In this chapter we list a number of commonly encountered problems in
Cannot open display
PCE tries to open the display from the address specified by the DISPLAY
environment variable. It ignores the `--display' command line option.
The display might also be specified explicitly using `display
PCE will open the display as soon as it needs X-resource values or it
needs graphical operations. This will fail if the specified address is
not legal, there is no X-server at that address or the X-server denies
the access. Examine the error message carefully. Make sure X-windows is
running at the specified address. Make sure you have access to this
server. See xauth (when running MIT_MAGIC_COOKIE)
and xhost. If PCE still complains, validate
the access rights by starting a normal X-application (e.g. xterm) in the
same context. Always restart PCE after a fatal or system error as the
system might be corrupted. This problem is not possible in the Win32
Bad integer reference
This is a PCE/Prolog interface warning. It implies the integer object
reference given to send/[2-12],
etc. is not valid. The most common reason is that the object has already
be freed, either explicitly or by PCE's incremental garbage collector.
See section E.
Attempt to create an instance of a non-existing class. Apart from the
common mistakes like mistyped class-names, etc. this might be caused by
1) giving a list argument to a send- or get- operation (class `.') or 2)
trying to pass a term through send/[2-12]
Illegal PCE object description
This implies a non-translatable Prolog datum was passed to the
interface. Normally this will be a non-ground20A
`ground' term is a Prolog term that has no unbound variables.
argument to new/2, send/[2-12]