Postscript Operators 'v'

version - version

string returns a string that identifies the version of the PostScript interpreter being used. This identification does not include information about the language features or the hardware or operating system environment in which the PostScript interpreter is running.

ERRORS: stackoverflow

SEE ALSO: languagelevel, product,

revision, serialnumber

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viewclip - viewclip

- DPS replaces the current view clipping path by a copy of the current path in the graphics state. The inside of the current path is determined by the normal non-zero winding number rule. viewclip implicitly closes any open subpaths of the view clipping path. After setting the view clip, viewclip resets the current path to empty, as if by newpath. viewclip is similar to clip in that it causes subsequent painting operations to affect only those areas of the current page that lie inside the new view clipping path. However, it differs from clip in three important respects:

The view clipping path is independent of the current clipping path, which is unaffected. A subsequent clippath returns the current clipping path, uninfluenced by the additional clipping imposed by the view clip.
viewclip entirely replaces the current view clipping path, whereas clip computes the intersection of the current and new clipping paths.
viewclip performs an implicit newpath at the end of its execution, whereas clip leaves the current path unchanged.

The view clipping path is independent of the graphics state; it is maintained separately for each execution context. Modifications to the view clipping path obey save and restore. The view clipping path can be described by a user path. This is accomplished by: newpath userpath uappend viewclip If userpath specifies ucache, this operation may take advantage of information in the user path cache.

ERRORS: limitcheck

SEE ALSO: initviewclip, viewclippath,

clip

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viewclippath - viewclippath - DPS

replaces the current path by a copy of the current view clipping path. If no view clipping path exists, it replaces the current path by one that exactly corresponds to the bounding rectangle of the imageable area of the output device.

EXAMPLE:
initviewclip viewclippath pathbbox

If the current device is a window device, this returns the bounding box of the window.

ERRORS: (none)

SEE ALSO: viewclip, initviewclip,

clippath

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VMerror (error)

An error has occurred in the virtual memory (VM) machinery. The most likely problems are:

An attempt to create a new composite object (string, array, dictionary, or packed array) would exhaust VM resources. Either the program's requirements exceed available capacity or, more likely, the program has failed to use the save/restore facility appropriately.
The interpreter has attempted to perform an operation that should be impossible due to access restrictions (for example, store into systemdict, which is read-only). This represents an internal error in the interpreter. The default handler for this error, unlike those for all other errors, does not snapshot the stacks.

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vmreclaim int vmreclaim - LEVEL 2

controls the garbage collection machinery as specified by int:

-2 Disable automatic collection in both local and global VM.

-1 Disable automatic collection in local VM.

0 Enable automatic collection.

1 Perform immediate collection in local VM.

2 Perform immediate collection in local and global VM.

This can take a long time, because it must consult the local VMs of all execution contexts. Garbage collection causes the memory occupied by the values of inaccessible objects to be reclaimed and made available for reuse. It does not have any effects that are visible to the PostScript language program. There is normally no need to execute the vmreclaim operator, because garbage collection is invoked automatically when necessary. However, there are a few situations in which this operator may be useful: o In an interactive application that is temporarily idle, the idle time can be put to good use by invoking an immediate garbage collection. This defers the need to perform an automatic collection subsequently. In a context that is under the control of a job server.

garbage collection is invoked automatically between jobs.

When monitoring the VM consumption of a program, one must invoke garbage
collection before executing vmstatus to obtain meaningful results.
When measuring the execution time of a program, one must disable automatic
garbage collection to obtain repeatable results. The negative values that disable
garbage collection apply only to the current execution context; that is, they do
not prevent collection from occurring during execution of other contexts.

Note that disabling garbage collection for too long may eventually cause a program to run out of memory and fail with a VMerror. Executing vmreclaim with an operand of 0, -1, or -2 has the same effect as setting the VMReclaim user parameter to the same value by means of setuserparams.

ERRORS: rangecheck, stackunderflow,

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vmstatus - vmstatus
level used maximum returns three integers describing the state of the PostScript interpreter's virtual memory (VM).

level is the current depth of save nesting-in other words, the number of saves that haven't been matched by a restore. used and maximum measure VM resources in units of 8-bit bytes; used is the number of bytes currently in use and maximum is the maximum available capacity. VM consumption is monitored separately for local and global VM.
The used and maximum values apply to either local or global VM according to the current VM allocation mode (see setglobal).
The used value is meaningful only immediately after a garbage collection has taken place (see vmreclaim). At other times, it may be too large because it includes memory occupied by objects that have become inaccessible, but have not yet been reclaimed.
The maximum value is an estimate of the maximum size to which the current VM (local or global) could grow, assuming that all other uses of available memory remain constant. Because that assumption is never valid in practice, there is some uncertainty about the maximum value.
Also, in some environments (workstations, for instance), the PostScript interpreter can obtain more memory from the operating system. In this case, memory is essentially inexhaustible and the maximum value is meaningless-it is an extremely large number.

ERRORS: stackoverflow

SEE ALSO: setuserparams

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Original file name: PSL2v.html