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Date: Thu, 22 May 2025 03:54:33 +0200
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From: "Johann Klammer (klammerj AT a1 DOT net) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject: [geda-user] --bg-image crashes pcb (lesstif gui)
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I tried loading a P6 pixmap as indicated in the documentation but got:

Program received signal SIGSEGV, Segmentation fault.
0x0000555555641742 in DrawBackgroundImage () at hid/lesstif/main.c:1155
1155              XPutPixel (bgi, x, y, bg[ir][ic]);

ir=-190
ic=0

very first iteration
x=0
(gdb) p pr
$9 = -6946757

increasing the board height makes it load. but scaling seems off..
zooming causes crash.

scaling down the image does not help.

This seems to fix things:

static unsigned long PickBgPixel(Pixel **bg,int rows,int cols,int r,int c)
{
        if((r<rows)&&(r>=0)&&(c<cols)&&(c>=0))return bg[r][c];
        else return bgcolor;
}

static void
DrawBackgroundImage ()
{
  int x, y, w, h;
  double xscale, yscale;

  if (!window || !bg)
    return;

  if (!bgi || view_width != bgi_w || view_height != bgi_h)
    {
      if (bgi)
        XDestroyImage (bgi);
      /* Cheat - get the image, which sets up the format too.  */
      bgi = XGetImage (XtDisplay(work_area),
                       window,
                       0, 0, view_width, view_height,
                       -1, ZPixmap);
      bgi_w = view_width;
      bgi_h = view_height;
    }

  w = view_width;
  h = view_height;

  xscale = (double)bg_w / PCB->MaxWidth;
  yscale = (double)bg_h / PCB->MaxHeight;

  for (y=0; y<h; y++)
    {
      int pr = Py(y);
      int ir = pr * yscale;
      for (x=0; x<w; x++)
        {
          int pc = Px(x);
          int ic = pc * xscale;
          XPutPixel (bgi, x, y, PickBgPixel(bg,bg_h,bg_w,ir,ic));
        }
    }
  XPutImage(display, main_pixmap, bg_gc,
            bgi,
            0, 0, 0, 0, w, h);
}

(my source tree is too hosed to be able to format a proper diff...)