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Add a migration guide section on size_request

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Matthias Clasen 2010-10-27 15:55:33 -04:00
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docs/reference/gtk/migrating-2to3.xml
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@ -343,6 +343,182 @@ cairo_destroy (cr);
have been either impossible or impractical.
</para>
<section>
<title>Replace size_request by get_preferred_width/height</title>
<para>
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has been replaced by a more flexible height-for-width system,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 <xref linkend="geometry-management"/>). As a consequence,
the ::size-request signal and vfunc has been removed from
#GtkWidgetClass. The replacement for size_request() can
take several levels of sophistication:
<itemizedlist>
<listitem>As a minimal replacement to keep current functionality,
you can simply implement the get_preferred_width() and
get_preferred_height() vfuncs by calling your existing
size_request() function. So you go from
<informalexample><programlisting>
static void
my_widget_class_init (MyWidgetClass *class)
{
GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
/* ... */
widget_class->size_request = my_widget_size_request;
/* ... */
}
</programlisting></informalexample>
to something that looks more like this:
<informalexample><programlisting>
static void
my_widget_get_preferred_width (GtkWidget *widget,
gint *minimal_width,
gint *natural_width)
{
GtkRequisition requisition;
my_widget_size_request (widget, &amp;requisition);
*minimal_width = *natural_width = requisition.width;
}
static void
my_widget_get_preferred_height (GtkWidget *widget,
gint *minimal_height,
gint *natural_height)
{
GtkRequisition requisition;
my_widget_size_request (widget, &amp;requisition);
*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;
/* ... */
}
</programlisting></informalexample>
Sometimes you can make things a little more streamlined
by replacing your existing size_request() implementation by
one that takes an orientation parameter:
<informalexample><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... */
*minimal_size = *natural_size = ...
}
}
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);
}
/* ... */
</programlisting></informalexample>
</listitem>
<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 get_preferred_width()/height()
functions return a smaller value for @minimal than for @natural.
For @minimal, you probably want to return the same value
that your size_request() function returned before (since
size_request() was defined as returning the minimal size
a widget can work with). A simple way to obtain good
values for @natural, in the case of containers, is to use
gtk_widget_get_preferred_width() and
gtk_widget_get_preferred_height() on the children of the
container, as in the following example:
<informalexample><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, &amp;child_min, &amp;child_nat);
*minimum = MAX (*minimum, child->y + child_min);
*natural = MAX (*natural, child->y + child_nat);
}
}
</programlisting></informalexample>
</listitem>
<listitem>To make full use of the new capabilities of the
height-for-width geometry management, you need to additionally
implement the get_preferred_height_for_width() and
get_preferred_width_for_height(). For details on these functions,
see <xref linkend="geometry-management"/>.
</listitem>
</itemizedlist>
</para>
</section>
<section>
<title>Replace GdkRegion by cairo_region_t</title>