http://www.cs.man.ac.uk/~toby/alan/software/

I compiled the dll under windows with the help of MingW.
I asked myself how to load that dll and use the functions.
The wiki suggested ffidl. However it's doesn't seem to be that easy to use.

Functions and typedefs that need to be defined can be found in the gpc.h.
http://pastebin.com/JQTWLULh

I first tried to define the custom typedefs...

::ffidl::typedef gpc_vertex double double
::ffidl::typedef gpc_vertex_list int gpc_vertex
::ffidl::typedef gpc_polygon int int gpc_vertex_list
::ffidl::typedef gpc_tristrip int gpc_vertex_list

... but how to define enums?

And how to bind the functions?
Could anyone give an example?

Thanks in advance!

here are commands and outputs (i used the tutorial as a reference http://www.swig.org/tutorial.html)
/include/tcl contains the tcl headers

% swig -tcl gpc.i
% gcc -fpic -c gpc.c gpc_wrap.c -I/include/tcl
gpc.c:1:0: Warnung: -fpic für Ziel ignoriert (der gesamte Code ist positionsunabhängig) [standardmäßig aktiviert]
gpc_wrap.c:1:0: Warnung: -fpic für Ziel ignoriert (der gesamte Code ist positionsunabhängig) [standardmäßig aktiviert]

% gcc -shared gpc.o gpc_wrap.o -o gpc.dll
gpc_wrap.o:gpc_wrap.c:(.text+0x96b): undefined reference to `_imp__Tcl_ResetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x97f): undefined reference to `_imp__Tcl_SetObjResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x9a3): undefined reference to `_imp__Tcl_SetErrorCode'
gpc_wrap.o:gpc_wrap.c:(.text+0x9b8): undefined reference to `_imp__Tcl_ResetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x9dc): undefined reference to `_imp__Tcl_SetErrorCode'
gpc_wrap.o:gpc_wrap.c:(.text+0xa07): undefined reference to `_imp__Tcl_AppendResult'
gpc_wrap.o:gpc_wrap.c:(.text+0xa24): undefined reference to `_imp__Tcl_NewStringObj'
gpc_wrap.o:gpc_wrap.c:(.text+0xa4c): undefined reference to `_imp__Tcl_ObjSetVar2'
gpc_wrap.o:gpc_wrap.c:(.text+0xad8): undefined reference to `_imp__Tcl_InitHashTable'
gpc_wrap.o:gpc_wrap.c:(.text+0xb82): undefined reference to `_imp__Tcl_DeleteHashEntry'
gpc_wrap.o:gpc_wrap.c:(.text+0xc00): undefined reference to `_imp__Tcl_VarEval'
gpc_wrap.o:gpc_wrap.c:(.text+0xc11): undefined reference to `_imp__Tcl_GetObjResult'
gpc_wrap.o:gpc_wrap.c:(.text+0xc29): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0xc3c): undefined reference to `_imp__Tcl_ResetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0xc53): undefined reference to `_imp__Tcl_ResetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0xc81): undefined reference to `_imp__Tcl_VarEval'
gpc_wrap.o:gpc_wrap.c:(.text+0xc92): undefined reference to `_imp__Tcl_ResetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0xca9): undefined reference to `_imp__Tcl_GetObjResult'
gpc_wrap.o:gpc_wrap.c:(.text+0xcbb): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0xda7): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0xe37): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0xf3b): undefined reference to `_imp__Tcl_NewStringObj'
gpc_wrap.o:gpc_wrap.c:(.text+0xfcc): undefined reference to `_imp__Tcl_NewStringObj'
gpc_wrap.o:gpc_wrap.c:(.text+0xfff): undefined reference to `_imp__Tcl_GetVar'
gpc_wrap.o:gpc_wrap.c:(.text+0x107d): undefined reference to `_imp__Tcl_SetVar'
gpc_wrap.o:gpc_wrap.c:(.text+0x10ed): undefined reference to `_imp__TclFreeObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1140): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1164): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1211): undefined reference to `_imp__Tcl_DeleteCommandFromToken'
gpc_wrap.o:gpc_wrap.c:(.text+0x13ff): undefined reference to `_imp__TclFreeObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1445): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1469): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1511): undefined reference to `_imp__TclFreeObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1556): undefined reference to `_imp__Tcl_DuplicateObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1567): undefined reference to `_imp__Tcl_SetObjResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x15bb): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x15da): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1622): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x165b): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1731): undefined reference to `_imp__TclFreeObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x17bb): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x17f9): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1820): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1850): undefined reference to `_imp__Tcl_GetStringResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x18e3): undefined reference to `_imp__Tcl_AppendElement'
gpc_wrap.o:gpc_wrap.c:(.text+0x197e): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x199c): undefined reference to `_imp__Tcl_GetCommandInfo'
gpc_wrap.o:gpc_wrap.c:(.text+0x19c6): undefined reference to `_imp__Tcl_DuplicateObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1a08): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1a30): undefined reference to `_imp__Tcl_CreateObjCommand'
gpc_wrap.o:gpc_wrap.c:(.text+0x1ab4): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1aeb): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1b73): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1c02): undefined reference to `_imp__Tcl_GetObjResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1c0c): undefined reference to `_imp__Tcl_DuplicateObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1c2e): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1c66): undefined reference to `_imp__Tcl_DuplicateObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1c84): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1ca6): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1ccd): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1d2b): undefined reference to `_imp__TclFreeObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1db0): undefined reference to `_imp__Tcl_CreateObjCommand'
gpc_wrap.o:gpc_wrap.c:(.text+0x1e2f): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x1e8e): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1f03): undefined reference to `_imp__Tcl_GetLongFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x1fa5): undefined reference to `_imp__Tcl_GetDoubleFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x2027): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x2049): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x2068): undefined reference to `_imp__Tcl_GetStringFromObj'
gpc_wrap.o:gpc_wrap.c:(.text+0x2127): undefined reference to `_imp__Tcl_SetResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x21bc): undefined reference to `_imp__Tcl_AppendResult'
gpc_wrap.o:gpc_wrap.c:(.text+0x251c): undefined reference to `_imp__Tcl_InitHashTable'
gpc_wrap.o:gpc_wrap.c:(.text+0x2676): undefined reference to `_imp__Tcl_InitHashTable'
gpc_wrap.o:gpc_wrap.c:(.text+0x270f): undefined reference to `_imp__Tcl_PkgProvide'
gpc_wrap.o:gpc_wrap.c:(.text+0x2724): undefined reference to `_imp__Tcl_Eval'
gpc_wrap.o:gpc_wrap.c:(.text+0x2797): undefined reference to `_imp__Tcl_CreateObjCommand'
gpc_wrap.o:gpc_wrap.c:(.text+0x27eb): undefined reference to `_imp__Tcl_SetVar'
gpc_wrap.o:gpc_wrap.c:(.text+0x2833): undefined reference to `_imp__Tcl_TraceVar'
gpc_wrap.o:gpc_wrap.c:(.text+0x287b): undefined reference to `_imp__Tcl_TraceVar'
collect2.exe: Fehler: ld gab 1 als Ende-Status zurück

as you can see the dll is not compiled.
my gpc.i contains the following data:

%module gpc
%{
#include "gpc.h"
%}
#include "gpc.h"

gcc -fpic -DUSE_TCL_STUBS -c gpc.c gpc_wrap.c -I/include/tcl
gcc -shared gpc.o gpc_wrap.o -o gpc.dll /lib/tcl/tclstub85.lib
# adopt the path to the lib file to get it to link

I don't know about the current status of gcc linking against static
libraries for Visual C (I asumed it is simply working), and I don't have
this setup here now to test it for you, sorry.

i tried the same procedure on another computer with a different activestate tcl version.

i used activestate's tcl headers and the tclstub85.lib, which came with it.
my swig inpute file had an error, which i fixed.

and guess what? it linked and compiled just fine!

the dll is now loadable in activestate's wish.

% join [info commands gpc_*] \n
gpc_vertex_list_vertex_get
gpc_vertex_list_num_vertices_get
gpc_tristrip_num_strips_set
gpc_tristrip_strip_get
gpc_tristrip
gpc_vertex_x_get
gpc_write_polygon
gpc_tristrip_num_strips_get
gpc_add_contour
gpc_polygon_to_tristrip
gpc_polygon_num_contours_set
gpc_polygon_contour_set
gpc_polygon
gpc_free_polygon
gpc_free_tristrip
gpc_polygon_clip
gpc_vertex_y_set
gpc_polygon_num_contours_get
gpc_polygon_contour_get
gpc_vertex_list
gpc_tristrip_clip
gpc_polygon_hole_set
gpc_vertex_y_get
gpc_vertex
gpc_vertex_list_vertex_set
gpc_vertex_list_num_vertices_set
gpc_read_polygon
gpc_tristrip_strip_set
gpc_polygon_hole_get
gpc_vertex_x_set

as you can see the commands are all there now!
thanks so far.

i now need to figure out how to use that monster lol.

typedef struct                      /* Vertex list structure             */
{
  int                 num_vertices; /* Number of vertices in list        */
  gpc_vertex         *vertex;       /* Vertex array pointer              */

my example.....

load gpc.dll

set vertex1 [gpc_vertex]
set vertex2 [gpc_vertex]
set vertex3 [gpc_vertex]

$vertex1 configure -x 0 -y 0
$vertex2 configure -x 1 -y 0
$vertex2 configure -x 0 -y 1

set vertex_list1 [gpc_vertex_list]

$vertex_list1 configure -num_vertices 3 -vertex [list $vertex1 $vertex2 $vertex3]

it returns:

gpc_vertex_list makelist(int n) {
        gpc_vertex_list result;
        result.num_vertices=n;
        result.vertex = malloc(sizeof(gpc_vertex)*n);
        return result;

set new_vert [makelist 5]

to construct the vertex list. There is a need to add another accessor
function to be actually able to use it; it could look like this:

void set_vertex(gpc_vertex_list *list, int n, double x, double y) {
        if (n<0 || n>= list->num_vertices) {
                // throw error. This is painful if not using C++
                // so I simply ignore it here
        } else {
                list->vertex[n].x=x;
                list->vertex[n].y=y;
        }

// here we use the fact that SWIG returns a list of two values
// from the return value and from output
double get_vertex(gpc_vertex_list *list, int n, double *OUTPUT) {
        double x=list->vertex[n].x;
        OUTPUT=list->vertex[n].y;
        return x;

set new_vert [makelist 5]
set_vertex $new_vert 0 1.0 2.0
get_vertex $new_vert 0

etc...

Beware that I have NOT tried to compile this code.

I will not really try nor go on about it. You have to be able to use the
lib from C before you can do this, of course. Fortunately (I had a quick
look at the header file), from that point on it should almost work: It
seems you can use gpc_add_contour to build up your gpc_polygon from
vertex lists (though you need a way to make an uninitialized
gpc_polygon, where n=0). You'll also need to tell SWIG which of the
parameters are actually output parameters. YOu do this by typemaps. For
example, for gpc_polygon_clip to work, you must write

#ifdef SWIG
%apply gpc_polygon *OUTPUT { gpc_polygon * result_polygon };
#endif

*before* SWIG reads the definition for gpc_polygon_clip.

Yes, I know this is not as easy as you might have hoped. That's because
C isn't really object oriented and building the data structures in
memory is also a low-level thing in C. If it would be an equivalent C++
class, it would be easier, because than there is the semantics of
constructors, destructors, and accessors that allow SWIG to do
meaningful wrapping. In pure C, SWIG can't know whether a pointer
parameter is meant to hold an array, return a value, or an input
parameter. You can make using the lib from Tcl less painful by moving
the pain into these wrapper functions.

i played around with the examples you gave me.
as a result, i ended up with the following functions in C.

gpc_vertex_list gpc_vertex_list_make(int n) {
    gpc_vertex_list result;
    result.num_vertices=n;
    result.vertex = malloc(sizeof(gpc_vertex)*n);
    return result;

console show

load gpc.dll

set vertex_list [gpc_vertex_list_make 4]
gpc_vertex_set $vertex_list 0 0 0
gpc_vertex_set $vertex_list 1 1 0
gpc_vertex_set $vertex_list 2 1 1
gpc_vertex_set $vertex_list 3 0 1

set vertex_list2 [gpc_vertex_list_make 4]
gpc_vertex_set $vertex_list2 0 3 3
gpc_vertex_set $vertex_list2 1 4 3
gpc_vertex_set $vertex_list2 2 4 4
gpc_vertex_set $vertex_list2 3 3 4

set polygon1 [gpc_polygon_create $vertex_list]

gpc_add_contour $polygon1 $vertex_list2 0

the last command doesn't work somehow. it crashes my wish instance.
i guess my gpc_polygon_create function is wrong?
it's kinda weird, because the lib function gpc_write_polygon (creates a text file with all the points in it) works just fine with the polygon created with gpc_polygon_create!

I had a quick look at your code, but beware that it's hard to find the
error without being able to compile this.

In generally, to find such an error you should compile with -g flag (to
include debug information) and run the program under a debugger. It will
tell you, at which line the program crashed. I don't know about mingw,
in Linux it would be

gdb tclsh
r crash.tcl

Just what I see immediately:
Am 14.11.12 11:57, schrieb Thomas:

gpc_polygon gpc_polygon_create(gpc_vertex_list *list, int hole) {
        gpc_polygon result;
        result.num_contours = 1;
        // create an array with one element of type int
        result.hole = malloc(sizeof(int));
        // assign hole to the first element
        result.hole[0]=hole;

        result.contour = list;
        return result;

--header file ---
#ifdef SWIG
%apply double *OUTPUT {double *x, double *y };
#endif
void gpc_vertex_get(gpc_vertex_list *list, int n, double *x, double *y);
#ifdef SWIG
%clear double *x;
%clear double *y;
#endif

---- c file ---
  void gpc_vertex_get(gpc_vertex_list *list, int n, double *x, double *y) {
        if (n < 0 || n >= list->num_vertices) {
           // throw error. This is painful if not using C++
           // so I simply ignore it here
                *x=0; *y=0;
        } else {
                *x=list->vertex[n].x;
                *y=list->vertex[n].y;
        }
  }

--- end ---

This tells SWIG that for the function gpc_vertex_get, it should apply
the output rule for the x and y parameters.

Again, no guarantee for success, as I haven't compiled that code. Next
time you could upload the code so that anybody can try to really compile
that stuff.

Hope this gets you started,

sorry for the delay.
here's the stuff i got so far.

it's working quiet well, even tho it might not be perfect.
And i didn't add any credits/licence information yet.