regions.c

source code: Covert TXT to PDF

a call back to the REGIONS module.
:li.ChangeDirection will call whatever function is in the region
structure; for Interior, this function is 'newfilledge'.
:li.Newfilledge will call NewEdge to create a new edgelist structure,
then, call SortSwath to sort it onto the linked list being built at
the region "anchor".
:eol.
 
By making the function called by ChangeDirection be a parameter of the
region, we allow the same ChangeDirection logic to be used by stroking.
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
 
struct region *Interior(p, fillrule)
       register struct segment *p;    /* take interior of this path          */
       register int fillrule;         /* rule to follow if path crosses itself */
{
       register fractpel x,y;  /* keeps ending point of path segment         */
       fractpel lastx,lasty; /* previous x,y from path segment before        */
       register struct region *R;  /* region I will build                    */
       register struct segment *nextP; /* next segment of path */
       struct fractpoint hint; /* accumulated hint value */
       char tempflag;        /* flag; is path temporary?                     */
       char Cflag;           /* flag; should we apply continuity?            */
 
       IfTrace2((MustTraceCalls),".  INTERIOR(%p, %d)\n", p, (LONG) fillrule);
 
       if (p == NULL)
               return(NULL);
/*
Establish the 'Cflag' continuity flag based on user's fill rule and
our own 'Continuity' pragmatic (0: never do continuity, 1: do what
user asked, >1: do it regardless).
*/
       if (fillrule > 0) {
               Cflag = Continuity > 0;
               fillrule -= CONTINUITY;
       }
       else
               Cflag = Continuity > 1;
 
       ARGCHECK((fillrule != WINDINGRULE && fillrule != EVENODDRULE),
                       "Interior: bad fill rule", NULL, NULL, (1,p), struct region *);
 
       if (p->type == TEXTTYPE)
/*             if (fillrule != EVENODDRULE)
               else */
                       return((struct region *)UniquePath(p));
       if (p->type == STROKEPATHTYPE){
	 if (fillrule == WINDINGRULE)
	   return((struct region *)DoStroke(p));
	 else
	   p = CoercePath(p);
       }
       
 
       R = (struct region *)Allocate(sizeof(struct region), &EmptyRegion, 0);
 
       ARGCHECK(!ISPATHANCHOR(p), "Interior:  bad path", p, R, (0), struct region *);
       ARGCHECK((p->type != MOVETYPE), "Interior:  path not closed", p, R, (0), struct region *);
 
 
/* changed definition from !ISPERMANENT to references <= 1 3-26-91 PNM */
       tempflag =  (p->references <= 1); /* only first segment in path is so marked */
       if (!ISPERMANENT(p->flag)) p->references -= 1;
 
       R->newedgefcn = newfilledge;
/*
Believe it or not, "R" is now completely initialized.  We are counting
on the copy of template to get other fields the way we want them,
namely
:ol.
:li.anchor = NULL
:li.xmin, ymin, xmax, ymax, to minimum and maximum values respectively.
:eol.
Anchor = NULL is very
important to ChangeDirection.
See :hdref refid=CD..
 
To minimize problems of "wrapping" in our pel arithmetic, we keep an
origin of the region which is the first move.  Hopefully, that keeps
numbers within plus or minus 32K pels.
*/
       R->origin.x = 0/*TOFRACTPEL(NEARESTPEL(p->dest.x))*/;
       R->origin.y = 0/*TOFRACTPEL(NEARESTPEL(p->dest.y))*/;
       lastx = - R->origin.x;
       lasty = - R->origin.y;
/*
ChangeDirection initializes other important fields in R, such as
lastdy, edge, edgeYstop, edgexmin, and edgexmax.  The first segment
is a MOVETYPE, so it will be called first.
*/
/*
The hints data structure must be initialized once for each path.
*/
 
       if (ProcessHints)
               InitHints(); /* initialize hint data structure */
 
       while (p != NULL)  {
 
               x = lastx + p->dest.x;
               y = lasty + p->dest.y;
 
               IfTrace2((HintDebug > 0),"Ending point = (%d,%d)\n",
			x,
			y);
 
               nextP = p->link;
 
/*
Here we start the hints processing by initializing the hint value to
zero.  If ProcessHints is FALSE, the value will remain zero.
Otherwise, hint accumulates the computed hint values.
*/
 
               hint.x = hint.y = 0;
 
/*
If we are processing hints, and this is a MOVE segment (other than
the first on the path), we need to close (reverse) any open hints.
*/
 
               if (ProcessHints)
                       if ((p->type == MOVETYPE) && (p->last == NULL)) {
                               CloseHints(&hint);
                               IfTrace2((HintDebug>0),"Closed point= (%d,%d)\n",
					x+hint.x,
					y+hint.y);
                       }
 
/*
Next we run through all the hint segments (if any) attached to this
segment.  If ProcessHints is TRUE, we will accumulate computed hint
values.  In either case, nextP will be advanced to the first non-HINT
segment (or NULL), and each hint segment will be freed if necessary.
*/
 
               while ((nextP != NULL) && (nextP->type == HINTTYPE))  {
                       if (ProcessHints)
                               ProcessHint(nextP, x + hint.x, y + hint.y, &hint);
		       
                       {
                               register struct segment *saveP = nextP;
 
                               nextP = nextP->link;
                               if (tempflag)
                                       Free(saveP);
                       }
               }
 
/*
We now apply the full hint value to the ending point of the path segment.
*/
	       /*  printf("Applying hints (x=%d,y=%d)\n", hint.x, hint.y);*/
 
               x += hint.x;
               y += hint.y;
 
               IfTrace2((HintDebug>0),"Hinted ending point = (%d,%d)\n", 
			x, y);
 
               switch(p->type) {
 
                   case LINETYPE:
                       StepLine(R, lastx, lasty, x, y);
                       break;
 
                   case CONICTYPE:
                   {
 
/*
For a conic curve, we apply half the hint value to the conic midpoint.
*/
 
                   }
                       break;
 
                   case BEZIERTYPE:
                   {
                       register struct beziersegment *bp = (struct beziersegment *) p;
 
/*
For a Bezier curve, we apply the full hint value to the Bezier C point.
*/
 
                       StepBezier(R, lastx, lasty,
                                 lastx + bp->B.x, lasty + bp->B.y,
                                 lastx + bp->C.x + hint.x,
                                 lasty + bp->C.y + hint.y,
                                 x, y);
                   }
                       break;
 
                   case MOVETYPE:
/*
At this point we have encountered a MOVE segment.  This breaks the
path, making it disjoint.
*/
                       if (p->last == NULL) /* i.e., not first in path */
                               ChangeDirection(CD_LAST, R, lastx, lasty, (fractpel) 0);
 
                       ChangeDirection(CD_FIRST, R, x, y, (fractpel) 0);
/*
We'll just double check for closure here.  We forgive an appended
MOVETYPE at the end of the path, if it isn't closed:
*/
                       if (!ISCLOSED(p->flag) && p->link != NULL)
                               return((struct region *)ArgErr("Fill: sub-path not closed", p, NULL));
                       break;
 
                   default:
                       abort("Interior: path type error", 30);
               }
/*
We're done with this segment.  Advance to the next path segment in
the list, freeing this one if necessary:
*/
               lastx = x;  lasty = y;
 
               if (tempflag)
                       Free(p);
               p = nextP;
       }
       ChangeDirection(CD_LAST, R, lastx, lasty, (fractpel) 0);
       R->ending.x = lastx;
       R->ending.y = lasty;
/*
Finally, clean up the region's based on the user's 'fillrule' request:
*/
       if (Cflag)
             ApplyContinuity(R);
       if (fillrule == WINDINGRULE)
             Unwind(R->anchor);
       return(R);
}
/*
:h4.Unwind() - Discards Edges That Fail the Winding Rule Test
 
The winding rule says that upward going edges should be paired with
downward going edges only, and vice versa.  So, if two upward edges
or two downward edges are nominally left/right pairs, Unwind() should
discard the second one.  Everything should balance; we should discard
an even number of edges; of course, we abort if we don't.
*/
static int Unwind(area)
       register struct edgelist *area;  /* input area modified in place      */
{
       register struct edgelist *last=NULL,*next;  /* struct before and after current one */
       register int y;       /* ymin of current swath                        */
       register int count,newcount;  /* winding count registers              */
 
       IfTrace1((RegionDebug>0),"...Unwind(%p)\n", area);
 
       while (VALIDEDGE(area)) {
 
               count = 0;
               y = area->ymin;
 
               do {
                       next = area->link;
 
                       if (ISDOWN(area->flag))
                               newcount = count + 1;
                       else
                               newcount = count - 1;
 
                       if (count == 0 || newcount == 0)
                               last = area;
                       else
                               discard(last, next);
 
                       count = newcount;
                       area = next;
 
               } while (area != NULL && area->ymin == y);
 
               if (count != 0)
                       abort("Unwind:  uneven edges", 31);
       }
       /* We retunr a value for ANSI-C-compiler */
       return(0);
       
}
/*
:h3."workedge" Array
 
This is a statically allocated array where edges are built
before being copied into more permanent storage by NewEdge().
*/
 
#ifndef   MAXEDGE
#define   MAXEDGE     1000
#endif
 
static pel workedge[MAXEDGE];
static pel *currentworkarea = workedge;
static pel currentsize = MAXEDGE;
 
/*
:h3 id=cd.ChangeDirection() - Called When Y Direction Changes
 
The rasterizing routines call this entry point when they detect
a change in Y.  We then build the current edge and sort it into
emerging edgelist at 'anchor' by calling whatever "newedgefcn"
is appropriate.
*/
 
void ChangeDirection(type, R, x, y, dy)
       int type;             /* CD_FIRST, CD_CONTINUE, or CD_LAST            */
       register struct region *R;  /* region in which we are changing direction */
       fractpel x,y;         /* current beginning x,y                        */
       fractpel dy;          /* direction and magnitude of change in y       */
{
       register fractpel ymin,ymax;  /* minimum and maximum Y since last call */
       register fractpel x_at_ymin,x_at_ymax;  /* their respective X's       */
       register pel iy;      /* nearest integer pel to 'y'                   */
       register pel idy;     /* nearest integer pel to 'dy'                  */
       register int ydiff;   /* allowed Y difference in 'currentworkarea'    */
 
       IfTrace4((RegionDebug>0),"Change Y direction (%d) from (%d,%d), dy=%d\n",
                                         (LONG) type, x, y, dy);
 
       if (type != CD_FIRST) {
 
               if (R->lastdy > 0) {
                       ymin = R->firsty;
                       x_at_ymin = R->firstx;
                       ymax = y;
                       x_at_ymax = x;
               }
               else {
                       ymin = y;
                       x_at_ymin = x;
                       ymax = R->firsty;
                       x_at_ymax = R->firstx;
               }
 
               if (ymax < ymin)
                       abort("negative sized edge?", 32);
 
 
               (*R->newedgefcn)(R, R->edgexmin, R->edgexmax, ymin, ymax,
                                   R->lastdy > 0, x_at_ymin, x_at_ymax);
 
       }
 
       R->firsty = y;
       R->firstx = x;
       R->lastdy = dy;
 
       iy = NEARESTPEL(y);
       idy = NEARESTPEL(dy);
       if (currentworkarea != workedge && idy < MAXEDGE && idy > -MAXEDGE) {
               NonObjectFree(currentworkarea);
               currentworkarea = workedge;