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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>GtkDrawingArea: GTK+ 3 Reference Manual</title>
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<a href="#GtkDrawingArea.description" class="shortcut">Description</a></span><span id="nav_hierarchy"> <span class="dim">|</span>
<a href="#GtkDrawingArea.object-hierarchy" class="shortcut">Object Hierarchy</a></span><span id="nav_interfaces"> <span class="dim">|</span>
<a href="#GtkDrawingArea.implemented-interfaces" class="shortcut">Implemented Interfaces</a></span>
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<a name="GtkDrawingArea"></a><div class="titlepage"></div>
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<td valign="top">
<h2><span class="refentrytitle"><a name="GtkDrawingArea.top_of_page"></a>GtkDrawingArea</span></h2>
<p>GtkDrawingArea — A widget for custom user interface elements</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
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<div class="refsect1">
<a name="GtkDrawingArea.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody><tr>
<td class="function_type">
<a class="link" href="GtkWidget.html" title="GtkWidget"><span class="returnvalue">GtkWidget</span></a> *
</td>
<td class="function_name">
<a class="link" href="GtkDrawingArea.html#gtk-drawing-area-new" title="gtk_drawing_area_new ()">gtk_drawing_area_new</a> <span class="c_punctuation">()</span>
</td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody><tr>
<td class="datatype_keyword">struct</td>
<td class="function_name"><a class="link" href="GtkDrawingArea.html#GtkDrawingArea-struct" title="struct GtkDrawingArea">GtkDrawingArea</a></td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.object-hierarchy"></a><h2>Object Hierarchy</h2>
<pre class="screen"> <a href="https://developer.gnome.org/gobject/unstable/gobject-The-Base-Object-Type.html#GObject-struct">GObject</a>
<span class="lineart">╰──</span> <a href="https://developer.gnome.org/gobject/unstable/gobject-The-Base-Object-Type.html#GInitiallyUnowned">GInitiallyUnowned</a>
<span class="lineart">╰──</span> <a class="link" href="GtkWidget.html" title="GtkWidget">GtkWidget</a>
<span class="lineart">╰──</span> GtkDrawingArea
</pre>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.implemented-interfaces"></a><h2>Implemented Interfaces</h2>
<p>
GtkDrawingArea implements
AtkImplementorIface and <a class="link" href="GtkBuildable.html" title="GtkBuildable">GtkBuildable</a>.</p>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.includes"></a><h2>Includes</h2>
<pre class="synopsis">#include <gtk/gtk.h>
</pre>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.description"></a><h2>Description</h2>
<p>The <a class="link" href="GtkDrawingArea.html" title="GtkDrawingArea"><span class="type">GtkDrawingArea</span></a> widget is used for creating custom user interface
elements. It’s essentially a blank widget; you can draw on it. After
creating a drawing area, the application may want to connect to:</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>Mouse and button press signals to respond to input from
the user. (Use <a class="link" href="GtkWidget.html#gtk-widget-add-events" title="gtk_widget_add_events ()"><code class="function">gtk_widget_add_events()</code></a> to enable events
you wish to receive.)</p></li>
<li class="listitem"><p>The <a class="link" href="GtkWidget.html#GtkWidget-realize" title="The “realize” signal"><span class="type">“realize”</span></a> signal to take any necessary actions
when the widget is instantiated on a particular display.
(Create GDK resources in response to this signal.)</p></li>
<li class="listitem"><p>The <a class="link" href="GtkWidget.html#GtkWidget-size-allocate" title="The “size-allocate” signal"><span class="type">“size-allocate”</span></a> signal to take any necessary
actions when the widget changes size.</p></li>
<li class="listitem"><p>The <a class="link" href="GtkWidget.html#GtkWidget-draw" title="The “draw” signal"><span class="type">“draw”</span></a> signal to handle redrawing the
contents of the widget.</p></li>
</ul></div>
<p>The following code portion demonstrates using a drawing
area to display a circle in the normal widget foreground
color.</p>
<p>Note that GDK automatically clears the exposed area before sending
the expose event, and that drawing is implicitly clipped to the exposed
area. If you want to have a theme-provided background, you need
to call <a class="link" href="GtkStyleContext.html#gtk-render-background" title="gtk_render_background ()"><code class="function">gtk_render_background()</code></a> in your ::draw method.</p>
<div class="refsect3">
<a name="id-1.3.19.4.8.6"></a><h4>Simple GtkDrawingArea usage</h4>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
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<td class="listing_code"><pre class="programlisting">gboolean
<span class="function">draw_callback</span> <span class="gtkdoc opt">(</span>GtkWidget <span class="gtkdoc opt">*</span>widget<span class="gtkdoc opt">,</span> cairo_t <span class="gtkdoc opt">*</span>cr<span class="gtkdoc opt">,</span> gpointer data<span class="gtkdoc opt">)</span>
<span class="gtkdoc opt">{</span>
guint width<span class="gtkdoc opt">,</span> height<span class="gtkdoc opt">;</span>
GdkRGBA color<span class="gtkdoc opt">;</span>
GtkStyleContext <span class="gtkdoc opt">*</span>context<span class="gtkdoc opt">;</span>
context <span class="gtkdoc opt">=</span> <span class="function"><a href="GtkWidget.html#gtk-widget-get-style-context">gtk_widget_get_style_context</a></span> <span class="gtkdoc opt">(</span>widget<span class="gtkdoc opt">);</span>
width <span class="gtkdoc opt">=</span> <span class="function"><a href="GtkWidget.html#gtk-widget-get-allocated-width">gtk_widget_get_allocated_width</a></span> <span class="gtkdoc opt">(</span>widget<span class="gtkdoc opt">);</span>
height <span class="gtkdoc opt">=</span> <span class="function"><a href="GtkWidget.html#gtk-widget-get-allocated-height">gtk_widget_get_allocated_height</a></span> <span class="gtkdoc opt">(</span>widget<span class="gtkdoc opt">);</span>
<span class="function"><a href="GtkStyleContext.html#gtk-render-background">gtk_render_background</a></span> <span class="gtkdoc opt">(</span>context<span class="gtkdoc opt">,</span> cr<span class="gtkdoc opt">,</span> <span class="number">0</span><span class="gtkdoc opt">,</span> <span class="number">0</span><span class="gtkdoc opt">,</span> width<span class="gtkdoc opt">,</span> height<span class="gtkdoc opt">);</span>
<span class="function">cairo_arc</span> <span class="gtkdoc opt">(</span>cr<span class="gtkdoc opt">,</span>
width <span class="gtkdoc opt">/</span> <span class="number">2.0</span><span class="gtkdoc opt">,</span> height <span class="gtkdoc opt">/</span> <span class="number">2.0</span><span class="gtkdoc opt">,</span>
<span class="function"><a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#MIN:CAPS">MIN</a></span> <span class="gtkdoc opt">(</span>width<span class="gtkdoc opt">,</span> height<span class="gtkdoc opt">) /</span> <span class="number">2.0</span><span class="gtkdoc opt">,</span>
<span class="number">0</span><span class="gtkdoc opt">,</span> <span class="number">2</span> <span class="gtkdoc opt">*</span> G_PI<span class="gtkdoc opt">);</span>
<span class="function"><a href="GtkStyleContext.html#gtk-style-context-get-color">gtk_style_context_get_color</a></span> <span class="gtkdoc opt">(</span>context<span class="gtkdoc opt">,</span>
<span class="function"><a href="GtkStyleContext.html#gtk-style-context-get-state">gtk_style_context_get_state</a></span> <span class="gtkdoc opt">(</span>context<span class="gtkdoc opt">),</span>
<span class="gtkdoc opt">&</span>color<span class="gtkdoc opt">);</span>
<span class="function"><a href="http://developer.gnome.org/gdk3/gdk4-Cairo-Interaction.html#gdk-cairo-set-source-rgba">gdk_cairo_set_source_rgba</a></span> <span class="gtkdoc opt">(</span>cr<span class="gtkdoc opt">, &</span>color<span class="gtkdoc opt">);</span>
<span class="function">cairo_fill</span> <span class="gtkdoc opt">(</span>cr<span class="gtkdoc opt">);</span>
<span class="keyword">return</span> FALSE<span class="gtkdoc opt">;</span>
<span class="gtkdoc opt">}</span>
<span class="gtkdoc opt">[...]</span>
GtkWidget <span class="gtkdoc opt">*</span>drawing_area <span class="gtkdoc opt">=</span> <span class="function"><a href="GtkDrawingArea.html#gtk-drawing-area-new">gtk_drawing_area_new</a></span> <span class="gtkdoc opt">();</span>
<span class="function"><a href="GtkWidget.html#gtk-widget-set-size-request">gtk_widget_set_size_request</a></span> <span class="gtkdoc opt">(</span>drawing_area<span class="gtkdoc opt">,</span> <span class="number">100</span><span class="gtkdoc opt">,</span> <span class="number">100</span><span class="gtkdoc opt">);</span>
<span class="function"><a href="https://developer.gnome.org/gobject/unstable/gobject-Signals.html#g-signal-connect">g_signal_connect</a></span> <span class="gtkdoc opt">(</span><span class="function"><a href="https://developer.gnome.org/gobject/unstable/gobject-The-Base-Object-Type.html#G-OBJECT:CAPS">G_OBJECT</a></span> <span class="gtkdoc opt">(</span>drawing_area<span class="gtkdoc opt">),</span> <span class="string">"draw"</span><span class="gtkdoc opt">,</span>
<span class="function"><a href="https://developer.gnome.org/gobject/unstable/gobject-Closures.html#G-CALLBACK:CAPS">G_CALLBACK</a></span> <span class="gtkdoc opt">(</span>draw_callback<span class="gtkdoc opt">),</span> NULL<span class="gtkdoc opt">);</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p></p>
<p>Draw signals are normally delivered when a drawing area first comes
onscreen, or when it’s covered by another window and then uncovered.
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" title="gtk_widget_queue_draw_area ()"><code class="function">gtk_widget_queue_draw_area()</code></a> and
<a href="http://developer.gnome.org/gdk3/gdk4-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 a draw signal for the invalid region.</p>
<p>The available routines for drawing are documented on the
GDK Drawing Primitives page
and the cairo documentation.</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" title="gtk_widget_add_events ()"><code class="function">gtk_widget_add_events()</code></a>. To receive keyboard events, you
will need to set the “can-focus” property on the drawing area, and you
should probably draw some user-visible indication that the drawing
area is focused. Use <a class="link" href="GtkWidget.html#gtk-widget-has-focus" title="gtk_widget_has_focus ()"><code class="function">gtk_widget_has_focus()</code></a> in your expose event
handler to decide whether to draw the focus indicator. See
<a class="link" href="GtkStyleContext.html#gtk-render-focus" title="gtk_render_focus ()"><code class="function">gtk_render_focus()</code></a> for one way to draw focus.</p>
</div>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="gtk-drawing-area-new"></a><h3>gtk_drawing_area_new ()</h3>
<pre class="programlisting"><a class="link" href="GtkWidget.html" title="GtkWidget"><span class="returnvalue">GtkWidget</span></a> *
gtk_drawing_area_new (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>Creates a new drawing area.</p>
<div class="refsect3">
<a name="gtk-drawing-area-new.returns"></a><h4>Returns</h4>
<p> a new <a class="link" href="GtkDrawingArea.html" title="GtkDrawingArea"><span class="type">GtkDrawingArea</span></a></p>
</div>
</div>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="GtkDrawingArea-struct"></a><h3>struct GtkDrawingArea</h3>
<pre class="programlisting">struct GtkDrawingArea;</pre>
</div>
</div>
<div class="refsect1">
<a name="GtkDrawingArea.see-also"></a><h2>See Also</h2>
<p><a class="link" href="GtkImage.html" title="GtkImage"><span class="type">GtkImage</span></a></p>
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