paths.c

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/* $XConsortium: paths.c,v 1.4 91/10/10 11:18:40 rws Exp $ */
/* Copyright International Business Machines, Corp. 1991
 * All Rights Reserved
 * Copyright Lexmark International, Inc. 1991
 * All Rights Reserved
 *
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 * provided that the above copyright notice appear in all copies and that
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 * used in advertising or publicity pertaining to distribution of the
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 * AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.  THE ENTIRE RISK AS TO THE
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 /* PATHS    CWEB         V0021 ********                             */
/*
:h1 id=paths.PATHS Module - Path Operator Handler
 
This is the module that is responsible for building and transforming
path lists.
 
&author. Jeffrey B. Lotspiech ([e-mail])
 
 
:h3.Include Files
 
The included files are:
*/

#include  <stdio.h>
#include <stdlib.h>
                             /*   after the system includes  (dsr)           */
#include  "types.h"
#include  "objects.h"
#include  "spaces.h"
#include  "paths.h"
#include  "regions.h"      /* understands about Union                      */
#include  "fonts.h"        /* understands about TEXTTYPEs                  */
#include  "pictures.h"     /* understands about handles                    */
#include  "strokes.h"      /* understands how to coerce stroke paths       */
#include  "trig.h"
static int UnClose();

/*
:h3.Routines Available to the TYPE1IMAGER User
 
The PATHS routines that are made available to the outside user are:
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
:h3.Functions Provided to Other Modules
 
The path routines that are made available to other TYPE1IMAGER modules
are defined here:
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
NOTE:  because of the casts put in the macros for Loc, ArcCA, Conic,
RoundConic, PathSegment, and JoinSegment, we cannot use the macro names
when the functions are actually defined.  We have to use the unique
names with their unique first two characters.  Thus, if anyone in the
future ever decided to change the first two characters, it would not be
enough just to change the macro (as it would for most other functions).
He would have to also change the function definition.
*/
/*
:h3.Macros Provided to Other Modules
 
The CONCAT macro is defined here and used in the STROKES module.  See
:hdref refid=pathmac..
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
 
/*
:h2.Path Segment Structures
 
A path is represented as a linked list of the following structure:
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
When 'link' is NULL, we are at the last segment in the path (surprise!).
 
'last' is only non-NULL on the first segment of a path,
for all the other segments 'last' == NULL.  We test for a non-NULL
'last' (ISPATHANCHOR predicate) when we are given an alleged path
to make sure the user is not trying to pull a fast one on us.
 
A path may be a collection of disjoint paths.  Every break in the
disjoint path is represented by a MOVETYPE segment.
 
Closed paths are discussed in :hdref refid=close..
 
:h3.CopyPath() - Physically Duplicating a Path
 
This simple function illustrates moving through the path linked list.
Duplicating a segment just involves making a copy of it, except for
text, which has some auxilliary things involved.  We don't feel
competent to duplicate text in this module, so we call someone who
knows how (in the FONTS module).
*/
struct segment *CopyPath(p0)
       register struct segment *p0;  /* path to duplicate                    */
{
       register struct segment *p,*n=NULL,*last=NULL,*anchor;
 
       for (p = p0, anchor = NULL; p != NULL; p = p->link) {
 
               ARGCHECK((!ISPATHTYPE(p->type) || (p != p0 && p->last != NULL)),
                       "CopyPath: invalid segment", p, NULL, (0), struct segment *);
 
               if (p->type == TEXTTYPE)
                       n = (struct segment *) CopyText(p);
               else
                       n = (struct segment *)Allocate(p->size, p, 0);
               n->last = NULL;
               if (anchor == NULL)
                       anchor = n;
               else
                       last->link = n;
               last = n;
       }
/*
At this point we have a chain of newly allocated segments hanging off
'anchor'.  We need to make sure the first segment points to the last:
*/
       if (anchor != NULL) {
               n->link = NULL;
               anchor->last = n;
       }
 
       return(anchor);
}
/*
:h3.KillPath() - Destroying a Path
 
Destroying a path is simply a matter of freeing each segment in the
linked list.  Again, we let the experts handle text.
*/
void KillPath(p)
       register struct segment *p;  /* path to destroy                       */
{
       register struct segment *linkp;  /* temp register holding next segment*/
 
       /* return conditional based on reference count 3-26-91 PNM */
       if ( (--(p->references) > 1) ||
          ( (p->references == 1) && !ISPERMANENT(p->flag) ) )
           return;
 
       while (p != NULL) {
               if (!ISPATHTYPE(p->type)) {
                       ArgErr("KillPath: bad segment", p, NULL);
                       return;
               }
               linkp = p->link;
               if (p->type == TEXTTYPE)
                       KillText(p);
               else
                       Free(p);
               p = linkp;
       }
}
 
/*
:h2 id=location."location" Objects
 
The TYPE1IMAGER user creates and destroys objects of type "location".  These
objects locate points for the primitive path operators.  We play a trick
here and store these objects in the same "segment" structure used for
paths, with a type field == MOVETYPE.
 
This allows the Line() operator, for example, to be very trivial:
It merely stamps its input structure as a LINETYPE and returns it to the
caller--assuming, of course, the input structure was not permanent (as
it usually isn't).
 
:h3.The "movesegment" Template Structure
 
This template is used as a generic segment structure for Allocate:
*/
 
/* added reference field 1 to temporary template below 3-26-91 PNM */
static struct segment movetemplate = { MOVETYPE, 0, 1, sizeof(struct segment), 0,
                NULL, NULL, {0, 0} };
/*
:h3.Loc() - Create an "Invisible Line" Between (0,0) and a Point
 
*/
 
struct segment *t1_Loc(S, x, y)
       register struct XYspace *S;  /* coordinate space to interpret X,Y     */
       DOUBLE x,y;           /* destination point                            */
{
       register struct segment *r;
 
 
       IfTrace3((MustTraceCalls),"..Loc(S=%p, x=%f, y=%f)\n", S, x, y);
 
       r = (struct segment *)Allocate(sizeof(struct segment), &movetemplate, 0);
       TYPECHECK("Loc", S, SPACETYPE, r, (0), struct segment *);
 
       r->last = r;
       r->context = S->context;
       (*S->convert)(&r->dest, S, x, y);
       ConsumeSpace(S);
       return(r);
}
/*
:h3.ILoc() - Loc() With Integer Arguments
 
*/
struct segment *ILoc(S, x, y)
       register struct XYspace *S;  /* coordinate space to interpret X,Y     */
       register int x,y;        /* destination point                         */
{
       register struct segment *r;
 
       IfTrace3((MustTraceCalls),"..ILoc(S=%p, x=%d, y=%d)\n",
                                    S, (LONG) x, (LONG) y);
       r = (struct segment *)Allocate(sizeof(struct segment), &movetemplate, 0);
       TYPECHECK("Loc", S, SPACETYPE, r, (0), struct segment *);
 
       r->last = r;
       r->context = S->context;
       (*S->iconvert)(&r->dest, S, (LONG) x, (LONG) y);
       ConsumeSpace(S);
       return(r);
}
 
/*
:h3.SubLoc() - Vector Subtraction of Two Locition Objects
 
This user operator subtracts two location objects, yielding a new
location object that is the result.
 
The symmetrical function AddLoc() is totally redundent with Join(),
so it is not provided.
*/
 
struct segment *SubLoc(p1, p2)
       register struct segment *p1;
       register struct segment *p2;
{
       IfTrace2((MustTraceCalls),"SubLoc(%p, %p)\n", p1, p2);
 
       ARGCHECK(!ISLOCATION(p1), "SubLoc: bad first arg", p1, NULL, (0), struct segment *);
       ARGCHECK(!ISLOCATION(p2), "SubLoc: bad second arg", p2, NULL, (0), struct segment *);
       p1 = UniquePath(p1);
       p1->dest.x -= p2->dest.x;
       p1->dest.y -= p2->dest.y;
       ConsumePath(p2);
       return(p1);
}
 
/*
:h2.Straight Line Segments
 
:h3.PathSegment() - Create a Generic Path Segment
 
Many routines need a LINETYPE or MOVETYPE path segment, but do not
want to go through the external user's interface, because, for example,
they already know the "fractpel" destination of the segment and the
conversion is unnecessary.  PathSegment() is an internal routine
provided to the rest of TYPE1IMAGER for handling these cases.
*/
 
struct segment *t1_PathSegment(type, x, y)
       int type;             /* LINETYPE or MOVETYPE                         */
       fractpel x,y;         /* where to go to, if known                     */
{
       register struct segment *r;  /* newly created segment                 */
 
       r = (struct segment *)Allocate(sizeof(struct segment), &movetemplate, 0);
       r->type = type;
       r->last = r;          /* last points to itself for singleton          */
       r->dest.x = x;
       r->dest.y = y;
       return(r);
}
/*
:h3.Line() - Create a Line Segment Between (0,0) and a Point P
 
This involves just creating and filling out a segment structure:
*/
struct segment *Line(P)
       register struct segment *P;  /* relevant coordinate space             */
{
 
       IfTrace1((MustTraceCalls),"..Line(%p)\n", P);
       ARGCHECK(!ISLOCATION(P), "Line: arg not a location", P, NULL, (0), struct segment *);
 
       P = UniquePath(P);
       P->type = LINETYPE;
       return(P);
}
/*
:h2.Curved Path Segments
 
We need more points to describe curves.  So, the structures for curved
path segments are slightly different.  The first part is identical;
the curved structures are larger with the extra points on the end.
 
:h3.Bezier Segment Structure
 
We support third order Bezier curves.  They are specified with four
control points A, B, C, and D.  The curve starts at A with slope AB
and ends at D with slope CD.  The curvature at the point A is inversely
related to the length |AB|, and the curvature at the point D is
inversely related to the length |CD|.  Point A is always point (0,0).
 
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
:h3.Bezier() - Generate a Bezier Segment
 
This is just a simple matter of filling out a 'beziersegment' structure:
*/
 
struct beziersegment *Bezier(B, C, D)
       register struct segment *B;  /* second control point                  */
       register struct segment *C;  /* third control point                   */
       register struct segment *D;  /* fourth control point (ending point)   */
{
/* added reference field of 1 to temporary template below 3-26-91  PNM */
       static struct beziersegment template =
                    { BEZIERTYPE, 0, 1, sizeof(struct beziersegment), 0,
                      NULL, NULL, { 0, 0 }, { 0, 0 }, { 0, 0 } };
 
       register struct beziersegment *r;  /* output segment                  */
 
       IfTrace3((MustTraceCalls),"..Bezier(%p, %p, %p)\n", B, C, D);
       ARGCHECK(!ISLOCATION(B), "Bezier: bad B", B, NULL, (2,C,D), struct beziersegment *);
       ARGCHECK(!ISLOCATION(C), "Bezier: bad C", C, NULL, (2,B,D), struct beziersegment *);
       ARGCHECK(!ISLOCATION(D), "Bezier: bad D", D, NULL, (2,B,C), struct beziersegment *);
 
       r = (struct beziersegment *)Allocate(sizeof(struct beziersegment), &template, 0);
       r->last = (struct segment *) r;
       r->dest.x = D->dest.x;
       r->dest.y = D->dest.y;
       r->B.x = B->dest.x;
       r->B.y = B->dest.y;
       r->C.x = C->dest.x;
       r->C.y = C->dest.y;
 
       ConsumePath(B);
       ConsumePath(C);
       ConsumePath(D);
       return(r);
}
 
/*
:h2.Font "Hint" Segments
 
:h3.Hint() - A Font 'Hint' Segment
 
This is temporary code while we experiment with hints.
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
struct hintsegment *Hint(S, ref, width, orientation, hinttype, adjusttype, direction, label)
       struct XYspace *S;