Re: gEDA-user: Snap-to-pins, was: Stupid newbie question

[Ales Hvezda <ahvezda@moria.seul.org>]

Hi,

[snip]
>1. Can anybody can help me figure out how to iterate across the available pins
>to find one to snap to.


  There are two ways.  The easy way or the hard way (or stated another
  way: the wrong way or the right way respectively :-).  The easy way
  is as follows:

...
{
  OBJECT *o_current;
   
  /* Start at the beginning of the object list */ 
  /* skip over the head node */
  o_current = w_current->page_current->object_head->next;

  while (o_current != NULL) 
  {
    switch(o_current->type)
    {
       case (OBJ_NET):

	...
    
        break;

       case (OBJ_PIN):

	 /* coordinate structures for pins and nets are the same */

         /* first coordinate point */
         o_current->line->x[0] = ... 
         o_current->line->y[0] = ... 

         /* second coordinate point */
         o_current->line->x[1] = ... 
         o_current->line->y[2] = ... 

   	 /* also relavent to pins only is whichend */
         /* which end tells you which point of ...->line->x[ ] is the */
	 /* active connecting point */
	 if (o_current->whichend == 0) 
	   ...

	 if (o_current->whichend == 1) 
	   ...

         break;
    }

    o_current = o_current->next;
  } 

  ...
     

  You will need access to a w_current pointer (TOPLEVEL *), but those are
  very easy to come by as almost function has a valid one. 
  
  The above code is the easy/wrong way because it iterates over all objects
  and this does not scale for large schematics.  The hard way uses the 
  internal tiling mechanism which does scale, but is a little more 
  complicated.  For now get the snap to endpoint working with the easy way
  and I'll worry about the hard way when I integrate the patch.
  
  

>
>2. Should I add a utility function like snap_grid() so other developers could 
>do pin-snaps in the future? Not sure why you would, but it could be done that 
>way. Or should I just add it to o_net and keep it simple?


  Keep it simple. :)  Actually if you look at gschem/noweb/o_net.nw in the
  function o_net_start() you will see code like this at the beginning:

#if 0 /* not ready for prime time use, this is the snap any point #if 0 */
  ...

#endif

  this was my attempt at doing exactly what you want to add.  Ignore it, it
  did not work and was a work in progress.

  I would recommend you get the snapping to work as best you can and then
  we'll work from there.  


>
>Maybe we should take this discussion off list?


  Maybe onto the geda-dev mailing list.

  Please ask questions and I'll answer them to my best ability.

								-Ales