gtk2/gtk/gtkscrollable.c
Ivan Molodetskikh 8f2be7e840 scrollable: Clarify when to set adjustment props
Instead of populating the properties right away (when the widget might
not have been allocated yet, and hence cannot know the right values),
the widget should queue an allocation, where it will populate the
values.
2022-04-21 19:24:52 -04:00

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/* gtkscrollable.c
* Copyright (C) 2008 Tadej Borovšak <tadeboro@gmail.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* GtkScrollable:
*
* `GtkScrollable` is an interface for widgets with native scrolling ability.
*
* To implement this interface you should override the
* [property@Gtk.Scrollable:hadjustment] and
* [property@Gtk.Scrollable:vadjustment] properties.
*
* ## Creating a scrollable widget
*
* All scrollable widgets should do the following.
*
* - When a parent widget sets the scrollable child widgets adjustments,
* the widget should connect to the [signal@Gtk.Adjustment::value-changed]
* signal. The child widget should then populate the adjustments properties
* as soon as possible, which usually means queueing an allocation right away
* and populating the properties in the [vfunc@Gtk.Widget.size_allocate]
* implementation.
*
* - Because its preferred size is the size for a fully expanded widget,
* the scrollable widget must be able to cope with underallocations.
* This means that it must accept any value passed to its
* [vfunc@Gtk.Widget.size_allocate] implementation.
*
* - When the parent allocates space to the scrollable child widget,
* the widget must ensure the adjustments property values are correct and up
* to date, for example using [method@Gtk.Adjustment.configure].
*
* - When any of the adjustments emits the [signal@Gtk.Adjustment::value-changed]
* signal, the scrollable widget should scroll its contents.
*/
#include "config.h"
#include "gtkscrollable.h"
#include "gtkadjustment.h"
#include "gtkprivate.h"
#include "gtktypebuiltins.h"
#include "gtkintl.h"
G_DEFINE_INTERFACE (GtkScrollable, gtk_scrollable, G_TYPE_OBJECT)
static void
gtk_scrollable_default_init (GtkScrollableInterface *iface)
{
GParamSpec *pspec;
/**
* GtkScrollable:hadjustment: (attributes org.gtk.Property.get=gtk_scrollable_get_hadjustment org.gtk.Property.set=gtk_scrollable_set_hadjustment)
*
* Horizontal `GtkAdjustment` of the scrollable widget.
*
* This adjustment is shared between the scrollable widget and its parent.
*/
pspec = g_param_spec_object ("hadjustment",
P_("Horizontal adjustment"),
P_("Horizontal adjustment that is shared "
"between the scrollable widget and its "
"controller"),
GTK_TYPE_ADJUSTMENT,
GTK_PARAM_READWRITE | G_PARAM_CONSTRUCT);
g_object_interface_install_property (iface, pspec);
/**
* GtkScrollable:vadjustment: (attributes org.gtk.Property.get=gtk_scrollable_get_vadjustment org.gtk.Property.set=gtk_scrollable_set_vadjustment)
*
* Vertical `GtkAdjustment` of the scrollable widget.
*
* This adjustment is shared between the scrollable widget and its parent.
*/
pspec = g_param_spec_object ("vadjustment",
P_("Vertical adjustment"),
P_("Vertical adjustment that is shared "
"between the scrollable widget and its "
"controller"),
GTK_TYPE_ADJUSTMENT,
GTK_PARAM_READWRITE | G_PARAM_CONSTRUCT);
g_object_interface_install_property (iface, pspec);
/**
* GtkScrollable:hscroll-policy: (attributes org.gtk.Property.get=gtk_scrollable_get_hscroll_policy org.gtk.Property.set=gtk_scrollable_set_hscroll_policy)
*
* Determines when horizontal scrolling should start.
*/
pspec = g_param_spec_enum ("hscroll-policy",
P_("Horizontal Scrollable Policy"),
P_("How the size of the content should be determined"),
GTK_TYPE_SCROLLABLE_POLICY,
GTK_SCROLL_MINIMUM,
GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY);
g_object_interface_install_property (iface, pspec);
/**
* GtkScrollable:vscroll-policy: (attributes org.gtk.Property.get=gtk_scrollable_get_vscroll_policy org.gtk.Property.set=gtk_scrollable_set_vscroll_policy)
*
* Determines when vertical scrolling should start.
*/
pspec = g_param_spec_enum ("vscroll-policy",
P_("Vertical Scrollable Policy"),
P_("How the size of the content should be determined"),
GTK_TYPE_SCROLLABLE_POLICY,
GTK_SCROLL_MINIMUM,
GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY);
g_object_interface_install_property (iface, pspec);
}
/**
* gtk_scrollable_get_hadjustment: (attributes org.gtk.Method.get_property=hadjustment)
* @scrollable: a `GtkScrollable`
*
* Retrieves the `GtkAdjustment` used for horizontal scrolling.
*
* Returns: (transfer none) (nullable): horizontal `GtkAdjustment`.
*/
GtkAdjustment *
gtk_scrollable_get_hadjustment (GtkScrollable *scrollable)
{
GtkAdjustment *adj = NULL;
g_return_val_if_fail (GTK_IS_SCROLLABLE (scrollable), NULL);
g_object_get (scrollable, "hadjustment", &adj, NULL);
/* Horrid hack; g_object_get() returns a new reference but
* that contradicts the memory management conventions
* for accessors.
*/
if (adj)
g_object_unref (adj);
return adj;
}
/**
* gtk_scrollable_set_hadjustment: (attributes org.gtk.Method.set_property=hadjustment)
* @scrollable: a `GtkScrollable`
* @hadjustment: (nullable): a `GtkAdjustment`
*
* Sets the horizontal adjustment of the `GtkScrollable`.
*/
void
gtk_scrollable_set_hadjustment (GtkScrollable *scrollable,
GtkAdjustment *hadjustment)
{
g_return_if_fail (GTK_IS_SCROLLABLE (scrollable));
g_return_if_fail (hadjustment == NULL || GTK_IS_ADJUSTMENT (hadjustment));
g_object_set (scrollable, "hadjustment", hadjustment, NULL);
}
/**
* gtk_scrollable_get_vadjustment: (attributes org.gtk.Method.get_property=vadjustment)
* @scrollable: a `GtkScrollable`
*
* Retrieves the `GtkAdjustment` used for vertical scrolling.
*
* Returns: (transfer none) (nullable): vertical `GtkAdjustment`.
*/
GtkAdjustment *
gtk_scrollable_get_vadjustment (GtkScrollable *scrollable)
{
GtkAdjustment *adj = NULL;
g_return_val_if_fail (GTK_IS_SCROLLABLE (scrollable), NULL);
g_object_get (scrollable, "vadjustment", &adj, NULL);
/* Horrid hack; g_object_get() returns a new reference but
* that contradicts the memory management conventions
* for accessors.
*/
if (adj)
g_object_unref (adj);
return adj;
}
/**
* gtk_scrollable_set_vadjustment: (attributes org.gtk.Method.set_property=vadjustment)
* @scrollable: a `GtkScrollable`
* @vadjustment: (nullable): a `GtkAdjustment`
*
* Sets the vertical adjustment of the `GtkScrollable`.
*/
void
gtk_scrollable_set_vadjustment (GtkScrollable *scrollable,
GtkAdjustment *vadjustment)
{
g_return_if_fail (GTK_IS_SCROLLABLE (scrollable));
g_return_if_fail (vadjustment == NULL || GTK_IS_ADJUSTMENT (vadjustment));
g_object_set (scrollable, "vadjustment", vadjustment, NULL);
}
/**
* gtk_scrollable_get_hscroll_policy: (attributes org.gtk.Method.get_property=hscroll-policy)
* @scrollable: a `GtkScrollable`
*
* Gets the horizontal `GtkScrollablePolicy`.
*
* Returns: The horizontal `GtkScrollablePolicy`.
*/
GtkScrollablePolicy
gtk_scrollable_get_hscroll_policy (GtkScrollable *scrollable)
{
GtkScrollablePolicy policy;
g_return_val_if_fail (GTK_IS_SCROLLABLE (scrollable), GTK_SCROLL_MINIMUM);
g_object_get (scrollable, "hscroll-policy", &policy, NULL);
return policy;
}
/**
* gtk_scrollable_set_hscroll_policy: (attributes org.gtk.Method.set_property=hscroll-policy)
* @scrollable: a `GtkScrollable`
* @policy: the horizontal `GtkScrollablePolicy`
*
* Sets the `GtkScrollablePolicy`.
*
* The policy determines whether horizontal scrolling should start
* below the minimum width or below the natural width.
*/
void
gtk_scrollable_set_hscroll_policy (GtkScrollable *scrollable,
GtkScrollablePolicy policy)
{
g_return_if_fail (GTK_IS_SCROLLABLE (scrollable));
g_object_set (scrollable, "hscroll-policy", policy, NULL);
}
/**
* gtk_scrollable_get_vscroll_policy: (attributes org.gtk.Method.get_property=vscroll-policy)
* @scrollable: a `GtkScrollable`
*
* Gets the vertical `GtkScrollablePolicy`.
*
* Returns: The vertical `GtkScrollablePolicy`.
*/
GtkScrollablePolicy
gtk_scrollable_get_vscroll_policy (GtkScrollable *scrollable)
{
GtkScrollablePolicy policy;
g_return_val_if_fail (GTK_IS_SCROLLABLE (scrollable), GTK_SCROLL_MINIMUM);
g_object_get (scrollable, "vscroll-policy", &policy, NULL);
return policy;
}
/**
* gtk_scrollable_set_vscroll_policy: (attributes org.gtk.Method.set_property=vscroll-policy)
* @scrollable: a `GtkScrollable`
* @policy: the vertical `GtkScrollablePolicy`
*
* Sets the `GtkScrollablePolicy`.
*
* The policy determines whether vertical scrolling should start
* below the minimum height or below the natural height.
*/
void
gtk_scrollable_set_vscroll_policy (GtkScrollable *scrollable,
GtkScrollablePolicy policy)
{
g_return_if_fail (GTK_IS_SCROLLABLE (scrollable));
g_object_set (scrollable, "vscroll-policy", policy, NULL);
}
/**
* gtk_scrollable_get_border:
* @scrollable: a `GtkScrollable`
* @border: (out caller-allocates): return location for the results
*
* Returns the size of a non-scrolling border around the
* outside of the scrollable.
*
* An example for this would be treeview headers. GTK can use
* this information to display overlaid graphics, like the
* overshoot indication, at the right position.
*
* Returns: %TRUE if @border has been set
*/
gboolean
gtk_scrollable_get_border (GtkScrollable *scrollable,
GtkBorder *border)
{
g_return_val_if_fail (GTK_IS_SCROLLABLE (scrollable), FALSE);
g_return_val_if_fail (border != NULL, FALSE);
if (GTK_SCROLLABLE_GET_IFACE (scrollable)->get_border)
return GTK_SCROLLABLE_GET_IFACE (scrollable)->get_border (scrollable, border);
return FALSE;
}