gtkdrawingarea.html

最新gtk中文资料集

<p>
</p>
<p>
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.
</p>
<div class="example">
<a name="id4218805"></a><p class="title"><b>Example&#160;43.&#160;Simple <span class="structname">GtkDrawingArea</span> usage.</b></p>
<div class="example-contents"><pre class="programlisting">
gboolean
expose_event_callback (GtkWidget *widget, GdkEventExpose *event, gpointer data)
{
  gdk_draw_arc (widget-&gt;window,
                widget-&gt;style-&gt;fg_gc[GTK_WIDGET_STATE (widget)],
                TRUE,
                0, 0, widget-&gt;allocation.width, widget-&gt;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);
</pre></div>
</div>
<br class="example-break"><p>
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; <a class="link" href="GtkWidget.html#gtk-widget-queue-draw-area"><code class="function">gtk_widget_queue_draw_area()</code></a> and
<a
href="/usr/share/gtk-doc/html/gdk/gdk-Windows.html#gdk-window-invalidate-rect"
><code class="function">gdk_window_invalidate_rect()</code></a> are equally good ways to do this. You'll
then get an expose event for the invalid region.
</p>
<p>
The available routines for drawing are documented on the <a
href="/usr/share/gtk-doc/html/gdk/gdk-Drawing-Primitives.html"
>GDK Drawing Primitives</a> page.
See also <a
href="/usr/share/gtk-doc/html/gdk/gdk-Drawing-Primitives.html#gdk-draw-pixbuf"
><code class="function">gdk_draw_pixbuf()</code></a> for drawing a <a
href="/usr/share/gtk-doc/html/gdk-pixbuf/gdk-pixbuf-gdk-pixbuf.html#GdkPixbuf"
><span class="type">GdkPixbuf</span></a>.
</p>
<p>
To receive mouse events on a drawing area, you will need to enable
them with <a class="link" href="GtkWidget.html#gtk-widget-add-events"><code class="function">gtk_widget_add_events()</code></a>. To receive keyboard events, you
will need to set the <a class="link" href="GtkWidget.html#GTK-CAN-FOCUS:CAPS"><span class="type">GTK_CAN_FOCUS</span></a> flag on the drawing area, and
should probably draw some user-visible indication that the drawing
area is focused. Use the <a class="link" href="GtkWidget.html#GTK-HAS-FOCUS:CAPS"><code class="function">GTK_HAS_FOCUS()</code></a> macro in your expose event
handler to decide whether to draw the focus indicator. See
<a class="link" href="GtkStyle.html#gtk-paint-focus"><code class="function">gtk_paint_focus()</code></a> for one way to draw focus.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id4218953"></a><h2>Details</h2>
<div class="refsect2" lang="en">
<a name="id4218963"></a><h3>
<a name="GtkDrawingArea-struct"></a>GtkDrawingArea</h3>
<a class="indexterm" name="id4218977"></a><pre class="programlisting">typedef struct _GtkDrawingArea GtkDrawingArea;</pre>
<p>
The <a class="link" href="GtkDrawingArea.html" title="GtkDrawingArea"><span class="type">GtkDrawingArea</span></a> struct contains private data only, and
should be accessed using the functions below.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id4219002"></a><h3>
<a name="gtk-drawing-area-new"></a>gtk_drawing_area_new ()</h3>
<a class="indexterm" name="id4219015"></a><pre class="programlisting"><a class="link" href="GtkWidget.html" title="GtkWidget">GtkWidget</a>*          gtk_drawing_area_new                (void);</pre>
<p>
Creates a new drawing area.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span>&#160;:</span></p></td>
<td>a new <a class="link" href="GtkDrawingArea.html" title="GtkDrawingArea"><span class="type">GtkDrawingArea</span></a>


</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id4219060"></a><h3>
<a name="gtk-drawing-area-size"></a>gtk_drawing_area_size ()</h3>
<a class="indexterm" name="id4219076"></a><pre class="programlisting">void                gtk_drawing_area_size               (<a class="link" href="GtkDrawingArea.html" title="GtkDrawingArea">GtkDrawingArea</a> *darea,
                                                         <a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> width,
                                                         <a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> height);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">gtk_drawing_area_size</code> is deprecated and should not be used in newly-written code.</p>
</div>
<p>
(Use <a class="link" href="GtkWidget.html#gtk-widget-set-size-request"><code class="function">gtk_widget_set_size_request()</code></a> 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.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>darea</code></em>&#160;:</span></p></td>
<td>a <a class="link" href="GtkDrawingArea.html" title="GtkDrawingArea"><span class="type">GtkDrawingArea</span></a>.
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>width</code></em>&#160;:</span></p></td>
<td>the width to request.
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>height</code></em>&#160;:</span></p></td>
<td>the height to request.


</td>
</tr>
</tbody>
</table></div>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id4219203"></a><h2>See Also</h2>
<p>
Sometimes <a class="link" href="GtkImage.html" title="GtkImage"><span class="type">GtkImage</span></a> is a useful alternative to a drawing area. 
You can put a <a
href="/usr/share/gtk-doc/html/gdk/gdk-Bitmaps-and-Pixmaps.html#GdkPixmap"
><span class="type">GdkPixmap</span></a> in the <a class="link" href="GtkImage.html" title="GtkImage"><span class="type">GtkImage</span></a> and draw to the <a
href="/usr/share/gtk-doc/html/gdk/gdk-Bitmaps-and-Pixmaps.html#GdkPixmap"
><span class="type">GdkPixmap</span></a>, 
calling <a class="link" href="GtkWidget.html#gtk-widget-queue-draw"><code class="function">gtk_widget_queue_draw()</code></a> on the <a class="link" href="GtkImage.html" title="GtkImage"><span class="type">GtkImage</span></a> when you want to 
refresh to the screen.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id4219266"></a><div class="refsect2" lang="en"><a name="id4219267"></a></div>
<hr>
<div class="refsect2" lang="en"><a name="id4219268"></a></div>
</div>
</div>
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