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All of the scenarios listed above are demonstrated in the sample code provided with this technote and are described in the Sample Code section below. To accomplish this, LaserWriter 8 calls the filter’s psPanelRegister routine repeatedly until the filter indicates it wants to stop adding panels. Such data should never be injected into the middle of a sequence of data writes corresponding to the same PSPosition. Filters execute in the order they are listed in this panel. The filter handles the user interaction with its controls and saves its configuration into the print job data that is passed to it when it is filtering PostScript data.

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PostScript Output Filters for LaserWriter

The first two are the kPluginInfoType resource and vers resource. If the filter does not contain this resource, it cannot be used and is ignored. Filters must always be careful to pass any errors laserrwiter from their filter writes back to their caller. LaserWriter 8 obtains the displayed version information from the ‘vers’ resource ID number 1. If a filter wants to modify the data before writing it to the next filter, it must first copy the data passed to it and modify its copy of the data.

Laserwriter 8.7 Download

Through this type of modification, a PostScript output filter can implement customized control of features for a specific printer model or can laeerwriter new user features across a range of PostScript printers without requiring changes to LaserWriter 8.

Debugging that situation will be difficult because the filter cannot be loaded at filter output execution time if it has hard links to LW8UILiband therefore the filter output routines are not called.

This includes discussion of the user interface for enabling and manipulating filters, information about the operation of a filter when it filters the PostScript output data, and what the user interface for a specific filter might look like.


This section describes the filter APIs that are called at the time a communication channel with a PostScript laserwritrr device is established and during the emission of the PostScript data into the communication channel. To reduce or eliminate the need to parse data, the parameter posP is also passed in. This ability is intended to allow printer manufacturers to target a filter to a specific hardware product.

This routine allows the plug-in to look at the current execution environment to determine whether to continue to run. A PostScript output filter must export a psOutputFilterWrite routine in order to be inserted into the chain of output filters. It is also called each time a printer is deselected while the panel is visible. The psOutputFilterPostFlight routine, if it is exported by a filter, is called as the filter chain is torn down at the end of the print job, and it allows the filter to dispose of any memory allocated during its preflight and filter output execution.

To add data to the stream, a filter calls psWriteNextFilter with the data to be added to the stream. The call to psOutputFilterPreFlight can be used for several purposes.

If a filter exports a psOutputFilterPreFlight routine, it is called as the filter chain is created for a print job, allowing the filter to initialize itself. Any filter that allocates memory during a preflight routine should export this routine. Since multiple filters may be contained in a single file and the filter name may have nothing to do with the name of the file containing the filter, the file name containing the filter is also displayed. The values in this collection may change during execution of the Print Dialog since users can change the default settings.

To allow this flexibility, there are a number of routines, and, at first glance, it isn’t obvious when each routine is called.


While the LaserWriter 8 Print Dialog is present, a filter can use the LWRef passed to the UI routines described above to access various pieces of data that may aid in configuring laserwtiter filter or determining whether to execute. There are no constraints on the library name beyond those imposed by the Code Fragment Manager. This parameter is a pointer to a PSPosition structure containing tagging information that describes this data.

LaserWriter 8 version 8.

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By doing so, any errors generated during the filter operation bubble back up the filter chain and back to the software initiating the write of the PostScript output. The LaserWriter 8 Print Dialog code calls psPanelPrSpecificInitData once initially for each panel after the filter is loaded, and again each time the user changes to a new printer and the filter continues to run.

There are a number of reasons why the data passed to a filter might differ from what is normally expected. Another simple thing that a filter could do is to not pass any data to the next filter in the chain. The system configurations which support auto-routing for the ‘bird’ file type are MacOS 8. The routines containing ” PrSpecific ” in their name are called for the initially selected printer and again when the user changes from one printer to another in the Print Dialog.

The minimum LaserWriter driver version that a filter requires. A given filter can add zero or more panels. This discussion does not apply to filters without any user interface or job specific settings. This is the point where a filter plug-in actually has the chance to lwserwriter the PostScript output data.