XFree86® and DPS : The DPS client side
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## 2. The DPS client side

The DPS client side consists of four libraries and a number of basic tools for programming and configuration; these are all included with XFree86.

### 2.1. Libraries

The `libpsres` library is a library for management of PostScript resources, on-disk files representing PostScript data structures such as fonts, font encodings, procsets, etc. It is closely related to the `makepsres` tool (see client-side tools later in this document).

The basic DPS client library is `libdps`. This library contains a number of functions for connection establishment, resource management, as well as stubs for all standard PostScript operators. Normally, all DPS clients should link with `libdps`; in addition, `libdps` may be used for printing by non-DPS clients (this is done, for example, by Sun's JDK). This library is documented in [CLRM] and [CLSX].

The `libdpstk` library contains a number of additional utilities for managing DPS contexts, user paths and user objects, and for previewing EPS files. It is documented in [DPTX].

The `libdpstkXm` library contains four Motif widgets. The DPS Scrolling Widget is a DPS drawing area that automatically manages issues such as scrolling, scaling, client-side backing store, incremental redisplay, etc. The Font Selection Box, and its associated Font Preview, present a convenient and powerful interface for choosing scalable fonts. Finally, the Color Picker presents an interface for choosing colours using either of the RGB or HSV spaces. The latter three widgets are documented in [DPTX]; some summary Scrolling Widget documentation is available in the `doc` subdirectory of the `DPS.tar.gz` file, available from ftp://dps.sourceforge.net/pub/dps/DPS.tar.gz.

The source code for `libdpstkXm` is included with XFree86; however, as it depends on Motif, this library is not built by default. A GTK-based library providing some of the functionality of `libdpstkXm` is available from the gtkDPS site.

#### 2.1.1. Libdps and Xt

In X11R5, `libdps` did not depend on `libXt`. In X11R6, however, code was added to make the Xt main loop dispatch to sundry code on DPS events; with this addition, all programs that link with `libdps` need to link with `libXt`, whether they use Xt or not.

This state of affairs is unfortunately true of the version of `libdps` included with XFree86. We are currently considering various solutions to this problem (including the use of weak linker symbols or splitting off the guilty functions into a separate library).

### 2.2. Client-side tools

In addition to the libraries, the client side of DPS consists of two utilities.

The `makepsres` utility is used for managing PostScript resources. Its basic operation consists in walking recursively a filesystem tree, noting all resources, and then writing out a ``Unix PostScript Resources,'' file, basically a directory of all the resources found. This utility is documented in the makepsres(1) manual page.

The `pswrap` utility is a stub generator for PostScript clients. Roughly speaking, it takes as its input textual PostScript code, and generates a collection of C functions that transmit that code in pre-tokenised form to the DPS extension. `Pswrap` is documented in [PSWRAP].

### 2.3. Sample clients

XFree86 contains three sample DPS clients, `dpsinfo`, `dpsexec` and `texteroids`. They are documented in their respective manual pages.

A number of sample clients that depend on Motif are available in ftp://dps.sourceforge.net/pub/ftp/DPS.tar.gz. Additional sample clients can be found as part of GtkDPS (see above).

The GNUstep environment can be compiled to use DPS for all rendering; for more information, please see the GNUstep site.

XFree86® and DPS : The DPS client side
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