<refentry id="GtkDrawingArea">
<refmeta>
<refentrytitle>GtkDrawingArea</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>GTK Library</refmiscinfo>
</refmeta>

<refnamediv>
<refname>GtkDrawingArea</refname><refpurpose>a widget for custom user interface elements.</refpurpose>
</refnamediv>

<refsynopsisdiv><title>Synopsis</title>
<synopsis>

#include &lt;gtk/gtk.h&gt;


struct      <link linkend="GtkDrawingArea-struct">GtkDrawingArea</link>;
<link linkend="GtkWidget">GtkWidget</link>*  <link linkend="gtk-drawing-area-new">gtk_drawing_area_new</link>            (void);
void        <link linkend="gtk-drawing-area-size">gtk_drawing_area_size</link>           (<link linkend="GtkDrawingArea">GtkDrawingArea</link> *darea,
                                             <link linkend="gint">gint</link> width,
                                             <link linkend="gint">gint</link> height);


</synopsis>
</refsynopsisdiv>

<refsect1>
<title>Object Hierarchy</title>
<synopsis>

  <link linkend="GObject">GObject</link>
   +----<link linkend="GtkObject">GtkObject</link>
         +----<link linkend="GtkWidget">GtkWidget</link>
               +----GtkDrawingArea
</synopsis>

</refsect1>




<refsect1>
<title>Description</title>
<para>

The <link linkend="GtkDrawingArea">GtkDrawingArea</link> widget is used for creating custom user interface
elements. It's essentially a blank widget; you can draw on
<literal>widget-&gt;window</literal>. After creating a drawing area,
the application may want to connect to:

<itemizedlist>
  <listitem>
    <para>
    Mouse and button press signals to respond to input from
    the user. (Use <link linkend="gtk-widget-add-events">gtk_widget_add_events</link>() to enable events 
    you wish to receive.)
    </para>
  </listitem>
  <listitem>
    <para>
    The "realize" signal to take any necessary actions
    when the widget is instantiated on a particular display.
    (Create GDK resources in response to this signal.)
    </para>
  </listitem>
  <listitem>
    <para>
    The "configure_event" signal to take any necessary actions
    when the widget changes size.
    </para>
  </listitem>
  <listitem>
    <para>
    The "expose_event" signal to handle redrawing the
    contents of the widget.
    </para>
  </listitem>
</itemizedlist>
</para>
<para>
The following code portion demonstrates using a drawing
area to display a circle in the normal widget foreground 
color.
Note that GDK automatically clears the exposed area
to the background color before sending the expose event, and 
that drawing is implicitly clipped to the exposed area.
</para>
<example>
<title>Simple <structname>GtkDrawingArea</structname> usage.</title>
<programlisting>
gboolean
expose_event_callback (GtkWidget *widget, GdkEventExpose *event, gpointer data)
{
  gdk_draw_arc (widget->window,
                widget->style->fg_gc[GTK_WIDGET_STATE (widget)],
                TRUE,
                0, 0, widget->allocation.width, widget->allocation.height,
                0, 64 * 360);
 
  return TRUE;
}
[...]
  GtkWidget *drawing_area = gtk_drawing_area_new (<!-- -->);
  gtk_widget_set_size_request (drawing_area, 100, 100);
  g_signal_connect (G_OBJECT (drawing_area), "expose_event",  
                    G_CALLBACK (expose_event_callback), NULL);
</programlisting>
</example>

<para>
Expose events are normally delivered when a drawing area first comes
onscreen, or when it's covered by another window and then uncovered
(exposed). You can also force an expose event by adding to the "damage
region" of the drawing area's window; <link linkend="gtk-widget-queue-draw-area">gtk_widget_queue_draw_area</link>() and
<link linkend="gdk-window-invalidate-rect">gdk_window_invalidate_rect</link>() are equally good ways to do this. You'll
then get an expose event for the invalid region.
</para>

<para>
The available routines for drawing are documented on the <link
linkend="gdk-Drawing-Primitives">GDK Drawing Primitives</link> page.
See also <link linkend="gdk-pixbuf-render-to-drawable">gdk_pixbuf_render_to_drawable</link>() for drawing a <link linkend="GdkPixbuf">GdkPixbuf</link>.
</para>

<para>
To receive mouse events on a drawing area, you will need to enable
them with <link linkend="gtk-widget-add-events">gtk_widget_add_events</link>(). To receive keyboard events, you
will need to set the <link linkend="GTK-CAN-FOCUS-CAPS">GTK_CAN_FOCUS</link> flag on the drawing area, and
should probably draw some user-visible indication that the drawing
area is focused. Use the <link linkend="GTK-HAS-FOCUS-CAPS">GTK_HAS_FOCUS</link>() macro in your expose event
handler to decide whether to draw the focus indicator. See
<link linkend="gtk-paint-focus">gtk_paint_focus</link>() for one way to draw focus.
</para>
</refsect1>

<refsect1>
<title>Details</title>
<refsect2>
<title><anchor id="GtkDrawingArea-struct">struct GtkDrawingArea</title>
<programlisting>struct GtkDrawingArea;</programlisting>
<para>
The <link linkend="GtkDrawingArea">GtkDrawingArea</link> struct contains private data only, and
should be accessed using the functions below.
</para></refsect2>
<refsect2>
<title><anchor id="gtk-drawing-area-new">gtk_drawing_area_new ()</title>
<programlisting><link linkend="GtkWidget">GtkWidget</link>*  gtk_drawing_area_new            (void);</programlisting>
<para>
Creates a new drawing area.
</para><informaltable pgwide="1" frame="none" role="params">
<tgroup cols="2">
<colspec colwidth="2*">
<colspec colwidth="8*">
<tbody>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>a new <link linkend="GtkDrawingArea">GtkDrawingArea</link>


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="gtk-drawing-area-size">gtk_drawing_area_size ()</title>
<programlisting>void        gtk_drawing_area_size           (<link linkend="GtkDrawingArea">GtkDrawingArea</link> *darea,
                                             <link linkend="gint">gint</link> width,
                                             <link linkend="gint">gint</link> height);</programlisting>
<warning>
<para>
<literal>gtk_drawing_area_size</literal> is deprecated and should not be used in newly-written code.
</para>
</warning>
<para>
(Use <link linkend="gtk-widget-set-size-request">gtk_widget_set_size_request</link>() instead.)
Sets the size that the drawing area will request
in response to a "size_request" signal. The 
drawing area may actually be allocated a size
larger than this depending on how it is packed
within the enclosing containers.
</para><informaltable pgwide="1" frame="none" role="params">
<tgroup cols="2">
<colspec colwidth="2*">
<colspec colwidth="8*">
<tbody>
<row><entry align="right"><parameter>darea</parameter>&nbsp;:</entry>
<entry>a <link linkend="GtkDrawingArea">GtkDrawingArea</link>.
</entry></row>
<row><entry align="right"><parameter>width</parameter>&nbsp;:</entry>
<entry>the width to request.
</entry></row>
<row><entry align="right"><parameter>height</parameter>&nbsp;:</entry>
<entry>the height to request.


</entry></row>
</tbody></tgroup></informaltable></refsect2>

</refsect1>



<refsect1>
<title>See Also</title>
<para>
Sometimes <link linkend="GtkImage">GtkImage</link> is a useful alternative to a drawing area. 
You can put a <link linkend="GdkPixmap">GdkPixmap</link> in the <link linkend="GtkImage">GtkImage</link> and draw to the <link linkend="GdkPixmap">GdkPixmap</link>, 
calling <link linkend="gtk-widget-queue-draw">gtk_widget_queue_draw</link>() on the <link linkend="GtkImage">GtkImage</link> when you want to 
refresh to the screen.
</para>
</refsect1>

</refentry>
