mipolyutil.c

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/***********************************************************
Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts,
and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
 
                        All Rights Reserved
 
Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in 
supporting documentation, and that the names of Digital or MIT not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.  
 
DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.
 
 ******************************************************************/
/* $XConsortium: mipolyutil.c,v 1.14 89/03/22 10:50:55 rws Exp $ */
#include <stdlib.h>
#include "miscstruct.h"
#include "gc.h"
#include "miscanfill.h"
#include "mipoly.h"
 
extern void miFreeStorage();
 
#define MAXINT 0x7fffffff
#define MININT -MAXINT
 
/*
 *     fillUtils.c
 *
 *     Written by Brian Kelleher;  Oct. 1985
 *
 *     This module contains all of the utility functions
 *     needed to scan convert a polygon.
 *
 */
 
/*
 *     InsertEdgeInET
 *
 *     Insert the given edge into the edge table.
 *     First we must find the correct bucket in the
 *     Edge table, then find the right slot in the
 *     bucket.  Finally, we can insert it.
 *
 */
Bool
miInsertEdgeInET(ET, ETE, scanline, SLLBlock, iSLLBlock)
EdgeTable *ET;
EdgeTableEntry *ETE;
int scanline;
ScanLineListBlock **SLLBlock;
int *iSLLBlock;
{
    register EdgeTableEntry *start, *prev;
    register ScanLineList *pSLL, *pPrevSLL;
    ScanLineListBlock *tmpSLLBlock;
 
    /*
     * find the right bucket to put the edge into
     */
    pPrevSLL = &ET->scanlines;
    pSLL = pPrevSLL->next;
    while (pSLL && (pSLL->scanline < scanline)) {
        pPrevSLL = pSLL;
        pSLL = pSLL->next;
    }
 
    /*
     * reassign pSLL (pointer to ScanLineList) if necessary
     */
    if ((!pSLL) || (pSLL->scanline > scanline)) {
        if (*iSLLBlock > SLLSPERBLOCK - 1) {
            tmpSLLBlock =
                    (ScanLineListBlock *) malloc(sizeof (ScanLineListBlock));
            if (!tmpSLLBlock)
                return FALSE;
            (*SLLBlock)->next = tmpSLLBlock;
            tmpSLLBlock->next = (ScanLineListBlock *) NULL;
            *SLLBlock = tmpSLLBlock;
            *iSLLBlock = 0;
        }
        pSLL = &((*SLLBlock)->SLLs[(*iSLLBlock)++]);
 
        pSLL->next = pPrevSLL->next;
        pSLL->edgelist = (EdgeTableEntry *) NULL;
        pPrevSLL->next = pSLL;
    }
    pSLL->scanline = scanline;
 
    /*
     * now insert the edge in the right bucket
     */
    prev = (EdgeTableEntry *) NULL;
    start = pSLL->edgelist;
    while (start && (start->bres.minor < ETE->bres.minor)) {
        prev = start;
        start = start->next;
    }
    ETE->next = start;
 
    if (prev)
        prev->next = ETE;
    else
        pSLL->edgelist = ETE;
    return TRUE;
}
 
/*
 *     CreateEdgeTable
 *
 *     This routine creates the edge table for
 *     scan converting polygons. 
 *     The Edge Table (ET) looks like:
 *
 *    EdgeTable
 *     --------
 *    |  ymax  |        ScanLineLists
 *    |scanline|-->------------>-------------->...
 *     --------   |scanline|   |scanline|
 *                |edgelist|   |edgelist|
 *                ---------    ---------
 *                    |             |
 *                    |             |
 *                    V             V
 *              list of ETEs   list of ETEs
 *
 *     where ETE is an EdgeTableEntry data structure,
 *     and there is one ScanLineList per scanline at
 *     which an edge is initially entered.
 *
 */
 
Bool
miCreateETandAET(count, pts, ET, AET, pETEs, pSLLBlock)
register int count;
register DDXPointPtr pts;
EdgeTable *ET;
EdgeTableEntry *AET;
register EdgeTableEntry *pETEs;
ScanLineListBlock *pSLLBlock;
{
    register DDXPointPtr top, bottom;
    register DDXPointPtr PrevPt, CurrPt;
    int iSLLBlock = 0;
 
    int dy;
 
    if (count < 2) return TRUE;
 
    /*
     *  initialize the Active Edge Table
     */
    AET->next = (EdgeTableEntry *) NULL;
    AET->back = (EdgeTableEntry *) NULL;
    AET->nextWETE = (EdgeTableEntry *) NULL;
    AET->bres.minor = MININT;
 
    /*
     *  initialize the Edge Table.
     */
    ET->scanlines.next = (ScanLineList *) NULL;
    ET->ymax = MININT;
    ET->ymin = MAXINT;
    pSLLBlock->next = (ScanLineListBlock *) NULL;
 
    PrevPt = &pts[count - 1];
 
    /*
     *  for each vertex in the array of points.
     *  In this loop we are dealing with two vertices at
     *  a time -- these make up one edge of the polygon.
     */
    while (count--) {
        CurrPt = pts++;
 
        /*
         *  find out which point is above and which is below.
         */
        if (PrevPt->y > CurrPt->y) {
            bottom = PrevPt, top = CurrPt;
            pETEs->ClockWise = 0;
        } else {
            bottom = CurrPt, top = PrevPt;
            pETEs->ClockWise = 1;
        }
 
        /*
         * don't add horizontal edges to the Edge table.
         */
        if (bottom->y != top->y) {
            pETEs->ymax = bottom->y - 1; /* -1 so we don't get last scanline */
 
            /*
             *  initialize integer edge algorithm
             */
            dy = bottom->y - top->y;
            BRESINITPGONSTRUCT(dy, top->x, bottom->x, pETEs->bres);
 
            if (!miInsertEdgeInET(ET, pETEs, top->y, &pSLLBlock, &iSLLBlock)) {
                miFreeStorage(pSLLBlock->next);
                return FALSE;
            }
 
            ET->ymax = max(ET->ymax, PrevPt->y);
            ET->ymin = min(ET->ymin, PrevPt->y);
            pETEs++;
        }
 
        PrevPt = CurrPt;
    }
    return TRUE;
}
 
/*
 *     loadAET
 *
 *     This routine moves EdgeTableEntries from the
 *     EdgeTable into the Active Edge Table,
 *     leaving them sorted by smaller x coordinate.
 *
 */
 
void
miloadAET(AET, ETEs)
register EdgeTableEntry *AET, *ETEs;
{
    register EdgeTableEntry *pPrevAET;
    register EdgeTableEntry *tmp;
 
    pPrevAET = AET;
    AET = AET->next;
    while (ETEs) {
        while (AET && (AET->bres.minor < ETEs->bres.minor)) {
            pPrevAET = AET;
            AET = AET->next;
        }
        tmp = ETEs->next;
        ETEs->next = AET;
        if (AET)
            AET->back = ETEs;
        ETEs->back = pPrevAET;
        pPrevAET->next = ETEs;
        pPrevAET = ETEs;
 
        ETEs = tmp;
    }
}
 
/*
 *     computeWAET
 *
 *     This routine links the AET by the
 *     nextWETE (winding EdgeTableEntry) link for
 *     use by the winding number rule.  The final 
 *     Active Edge Table (AET) might look something
 *     like:
 *
 *     AET
 *     ----------  ---------   ---------
 *     |ymax    |  |ymax    |  |ymax    | 
 *     | ...    |  |...     |  |...     |
 *     |next    |->|next    |->|next    |->...
 *     |nextWETE|  |nextWETE|  |nextWETE|
 *     ---------   ---------   ^--------
 *         |                   |       |
 *         V------------------->       V---> ...
 *
 */
void
micomputeWAET(AET)
register EdgeTableEntry *AET;
{
    register EdgeTableEntry *pWETE;
    register int inside = 1;
    register int isInside = 0;
 
    AET->nextWETE = (EdgeTableEntry *) NULL;
    pWETE = AET;
    AET = AET->next;
    while (AET) {
        if (AET->ClockWise)
            isInside++;
        else
            isInside--;
 
        if ((!inside && !isInside) ||
                (inside && isInside)) {
            pWETE->nextWETE = AET;
            pWETE = AET;
            inside = !inside;
        }
        AET = AET->next;
    }
    pWETE->nextWETE = (EdgeTableEntry *) NULL;
}
 
/*
 *     InsertionSort
 *
 *     Just a simple insertion sort using
 *     pointers and back pointers to sort the Active
 *     Edge Table.
 *
 */
 
int
miInsertionSort(AET)
register EdgeTableEntry *AET;
{
    register EdgeTableEntry *pETEchase;
    register EdgeTableEntry *pETEinsert;
    register EdgeTableEntry *pETEchaseBackTMP;
    register int changed = 0;
 
    AET = AET->next;
    while (AET) {
        pETEinsert = AET;
        pETEchase = AET;
        while (pETEchase->back->bres.minor > AET->bres.minor)
            pETEchase = pETEchase->back;
 
        AET = AET->next;
        if (pETEchase != pETEinsert) {
            pETEchaseBackTMP = pETEchase->back;
            pETEinsert->back->next = AET;
            if (AET)
                AET->back = pETEinsert->back;
            pETEinsert->next = pETEchase;
            pETEchase->back->next = pETEinsert;
            pETEchase->back = pETEinsert;
            pETEinsert->back = pETEchaseBackTMP;
            changed = 1;
        }
    }
    return (changed);
}
 
/*
 *     Clean up our act.
 */
void
miFreeStorage(pSLLBlock)
register ScanLineListBlock *pSLLBlock;
{
    register ScanLineListBlock *tmpSLLBlock;
 
    while (pSLLBlock) {
        tmpSLLBlock = pSLLBlock->next;
        free(pSLLBlock);
        pSLLBlock = tmpSLLBlock;
    }
}