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  19 <th width="100%" align="center">LibGlbarcode 3.0 Reference Manual</th>
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  26 <h2><span class="refentrytitle"><a name="libglbarcode-intro.top_of_page"></a>Introduction</span></h2>
  27 <p>Introduction —
  28 Introduction to libglbarcode library
  29 </p>
  30 </td>
  31 <td valign="top" align="right"></td>
  32 </tr></table></div>
  33 <div class="refsect1">
  34 <a name="id2963460"></a><h2>Overview</h2>
  35 <p>
  36 Libglbarcode provides the core barcode functionality for <span class="application">glabels</span>.  It provides
  37 an intermediate barcode format, a small set of built-in barcode back-ends, and a cairo renderer.  While
  38 libglbarcode does not currently include a large set of built-in barcode back-ends or renderers, its
  39 simple architecture would easily support extending its functionality beyond the needs of
  40 <span class="application">glabels</span>.
  41 </p>
  42 </div>
  43 <div class="refsect1">
  44 <a name="id2963536"></a><h2>Basic Usage</h2>
  45 <pre class="programlisting">
  46
  47 #include &lt;libglbarcode/lgl-barcode-create.h&gt;
  48 #include &lt;libglbarcode/lgl-barcode-render-to-cairo.h&gt;
  49
  50 void
  51 example (gchar   *data,
  52          cairo_t *cr)
  53 {
  54         glBarcode *bc;
  55
  56         bc = lgl_barcode_create (LGL_BARCODE_TYPE_CODE39, TRUE, FALSE, 0, 0, data);
  57
  58         /* Render to cairo context.  Assume context has appropriate scale and translation.
  59          * Scale should be such that world units are points (1 point = 1/72 inch) and that
  60          * positive y values go downward.
  61          */
  62         lgl_barcode_render_to_cairo (bc, cr);
  63
  64         lgl_free (bc);
  65 }
  66
  67 </pre>
  68 </div>
  69 <div class="refsect1">
  70 <a name="id2963569"></a><h2>Writing Renderers</h2>
  71 <p>
  72 The <a class="link" href="libglbarcode-3.0-lgl-barcode.html#lglBarcode" title="lglBarcode">lglBarcode</a> structure is independent of
  73 barcode type, and consists of a simple list of drawing primitives.
  74 A renderer simply traverses this list translating these primitives into native
  75 drawing commands for its target format or device.
  76 All renderers will follow this simple pattern as illustrated in the example
  77 below.
  78 </p>
  79 <pre class="programlisting">
  80
  81 #include &lt;libglbarcode/lgl-barcode.h&gt;
  82 #include &lt;xxx.h&gt;
  83
  84 void
  85 lgl_barcode_render_to_xxx (const lglBarcode  *bc)
  86 {
  87         GList                  *p;
  88
  89         lglBarcodeShape        *shape;
  90         lglBarcodeShapeLine    *line;
  91         lglBarcodeShapeBox     *box;
  92         lglBarcodeShapeChar    *bchar;
  93         lglBarcodeShapeString  *bstring;
  94         lglBarcodeShapeRing    *ring;
  95         lglBarcodeShapeHexagon *hexagon;
  96
  97
  98         for (p = bc-&gt;shapes; p != NULL; p = p-&gt;next) {
  99
 100                 shape = (lglBarcodeShape *)p-&gt;data;
 101
 102                 switch (shape-&gt;type)
 103                 {
 104
 105                 case LGL_BARCODE_SHAPE_LINE:
 106                         line = (lglBarcodeShapeLine *) shape;
 107
 108                         xxx_plot_line (line-&gt;x, line-&gt;y,
 109                                        line-&gt;x, line-&gt;y + line-&gt;length,
 110                                        line-&gt;width );
 111                         break;
 112
 113                 case LGL_BARCODE_SHAPE_BOX:
 114                         box = (lglBarcodeShapeBox *) shape;
 115
 116                         xxx_plot_rectangle (box-&gt;x, box-&gt;y,
 117                                             box-&gt;width, box-&gt;height);
 118                         break;
 119
 120                 case LGL_BARCODE_SHAPE_CHAR:
 121                         bchar = (lglBarcodeShapeChar *) shape;
 122
 123                         ...
 124                         xxx_plot_char (...);
 125                         break;
 126
 127                 case LGL_BARCODE_SHAPE_STRING:
 128                         bstring = (lglBarcodeShapeString *) shape;
 129
 130                         ...
 131                         xxx_plot_string (...);
 132                         break;
 133
 134                 case LGL_BARCODE_SHAPE_RING:
 135                         ring = (lglBarcodeShapeRing *) shape;
 136
 137                         ...
 138                         xxx_plot_circle (...);
 139                         break;
 140
 141                 case LGL_BARCODE_SHAPE_HEXAGON:
 142                         hexagon = (lglBarcodeShapeHexagon *) shape;
 143
 144                         ...
 145                         xxx_plot_polygon (...);
 146                         break;
 147
 148                 default:
 149                         g_assert_not_reached ();
 150                         break;
 151
 152                 }
 153
 154         }
 155
 156 }
 157
 158
 159 </pre>
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