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217 lines
9.0 KiB
217 lines
9.0 KiB
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PPD API introduction for CUPS. |
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Copyright 2007-2012 by Apple Inc. |
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Copyright 1997-2006 by Easy Software Products, all rights reserved. |
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These coded instructions, statements, and computer programs are the |
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property of Apple Inc. and are protected by Federal copyright |
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law. Distribution and use rights are outlined in the file "LICENSE.txt" |
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which should have been included with this file. If this file is |
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file is missing or damaged, see the license at "http://www.cups.org/". |
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--> |
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<h2 class='title'><a name='OVERVIEW'>Overview</a></h2> |
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<blockquote>The PPD API is deprecated starting in CUPS 1.6/macOS 10.8. Please use the new Job Ticket APIs in the <a href="api-cups.html">CUPS API</a> documentation. These functions will be removed in a future release of CUPS.</blockquote> |
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<p>The CUPS PPD API provides read-only access the data in PostScript Printer |
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Description ("PPD") files which are used for all printers with a driver. With |
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it you can obtain the data necessary to display printer options to users, mark |
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option choices and check for conflicting choices, and output marked choices in |
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PostScript output. The <a href="#ppd_file_t"><code>ppd_file_t</code></a> |
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structure contains all of the information in a PPD file.</p> |
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<blockquote><b>Note:</b> |
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<p>The CUPS PPD API uses the terms "option" and "choice" instead of the Adobe |
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terms "MainKeyword" and "OptionKeyword" to refer to specific printer options and |
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features. CUPS also treats option ("MainKeyword") and choice ("OptionKeyword") |
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values as case-insensitive strings, so option "InputSlot" and choice "Upper" |
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are equivalent to "inputslot" and "upper", respectively.</p> |
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</blockquote> |
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<h3><a name="LOADING">Loading a PPD File</a></h3> |
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<p>The <a href="#ppdOpenFile"><code>ppdOpenFile</code></a> function "opens" a |
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PPD file and loads it into memory. For example, the following code opens the |
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current printer's PPD file in a CUPS filter:</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd = <a href="#ppdOpenFile">ppdOpenFile</a>(getenv("PPD")); |
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</pre> |
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<p>The return value is a pointer to a new |
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<a href="#ppd_file_t"><code>ppd_file_t</code></a> structure or <code>NULL</code> |
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if the PPD file does not exist or cannot be loaded. The |
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<a href="#ppdClose"><code>ppdClose</code></a> function frees the memory used |
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by the structure:</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd; |
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<a href="#ppdClose">ppdClose</a>(ppd); |
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</pre> |
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<p>Once closed, pointers to the <a href="#ppd_file_t"><code>ppd_file_t</code></a> |
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structure and any data in it will no longer be valid.</p> |
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<h3><a name="OPTIONS_AND_GROUPS">Options and Groups</a></h3> |
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<p>PPD files support multiple options, which are stored in arrays of |
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<a href="#ppd_option_t"><code>ppd_option_t</code></a> and |
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<a href="#ppd_choice_t"><code>ppd_choice_t</code></a> structures.</p> |
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<p>Each option in turn is associated with a group stored in a |
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<a href="#ppd_group_t"><code>ppd_group_t</code></a> structure. Groups can be |
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specified in the PPD file; if an option is not associated with a group |
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then it is put in an automatically-generated "General" group. Groups can also |
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have sub-groups, however CUPS currently ignores sub-groups because of past |
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abuses of this functionality.</p> |
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<p>Option choices are selected by marking them using one of three functions. The |
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first is <a href="#ppdMarkDefaults"><code>ppdMarkDefaults</code></a> which |
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selects all of the default options in the PPD file:</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd; |
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<a href="#ppdMarkDefaults">ppdMarkDefaults</a>(ppd); |
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</pre> |
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<p>The second is <a href="#ppdMarkOption"><code>ppdMarkOption</code></a> |
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which selects a single option choice in the PPD file. For example, the following |
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code selects the upper paper tray:</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd; |
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<a href="#ppdMarkOption">ppdMarkOption</a>(ppd, "InputSlot", "Upper"); |
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</pre> |
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<p>The last function is |
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<a href="#cupsMarkOptions"><code>cupsMarkOptions</code></a> which selects |
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multiple option choices in the PPD file from an array of CUPS options, mapping |
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IPP attributes like "media" and "sides" to their corresponding PPD options. You |
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typically use this function in a print filter with |
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<code>cupsParseOptions</code> and |
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<a href="#ppdMarkDefaults"><code>ppdMarkDefaults</code></a> to select all of |
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the option choices needed for the job, for example:</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd = <a href="#ppdOpenFile">ppdOpenFile</a>(getenv("PPD")); |
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cups_option_t *options = NULL; |
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int num_options = cupsParseOptions(argv[5], 0, &options); |
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<a href="#ppdMarkDefaults">ppdMarkDefaults</a>(ppd); |
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<a href="#cupsMarkOptions">cupsMarkOptions</a>(ppd, num_options, options); |
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cupsFreeOptions(num_options, options); |
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</pre> |
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<h3><a name="CONSTRAINTS">Constraints</a></h3> |
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<p>PPD files support specification of conflict conditions, called |
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constraints, between different options. Constraints are stored in an array of |
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<a href="#ppd_const_t"><code>ppd_const_t</code></a> structures which specify |
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the options and choices that conflict with each other. The |
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<a href="#ppdConflicts"><code>ppdConflicts</code></a> function tells you |
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how many of the selected options are incompatible. Since constraints are |
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normally specified in pairs, the returned value is typically an even number.</p> |
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<h3><a name="PAGE_SIZES">Page Sizes</a></h3> |
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<p>Page sizes are special options which have physical dimensions and margins |
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associated with them. The size information is stored in |
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<a href="#ppd_size_t"><code>ppd_size_t</code></a> structures and is available |
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by looking up the named size with the |
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<a href="#ppdPageSize"><code>ppdPageSize</code></a> function. The page size and |
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margins are returned in units called points; there are 72 points per inch. If |
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you pass <code>NULL</code> for the size, the currently selected size is |
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returned:</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd; |
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<a href="#ppd_size_t">ppd_size_t</a> *size = <a href="#ppdPageSize">ppdPageSize</a>(ppd, NULL); |
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</pre> |
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<p>Besides the standard page sizes listed in a PPD file, some printers |
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support variable or custom page sizes. Custom page sizes are supported if the |
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<code>variables_sizes</code> member of the |
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<a href="#ppd_file_t"><code>ppd_file_t</code></a> structure is non-zero. |
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The <code>custom_min</code>, <code>custom_max</code>, and |
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<code>custom_margins</code> members of the |
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<a href="#ppd_file_t"><code>ppd_file_t</code></a> structure define the limits |
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of the printable area. To get the resulting media size, use a page size string |
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of the form "Custom.<I>width</I>x<I>length</I>", where "width" and "length" are |
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in points. Custom page size names can also be specified in inches |
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("Custom.<i>width</i>x<i>height</i>in"), centimeters |
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("Custom.<i>width</i>x<i>height</i>cm"), or millimeters |
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("Custom.<i>width</i>x<i>height</i>mm"):</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd; |
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/* Get an 576x720 point custom page size */ |
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<a href="#ppd_size_t">ppd_size_t</a> *size = <a href="#ppdPageSize">ppdPageSize</a>(ppd, "Custom.576x720"); |
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/* Get an 8x10 inch custom page size */ |
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<a href="#ppd_size_t">ppd_size_t</a> *size = <a href="#ppdPageSize">ppdPageSize</a>(ppd, "Custom.8x10in"); |
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/* Get a 100x200 millimeter custom page size */ |
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<a href="#ppd_size_t">ppd_size_t</a> *size = <a href="#ppdPageSize">ppdPageSize</a>(ppd, "Custom.100x200mm"); |
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/* Get a 12.7x34.5 centimeter custom page size */ |
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<a href="#ppd_size_t">ppd_size_t</a> *size = <a href="#ppdPageSize">ppdPageSize</a>(ppd, "Custom.12.7x34.5cm"); |
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</pre> |
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<p>If the PPD does not support variable page sizes, the |
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<a href="#ppdPageSize"><code>ppdPageSize</code></a> function will return |
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<code>NULL</code>.</p> |
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<h3><a name="ATTRIBUTES">Attributes</a></h3> |
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<p>Every PPD file is composed of one or more attributes. Most of these |
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attributes are used to define groups, options, choices, and page sizes, |
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however several informational attributes may be present which you can access |
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in your program or filter. Attributes normally look like one of the following |
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examples in a PPD file:</p> |
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<pre class="example"> |
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*name: "value" |
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*name spec: "value" |
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*name spec/text: "value" |
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</pre> |
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<p>The <a href="#ppdFindAttr"><code>ppdFindAttr</code></a> and |
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<a href="#ppdFindNextAttr"><code>ppdFindNextAttr</code></a> functions find the |
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first and next instances, respectively, of the named attribute with the given |
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"spec" string and return a <a href="#ppd_attr_t"><code>ppd_attr_t</code></a> |
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structure. If you provide a NULL specifier string, all attributes with the |
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given name will be returned. For example, the following code lists all of the |
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<code>Product</code> attributes in a PPD file:</p> |
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<pre class="example"> |
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#include <cups/ppd.h> |
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<a href="#ppd_file_t">ppd_file_t</a> *ppd; |
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<a href="#ppd_attr_t">ppd_attr_t</a> *attr; |
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for (attr = <a href="#ppdFindAttr">ppdFindAttr</a>(ppd, "Product", NULL); |
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attr != NULL; |
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attr = <a href="#ppdFindNextAttr">ppdFindNextAttr</a>(ppd, "Product", NULL)) |
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puts(attr->value); |
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</pre>
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