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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id-1.6.3.4"></a>Changes that need to be done at the time of the switch</h2></div></div></div>

 This section outlines porting tasks that you need to tackle when
 you get to the point that you actually build your application against
 GTK+ 3. Making it possible to prepare for these in GTK+ 2.24 would
 have been either impossible or impractical.
 
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.3"></a>Replace size_request by get_preferred_width/height</h3></div></div></div>

 The request-phase of the traditional GTK+ geometry management
 has been replaced by a more flexible height-for-width system,
 which is described in detail in the API documentation
 (see <a class="xref" href="GtkWidget.html#geometry-management" title="Height-for-width Geometry Management">the section called “Height-for-width Geometry Management”</a>). As a consequence,
 the ::size-request signal and vfunc has been removed from
 <a class="link" href="GtkWidget.html#GtkWidgetClass" title="struct GtkWidgetClass">GtkWidgetClass</a>. The replacement for <code class="function">size_request()</code> can
 take several levels of sophistication:
 
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">

 As a minimal replacement to keep current functionality,
 you can simply implement the <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-width"><code class="function">GtkWidgetClass.get_preferred_width()</code></a> and
 <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-height"><code class="function">GtkWidgetClass.get_preferred_height()</code></a> vfuncs by calling your existing
 <code class="function">size_request()</code> function. So you go from
 
<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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11</pre></td>
 <td class="listing_code"><pre class="programlisting">static void
my_widget_class_init (MyWidgetClass *class)
{
 GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);

/* ... */

widget_class->size_request = my_widget_size_request;

/* ... */
}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

to something that looks more like this:
 

 
<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">static void
my_widget_get_preferred_width (GtkWidget *widget,
 gint *minimal_width,
 gint *natural_width)
{
 GtkRequisition requisition;

my_widget_size_request (widget, &requisition);

*minimal_width = *natural_width = requisition.width;
}

*minimal_height = *natural_height = requisition.height;
}

/* ... */

static void
my_widget_class_init (MyWidgetClass *class)
{
 GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);

/* ... */

widget_class->get_preferred_width = my_widget_get_preferred_width;
 widget_class->get_preferred_height = my_widget_get_preferred_height;

/* ... */

}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

Sometimes you can make things a little more streamlined
 by replacing your existing <code class="function">size_request()</code> implementation by
 one that takes an orientation parameter:
 

 
<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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46</pre></td>
 <td class="listing_code"><pre class="programlisting">static void
my_widget_get_preferred_size (GtkWidget *widget,
 GtkOrientation orientation,
 gint *minimal_size,
 gint *natural_size)
{

/* do things that are common for both orientations ... */

if (orientation == GTK_ORIENTATION_HORIZONTAL)
 {
 /* do stuff that only applies to width... */

*minimal_size = *natural_size = ...
 }
 else
 {
 /* do stuff that only applies to height... */

static void
my_widget_get_preferred_width (GtkWidget *widget,
 gint *minimal_width,
 gint *natural_width)
{
 my_widget_get_preferred_size (widget,
 GTK_ORIENTATION_HORIZONTAL,
 minimal_width,
 natural_width);
}

static void
my_widget_get_preferred_height (GtkWidget *widget,
 gint *minimal_height,
 gint *natural_height)
{
 my_widget_get_preferred_size (widget,
 GTK_ORIENTATION_VERTICAL,
 minimal_height,
 natural_height);
}

/* ... */</pre></td>
 </tr>
 </tbody>
 </table>
</div>

</li>
<li class="listitem">
If your widget can cope with a small size,
 but would appreciate getting some more space (a common
 example would be that it contains ellipsizable labels),
 you can do that by making your <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-width"><code class="function">GtkWidgetClass.get_preferred_width()</code></a> /
 <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-height"><code class="function">GtkWidgetClass.get_preferred_height()</code></a>
 functions return a smaller value for <code>minimal</code> than for <code>natural</code>.
 For <code>minimal</code>, you probably want to return the same value
 that your <code class="function">size_request()</code> function returned before (since
 <code class="function">size_request()</code> was defined as returning the minimal size
 a widget can work with). A simple way to obtain good
 values for <code>natural</code>, in the case of containers, is to use
 <a class="link" href="GtkWidget.html#gtk-widget-get-preferred-width" title="gtk_widget_get_preferred_width ()"><code class="function">gtk_widget_get_preferred_width()</code></a> and
 <a class="link" href="GtkWidget.html#gtk-widget-get-preferred-height" title="gtk_widget_get_preferred_height ()"><code class="function">gtk_widget_get_preferred_height()</code></a> on the children of the
 container, as in the following example:
 
<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">static void
gtk_fixed_get_preferred_height (GtkWidget *widget,
 gint *minimum,
 gint *natural)
{
 GtkFixed *fixed = GTK_FIXED (widget);
 GtkFixedPrivate *priv = fixed->priv;
 GtkFixedChild *child;
 GList *children;
 gint child_min, child_nat;

*minimum = 0;
 *natural = 0;

for (children = priv->children; children; children = children->next)
 {
 child = children->data;

if (!gtk_widget_get_visible (child->widget))
 continue;

gtk_widget_get_preferred_height (child->widget, &child_min, &child_nat);

*minimum = MAX (*minimum, child->y + child_min);
 *natural = MAX (*natural, child->y + child_nat);
 }
}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

</li>
<li class="listitem">
 Note that the <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-width"><code class="function">GtkWidgetClass.get_preferred_width()</code></a> /
 <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-height"><code class="function">GtkWidgetClass.get_preferred_height()</code></a> functions
 only allow you to deal with one dimension at a time. If your
 <code class="function">size_request()</code> handler is doing things that involve both
 width and height at the same time (e.g. limiting the aspect
 ratio), you will have to implement
 <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-height-for-width"><code class="function">GtkWidgetClass.get_preferred_height_for_width()</code></a>
 and <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-width-for-height"><code class="function">GtkWidgetClass.get_preferred_width_for_height()</code></a>.
 </li>
<li class="listitem">
 To make full use of the new capabilities of the
 height-for-width geometry management, you need to additionally
 implement the <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-height-for-width"><code class="function">GtkWidgetClass.get_preferred_height_for_width()</code></a> and
 <a class="link" href="GtkWidget.html#GtkWidgetClass.get-preferred-width-for-height"><code class="function">GtkWidgetClass.get_preferred_width_for_height()</code></a>. For details on
 these functions, see <a class="xref" href="GtkWidget.html#geometry-management" title="Height-for-width Geometry Management">the section called “Height-for-width Geometry Management”</a>.
 </li>
</ul></div>

 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.4"></a>Replace GdkRegion by cairo_region_t</h3></div></div></div>

 Starting with version 1.10, cairo provides a region API that is
 equivalent to the GDK region API (which was itself copied from
 the X server). Therefore, the region API has been removed in GTK+ 3.
 

 Porting your application to the cairo region API should be a straight
 find-and-replace task. Please refer to the following table:
 
<div class="table">
<a name="id-1.6.3.4.4.3.1"></a>Table 14. 
<div class="table-contents"><table class="table" border="1">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>GDK</th>
<th>cairo</th>
</tr></thead>
<tbody>
<tr>
<td>GdkRegion</td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-t">cairo_region_t</a></td>
</tr>
<tr>
<td><a href="../html/gdk3-Points-Rectangles-and-Regions.html#GdkRectangle">GdkRectangle</a></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Types.html#cairo-rectangle-int-t">cairo_rectangle_int_t</a></td>
</tr>
<tr>
<td><a href="../html/gdk3-Points-Rectangles-and-Regions.html#gdk-rectangle-intersect"><code class="function">gdk_rectangle_intersect()</code></a></td>
<td>this function is still there</td>
</tr>
<tr>
<td><a href="../html/gdk3-Points-Rectangles-and-Regions.html#gdk-rectangle-union"><code class="function">gdk_rectangle_union()</code></a></td>
<td>this function is still there</td>
</tr>
<tr>
<td><code class="function">gdk_region_new()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-create"><code class="function">cairo_region_create()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_copy()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-copy"><code class="function">cairo_region_copy()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_destroy()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-destroy"><code class="function">cairo_region_destroy()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_rectangle()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-create-rectangle"><code class="function">cairo_region_create_rectangle()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_get_clipbox()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-get-extents"><code class="function">cairo_region_get_extents()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_get_rectangles()</code></td>
<td>
<a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-num-rectangles"><code class="function">cairo_region_num_rectangles()</code></a> and
 <a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-get-rectangle"><code class="function">cairo_region_get_rectangle()</code></a>
</td>
</tr>
<tr>
<td><code class="function">gdk_region_empty()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-is-empty"><code class="function">cairo_region_is_empty()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_equal()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-equal"><code class="function">cairo_region_equal()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_point_in()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-contains-point"><code class="function">cairo_region_contains_point()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_rect_in()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-contains-rectangle"><code class="function">cairo_region_contains_rectangle()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_offset()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-translate"><code class="function">cairo_region_translate()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_union_with_rect()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-union-rectangle"><code class="function">cairo_region_union_rectangle()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_intersect()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-intersect"><code class="function">cairo_region_intersect()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_union()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-union"><code class="function">cairo_region_union()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_subtract()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-subtract"><code class="function">cairo_region_subtract()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_xor()</code></td>
<td><a href="/usr/share/gtk-doc/html/cairo/cairo-Regions.html#cairo-region-xor"><code class="function">cairo_region_xor()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_region_shrink()</code></td>
<td>no replacement</td>
</tr>
<tr>
<td><code class="function">gdk_region_polygon()</code></td>
<td>no replacement, use cairo paths instead</td>
</tr>
</tbody>
</table></div>
</div>
 
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.5"></a>Replace GdkPixmap by cairo surfaces</h3></div></div></div>

 The GdkPixmap object and related functions have been removed.
 In the cairo-centric world of GTK+ 3, cairo surfaces take over
 the role of pixmaps.
 
<div class="example">
<a name="id-1.6.3.4.5.3"></a>Example 41. Creating custom cursors
<div class="example-contents">

 One place where pixmaps were commonly used is to create custom
 cursors:
 
<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">GdkCursor *cursor;
GdkPixmap *pixmap;
cairo_t *cr;
GdkColor fg = { 0, 0, 0, 0 };

pixmap = gdk_pixmap_new (NULL, 1, 1, 1);

cr = gdk_cairo_create (pixmap);
cairo_rectangle (cr, 0, 0, 1, 1);
cairo_fill (cr);
cairo_destroy (cr);

cursor = gdk_cursor_new_from_pixmap (pixmap, pixmap, &fg, &fg, 0, 0);

g_object_unref (pixmap);</pre></td>
 </tr>
 </tbody>
 </table>
</div>

The same can be achieved without pixmaps, by drawing onto
 an image surface:
 
<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">GdkCursor *cursor;
cairo_surface_t *s;
cairo_t *cr;
GdkPixbuf *pixbuf;

s = cairo_image_surface_create (CAIRO_FORMAT_A1, 3, 3);
cr = cairo_create (s);
cairo_arc (cr, 1.5, 1.5, 1.5, 0, 2 * M_PI);
cairo_fill (cr);
cairo_destroy (cr);

pixbuf = gdk_pixbuf_get_from_surface (s,
 0, 0,
 3, 3);

cairo_surface_destroy (s);

cursor = gdk_cursor_new_from_pixbuf (display, pixbuf, 0, 0);

g_object_unref (pixbuf);</pre></td>
 </tr>
 </tbody>
 </table>
</div>

</div>
</div>
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.6"></a>Replace GdkColormap by GdkVisual</h3></div></div></div>

 For drawing with cairo, it is not necessary to allocate colors, and
 a <a href="../html/gdk3-Visuals.html#GdkVisual-struct">GdkVisual</a> provides enough information for cairo to handle colors
 in 'native' surfaces. Therefore, GdkColormap and related functions
 have been removed in GTK+ 3, and visuals are used instead. The
 colormap-handling functions of <a class="link" href="GtkWidget.html" title="GtkWidget">GtkWidget</a> (<code class="function">gtk_widget_set_colormap()</code>,
 etc) have been removed and <a class="link" href="GtkWidget.html#gtk-widget-set-visual" title="gtk_widget_set_visual ()"><code class="function">gtk_widget_set_visual()</code></a> has been added.
 
<div class="example">
<a name="id-1.6.3.4.6.3"></a>Example 42. Setting up a translucent window
<div class="example-contents">
You might have a screen-changed handler like the following
 to set up a translucent window with an alpha-channel:
 
<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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13</pre></td>
 <td class="listing_code"><pre class="programlisting">static void
on_alpha_screen_changed (GtkWidget *widget,
 GdkScreen *old_screen,
 GtkWidget *label)
{
 GdkScreen *screen = gtk_widget_get_screen (widget);
 GdkColormap *colormap = gdk_screen_get_rgba_colormap (screen);

if (colormap == NULL)
 colormap = gdk_screen_get_default_colormap (screen);

gtk_widget_set_colormap (widget, colormap);
}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

With visuals instead of colormaps, this will look as follows:
 
<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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13</pre></td>
 <td class="listing_code"><pre class="programlisting">static void
on_alpha_screen_changed (GtkWindow *window,
 GdkScreen *old_screen,
 GtkWidget *label)
{
 GdkScreen *screen = gtk_widget_get_screen (GTK_WIDGET (window));
 GdkVisual *visual = gdk_screen_get_rgba_visual (screen);

if (visual == NULL)
 visual = gdk_screen_get_system_visual (screen);

gtk_widget_set_visual (window, visual);
}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

</div>
</div>
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.7"></a>GdkDrawable is gone</h3></div></div></div>

 GdkDrawable has been removed in GTK+ 3, together with GdkPixmap
 and GdkImage. The only remaining drawable class is <a href="../html/gdk3-Windows.html#GdkWindow-struct">GdkWindow</a>.
 For dealing with image data, you should use a <a href="/usr/share/gtk-doc/html/cairo/cairo-cairo-surface-t.html#cairo-surface-t">cairo_surface_t</a> or
 a GdkPixbuf.
 

 GdkDrawable functions that are useful with windows have been replaced
 by corresponding GdkWindow functions:
 
<div class="table">
<a name="id-1.6.3.4.7.3.1"></a>Table 15. GdkDrawable to GdkWindow
<div class="table-contents"><table class="table" summary="GdkDrawable to GdkWindow" border="1">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>GDK 2.x</th>
<th>GDK 3</th>
</tr></thead>
<tbody>
<tr>
<td><code class="function">gdk_drawable_get_visual()</code></td>
<td><a href="../html/gdk3-Windows.html#gdk-window-get-visual"><code class="function">gdk_window_get_visual()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_drawable_get_size()</code></td>
<td>
<a href="../html/gdk3-Windows.html#gdk-window-get-width"><code class="function">gdk_window_get_width()</code></a>
 <a href="../html/gdk3-Windows.html#gdk-window-get-height"><code class="function">gdk_window_get_height()</code></a>
</td>
</tr>
<tr>
<td><code class="function">gdk_pixbuf_get_from_drawable()</code></td>
<td><a href="../html/gdk3-Pixbufs.html#gdk-pixbuf-get-from-window"><code class="function">gdk_pixbuf_get_from_window()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_drawable_get_clip_region()</code></td>
<td><a href="../html/gdk3-Windows.html#gdk-window-get-clip-region"><code class="function">gdk_window_get_clip_region()</code></a></td>
</tr>
<tr>
<td><code class="function">gdk_drawable_get_visible_region()</code></td>
<td><a href="../html/gdk3-Windows.html#gdk-window-get-visible-region"><code class="function">gdk_window_get_visible_region()</code></a></td>
</tr>
</tbody>
</table></div>
</div>
 
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.8"></a>Event filtering</h3></div></div></div>

 If your application uses the low-level event filtering facilities in GDK,
 there are some changes you need to be aware of.
 

 The special-purpose GdkEventClient events and the <code class="function">gdk_add_client_message_filter()</code> and <code class="function">gdk_display_add_client_message_filter()</code> functions have been
 removed. Receiving X11 ClientMessage events is still possible, using
 the general <a href="../html/gdk3-Windows.html#gdk-window-add-filter"><code class="function">gdk_window_add_filter()</code></a> API. A client message filter like

<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12</pre></td>
 <td class="listing_code"><pre class="programlisting">static GdkFilterReturn
message_filter (GdkXEvent *xevent, GdkEvent *event, gpointer data)
{
 XClientMessageEvent *evt = (XClientMessageEvent *)xevent;

/* do something with evt ... */
}

...

message_type = gdk_atom_intern ("MANAGER", FALSE);
gdk_display_add_client_message_filter (display, message_type, message_filter, NULL);</pre></td>
 </tr>
 </tbody>
 </table>
</div>

then looks like this:
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21</pre></td>
 <td class="listing_code"><pre class="programlisting">static GdkFilterReturn
event_filter (GdkXEvent *xevent, GdkEvent *event, gpointer data)
{
 XClientMessageEvent *evt;
 GdkAtom message_type;

if (((XEvent *)xevent)->type != ClientMessage)
 return GDK_FILTER_CONTINUE;

evt = (XClientMessageEvent *)xevent;
 message_type = XInternAtom (evt->display, "MANAGER", FALSE);

if (evt->message_type != message_type)
 return GDK_FILTER_CONTINUE;

/* do something with evt ... */
}

...

gdk_window_add_filter (NULL, message_filter, NULL);</pre></td>
 </tr>
 </tbody>
 </table>
</div>

One advantage of using an event filter is that you can actually
 remove the filter when you don't need it anymore, using
 <a href="../html/gdk3-Windows.html#gdk-window-remove-filter"><code class="function">gdk_window_remove_filter()</code></a>.
 

 The other difference to be aware of when working with event filters
 in GTK+ 3 is that GDK now uses XI2 by default when available. That
 means that your application does not receive core X11 key or button
 events. Instead, all input events are delivered as XIDeviceEvents.
 As a short-term workaround for this, you can force your application
 to not use XI2, with <a href="../html/GdkDeviceManager.html#gdk-disable-multidevice"><code class="function">gdk_disable_multidevice()</code></a>. In the long term,
 you probably want to rewrite your event filter to deal with
 XIDeviceEvents.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.9"></a>Backend-specific code</h3></div></div></div>

 In GTK+ 2.x, GDK could only be compiled for one backend at a time,
 and the <a href="../html/gdk3-General.html#GDK-WINDOWING-X11:CAPS"><code class="literal">GDK_WINDOWING_X11</code></a> or <a href="../html/gdk3-General.html#GDK-WINDOWING-WIN32:CAPS"><code class="literal">GDK_WINDOWING_WIN32</code></a> macros could
 be used to find out which one you are dealing with:
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7</pre></td>
 <td class="listing_code"><pre class="programlisting">#ifdef GDK_WINDOWING_X11
 if (timestamp != GDK_CURRENT_TIME)
 gdk_x11_window_set_user_time (gdk_window, timestamp);
#endif
#ifdef GDK_WINDOWING_WIN32
 /* ... win32 specific code ... */
#endif</pre></td>
 </tr>
 </tbody>
 </table>
</div>

In GTK+ 3, GDK can be built with multiple backends, and currently
 used backend has to be determined at runtime, typically using
 type-check macros on a <a href="../html/GdkDisplay.html#GdkDisplay-struct">GdkDisplay</a> or <a href="../html/gdk3-Windows.html#GdkWindow-struct">GdkWindow</a>. You still need
 to use the GDK_WINDOWING macros to only compile code referring
 to supported backends:
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18</pre></td>
 <td class="listing_code"><pre class="programlisting">#ifdef GDK_WINDOWING_X11
 if (GDK_IS_X11_DISPLAY (display))
 {
 if (timestamp != GDK_CURRENT_TIME)
 gdk_x11_window_set_user_time (gdk_window, timestamp);
 }
 else
#endif
#ifdef GDK_WINDOWING_WIN32
 if (GDK_IS_WIN32_DISPLAY (display))
 {
 /* ... win32 specific code ... */
 }
 else
#endif
 {
 g_warning ("Unsupported GDK backend");
 }</pre></td>
 </tr>
 </tbody>
 </table>
</div>

If you used the pkg-config variable <code class="varname">target</code> to
 conditionally build part of your project depending on the GDK backend,
 for instance like this:
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1</pre></td>
 <td class="listing_code"><pre class="programlisting">AM_CONDITIONAL(BUILD_X11, test `$PKG_CONFIG --variable=target gtk+-2.0` = "x11")</pre></td>
 </tr>
 </tbody>
 </table>
</div>

then you should now use the M4 macro provided by GTK+ itself:
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2</pre></td>
 <td class="listing_code"><pre class="programlisting">GTK_CHECK_BACKEND([x11], [3.0.2], [have_x11=yes], [have_x11=no])
AM_CONDITIONAL(BUILD_x11, [test "x$have_x11" = "xyes"])</pre></td>
 </tr>
 </tbody>
 </table>
</div>

</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.10"></a>GtkPlug and GtkSocket</h3></div></div></div>

 The <a class="link" href="GtkPlug.html" title="GtkPlug">GtkPlug</a> and <a class="link" href="GtkSocket.html" title="GtkSocket">GtkSocket</a> widgets are now X11-specific, and you
 have to include the <code class="filename"><gtk/gtkx.h></code> header
 to use them. The previous section about proper handling of
 backend-specific code applies, if you care about other backends.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.11"></a>The GtkWidget::draw signal</h3></div></div></div>

 The GtkWidget “expose-event” signal has been replaced by
 a new <a class="link" href="GtkWidget.html#GtkWidget-draw" title="The “draw” signal">“draw”</a> signal, which takes a <a href="/usr/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-t">cairo_t</a> instead of
 an expose event. The cairo context is being set up so that the origin
 at (0, 0) coincides with the upper left corner of the widget, and
 is properly clipped.
 
<div class="note">In other words, the cairo context of the draw signal is set
 up in 'widget coordinates', which is different from traditional expose
 event handlers, which always assume 'window coordinates'.
 </div>

 The widget is expected to draw itself with its allocated size, which
 is available via the new <a class="link" href="GtkWidget.html#gtk-widget-get-allocated-width" title="gtk_widget_get_allocated_width ()"><code class="function">gtk_widget_get_allocated_width()</code></a> and
 <a class="link" href="GtkWidget.html#gtk-widget-get-allocated-height" title="gtk_widget_get_allocated_height ()"><code class="function">gtk_widget_get_allocated_height()</code></a> functions. It is not necessary to
 check for <a class="link" href="GtkWidget.html#gtk-widget-is-drawable" title="gtk_widget_is_drawable ()"><code class="function">gtk_widget_is_drawable()</code></a>, since GTK+ already does this check
 before emitting the <a class="link" href="GtkWidget.html#GtkWidget-draw" title="The “draw” signal">“draw”</a> signal.
 

 There are some special considerations for widgets with multiple windows.
 Expose events are window-specific, and widgets with multiple windows
 could expect to get an expose event for each window that needs to be
 redrawn. Therefore, multi-window expose event handlers typically look
 like this:
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9</pre></td>
 <td class="listing_code"><pre class="programlisting">if (event->window == widget->window1)
 {
 /* ... draw window1 ... */
 }
else if (event->window == widget->window2)
 {
 /* ... draw window2 ... */
 }
...</pre></td>
 </tr>
 </tbody>
 </table>
</div>

In contrast, the <a class="link" href="GtkWidget.html#GtkWidget-draw" title="The “draw” signal">“draw”</a> signal handler may have to draw multiple
 windows in one call. GTK+ has a convenience function
 <a class="link" href="GtkWidget.html#gtk-cairo-should-draw-window" title="gtk_cairo_should_draw_window ()"><code class="function">gtk_cairo_should_draw_window()</code></a> that can be used to find out if
 a window needs to be drawn. With that, the example above would look
 like this (note that the 'else' is gone):
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9</pre></td>
 <td class="listing_code"><pre class="programlisting">if (gtk_cairo_should_draw_window (cr, widget->window1)
 {
 /* ... draw window1 ... */
 }
if (gtk_cairo_should_draw_window (cr, widget->window2)
 {
 /* ... draw window2 ... */
 }
...</pre></td>
 </tr>
 </tbody>
 </table>
</div>

Another convenience function that can help when implementing
 ::draw for multi-window widgets is <a class="link" href="GtkWidget.html#gtk-cairo-transform-to-window" title="gtk_cairo_transform_to_window ()"><code class="function">gtk_cairo_transform_to_window()</code></a>,
 which transforms a cairo context from widget-relative coordinates
 to window-relative coordinates. You may want to use <a href="/usr/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-save"><code class="function">cairo_save()</code></a> and
 <a href="/usr/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-restore"><code class="function">cairo_restore()</code></a> when modifying the cairo context in your draw function.
 

 All GtkStyle drawing functions (<a class="link" href="GtkStyle.html#gtk-paint-box" title="gtk_paint_box ()"><code class="function">gtk_paint_box()</code></a>, etc) have been changed
 to take a <a href="/usr/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-t">cairo_t</a> instead of a window and a clip area. ::draw
 implementations will usually just use the cairo context that has been
 passed in for this.
 
<div class="example">
<a name="id-1.6.3.4.11.7"></a>Example 43. A simple ::draw function
<div class="example-contents">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20</pre></td>
 <td class="listing_code"><pre class="programlisting">gboolean
gtk_arrow_draw (GtkWidget *widget,
 cairo_t *cr)
{
 GtkStyleContext *context;
 gint x, y;
 gint width, height;
 gint extent;

context = gtk_widget_get_style_context (widget);

width = gtk_widget_get_allocated_width (widget);
 height = gtk_widget_get_allocated_height (widget);

extent = MIN (width - 2 * PAD, height - 2 * PAD);
 x = PAD;
 y = PAD;

gtk_render_arrow (context, rc, G_PI / 2, x, y, extent);
}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

</div>
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.12"></a>GtkProgressBar orientation</h3></div></div></div>

 In GTK+ 2.x, <a class="link" href="GtkProgressBar.html" title="GtkProgressBar">GtkProgressBar</a> and <a class="link" href="GtkCellRendererProgress.html" title="GtkCellRendererProgress">GtkCellRendererProgress</a> were using the
 GtkProgressBarOrientation enumeration to specify their orientation and
 direction. In GTK+ 3, both the widget and the cell renderer implement
 <a class="link" href="gtk3-Orientable.html#GtkOrientable">GtkOrientable</a>, and have an additional 'inverted' property to determine
 their direction. Therefore, a call to <code class="function">gtk_progress_bar_set_orientation()</code>
 needs to be replaced by a pair of calls to
 <a class="link" href="gtk3-Orientable.html#gtk-orientable-set-orientation" title="gtk_orientable_set_orientation ()"><code class="function">gtk_orientable_set_orientation()</code></a> and <a class="link" href="GtkProgressBar.html#gtk-progress-bar-set-inverted" title="gtk_progress_bar_set_inverted ()"><code class="function">gtk_progress_bar_set_inverted()</code></a>.
 The following values correspond:
 
<div class="table">
<a name="id-1.6.3.4.12.2.7"></a>Table 16. 
<div class="table-contents"><table class="table" border="1">
<colgroup>
<col class="1">
<col class="2">
<col class="3">
</colgroup>
<thead>
<tr>
<th>GTK+ 2.x</th>
<th colspan="2">GTK+ 3</th>
</tr>
<tr>
<th>GtkProgressBarOrientation</th>
<th>GtkOrientation</th>
<th>inverted</th>
</tr>
</thead>
<tbody>
<tr>
<td>GTK_PROGRESS_LEFT_TO_RIGHT</td>
<td>GTK_ORIENTATION_HORIZONTAL</td>
<td>FALSE</td>
</tr>
<tr>
<td>GTK_PROGRESS_RIGHT_TO_LEFT</td>
<td>GTK_ORIENTATION_HORIZONTAL</td>
<td>TRUE</td>
</tr>
<tr>
<td>GTK_PROGRESS_TOP_TO_BOTTOM</td>
<td>GTK_ORIENTATION_VERTICAL</td>
<td>FALSE</td>
</tr>
<tr>
<td>GTK_PROGRESS_BOTTOM_TO_TOP</td>
<td>GTK_ORIENTATION_VERTICAL</td>
<td>TRUE</td>
</tr>
</tbody>
</table></div>
</div>
 
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.13"></a>Check your expand and fill flags</h3></div></div></div>

 The behaviour of expanding widgets has changed slightly in GTK+ 3,
 compared to GTK+ 2.x. It is now 'inherited', i.e. a container that
 has an expanding child is considered expanding itself. This is often
 the desired behaviour. In places where you don't want this to happen,
 setting the container explicity as not expanding will stop the
 expand flag of the child from being inherited. See
 <a class="link" href="GtkWidget.html#gtk-widget-set-hexpand" title="gtk_widget_set_hexpand ()"><code class="function">gtk_widget_set_hexpand()</code></a> and <a class="link" href="GtkWidget.html#gtk-widget-set-vexpand" title="gtk_widget_set_vexpand ()"><code class="function">gtk_widget_set_vexpand()</code></a>.
 

 If you experience sizing problems with widgets in ported code,
 carefully check the <a class="link" href="GtkBox.html" title="GtkBox">GtkBox</a> expand and <a class="link" href="GtkBox.html" title="GtkBox">GtkBox</a> fill child properties of your
 boxes.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.14"></a>Scrolling changes</h3></div></div></div>

 The default values for the <a class="link" href="GtkScrolledWindow.html#GtkScrolledWindow--hscrollbar-policy" title="The “hscrollbar-policy” property">“hscrollbar-policy”</a> and
 <a class="link" href="GtkScrolledWindow.html#GtkScrolledWindow--vscrollbar-policy" title="The “vscrollbar-policy” property">“vscrollbar-policy”</a> properties have been changed from
 'never' to 'automatic'. If your application was relying on the default
 value, you will have to set it explicitly.
 

 The ::set-scroll-adjustments signal on GtkWidget has been replaced
 by the <a class="link" href="GtkScrollable.html" title="GtkScrollable">GtkScrollable</a> interface which must be implemented by a widget
 that wants to be placed in a <a class="link" href="GtkScrolledWindow.html" title="GtkScrolledWindow">GtkScrolledWindow</a>. Instead of emitting
 ::set-scroll-adjustments, the scrolled window simply sets the
 <a class="link" href="GtkScrollable.html#GtkScrollable--hadjustment" title="The “hadjustment” property">“hadjustment”</a> and <a class="link" href="GtkScrollable.html#GtkScrollable--vadjustment" title="The “vadjustment” property">“vadjustment”</a> properties.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.15"></a>GtkObject is gone</h3></div></div></div>

 GtkObject has been removed in GTK+ 3. Its remaining functionality,
 the ::destroy signal, has been moved to GtkWidget. If you have non-widget
 classes that are directly derived from GtkObject, you have to make
 them derive from <a href="/usr/share/gtk-doc/html/gobject/gobject-The-Base-Object-Type.html#GInitiallyUnowned">GInitiallyUnowned</a> (or, if you don't need the floating
 functionality, <a href="/usr/share/gtk-doc/html/gobject/gobject-The-Base-Object-Type.html#GObject-struct">GObject</a>). If you have widgets that override the
 destroy class handler, you have to adjust your class_init function,
 since destroy is now a member of GtkWidgetClass:
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3</pre></td>
 <td class="listing_code"><pre class="programlisting">GtkObjectClass *object_class = GTK_OBJECT_CLASS (class);

object_class->destroy = my_destroy;</pre></td>
 </tr>
 </tbody>
 </table>
</div>

becomes
 
<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3</pre></td>
 <td class="listing_code"><pre class="programlisting">GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);

widget_class->destroy = my_destroy;</pre></td>
 </tr>
 </tbody>
 </table>
</div>

In the unlikely case that you have a non-widget class that is derived
 from GtkObject and makes use of the destroy functionality, you have
 to implement ::destroy yourself.
 

 If your program used functions like gtk_object_get or gtk_object_set,
 these can be replaced directly with g_object_get or g_object_set. In
 fact, most every gtk_object_* function can be replaced with the
 corresponding g_object_ function, even in GTK+ 2 code. The one exception
 to this rule is gtk_object_destroy, which can be replaced with
 gtk_widget_destroy, again in both GTK+ 2 and GTK+ 3.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.16"></a>GtkEntryCompletion signal parameters</h3></div></div></div>

 The <a class="link" href="GtkEntryCompletion.html#GtkEntryCompletion-match-selected" title="The “match-selected” signal">“match-selected”</a> and
 <a class="link" href="GtkEntryCompletion.html#GtkEntryCompletion-cursor-on-match" title="The “cursor-on-match” signal">“cursor-on-match”</a> signals were erroneously
 given the internal filter model instead of the users model.
 This oversight has been fixed in GTK+ 3; if you have handlers
 for these signals, they will likely need slight adjustments.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.17"></a>Resize grips</h3></div></div></div>

 The resize grip functionality has been moved from <a class="link" href="GtkStatusbar.html" title="GtkStatusbar">GtkStatusbar</a>
 to <a class="link" href="GtkWindow.html" title="GtkWindow">GtkWindow</a>. Any window can now have resize grips, regardless whether
 it has a statusbar or not. The functions
 <code class="function">gtk_statusbar_set_has_resize_grip()</code> and <code class="function">gtk_statusbar_get_has_resize_grip()</code>
 have disappeared, and instead there are now
 <a class="link" href="GtkWindow.html#gtk-window-set-has-resize-grip" title="gtk_window_set_has_resize_grip ()"><code class="function">gtk_window_set_has_resize_grip()</code></a> and <a class="link" href="GtkWindow.html#gtk-window-get-has-resize-grip" title="gtk_window_get_has_resize_grip ()"><code class="function">gtk_window_get_has_resize_grip()</code></a>.
 

 In more recent versions of GTK+ 3, the resize grip functionality has
 been removed entirely, in favor of invisible resize borders around the
 window. When updating to newer versions of GTK+ 3, you should simply
 remove all code dealing with resize grips.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.18"></a>Prevent mixed linkage</h3></div></div></div>

 Linking against GTK+ 2.x and GTK+ 3 in the same process is problematic
 and can lead to hard-to-diagnose crashes. The <a class="link" href="gtk3-General.html#gtk-init" title="gtk_init ()"><code class="function">gtk_init()</code></a> function in
 both GTK+ 2.22 and in GTK+ 3 tries to detect this situation and abort
 with a diagnostic message, but this check is not 100% reliable (e.g. if
 the problematic linking happens only in loadable modules).
 

 Direct linking of your application against both versions of GTK+ is
 easy to avoid; the problem gets harder when your application is using
 libraries that are themselves linked against some version of GTK+.
 In that case, you have to verify that you are using a version of the
 library that is linked against GTK+ 3.
 

 If you are using packages provided by a distributor, it is likely that
 parallel installable versions of the library exist for GTK+ 2.x and
 GTK+ 3, e.g for vte, check for vte3; for webkitgtk look for webkitgtk3,
 and so on.
 
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.6.3.4.19"></a>Install GTK+ modules in the right place</h3></div></div></div>

 Some software packages install loadable GTK+ modules such as theme engines,
 gdk-pixbuf loaders or input methods. Since GTK+ 3 is parallel-installable
 with GTK+ 2.x, the two GTK+ versions have separate locations for their
 loadable modules. The location for GTK+ 2.x is
 <code class="filename"><code>libdir</code>/gtk-2.0</code>
 (and its subdirectories), for GTK+ 3 the location is
 <code class="filename"><code>libdir</code>/gtk-3.0</code>
 (and its subdirectories).
 

 For some kinds of modules, namely input methods and pixbuf loaders,
 GTK+ keeps a cache file with extra information about the modules.
 For GTK+ 2.x, these cache files are located in
 <code class="filename"><code>sysconfdir</code>/gtk-2.0</code>.
 For GTK+ 3, they have been moved to
 <code class="filename"><code>libdir</code>/gtk-3.0/3.0.0/</code>.
 The commands that create these cache files have been renamed with a -3
 suffix to make them parallel-installable.
 

 Note that GTK+ modules often link against libgtk, libgdk-pixbuf, etc.
 If that is the case for your module, you have to be careful to link the
 GTK+ 2.x version of your module against the 2.x version of the libraries,
 and the GTK+ 3 version against hte 3.x versions. Loading a module linked
 against libgtk 2.x into an application using GTK+ 3 will lead to
 unhappiness and must be avoided.
 
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