde 		Display environ, used to get various vaSR values... 	   |
|																		   |
| Note:  The following assumptions are made.							   |
|																		   |
|	0 <= dyPos <= yLen													   |
|	0 <= fclPt + yLen <= lcbTopicLen									   |
--------------------------------------------------------------------------*/

INLINE static int STDCALL WFindThumb(int dyPos, int yLen, VA va, DWORD ulcbLen,
	QDE qde)
{
	int  wMajor;
	int  wMinor;
	DWORD dbIntoTopic;

	// find a relative byte measure of where we are in the topic based on the VA:

	DWORD lcbBytesPerBlock;
	DWORD lcbBlocksInTopic;

	lcbBlocksInTopic =
		qde->top.mtop.vaNextSeqTopic.bf.blknum - qde->top.mtop.vaSR.bf.blknum;

	if (lcbBlocksInTopic) {
		// First calculate a measure of how many bytes are in an uncompressed
		// block:
		lcbBytesPerBlock = qde->top.cbTopic;  // raw uncompressed size
		// adjust for byte offset block overflow:
		lcbBytesPerBlock -=
		 qde->top.mtop.vaNextSeqTopic.bf.byteoff - qde->top.mtop.vaSR.bf.byteoff;
		// divide by the number of blocks:
		lcbBytesPerBlock /= lcbBlocksInTopic;
		dbIntoTopic = (va.bf.blknum - qde->top.mtop.vaSR.bf.blknum) * lcbBytesPerBlock;
		dbIntoTopic += (va.bf.byteoff - qde->top.mtop.vaSR.bf.byteoff);
	}
	else
		dbIntoTopic = va.bf.byteoff - qde->top.mtop.vaSR.bf.byteoff;

	// this may not always be true when compression fudging is innaccurate:
	//AssertF( (LONG)dbIntoTopic >= 0 );
	// Deal with fudging inaccuracies:
	if ((long) dbIntoTopic < 0)
		dbIntoTopic = 0;
	else if ((long) dbIntoTopic > qde->top.cbTopic)
		dbIntoTopic = qde->top.cbTopic;

	wMajor = WMulDiv(0x7FFF, dbIntoTopic, qde->top.cbTopic);
	wMinor = WMulDiv(0x7FFF, (long) dyPos, (long) yLen);

	/*
	 * And again, ulcbLen is a post-compression size whereas top.cbTopic is a
	 * precompression size. Since compression can actually grow the size, and
	 * WMulDiv() assumes arg2 <= arg3, we check for the relatively rare case
	 * where arg3 > arg2 and fudge it. Help3.1 ptr 1349.
	 */

	if (ulcbLen > (DWORD) qde->top.cbTopic)
		ulcbLen = (DWORD) qde->top.cbTopic;
	wMinor = WMulDiv(wMinor, ulcbLen, qde->top.cbTopic);

	// Deal more with fudging inaccuracies:
	if (wMajor + wMinor > 0x8000)
		return(0x8000);

	return(wMajor + wMinor);
}

/*----------------------------------------------------------------------------*\
| VaFromThumb( wThumb, qde )
|
| Calculates the VA position from a thumb position and the info in the DE.
| The scroll bar is assumed to range from 0 - 0x7FFF.
|
| Method: The wThumb value gives us a relative measure of how far into the
|		  topic to go.	Because the topic may be compressed on 2K boudaries
|		  we have to fudge around with the VAs (virtual addresses) in the
|		  DE structure:
|			de.top.mtop.vaSR - de.top.mtop.vaNextSeqTopic
|		  gives us a VA "span", we find the appropriate relative position
|		  within the span based on the relative pos of wThumb.	To help
|		  achieve this we calculate an average bytes-per-2K-block value.
|		  When compression is not on, this should end up being exactly 2K.
|
| Note:  This could be more efficient if we used 0x8000 as the range for
|		 scroll bars, but it might leave some error when the thumb was at
|		 the very bottom of the topic.
|
\*----------------------------------------------------------------------------*/

INLINE static VA STDCALL VaFromThumb(int wThumb, QDE qde)
{
	VA vaRet;
	DWORD lcbBytesPerBlock;
	DWORD lcbBlocksInTopic;
	DWORD lQ, lR, lLinear;

	lcbBlocksInTopic =
	 qde->top.mtop.vaNextSeqTopic.bf.blknum - qde->top.mtop.vaSR.bf.blknum;

	if( lcbBlocksInTopic ) {
		// First calculate a measure of how many bytes are in an uncompressed
		// block:
		lcbBytesPerBlock = qde->top.cbTopic;  // raw uncompressed size
		// adjust for byte offset block overflow:
		lcbBytesPerBlock -=
		 qde->top.mtop.vaNextSeqTopic.bf.byteoff - qde->top.mtop.vaSR.bf.byteoff;
		// divide by the number of blocks:
		lcbBytesPerBlock /= lcbBlocksInTopic;
	}

	// At this point, fcReturn = lcbTopic*(wThumb / 0x7FFF).

	lQ = ((qde->top.cbTopic-1) / 0x7FFF);
	lR = ((qde->top.cbTopic-1) % 0x7FFF);

	// At this point, fcReturn = wThumb*(lQ + lR/0x7FFF).

	// REVIEW: [ralphw] Looks like MulDiv would work here

	lLinear = (wThumb * lQ) + ((wThumb * lR) / 0x7FFF);

	// translate the linear offset into a VA:
	vaRet = qde->top.mtop.vaSR;
	if( lcbBlocksInTopic ) {
	  vaRet.bf.blknum += (vaRet.bf.byteoff + lLinear) / lcbBytesPerBlock;
	  vaRet.bf.byteoff = (vaRet.bf.byteoff + lLinear) % lcbBytesPerBlock;
	}
	else {
	  vaRet.bf.byteoff = (vaRet.bf.byteoff + lLinear);
	}

	/* h3.07 ptr 1270: the above arithmetic can cause vaRet to be lessened
	 * with certain large-NSR topics.  Must make sure this never
	 * happens cause otherwise we display the NSR in the SR region.
	 */
	if( vaRet.dword < qde->top.mtop.vaSR.dword )
	  vaRet = qde->top.mtop.vaSR;

	// Adjust for any slop which may have occurred w/ our
	// "guess the compression" arithmetic -- we must never return a VA
	// in the next topic...
	if( vaRet.dword >= qde->top.mtop.vaNextSeqTopic.dword ) {
	  vaRet = qde->top.mtop.vaNextSeqTopic;
	  if( vaRet.bf.byteoff ) {
		vaRet.bf.byteoff -= 1;
	  }
	  else {
		vaRet.bf.blknum -= 1;
		vaRet.bf.byteoff = cbBLOCK_SIZE;  // this is sleazy
	  }
	}
	return(vaRet);
}

/*******************
**
** Name:	   ShowDEScrollBar
**
** Purpose:    Shows or hides the scroll bar.
**
** Arguments:  qde	   - far pointer to a DE
**			   wWhich  - which scroll (SCROLL_VERT or SCROLL_HORZ)
**			   fShow - Shows if TRUE, Hides if FALSE
**
** Returns:    Nothing.
**
*******************/

extern BOOL fHorzBarPending;

static VOID STDCALL ShowDEScrollBar(QDE qde, WORD wWhich, BOOL fShow)
{
	if (!QDE_TOPIC(qde))
		return;

	switch (wWhich) {
		case SB_VERT:
			if (fShow == qde->fVerScrollVis)
				return;
			qde->fVerScrollVis = fShow;
			break;

		case SB_HORZ:
			if (fShow == qde->fHorScrollVis)
				return;

			if (fShow && (!qde->fHorScrollVis && qde->fVerScrollVis))
				fHorzBarPending = TRUE;
			qde->fHorScrollVis = fShow;
			break;
	}
	ShowScrollBar(qde->hwnd, wWhich, fShow);
	GetClientRect(qde->hwnd, &qde->rct);
}

INLINE static BOOL STDCALL FFindMatchRect(QDE qde, int ifcm, OBJRG objrg,
	LPRECT qrct)
{
	QLSM qlsm;
	int  ilsm;
	BOOL fFound = FALSE;
	QFCM qfcm = QfcmFromIfcm(qde, ifcm);

	ilsm = IFooFirstMRD(((QMRD)&qde->mrdLSM));
	while (ilsm != FOO_NIL) {
		qlsm = ((QLSM)QFooInMRD(((QMRD)&qde->mrdLSM), sizeof(LSM), ilsm));
		if (qlsm->ifcm == ifcm) {
			OBJRG objrgS;
			OBJRG cobjrg;

			objrgS = OBJRGFromSMP(&qlsm->smp, qfcm);
			cobjrg = COBJRGFromSMP(&qlsm->smp);
			if (objrg >= objrgS && objrg < objrgS + cobjrg) {
				*qrct = qlsm->rctFirst;
				fFound = TRUE;
				break;
			}
		}
		ilsm = IFooNextMRD(((QMRD)&qde->mrdLSM), sizeof(LSM), ilsm);
	}
	return fFound;
}