</p>          </div>          <p>            <b>Figure 4. Packing <tt class="CLASSNAME">            GtkBox</tt></b>          </p>        </div>        <p>          A box can contain two sets of widgets. The first set is          packed at the "start" (top or left) of the box; the          second at the "end" (bottom or right). If you pack three          widgets into the start of a box, the first widget you          pack appears topmost or leftmost; the second follows the          first; and the third appears closest to the center of the          box. If you then pack three widgets into the end of the          same box, the first appears bottommost or rightmost; the          second follows it; and the third appears closest to the          center. With all six widgets packed, the order from          top/left to bottom/right is: 1, 2, 3, 3, 2, 1. <a href=           "sec-containers.html#FIG-PACKSTARTEND">Figure 5</a> shows          this for <tt class="CLASSNAME">GtkVBox</tt>. Order of          packing is only important within each end of the box;          i.e., we could have alternated packing start and packing          end, with the same results.        </p>        <div class="FIGURE">          <a name="FIG-PACKSTARTEND"></a>          <p>            <img src="figures/packstartend.png">          </p>          <p>            <b>Figure 5. Buttons packed into a <tt class=            "CLASSNAME">GtkVBox</tt></b>          </p>        </div>        <div class="SECT3">          <h3 class="SECT3">            <a name="Z49"><tt class="CLASSNAME">GtkBox</tt> Layout            Details</a>          </h3>          <p>            Packing is affected by three parameters, which are the            same for both start and end packing; the meaning of            these parameters is somewhat complicated, because they            interact with the <span class="STRUCTNAME">            homogeneous</span> setting of the box and with each            other.          </p>          <p>            Here's how a <tt class="CLASSNAME">GtkBox</tt> computes            its size request for the "interesting" direction (width            for <tt class="CLASSNAME">GtkHBox</tt>, height for <tt            class="CLASSNAME">GtkVBox</tt>):          </p>          <ol type="1">            <li>              <p>                The total requested size of each child is                considered to be the child's size request, plus two                times the <span class="STRUCTNAME">padding</span>                value used to pack the child. A child's <span                class="STRUCTNAME">padding</span> is the amount of                blank space on either side of it. In short, Child                Size = (Child Widget's Size Request) + 2*(Child                Padding).&#13;              </p>            </li>            <li>              <p>                If the box is homogeneous, the base size request                for the entire box is equal to the size (request +                padding) of the largest child, times the number of                children. In a homogeneous box, all children are as                large as the largest child.&#13;              </p>            </li>            <li>              <p>                If the box is not homogeneous, the base size                request for the entire box is the sum of the size                (request + padding) of each child.&#13;              </p>            </li>            <li>              <p>                The box-wide <span class="STRUCTNAME">                spacing</span> setting determines how much blank                space to leave between children; so this value is                multiplied by the number of chilren minus one, and                added to the base size request. Note that <i class=                 "FIRSTTERM">spacing</i> does not belong to a child;                it is blank space between children and is                unaffected by the <span class="STRUCTNAME">                expand</span> and <span class="STRUCTNAME">                fill</span> parameters. <i class="FIRSTTERM">                Padding</i>, on the other hand, is the space around                each child and <i class="EMPHASIS">is</i> affected                by the child's packing parameters.&#13;              </p>            </li>            <li>              <p>                All containers have a "border width" setting; two                times the border width is added to the request,                representing a border on either side. Thus, the                total size requested by a <tt class="CLASSNAME">                GtkBox</tt> is: (Sum of Child Sizes) +                Spacing*(Number of Children - 1) + 2*(Border                Width).&#13;              </p>            </li>          </ol>          <p>            After computing its size request and delivering it to            its parent container, <tt class="CLASSNAME">GtkBox</tt>            will receive its size allocation and distribute it            among its children as follows:          </p>          <ol type="1">            <li>              <p>                Enough space for the border width and inter-child                spacing is subtracted from the allocation; the                remainder is the available space for children                themselves. This space is divided into two chunks:                the amount actually requested by the children                (child requisitions and padding), and the "extra."                Extra = (Allocation Size) - (Sum of Child                Sizes).&#13;              </p>            </li>            <li>              <p>                If the box is not homogeneous, the "extra" space is                divided among those children with the <span class=                 "STRUCTNAME">expand</span> parameter set to <span                class="STRUCTNAME">TRUE</span>. These children can                expand to fit available space. If no child can                expand, the extra is used to add more space in the                center of the box, between the start-packed widgets                and the end-packed widgets.&#13;              </p>            </li>            <li>              <p>                If the box is homogeneous, the extra is distributed                according to need; those children who requested                more space get less extra, so that everyone ends up                with the same amount of space. The <span class=                 "STRUCTNAME">expand</span> parameter is ignored for                homogeneous boxes---extra is distributed to all                children, not just the expandable ones.&#13;              </p>            </li>            <li>              <p>                When a child gets some extra space, there are two                possibilities. More padding can be added around the                child, or the child widget itself can be expanded.                The <span class="STRUCTNAME">fill</span> parameter                determines which will happen. If <span class=                 "STRUCTNAME">TRUE</span>, the child widget expands                to fill the space---that is, the entire space                becomes the child's allocation; if <span class=                 "STRUCTNAME">fill</span> is <span class=                "STRUCTNAME">FALSE</span>, the child's padding is                increased to fill the space, and the child is                allocated only the space it requested. Note that                <span class="STRUCTNAME">fill</span> has no effect                if <span class="STRUCTNAME">expand</span> is set to                <span class="STRUCTNAME">FALSE</span> and the box                is not homogeneous, because the child will never                receive any extra space to fill.&#13;              </p>            </li>          </ol>          <p>            Whew! Who wants to think about all that? Fortunately,            there are some common patterns of usage, so you don't            need to solve a multivariate equation to figure out how            to use the widget. The authors of the GTK+ Tutorial            boil things down nicely to five cases that occur in            practice; we'll follow in their footsteps here.          </p>        </div>        <div class="SECT3">          <h3 class="SECT3">            <a name="Z50">Non-Homogeneous Box Packing Patterns</a>          </h3>          <p>            There are three interesting ways to pack a            non-homogeneous box. First, you can pack all the            widgets into the end of the box, with their natural            size. This means setting the <span class="STRUCTNAME">            expand</span> parameter to <span class="STRUCTNAME">            FALSE</span>:          </p>          <table border="0" bgcolor="#E0E0E0" width="100%">            <tr>              <td><pre class="PROGRAMLISTING">&#13;  gtk_box_pack_start(GTK_BOX(box),                     child,                      FALSE, FALSE, 0);&#13;</pre>              </td>            </tr>          </table>          <p>            The result is shown in <a href=             "sec-containers.html#FIG-PACKNONHOMONOEXPANDNOFILL">            Figure 6</a>. The <span class="STRUCTNAME">            expand</span> parameter is the only one that matters in            this case; no children are receiving extra space, so            they wouldn't be able to fill it even if <span class=             "STRUCTNAME">fill</span> were <span class="STRUCTNAME">            TRUE</span>.          </p>          <div class="FIGURE">            <a name="FIG-PACKNONHOMONOEXPANDNOFILL"></a>            <p>              <img src="figures/packnonhomonoexpandnofill.png">            </p>            <p>              <b>Figure 6. Non-homogeneous, with <span class=               "STRUCTNAME">expand = FALSE</span></b>            </p>          </div>          <p>            Second, you can spread widgets throughout the box,            letting them keep their natural size as in <a href=             "sec-containers.html#FIG-PACKNONHOMOEXPANDNOFILL">            Figure 7</a>; this means setting the <span class=             "STRUCTNAME">expand</span> parameter to <span class=             "STRUCTNAME">TRUE</span>:          </p>          <table border="0" bgcolor="#E0E0E0" width="100%">            <tr>              <td><pre class="PROGRAMLISTING">&#13;  gtk_box_pack_start(GTK_BOX(box),                     child,                      TRUE, FALSE, 0);&#13;</pre>              </td>            </tr>          </table>          <div class="FIGURE">            <a name="FIG-PACKNONHOMOEXPANDNOFILL"></a>            <p>              <img src="figures/packnonhomoexpandnofill.png">            </p>            <p>              <b>Figure 7. Non-homogeneous, with <span class=               "STRUCTNAME">expand = TRUE</span> and <span class=               "STRUCTNAME">fill = FALSE</span></b>            </p>          </div>          <p>            Finally, you can fill the box with widgets (letting            larger children have more space) by setting the <span            class="STRUCTNAME">fill</span> parameter to <span            class="STRUCTNAME">TRUE</span> as well:          </p>          <table border="0" bgcolor="#E0E0E0" width="100%">            <tr>              <td><pre class="PROGRAMLISTING">&#13;  gtk_box_pack_start(GTK_BOX(box),                     child,                      TRUE, TRUE, 0);&#13;</pre>              </td>            </tr>          </table>          <p>            This configuration is shown in <a href=             "sec-containers.html#FIG-PACKNONHOMOEXPANDFILL">Figure            8</a>          </p>          <div class="FIGURE">            <a name="FIG-PACKNONHOMOEXPANDFILL"></a>            <p>              <img src="figures/packnonhomoexpandfill.png">            </p>            <p>              <b>Figure 8. Non-homogeneous, with <span class=               "STRUCTNAME">expand = TRUE</span> and <span class=               "STRUCTNAME">fill = TRUE</span></b>            </p>          </div>        </div>        <div class="SECT3">          <h3 class="SECT3">            <a name="Z51">Homogeneous Box Packing Patterns</a>          </h3>          <p>            There are only two interesting ways to pack a            homogeneous box. Recall that the <span class=            "STRUCTNAME">expand</span> parameter is irrelevant for            homogeneous boxes; so the two cases correspond to the            <span class="STRUCTNAME">fill</span> parameter's            setting.          </p>          <p>            If <span class="STRUCTNAME">fill</span> is <span class=             "STRUCTNAME">FALSE</span>, you get <a href=             "sec-containers.html#FIG-PACKHOMONOFILL">Figure 9</a>.            Notice that the box is logically divided into three            equal parts, but only the largest child widget occupies            its entire space. The others are padded to fill their            third of the area. If <span class="STRUCTNAME">            fill</span> is <span class="STRUCTNAME">TRUE</span>,            you get <a href="sec-containers.html#FIG-PACKHOMOFILL">            Figure 10</a>; all the widgets are the same size.          </p>          <div class="FIGURE">            <a name="FIG-PACKHOMONOFILL"></a>            <p>              <img src="figures/packhomonofill.png">            </p>