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   1 <refentry id="libglbarcode-intro" revision="07 Nov 2010">
   2 <refmeta>
   3 <refentrytitle role="top_of_page" id="libglbarcode-intro.top_of_page">Introduction</refentrytitle>
   4 <manvolnum>3</manvolnum>
   5 <refmiscinfo>
   6   LIBGLBARCODE-3.0 Library
   7 </refmiscinfo>
   8 </refmeta>
   9
  10 <refnamediv>
  11 <refname>Introduction</refname>
  12 <refpurpose>
  13 Introduction to libglbarcode library
  14 </refpurpose>
  15 </refnamediv>
  16
  17
  18 <refsect1>
  19 <title>Overview</title>
  20
  21 <para>
  22 Libglbarcode provides the core barcode functionality for <application>glabels</application>.  It provides
  23 an intermediate barcode format, a small set of built-in barcode back-ends, and a cairo renderer.  While
  24 libglbarcode does not currently include a large set of built-in barcode back-ends or renderers, its
  25 simple architecture would easily support extending its functionality beyond the needs of
  26 <application>glabels</application>.
  27 </para>
  28
  29 </refsect1>
  30
  31
  32 <refsect1>
  33 <title>Basic Usage</title>
  34
  35 <programlisting>
  36
  37 #include &lt;libglbarcode/lgl-barcode-create.h&gt;
  38 #include &lt;libglbarcode/lgl-barcode-render-to-cairo.h&gt;
  39
  40 void
  41 example (gchar   *data,
  42          cairo_t *cr)
  43 {
  44         glBarcode *bc;
  45
  46         bc = lgl_barcode_create (LGL_BARCODE_TYPE_CODE39, TRUE, FALSE, 0, 0, data);
  47
  48         /* Render to cairo context.  Assume context has appropriate scale and translation.
  49          * Scale should be such that world units are points (1 point = 1/72 inch) and that
  50          * positive y values go downward.
  51          */
  52         lgl_barcode_render_to_cairo (bc, cr);
  53
  54         lgl_free (bc);
  55 }
  56
  57 </programlisting>
  58
  59
  60 </refsect1>
  61
  62
  63 <refsect1>
  64 <title>Writing Renderers</title>
  65
  66 <para>
  67 The <link linkend="lglBarcode">lglBarcode</link> structure is independent of
  68 barcode type, and consists of a simple list of drawing primitives.
  69 A renderer simply traverses this list translating these primitives into native
  70 drawing commands for its target format or device.
  71 All renderers will follow this simple pattern as illustrated in the example
  72 below.
  73 </para>
  74
  75 <programlisting>
  76
  77 #include &lt;libglbarcode/lgl-barcode.h&gt;
  78 #include &lt;xxx.h&gt;
  79
  80 void
  81 lgl_barcode_render_to_xxx (const lglBarcode  *bc)
  82 {
  83         GList                  *p;
  84
  85         lglBarcodeShape        *shape;
  86         lglBarcodeShapeLine    *line;
  87         lglBarcodeShapeBox     *box;
  88         lglBarcodeShapeChar    *bchar;
  89         lglBarcodeShapeString  *bstring;
  90         lglBarcodeShapeRing    *ring;
  91         lglBarcodeShapeHexagon *hexagon;
  92
  93
  94         for (p = bc->shapes; p != NULL; p = p->next) {
  95
  96                 shape = (lglBarcodeShape *)p->data;
  97
  98                 switch (shape->type)
  99                 {
 100
 101                 case LGL_BARCODE_SHAPE_LINE:
 102                         line = (lglBarcodeShapeLine *) shape;
 103
 104                         xxx_plot_line (line->x, line->y,
 105                                        line->x, line->y + line->length,
 106                                        line->width );
 107                         break;
 108
 109                 case LGL_BARCODE_SHAPE_BOX:
 110                         box = (lglBarcodeShapeBox *) shape;
 111
 112                         xxx_plot_rectangle (box->x, box->y,
 113                                             box->width, box->height);
 114                         break;
 115
 116                 case LGL_BARCODE_SHAPE_CHAR:
 117                         bchar = (lglBarcodeShapeChar *) shape;
 118
 119                         ...
 120                         xxx_plot_char (...);
 121                         break;
 122
 123                 case LGL_BARCODE_SHAPE_STRING:
 124                         bstring = (lglBarcodeShapeString *) shape;
 125
 126                         ...
 127                         xxx_plot_string (...);
 128                         break;
 129
 130                 case LGL_BARCODE_SHAPE_RING:
 131                         ring = (lglBarcodeShapeRing *) shape;
 132
 133                         ...
 134                         xxx_plot_circle (...);
 135                         break;
 136
 137                 case LGL_BARCODE_SHAPE_HEXAGON:
 138                         hexagon = (lglBarcodeShapeHexagon *) shape;
 139
 140                         ...
 141                         xxx_plot_polygon (...);
 142                         break;
 143
 144                 default:
 145                         g_assert_not_reached ();
 146                         break;
 147
 148                 }
 149
 150         }
 151
 152 }
 153
 154
 155 </programlisting>
 156
 157
 158 </refsect1>
 159
 160
 161 </refentry>