sec-gc.html

gtk_text program sample&eg

      </p>
      <p>
        The <span class="STRUCTNAME">line_style</span> field can
        have one of three values:
      </p>
      <ul>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_LINE_SOLID</span> is the
            default; a solid line.&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_LINE_ON_OFF_DASH</span>
            draws a dashed line with the foreground color, leaving
            the "off" parts of the dash blank.&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_LINE_DOUBLE_DASH</span>
            draws a dashed line in the foreground color, but the
            "off" parts of the dash are drawn in the background
            color.&#13;
          </p>
        </li>
      </ul>
      <p>
        Dashes are specified with <tt class="FUNCTION">
        gdk_gc_set_dashes()</tt>; <span class="STRUCTNAME">
        GdkGCValues</span> does not include a field for this. <tt
        class="FUNCTION">gdk_gc_set_dashes()</tt> accepts three
        arguments:
      </p>
      <ul>
        <li>
          <p>
            <span class="STRUCTNAME">dash_list</span> is an array
            of dash lengths. Even-indexed lengths are "on" dashes;
            these are drawn in the foreground color. Odd-indexed
            lengths are "off" dashes; they are not drawn or drawn
            in the background color, depending on <span class= 
            "STRUCTNAME">line_style</span>. 0 is not a permitted
            value; all lengths must be positive.&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">dash_offset</span> is the
            index of the first pixel to use in the dash list. That
            is, if the dash list specifies 5 pixels "on" and 5
            "off", and the offset is 3, the line will begin in the
            middle of the "on" dash.&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">n</span> is simply the number
            of elements in <span class="STRUCTNAME">
            dash_list</span>.&#13;
          </p>
        </li>
      </ul>
      <p>
        You might set a whimsical dash pattern this way, for
        example:
      </p>
      <table border="0" bgcolor="#E0E0E0" width="100%">
        <tr>
          <td>
<pre class="PROGRAMLISTING">
&#13;  gchar dash_list[] = { 5, 5, 3, 3, 1, 1, 3, 3 };
  gdk_gc_set_dashes(gc, 0, dash_list, sizeof(dash_list));&#13;
</pre>
          </td>
        </tr>
      </table>
      <p>
        The default dash list is <span class="STRUCTNAME">{4,
        4}</span> with an offset of 0.
      </p>
      <p>
        <a href="sec-gc.html#FIG-DASHRAW">Figure 13</a> shows some
        dashed lines drawn with <span class="STRUCTNAME">
        GDK_LINE_DOUBLE_DASH</span>. The graphics context's
        foreground color is black, and its background color is a
        light gray. The first five lines are the default <span
        class="STRUCTNAME">{4, 4}</span> dash pattern with offsets
        of 0, 1, 2, 3, and 4. Remember that 0 is the default. <a
        href="sec-gc.html#FIG-DASHES-DEFAULT">Figure 14</a> shows a
        magnified view of these five lines. The last line is the
        whimsical dash pattern mentioned above; it's shown
        magnified in <a href="sec-gc.html#FIG-DASHES-WHIMSICAL">
        Figure 15</a>.
      </p>
      <div class="FIGURE">
        <a name="FIG-DASHRAW"></a>
        <p>
          <img src="figures/dashes-raw.png">
        </p>
        <p>
          <b>Figure 13. Five dashed lines, with <span class= 
          "STRUCTNAME">GDK_LINE_DOUBLE_DASH</span></b>
        </p>
      </div>
      <div class="FIGURE">
        <a name="FIG-DASHES-DEFAULT"></a>
        <p>
          <img src="figures/dashes-default.png">
        </p>
        <p>
          <b>Figure 14. Default dash pattern, with varied
          offsets</b>
        </p>
      </div>
      <div class="FIGURE">
        <a name="FIG-DASHES-WHIMSICAL"></a>
        <p>
          <img src="figures/dashes-whimsical.png">
        </p>
        <p>
          <b>Figure 15. A complex dash pattern</b>
        </p>
      </div>
      <p>
        <span class="STRUCTNAME">cap_style</span> determines how X
        draws line endpoints (or dash endpoints, if a line is
        dashed). It has four possible values:
      </p>
      <ul>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_CAP_BUTT</span> is the
            default; it means that lines have square ends (as you
            might expect). &#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_CAP_NOT_LAST</span>
            specifies that the last pixel is skipped for one-pixel
            lines. It is otherwise the same as <span class= 
            "STRUCTNAME">GDK_CAP_BUTT</span>.&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_CAP_ROUND</span> draws a
            small arc on the end of the line, extending beyond the
            line's endpoint. The center of the arc is on the
            endpoint, and the radius of the arc is one-half the
            width of the line. For one-pixel lines, it has no
            effect (since there is no way to draw a one-pixel-wide
            arc).&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_CAP_PROJECTING</span>
            extends the line past its endpoint by one-half its
            width. It has no effect on one-pixel lines.&#13;
          </p>
        </li>
      </ul>
      <p>
        The <span class="STRUCTNAME">join_style</span> parameter
        affects how lines are connected to one another, when
        drawing a polygon or drawing multiple lines in one function
        call. If you think of lines as long, thin rectangles, it is
        clear that they do not connect smoothly; there is a "notch"
        where the two endpoints come together. The three join
        styles fill in this notch:
      </p>
      <ul>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_JOIN_MITER</span> is the
            default; it draws a sharp angle where the lines
            intersect.&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_JOIN_ROUND</span> creates
            rounded corners by drawing an arc in the notch.&#13;
          </p>
        </li>
        <li>
          <p>
            <span class="STRUCTNAME">GDK_JOIN_BEVEL</span> creates
            a flat corner, filling the notch with the smallest
            possible shape.&#13;
          </p>
        </li>
      </ul>
      <div class="FIGURE">
        <a name="FL-GDKGC"></a>
        <div class="FUNCSYNOPSIS">
          <a name="FL-GDKGC.SYNOPSIS"></a>
          <table border="0" bgcolor="#E0E0E0" width="100%">
            <tr>
              <td>
<pre class="FUNCSYNOPSISINFO">
#include &lt;gdk/gdk.h&gt;
</pre>
              </td>
            </tr>
          </table>
          <p>
            <code><code class="FUNCDEF">GdkGC* <tt class=
            "FUNCTION">gdk_gc_new</tt></code>(GdkWindow* <tt class= 
            "PARAMETER"><i>window</i></tt>);</code>
          </p>
          <p>
            <code><code class="FUNCDEF">GdkGC* <tt class=
            "FUNCTION">
            gdk_gc_new_with_values</tt></code>(GdkWindow* <tt
            class="PARAMETER"><i>window</i></tt>, GdkGCValues* <tt
            class="PARAMETER"><i>values</i></tt>, GdkGCValuesMask
            <tt class="PARAMETER"><i>values_mask</i></tt>);</code>
          </p>
          <p>
            <code><code class="FUNCDEF">void <tt class="FUNCTION">
            gdk_gc_set_dashes</tt></code>(GdkGC* <tt class= 
            "PARAMETER"><i>gc</i></tt>, gint <tt class="PARAMETER">
            <i>dash_offset</i></tt>, gchar <tt class="PARAMETER">
            <i>dash_list</i></tt>, gint <tt class="PARAMETER"><i>
            n</i></tt>);</code>
          </p>
          <p>
            <code><code class="FUNCDEF">void <tt class="FUNCTION">
            gdk_gc_unref</tt></code>(GdkGC* <tt class="PARAMETER">
            <i>gc</i></tt>);</code>
          </p>
        </div>
        <p>
          <b>Figure 16. <span class="STRUCTNAME">GdkGC</span></b>
        </p>
      </div>
      <div class="TABLE">
        <a name="TAB-GDKGC"></a>
        <p>
          <b>Table 6. GC Attributes</b>
        </p>
        <table border="1" bgcolor="#E0E0E0" cellspacing="0"
        cellpadding="4" class="CALSTABLE">
          <tr>
            <th align="LEFT" valign="TOP">
              Attribute
            </th>
            <th align="LEFT" valign="TOP">
              <span class="STRUCTNAME">GdkGCValuesMask</span>
            </th>
            <th align="LEFT" valign="TOP">
              Modifying Function
            </th>
            <th align="LEFT" valign="TOP">
              Default Value
            </th>
          </tr>
          <tr>
            <td align="LEFT" valign="TOP">
              GdkColor foreground
            </td>
            <td align="LEFT" valign="TOP">
              <span class="STRUCTNAME">GDK_GC_FOREGROUND</span>
            </td>
            <td align="LEFT" valign="TOP">
              <tt class="FUNCTION">gdk_gc_set_foreground()</tt>
            </td>
            <td align="LEFT" valign="TOP">
              black
            </td>
          </tr>
          <tr>
            <td align="LEFT" valign="TOP">
              GdkColor background
            </td>
            <td align="LEFT" valign="TOP">
              <span class="STRUCTNAME">GDK_GC_BACKGROUND</span>
            </td>
            <td align="LEFT" valign="TOP">
              <tt class="FUNCTION">gdk_gc_set_background()</tt>
            </td>
            <td align="LEFT" valign="TOP">
              white
            </td>
          </tr>
          <tr>
            <td align="LEFT" valign="TOP">
              GdkFont *font