1.117.1 Instance variables

pce <-> application_data: directory

Directory for storing xpce-related application data. On Unix systems the default is ~/.xpce. On Windows it is <appdata>/xpce, where <appdata> is the directory from CSIDL_APPDATA. This directory typically contains the following files:

Defaults

User-level class variable values.

Geometry

Saved geometries for persistent frames (see persistent_frame.pl).

emacs_bookmarks

Bookmarks created by PceEmacs

Applications using the pce_config.pl library create additional files.

pce <- catch_error_signals: bool

Determines PCE's response to (normally) fatal error situations reported by the operating system. When such an error occurs, a [PCE SYSTEM ERROR] is generated. The following signals are considered fatal:

SIGQUIT		So, ^\ can be used to generate an error
SIGILL		Illegal instruction
SIGEMT		Emulator trap
SIGBUS		Bus error (illegal aligned pointer)
SIGSEGV		Segmentation fault (out-of-range pointer)
SIGSYS		Bad argument to system call
SIGPIPE		Broken pipe
SIGFPE		Floating point exception

See your Unix manual for details on these signals.

Defaults: The initial value is @off (do not trap signals). Some host languages switch this flag to @on at initialisation time.

See also

- pce->crash
- pce-print_c_stack

pce <- catched_errors: chain

Chain holding all errors currently catched. Each element is either an error_id or a chain with error_id’.

See also

- pce->catch_error
- class error

pce <- debugging: bool

Variable to indicate debugging-status of PCE. Set by pce ->trace' and program_object->trace‘.

Defaults: @off (no debugging)

See also

pce->debug

pce <-> defaults: source_sink|char_array

File/rc from which to load defaults. See pce->load_defaults, class class_variable and class_variable/4.

The default value is the file("$PCEHOME/Defaults")

A runtime application that wishes the defauts to be in the resource file should do:

resource(pce, defaults,	pce('Defaults')).

:- initialization
        send(@pce, defaults, rc(pce, defaults)).

pce <- exception_handlers: sheet

Sheet with exception handlers used by pce->exception. Each entry of this sheet maps an exception-name onto a code object which is executed when the corresponding exception occurs. The argument bindings for @arg1, ... are the second, ... argument passed to pce->exception. The following exceptions are currently defined:

• undefined_class An attempt is made to reference an non-existing class while doing one of the following:
• Create an object
• Load an object from file using source_sink<-object
• Create a subclass

  Parameters:
  
          @arg1:		class name

• undefined_error Called from error<-convert if the error id is not in @errors. If defined, it should create an error object with the requested identifier.

  Parameters:

  @arg1: 		identifier of missing error object.

• undefined_assoc An attempt is made to resolve a symbolic reference (i.e. @pce), but the reference is unknown. Parameters:

  @arg1:		reference name

• redefined_assoc An attempt is made to create an object with the same symbolic reference as an already existing object. Parameters:

  @arg1:		The existing reference name

• initialisation_failed The pce->initialisation method for some instance failed. Parameters:

  @arg1:		The (partial) instance
  @arg2 ...	The arguments given to ->initialise

  See also

  pce->exception

pce <- exit_messages: chain

Chain of code objects. When the PCE process is killed, each of these messages is executed in turn with the following argument:

@arg1	Exit status of the process

Filled by pce->exit_message.

See also

- !killed_on_exit
- pce->exit_message
- pce->die

pce -> home: [name]

Home directory of the pce system. Its value is used to find

• PostScript header file <HOME>/postscript/pce.ps
• Standard bitmaps <HOME>/bitmaps
• The sources <HOME>/src
• The online manual material <HOME>/man/reference The Prolog interface also adds the library directory

  <HOME>/prolog/lib

  containing the PCE libraries (manual, demo programs, pcedraw, utilities).

  See also

  - pce<-environment_variable
  - pce<-postscript_header

pce <-> last_error: name*

Last error catched by the application. See also pce->catch_error and pce->catch_pop.

See also

- pce<-os_error
- pce-error_object

pce <- machine: name

Identifier name for the hardware architecture used.

See also

pce-operating_system

pce <- operating_system: name

Identifier for the operating system running on your system. On Unix systems this is extracted from the autoconf standard system naming <os>-<vendor>-<cpu>. On MS-Windows this is one of:

win32 	The actual version could not be retreived
win32s	XPCE dowsn't run on this ..
win95	DOS-7 based Windows (95,98,ME,...)
winnt	NT based Windows (NT, 2000)

See also pce<-machine, pce<-window_system, pce<-window_system_revision and pce->has_feature.

See also

pce-machine

pce <- trap_errors: bool

This flag, which is only available in the development version, controls XPCE's behaviour if a runtime error is trapped in an application. When @on (default), the system will normally enter the tracer, allowing the user to inspect the context of the error. If @off, the system will use the object->report mechanism to report the error and the tracer will not be trapped. The latter behaviour is the only behaviour supported by the runtime system. See also pce->trace.

pce-version: name

Current version number of XPCE. When documenting this method:

'4.4.3, September 1992'

Its format:

• First digit (4) Current major release. Generally indicates major revisions and a large number of incompatible changes: version 4 is based on X-windows whereas version 3 was using SunView. Version 4 adds user-defined classes, type inferencing, completely reorganised graphics and many more. Version 5 is not (yet) foreseen.
• Second digit (4) Indicates minor releases with limited compatibility issues.
• Third digit (3) Patch number. No incompatibilities except for minor one's for which we do not expect any normal application to be sensitive.

  These fields are followed by an indication of the time of release.

  If the pce<-version is requested with the argument name, the time of the release is omitted (i.e. 4.4.3). Finally, if the version is requested as a number, the value 10000 * major + 100 + minor + patch is returned.

  See also

  - pce->banner
  - pce->info