z166.html

gtk_text program sample&eg

  nvis_children = 0;
  nexpand_children = 0;
  children = box->children;

  while (children)
    {
      child = children->data;
      children = children->next;

      if (GTK_WIDGET_VISIBLE (child->widget))
        {
          nvis_children += 1;
          if (child->expand)
            nexpand_children += 1;
        }
    }

  if (nvis_children > 0)
    {
      if (box->homogeneous)
        {
          height = (allocation->height -
                   GTK_CONTAINER (box)->border_width * 2 -
                   (nvis_children - 1) * box->spacing);
          extra = height / nvis_children;
        }
      else if (nexpand_children > 0)
        {
          height = (gint) allocation->height - (gint) widget->requisition.height;
          extra = height / nexpand_children;
        }
      else
        {
          height = 0;
          extra = 0;
        }

      y = allocation->y + GTK_CONTAINER (box)->border_width;
      child_allocation.x = allocation->x + GTK_CONTAINER (box)->border_width;
      child_allocation.width = MAX (1, (gint) allocation->width - (gint) GTK_CONTAINER (box)->border_width * 2);

      children = box->children;
      while (children)
        {
          child = children->data;
          children = children->next;

          if ((child->pack == GTK_PACK_START) && GTK_WIDGET_VISIBLE (child->widget))
            {
              if (box->homogeneous)
                {
                  if (nvis_children == 1)
                    child_height = height;
                  else
                    child_height = extra;

                  nvis_children -= 1;
                  height -= extra;
                }
              else
                {
                  GtkRequisition child_requisition;

                  gtk_widget_get_child_requisition (child->widget, &child_requisition);
                  child_height = child_requisition.height + child->padding * 2;

                  if (child->expand)
                    {
                      if (nexpand_children == 1)
                        child_height += height;
                      else
                        child_height += extra;

                      nexpand_children -= 1;
                      height -= extra;
                    }
                }

              if (child->fill)
                {
                  child_allocation.height = MAX (1, child_height - (gint)child->padding * 2);
                  child_allocation.y = y + child->padding;
                }
              else
                {
                  GtkRequisition child_requisition;

                  gtk_widget_get_child_requisition (child->widget, &child_requisition);
                  child_allocation.height = child_requisition.height;
                  child_allocation.y = y + (child_height - child_allocation.height) / 2;
                }

              gtk_widget_size_allocate (child->widget, &child_allocation);

              y += child_height + box->spacing;
            }
        }

      y = allocation->y + allocation->height - GTK_CONTAINER (box)->border_width;

      children = box->children;
      while (children)
        {
          child = children->data;
          children = children->next;

          if ((child->pack == GTK_PACK_END) && GTK_WIDGET_VISIBLE (child->widget))
            {
              GtkRequisition child_requisition;
              gtk_widget_get_child_requisition (child->widget, &child_requisition);

              if (box->homogeneous)
                {
                  if (nvis_children == 1)
                    child_height = height;
                  else
                    child_height = extra;

                  nvis_children -= 1;
                  height -= extra;
                }
              else
                {
                  child_height = child_requisition.height + child->padding * 2;

                  if (child->expand)
                    {
                      if (nexpand_children == 1)
                        child_height += height;
                      else
                        child_height += extra;

                      nexpand_children -= 1;
                      height -= extra;
                    }
                }

              if (child->fill)
                {
                  child_allocation.height = MAX (1, child_height - (gint)child->padding * 2);
                  child_allocation.y = y + child->padding - child_height;
                }
              else
                {
                  child_allocation.height = child_requisition.height;
                  child_allocation.y = y + (child_height - child_allocation.height) / 2 - child_height;
                }

              gtk_widget_size_allocate (child->widget, &child_allocation);

              y -= (child_height + box->spacing);
            }
        }
    }
}
      
</pre>
            </td>
          </tr>
        </table>
      </div>
      <div class="SECT2">
        <h2 class="SECT2">
          <a name="Z169">Child Arguments</a>
        </h2>
        <p>
          <tt class="CLASSNAME">GtkBox</tt> implements <i class= 
          "FIRSTTERM">child arguments</i>, which were briefly
          described in <a href="hc-objectargs.html#SEC-GETSETARG">
          the section called <i>Using Object Arguments in Your Own
          <span class="STRUCTNAME">GtkObject</span> Subclass</i> in
          the chapter called <i>The GTK+ Object and Type
          System</i></a>. Child arguments represent a property of a
          pair of objects. In this case, the box-packing flags for
          each child can be read and written using the object
          argument system.
        </p>
        <p>
          Here's how <tt class="CLASSNAME">GtkBox</tt> registers
          its child arguments, in <tt class="FUNCTION">
          gtk_box_class_init()</tt>:
        </p>
        <table border="0" bgcolor="#E0E0E0" width="100%">
          <tr>
            <td>
<pre class="PROGRAMLISTING">
&#13;  gtk_container_add_child_arg_type ("GtkBox::expand", GTK_TYPE_BOOL, GTK_ARG_READWRITE, CHILD_ARG_EXPAND);
  gtk_container_add_child_arg_type ("GtkBox::fill", GTK_TYPE_BOOL, GTK_ARG_READWRITE, CHILD_ARG_FILL);
  gtk_container_add_child_arg_type ("GtkBox::padding", GTK_TYPE_ULONG, GTK_ARG_READWRITE, CHILD_ARG_PADDING);
  gtk_container_add_child_arg_type ("GtkBox::pack_type", GTK_TYPE_PACK_TYPE, GTK_ARG_READWRITE, CHILD_ARG_PACK_TYPE);
  gtk_container_add_child_arg_type ("GtkBox::position", GTK_TYPE_LONG, GTK_ARG_READWRITE, CHILD_ARG_POSITION);

      
</pre>
            </td>
          </tr>
        </table>
        <p>
          <tt class="CLASSNAME">GtkBox</tt> then implements the
          <span class="STRUCTNAME">get_child_arg</span> and <span
          class="STRUCTNAME">set_child_arg</span> methods from
          <span class="STRUCTNAME">GtkContainerClass</span>. Here's
          <tt class="FUNCTION">gtk_box_get_child_arg()</tt>; the
          <tt class="FUNCTION">gtk_box_set_child_arg()</tt> is
          analagous.
        </p>
        <table border="0" bgcolor="#E0E0E0" width="100%">
          <tr>
            <td>
<pre class="PROGRAMLISTING">
&#13;static void
gtk_box_get_child_arg (GtkContainer   *container,
                       GtkWidget      *child,
                       GtkArg         *arg,
                       guint           arg_id)
{
  gboolean expand = 0;
  gboolean fill = 0;
  guint padding = 0;
  GtkPackType pack_type = 0;
  GList *list;

  if (arg_id != CHILD_ARG_POSITION)
    gtk_box_query_child_packing (GTK_BOX (container),
                                 child,
                                 &amp;expand,
                                 &amp;fill,
                                 &amp;padding,
                                 &amp;pack_type);
  
  switch (arg_id)
    {
    case CHILD_ARG_EXPAND:
      GTK_VALUE_BOOL (*arg) = expand;
      break;
    case CHILD_ARG_FILL:
      GTK_VALUE_BOOL (*arg) = fill;
      break;
    case CHILD_ARG_PADDING:
      GTK_VALUE_ULONG (*arg) = padding;
      break;
    case CHILD_ARG_PACK_TYPE:
      GTK_VALUE_ENUM (*arg) = pack_type;
      break;
    case CHILD_ARG_POSITION:
      GTK_VALUE_LONG (*arg) = 0;
      for (list = GTK_BOX (container)-&gt;children; list; list = list-&gt;next)
        {
          GtkBoxChild *child_entry;

          child_entry = list-&gt;data;
          if (child_entry-&gt;widget == child)
            break;
          GTK_VALUE_LONG (*arg)++;
        }
      if (!list)
        GTK_VALUE_LONG (*arg) = -1;
      break;
    default:
      arg-&gt;type = GTK_TYPE_INVALID;
      break;
    }
}
      
</pre>
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