hints.c

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               next->link = edge;
               edge->flag ^= ISLEFT(ON);
               edge->flag &= ~ISAMBIGUOUS(ON);
               next->flag ^= ISLEFT(ON);
               next->flag &= ~ISAMBIGUOUS(ON);
               edge = next;
       }
}
/*
:h3.DumpSubPaths()
 
A debug tool.
*/
 
static struct edgelist *before();  /* subroutine of DumpSubPaths             */
 
static void DumpSubPaths(anchor)
       struct edgelist *anchor;
{
 
       register struct edgelist *edge,*e,*e2;
       pel y;
 
       for (edge = anchor; VALIDEDGE(edge); edge = edge->link) {
               if (ISPERMANENT(edge->flag))
                       continue;
               IfTrace0(TRUE, "BEGIN Subpath\n");
               for (e2 = edge; !ISPERMANENT(e2->flag);) {
                       if (ISDOWN(e2->flag)) {
                               IfTrace1(TRUE, ". Downgoing edge's top at %x\n", e2);
                               for (e = e2;; e = e->subpath) {
                                       IfTrace4(TRUE, ". . [%5d] %5d    @ %x[%x]\n",
                                                e->ymin, *e->xvalues, e, e->flag);
                                       for (y=e->ymin+1; y < e->ymax; y++)
                                               IfTrace2(TRUE, ". . [%5d] %5d     \"\n", y, e->xvalues[y-e->ymin]);
                                       e->flag |= ISPERMANENT(ON);
                                       if (ISBREAK(e, e->subpath))
                                               break;
                               }
                       }
                       else {
                               IfTrace1(TRUE, ". Upgoing edge's top at %x\n", e2);
                               for (e = e2; !ISBREAK(e, e->subpath); e = e->subpath) { ; }
                               for (;; e=before(e)) {
                                       IfTrace4(TRUE, ". . [%5d] %5d    @ %x[%x]\n",
                                                e->ymax-1, e->xvalues[e->ymax-1-e->ymin], e, e->flag);
                                       for (y=e->ymax-2; y >= e->ymin; y--)
                                               IfTrace2(TRUE, ". . [%5d] %5d      \"\n", y, e->xvalues[y-e->ymin]);
                                       e->flag |= ISPERMANENT(ON);
                                       if (e == e2)
                                               break;
                               }
                       }
                       do {
                               e2 = before(e2);
                       } while (!ISBREAK(before(e2), e2));
               }
       }
}
 
static struct edgelist *before(e)
       struct edgelist *e;
{
       struct edgelist *r;
       for (r = e->subpath; r->subpath != e; r = r->subpath) { ; }
       return(r);
}
 
/*
:h2.Fixing Region Continuity Problems
 
Small regions may become disconnected when their connecting segments are
less than a pel wide.  This may be correct in some applications, but in
many (especially small font characters), it is more pleasing to keep
connectivity.  ApplyContinuity() (invoked by +CONTINUITY on the
Interior() fill rule) fixes connection breaks.  The resulting region
is geometrically less accurate, but may be more pleasing to the eye.
*/
/*
Here are some macros which we will need:
*/
 
#define IsValidPel(j) (j!=MINPEL)
 
/*
:h3.writeXofY() - Stuffs an X Value Into an "edgelist"
 
writeXofY writes an x value into an edge at position 'y'.  It must
update the edge's xmin and xmax.  If there is a possibility that this
new x might exceed the region's bounds, updating those are the
responsibility of the caller.
*/
 
static void writeXofY(e, y, x)
       struct edgelist *e;   /* relevant edgelist                            */
       int y;                /* y value                                      */
       int x;                /* new x value                                  */
{
       if (e->xmin > x)  e->xmin = x;
       if (e->xmax < x)  e->xmax = x;
       e->xvalues[y - e->ymin] = x;
}
 
/*-------------------------------------------------------------------------*/
/* the following three macros tell us whether we are at a birth point, a    */
/* death point, or simply in the middle of the character                */
/*-------------------------------------------------------------------------*/
#define WeAreAtTop(e,i) (ISTOP(e->flag) && e->ymin == i)
#define WeAreAtBottom(e,i) (ISBOTTOM(e->flag) && e->ymax-1 == i)
#define WeAreInMiddle(e,i) \
      ((!ISTOP(e->flag) && !ISBOTTOM(e->flag))||(i < e->ymax-1 && i > e->ymin))
/*
The following macro tests if two "edgelist" structures are in the same
swath:
*/
#define SAMESWATH(e1,e2)  (e1->ymin == e2->ymin)
 
/*
:h3.CollapseWhiteRun() - Subroutine of ApplyContinuity()
 
When we have a white run with an implied horizontal line above or
below it, we better have black on the other side of this line.  This
function both tests to see if black is there, and adjusts the end
points (collapses) the white run as necessary if it is not.  The
goal is to collapse the white run as little as possible.
*/
 
static void CollapseWhiteRun(anchor, yblack, left, right, ywhite)
        struct edgelist *anchor;  /* anchor of edge list                     */
        pel yblack;          /* y of (hopefully) black run above or below    */
        struct edgelist *left;  /* edgelist at left of WHITE run             */
        struct edgelist *right;  /* edgelist at right of WHITE run           */
        pel ywhite;          /* y location of white run                      */
{
       struct edgelist *edge;
       struct edgelist *swathstart = anchor;
       register pel x;
 
       if (XofY(left, ywhite) >= XofY(right, ywhite))
               return;
/*
Find the swath with 'yblack'.  If we don't find it, completely collapse
the white run and return:
*/
       while (VALIDEDGE(swathstart)) {
               if (yblack < swathstart->ymin)  {
                      writeXofY(left, ywhite, XofY(right, ywhite));
                      return;
               }
               if (yblack < swathstart->ymax) break;
               swathstart = swathstart->link->link;
       }
       if(!VALIDEDGE(swathstart)) {
               writeXofY(left, ywhite, XofY(right, ywhite));
               return;
       }
/*
Now we are in the swath that contains 'y', the reference line above
or below that we are trying to maintain continuity with.  If black
in this line begins in the middle of our white run, we must collapse
the white run from the left to that point.  If black ends in the
middle of our white run, we must collapse the white run from the right
to that point.
*/
       for (edge = swathstart; VALIDEDGE(edge); edge = edge->link) {
 
               if (!SAMESWATH(swathstart,edge))
                       break;
               if( XofY(edge, yblack) > XofY(left, ywhite)) {
                       if (ISLEFT(edge->flag)) {
                                x = XofY(edge, yblack);
                                if (XofY(right, ywhite) < x)
                                       x = XofY(right, ywhite);
                                writeXofY(left, ywhite, x);
                       }
                       else {
                                x = XofY(edge, yblack);
                                while (edge->link != NULL && SAMESWATH(edge, edge->link)
                                       && x >= XofY(edge->link, yblack) ) {
                                       edge = edge->link->link;
                                       x = XofY(edge, yblack);
                                }
                                if (x < XofY(right, ywhite))
                                       writeXofY(right, ywhite, x);
                                return;
                       }
               }
       }
       writeXofY(left, ywhite, XofY(right, ywhite));
}
 
/*
:h3.ApplyContinuity() - Fix False Breaks in a Region
 
This is the externally visible routine called from the REGIONS module
when the +CONTINUITY flag is on the Interior() fill rule.
*/
 
void ApplyContinuity(R)
struct region *R;
{
 struct edgelist *left;
 struct edgelist *right;
 struct edgelist *edge,*e2;
 pel rightXabove,rightXbelow,leftXabove,leftXbelow;
 pel leftX,rightX;
 int i;
 long newcenter,abovecenter,belowcenter;
 
 FixSubPaths(R);
 if (RegionDebug >= 3)
        DumpSubPaths(R->anchor);
 left = R->anchor;
/* loop through and do all of the easy checking. ( no tops or bottoms) */
 while(VALIDEDGE(left))
 {
  right = left->link;
  for(i=left->ymin;i<left->ymax;++i)
  {
   leftX       = findXofY(left,i);
   rightX      = findXofY(right,i);
   leftXbelow  = findXofY(left,i+1);
   rightXbelow = findXofY(right,i+1);
   if(rightX <= leftX)
   {
/* then, we have a break in a near vertical line */
     leftXabove  = findXofY(left,i-1);
     rightXabove = findXofY(right,i-1);
     if( IsValidPel(leftXabove) && IsValidPel(rightXabove) )
     {
      abovecenter = leftXabove + rightXabove;
     }
     else
     {
      abovecenter = leftX + rightX;
     }
     if( IsValidPel(leftXbelow) && IsValidPel(rightXbelow) )
     {
      belowcenter = leftXbelow + rightXbelow;
     }
     else
     {
      belowcenter = leftX + rightX;
     }
     newcenter = abovecenter + belowcenter;
     if( newcenter > 4*leftX )
     {
      rightX = rightX + 1;
     }
     else if( newcenter < 4*leftX)
     {
      leftX = leftX - 1;
     }
     else
     {
      rightX = rightX + 1;
     }
     writeXofY(right,i,rightX);
     writeXofY(left,i,leftX);
     if(rightX > R->xmax) {R->xmax = rightX;}
     if(leftX < R->xmin) {R->xmin = leftX;}
   }
   if( !WeAreAtBottom(left,i) && (leftXbelow>=rightX))
   {
/* then we have a break in a near horizontal line in the middle */
    writeXofY(right,i,leftXbelow);
   }
   if( !WeAreAtBottom(right,i) && (leftX >=rightXbelow))
   {
/* then we have a break in a near horizontal line in the middle */
    writeXofY(left,i,rightXbelow);
   }
  }
  left = right->link;
 }
/*
There may be "implied horizontal lines" between edges that have
implications for continuity.  This loop looks for white runs that
have implied horizontal lines on the top or bottom, and calls
CollapseWhiteRuns to check and fix any continuity problems from
them.
*/
      for (edge = R->anchor; VALIDEDGE(edge); edge = edge->link) {
              if ((!ISTOP(edge->flag) && !ISBOTTOM(edge->flag)) || ISLEFT(edge->flag))
                      continue;  /* at some future date we may want left edge logic here too */
              for (e2 = edge->link; VALIDEDGE(e2) && SAMESWATH(edge,e2); e2 = e2->link) {
                      if (ISTOP(e2->flag) && ISTOP(edge->flag)
                          && NONE != ImpliedHorizontalLine(edge,e2,edge->ymin)) {
                              if (ISLEFT(e2->flag))
                                      CollapseWhiteRun(R->anchor, edge->ymin-1,
                                                       edge, e2, edge->ymin);
                      }
                      if (ISBOTTOM(e2->flag) && ISBOTTOM(edge->flag)
                          && NONE != ImpliedHorizontalLine(edge,e2, edge->ymax)) {
                              if (ISLEFT(e2->flag))
                                      CollapseWhiteRun(R->anchor, edge->ymax,
                                                       edge, e2, edge->ymax-1);
                      }
              }
      }
}