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<h2><span class="refentrytitle"><a name="libglbarcode-intro.top_of_page"></a>Introduction</span></h2>
<p>Introduction — 
Introduction to libglbarcode library
</p>
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<div class="refsect1">
<a name="id-1.2.2.3"></a><h2>Overview</h2>
<p>
Libglbarcode provides the core barcode functionality for <span class="application">glabels</span>.  It provides
an intermediate barcode format, a small set of built-in barcode back-ends, and a cairo renderer.  While
libglbarcode does not currently include a large set of built-in barcode back-ends or renderers, its
simple architecture would easily support extending its functionality beyond the needs of
<span class="application">glabels</span>.
</p>
</div>
<div class="refsect1">
<a name="id-1.2.2.4"></a><h2>Basic Usage</h2>
<pre class="programlisting">

#include &lt;libglbarcode/lgl-barcode-create.h&gt;
#include &lt;libglbarcode/lgl-barcode-render-to-cairo.h&gt;

void
example (gchar   *data,
         cairo_t *cr)
{
        glBarcode *bc;

        bc = lgl_barcode_create (LGL_BARCODE_TYPE_CODE39, TRUE, FALSE, 0, 0, data);

        /* Render to cairo context.  Assume context has appropriate scale and translation.
         * Scale should be such that world units are points (1 point = 1/72 inch) and that
         * positive y values go downward.
         */
        lgl_barcode_render_to_cairo (bc, cr);

        lgl_free (bc);
}

</pre>
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<div class="refsect1">
<a name="id-1.2.2.5"></a><h2>Writing Renderers</h2>
<p>
The <a class="link" href="libglbarcode-3.0-lgl-barcode.html#lglBarcode" title="lglBarcode">lglBarcode</a> structure is independent of
barcode type, and consists of a simple list of drawing primitives.
A renderer simply traverses this list translating these primitives into native
drawing commands for its target format or device.
All renderers will follow this simple pattern as illustrated in the example
below.
</p>
<pre class="programlisting">

#include &lt;libglbarcode/lgl-barcode.h&gt;
#include &lt;xxx.h&gt;

void
lgl_barcode_render_to_xxx (const lglBarcode  *bc)
{
        GList                  *p;

        lglBarcodeShape        *shape;
        lglBarcodeShapeLine    *line;
        lglBarcodeShapeBox     *box;
        lglBarcodeShapeChar    *bchar;
        lglBarcodeShapeString  *bstring;
        lglBarcodeShapeRing    *ring;
        lglBarcodeShapeHexagon *hexagon;


        for (p = bc-&gt;shapes; p != NULL; p = p-&gt;next) {

                shape = (lglBarcodeShape *)p-&gt;data;

                switch (shape-&gt;type)
                {

                case LGL_BARCODE_SHAPE_LINE:
                        line = (lglBarcodeShapeLine *) shape;

                        xxx_plot_line (line-&gt;x, line-&gt;y,
                                       line-&gt;x, line-&gt;y + line-&gt;length,
                                       line-&gt;width );
                        break;

                case LGL_BARCODE_SHAPE_BOX:
                        box = (lglBarcodeShapeBox *) shape;

                        xxx_plot_rectangle (box-&gt;x, box-&gt;y,
                                            box-&gt;width, box-&gt;height);
                        break;

                case LGL_BARCODE_SHAPE_CHAR:
                        bchar = (lglBarcodeShapeChar *) shape;

                        ...
                        xxx_plot_char (...);
                        break;

                case LGL_BARCODE_SHAPE_STRING:
                        bstring = (lglBarcodeShapeString *) shape;

                        ...
                        xxx_plot_string (...);
                        break;

                case LGL_BARCODE_SHAPE_RING:
                        ring = (lglBarcodeShapeRing *) shape;

                        ...
                        xxx_plot_circle (...);
                        break;

                case LGL_BARCODE_SHAPE_HEXAGON:
                        hexagon = (lglBarcodeShapeHexagon *) shape;

                        ...
                        xxx_plot_polygon (...);
                        break;

                default:
                        g_assert_not_reached ();
                        break;

                }

        }

}


</pre>
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glabels-dev 3.4.0-2build2 / usr / share / gtk-doc / html / libglbarcode-3.0 / libglbarcode-intro.html
