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/* gbinding.c: Binding for object properties
*
* Copyright (C) 2010 Intel Corp.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* 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 2.1 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/>.
*
* Author: Emmanuele Bassi <ebassi@linux.intel.com>
*/
/**
* SECTION:gbinding
* @Title: GBinding
* @Short_Description: Bind two object properties
*
* #GBinding is the representation of a binding between a property on a
* #GObject instance (or source) and another property on another #GObject
* instance (or target).
*
* Whenever the source property changes, the same value is applied to the
* target property; for instance, the following binding:
*
* |[<!-- language="C" -->
* g_object_bind_property (object1, "property-a",
* object2, "property-b",
* G_BINDING_DEFAULT);
* ]|
*
* will cause the property named "property-b" of @object2 to be updated
* every time g_object_set() or the specific accessor changes the value of
* the property "property-a" of @object1.
*
* It is possible to create a bidirectional binding between two properties
* of two #GObject instances, so that if either property changes, the
* other is updated as well, for instance:
*
* |[<!-- language="C" -->
* g_object_bind_property (object1, "property-a",
* object2, "property-b",
* G_BINDING_BIDIRECTIONAL);
* ]|
*
* will keep the two properties in sync.
*
* It is also possible to set a custom transformation function (in both
* directions, in case of a bidirectional binding) to apply a custom
* transformation from the source value to the target value before
* applying it; for instance, the following binding:
*
* |[<!-- language="C" -->
* g_object_bind_property_full (adjustment1, "value",
* adjustment2, "value",
* G_BINDING_BIDIRECTIONAL,
* celsius_to_fahrenheit,
* fahrenheit_to_celsius,
* NULL, NULL);
* ]|
*
* will keep the "value" property of the two adjustments in sync; the
* @celsius_to_fahrenheit function will be called whenever the "value"
* property of @adjustment1 changes and will transform the current value
* of the property before applying it to the "value" property of @adjustment2.
*
* Vice versa, the @fahrenheit_to_celsius function will be called whenever
* the "value" property of @adjustment2 changes, and will transform the
* current value of the property before applying it to the "value" property
* of @adjustment1.
*
* Note that #GBinding does not resolve cycles by itself; a cycle like
*
* |[
* object1:propertyA -> object2:propertyB
* object2:propertyB -> object3:propertyC
* object3:propertyC -> object1:propertyA
* ]|
*
* might lead to an infinite loop. The loop, in this particular case,
* can be avoided if the objects emit the #GObject::notify signal only
* if the value has effectively been changed. A binding is implemented
* using the #GObject::notify signal, so it is susceptible to all the
* various ways of blocking a signal emission, like g_signal_stop_emission()
* or g_signal_handler_block().
*
* A binding will be severed, and the resources it allocates freed, whenever
* either one of the #GObject instances it refers to are finalized, or when
* the #GBinding instance loses its last reference.
*
* Bindings for languages with garbage collection can use
* g_binding_unbind() to explicitly release a binding between the source
* and target properties, instead of relying on the last reference on the
* binding, source, and target instances to drop.
*
* #GBinding is available since GObject 2.26
*/
#include "config.h"
#include <string.h>
#include "gbinding.h"
#include "genums.h"
#include "gmarshal.h"
#include "gobject.h"
#include "gsignal.h"
#include "gparamspecs.h"
#include "gvaluetypes.h"
#include "glibintl.h"
GType
g_binding_flags_get_type (void)
{
static gsize static_g_define_type_id = 0;
if (g_once_init_enter (&static_g_define_type_id))
{
static const GFlagsValue values[] = {
{ G_BINDING_DEFAULT, "G_BINDING_DEFAULT", "default" },
{ G_BINDING_BIDIRECTIONAL, "G_BINDING_BIDIRECTIONAL", "bidirectional" },
{ G_BINDING_SYNC_CREATE, "G_BINDING_SYNC_CREATE", "sync-create" },
{ G_BINDING_INVERT_BOOLEAN, "G_BINDING_INVERT_BOOLEAN", "invert-boolean" },
{ 0, NULL, NULL }
};
GType g_define_type_id =
g_flags_register_static (g_intern_static_string ("GBindingFlags"), values);
g_once_init_leave (&static_g_define_type_id, g_define_type_id);
}
return static_g_define_type_id;
}
/* Reference counted helper struct that is passed to all callbacks to ensure
* that they never work with already freed objects without having to store
* strong references for them.
*
* Using strong references anywhere is not possible because of the API
* requirements of GBinding, specifically that the initial reference of the
* GBinding is owned by the source/target and the caller and can be released
* either by the source/target being finalized or calling g_binding_unbind().
*
* As such, the only strong reference has to be owned by both weak notifies of
* the source and target and the first to be called has to release it.
*/
typedef struct {
GWeakRef binding;
GWeakRef source;
GWeakRef target;
gboolean binding_removed;
} BindingContext;
static BindingContext *
binding_context_ref (BindingContext *context)
{
return g_atomic_rc_box_acquire (context);
}
static void
binding_context_clear (BindingContext *context)
{
g_weak_ref_clear (&context->binding);
g_weak_ref_clear (&context->source);
g_weak_ref_clear (&context->target);
}
static void
binding_context_unref (BindingContext *context)
{
g_atomic_rc_box_release_full (context, (GDestroyNotify) binding_context_clear);
}
/* Reference counting for the transform functions to ensure that they're always
* valid while making use of them in the property notify callbacks.
*
* The transform functions are released when unbinding but unbinding can happen
* while the transform functions are currently in use inside the notify callbacks.
*/
typedef struct {
GBindingTransformFunc transform_s2t;
GBindingTransformFunc transform_t2s;
gpointer transform_data;
GDestroyNotify destroy_notify;
} TransformFunc;
static TransformFunc *
transform_func_new (GBindingTransformFunc transform_s2t,
GBindingTransformFunc transform_t2s,
gpointer transform_data,
GDestroyNotify destroy_notify)
{
TransformFunc *func = g_atomic_rc_box_new0 (TransformFunc);
func->transform_s2t = transform_s2t;
func->transform_t2s = transform_t2s;
func->transform_data = transform_data;
func->destroy_notify = destroy_notify;
return func;
}
static TransformFunc *
transform_func_ref (TransformFunc *func)
{
return g_atomic_rc_box_acquire (func);
}
static void
transform_func_clear (TransformFunc *func)
{
if (func->destroy_notify)
func->destroy_notify (func->transform_data);
}
static void
transform_func_unref (TransformFunc *func)
{
g_atomic_rc_box_release_full (func, (GDestroyNotify) transform_func_clear);
}
#define G_BINDING_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST ((klass), G_TYPE_BINDING, GBindingClass))
#define G_IS_BINDING_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), G_TYPE_BINDING))
#define G_BINDING_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), G_TYPE_BINDING, GBindingClass))
typedef struct _GBindingClass GBindingClass;
struct _GBinding
{
GObject parent_instance;
/* no reference is held on the objects, to avoid cycles */
BindingContext *context;
/* protects transform_func, source, target property notify and
* target_weak_notify_installed for unbinding */
GMutex unbind_lock;
/* transform functions, only NULL after unbinding */
TransformFunc *transform_func; /* LOCK: unbind_lock */
/* the property names are interned, so they should not be freed */
const gchar *source_property;
const gchar *target_property;
GParamSpec *source_pspec;
GParamSpec *target_pspec;
GBindingFlags flags;
guint source_notify; /* LOCK: unbind_lock */
guint target_notify; /* LOCK: unbind_lock */
gboolean target_weak_notify_installed; /* LOCK: unbind_lock */
/* a guard, to avoid loops */
guint is_frozen : 1;
};
struct _GBindingClass
{
GObjectClass parent_class;
};
enum
{
PROP_0,
PROP_SOURCE,
PROP_TARGET,
PROP_SOURCE_PROPERTY,
PROP_TARGET_PROPERTY,
PROP_FLAGS
};
static guint gobject_notify_signal_id;
G_DEFINE_TYPE (GBinding, g_binding, G_TYPE_OBJECT)
static void weak_unbind (gpointer user_data, GObject *where_the_object_was);
/* Must be called with the unbind lock held, context/binding != NULL and strong
* references to source/target or NULL.
* Return TRUE if the binding was actually removed and FALSE if it was already
* removed before. */
static gboolean
unbind_internal_locked (BindingContext *context, GBinding *binding, GObject *source, GObject *target)
{
gboolean binding_was_removed = FALSE;
g_assert (context != NULL);
g_assert (binding != NULL);
/* If the target went away we still have a strong reference to the source
* here and can clear it from the binding. Otherwise if the source went away
* we can clear the target from the binding. Finalizing an object clears its
* signal handlers and all weak references pointing to it before calling
* weak notify callbacks.
*
* If both still exist we clean up everything set up by the binding.
*/
if (source)
{
/* We always add/remove the source property notify and the weak notify
* of the source at the same time, and should only ever do that once. */
if (binding->source_notify != 0)
{
g_signal_handler_disconnect (source, binding->source_notify);
g_object_weak_unref (source, weak_unbind, context);
binding_context_unref (context);
binding->source_notify = 0;
}
g_weak_ref_set (&context->source, NULL);
}
/* As above, but with the target. If source==target then no weak notify was
* installed for the target, which is why that is stored as a separate
* boolean inside the binding. */
if (target)
{
/* There might be a target property notify without a weak notify on the
* target or the other way around, so these have to be handled
* independently here unlike for the source. */
if (binding->target_notify != 0)
{
g_signal_handler_disconnect (target, binding->target_notify);
binding->target_notify = 0;
}
g_weak_ref_set (&context->target, NULL);
/* Remove the weak notify from the target, at most once */
if (binding->target_weak_notify_installed)
{
g_object_weak_unref (target, weak_unbind, context);
binding_context_unref (context);
binding->target_weak_notify_installed = FALSE;
}
}
/* Make sure to remove the binding only once and return to the caller that
* this was the call that actually removed it. */
if (!context->binding_removed)
{
context->binding_removed = TRUE;
binding_was_removed = TRUE;
}
return binding_was_removed;
}
/* the basic assumption is that if either the source or the target
* goes away then the binding does not exist any more and it should
* be reaped as well. Each weak notify owns a strong reference to the
* binding that should be dropped here. */
static void
weak_unbind (gpointer user_data,
GObject *where_the_object_was)
{
BindingContext *context = user_data;
GBinding *binding;
GObject *source, *target;
gboolean binding_was_removed = FALSE;
TransformFunc *transform_func;
binding = g_weak_ref_get (&context->binding);
if (!binding)
{
/* The binding was already destroyed before so there's nothing to do */
binding_context_unref (context);
return;
}
g_mutex_lock (&binding->unbind_lock);
transform_func = g_steal_pointer (&binding->transform_func);
source = g_weak_ref_get (&context->source);
target = g_weak_ref_get (&context->target);
/* If this is called then either the source or target or both must be in the
* process of being disposed. If this happens as part of g_object_unref()
* then the weak references are actually cleared, otherwise if disposing
* happens as part of g_object_run_dispose() then they would still point to
* the disposed object.
*
* If the object this is being called for is either the source or the target
* and we actually got a strong reference to it nonetheless (see above),
* then signal handlers and weak notifies for it are already disconnected
* and they must not be disconnected a second time. Instead simply clear the
* weak reference and be done with it.
*
* See https://gitlab.gnome.org/GNOME/glib/-/issues/2266 */
if (source == where_the_object_was)
{
g_weak_ref_set (&context->source, NULL);
g_clear_object (&source);
}
if (target == where_the_object_was)
{
g_weak_ref_set (&context->target, NULL);
g_clear_object (&target);
}
binding_was_removed = unbind_internal_locked (context, binding, source, target);
g_mutex_unlock (&binding->unbind_lock);
/* Unref source, target and transform_func after the mutex is unlocked as it
* might release the last reference, which then accesses the mutex again */
g_clear_object (&target);
g_clear_object (&source);
g_clear_pointer (&transform_func, transform_func_unref);
/* This releases the strong reference we got from the weak ref above */
g_object_unref (binding);
/* This will take care of the binding itself. */
if (binding_was_removed)
g_object_unref (binding);
/* Each weak notify owns a reference to the binding context. */
binding_context_unref (context);
}
static gboolean
default_transform (GBinding *binding,
const GValue *value_a,
GValue *value_b,
gpointer user_data G_GNUC_UNUSED)
{
/* if it's not the same type, try to convert it using the GValue
* transformation API; otherwise just copy it
*/
if (!g_type_is_a (G_VALUE_TYPE (value_a), G_VALUE_TYPE (value_b)))
{
/* are these two types compatible (can be directly copied)? */
if (g_value_type_compatible (G_VALUE_TYPE (value_a),
G_VALUE_TYPE (value_b)))
{
g_value_copy (value_a, value_b);
return TRUE;
}
if (g_value_type_transformable (G_VALUE_TYPE (value_a),
G_VALUE_TYPE (value_b)))
{
if (g_value_transform (value_a, value_b))
return TRUE;
}
g_critical ("%s: Unable to convert a value of type %s to a "
"value of type %s",
G_STRLOC,
g_type_name (G_VALUE_TYPE (value_a)),
g_type_name (G_VALUE_TYPE (value_b)));
return FALSE;
}
g_value_copy (value_a, value_b);
return TRUE;
}
static gboolean
default_invert_boolean_transform (GBinding *binding,
const GValue *value_a,
GValue *value_b,
gpointer user_data G_GNUC_UNUSED)
{
gboolean value;
g_assert (G_VALUE_HOLDS_BOOLEAN (value_a));
g_assert (G_VALUE_HOLDS_BOOLEAN (value_b));
value = g_value_get_boolean (value_a);
value = !value;
g_value_set_boolean (value_b, value);
return TRUE;
}
static void
on_source_notify (GObject *source,
GParamSpec *pspec,
BindingContext *context)
{
GBinding *binding;
GObject *target;
TransformFunc *transform_func;
GValue from_value = G_VALUE_INIT;
GValue to_value = G_VALUE_INIT;
gboolean res;
binding = g_weak_ref_get (&context->binding);
if (!binding)
return;
if (binding->is_frozen)
{
g_object_unref (binding);
return;
}
target = g_weak_ref_get (&context->target);
if (!target)
{
g_object_unref (binding);
return;
}
/* Get the transform function safely */
g_mutex_lock (&binding->unbind_lock);
if (!binding->transform_func)
{
/* it was released already during unbinding, nothing to do here */
g_mutex_unlock (&binding->unbind_lock);
return;
}
transform_func = transform_func_ref (binding->transform_func);
g_mutex_unlock (&binding->unbind_lock);
g_value_init (&from_value, G_PARAM_SPEC_VALUE_TYPE (binding->source_pspec));
g_value_init (&to_value, G_PARAM_SPEC_VALUE_TYPE (binding->target_pspec));
g_object_get_property (source, binding->source_pspec->name, &from_value);
res = transform_func->transform_s2t (binding,
&from_value,
&to_value,
transform_func->transform_data);
transform_func_unref (transform_func);
if (res)
{
binding->is_frozen = TRUE;
(void) g_param_value_validate (binding->target_pspec, &to_value);
g_object_set_property (target, binding->target_pspec->name, &to_value);
binding->is_frozen = FALSE;
}
g_value_unset (&from_value);
g_value_unset (&to_value);
g_object_unref (target);
g_object_unref (binding);
}
static void
on_target_notify (GObject *target,
GParamSpec *pspec,
BindingContext *context)
{
GBinding *binding;
GObject *source;
TransformFunc *transform_func;
GValue from_value = G_VALUE_INIT;
GValue to_value = G_VALUE_INIT;
gboolean res;
binding = g_weak_ref_get (&context->binding);
if (!binding)
return;
if (binding->is_frozen)
{
g_object_unref (binding);
return;
}
source = g_weak_ref_get (&context->source);
if (!source)
{
g_object_unref (binding);
return;
}
/* Get the transform function safely */
g_mutex_lock (&binding->unbind_lock);
if (!binding->transform_func)
{
/* it was released already during unbinding, nothing to do here */
g_mutex_unlock (&binding->unbind_lock);
return;
}
transform_func = transform_func_ref (binding->transform_func);
g_mutex_unlock (&binding->unbind_lock);
g_value_init (&from_value, G_PARAM_SPEC_VALUE_TYPE (binding->target_pspec));
g_value_init (&to_value, G_PARAM_SPEC_VALUE_TYPE (binding->source_pspec));
g_object_get_property (target, binding->target_pspec->name, &from_value);
res = transform_func->transform_t2s (binding,
&from_value,
&to_value,
transform_func->transform_data);
transform_func_unref (transform_func);
if (res)
{
binding->is_frozen = TRUE;
(void) g_param_value_validate (binding->source_pspec, &to_value);
g_object_set_property (source, binding->source_pspec->name, &to_value);
binding->is_frozen = FALSE;
}
g_value_unset (&from_value);
g_value_unset (&to_value);
g_object_unref (source);
g_object_unref (binding);
}
static inline void
g_binding_unbind_internal (GBinding *binding,
gboolean unref_binding)
{
BindingContext *context = binding->context;
GObject *source, *target;
gboolean binding_was_removed = FALSE;
TransformFunc *transform_func;
g_mutex_lock (&binding->unbind_lock);
transform_func = g_steal_pointer (&binding->transform_func);
source = g_weak_ref_get (&context->source);
target = g_weak_ref_get (&context->target);
binding_was_removed = unbind_internal_locked (context, binding, source, target);
g_mutex_unlock (&binding->unbind_lock);
/* Unref source, target and transform_func after the mutex is unlocked as it
* might release the last reference, which then accesses the mutex again */
g_clear_object (&target);
g_clear_object (&source);
g_clear_pointer (&transform_func, transform_func_unref);
if (binding_was_removed && unref_binding)
g_object_unref (binding);
}
static void
g_binding_finalize (GObject *gobject)
{
GBinding *binding = G_BINDING (gobject);
g_binding_unbind_internal (binding, FALSE);
binding_context_unref (binding->context);
g_mutex_clear (&binding->unbind_lock);
G_OBJECT_CLASS (g_binding_parent_class)->finalize (gobject);
}
/* @key must have already been validated with is_valid()
* Modifies @key in place. */
static void
canonicalize_key (gchar *key)
{
gchar *p;
for (p = key; *p != 0; p++)
{
gchar c = *p;
if (c == '_')
*p = '-';
}
}
/* @key must have already been validated with is_valid() */
static gboolean
is_canonical (const gchar *key)
{
return (strchr (key, '_') == NULL);
}
static void
g_binding_set_property (GObject *gobject,
guint prop_id,
const GValue *value,
GParamSpec *pspec)
{
GBinding *binding = G_BINDING (gobject);
switch (prop_id)
{
case PROP_SOURCE:
g_weak_ref_set (&binding->context->source, g_value_get_object (value));
break;
case PROP_TARGET:
g_weak_ref_set (&binding->context->target, g_value_get_object (value));
break;
case PROP_SOURCE_PROPERTY:
case PROP_TARGET_PROPERTY:
{
gchar *name_copy = NULL;
const gchar *name = g_value_get_string (value);
const gchar **dest;
/* Ensure the name we intern is canonical. */
if (!is_canonical (name))
{
name_copy = g_value_dup_string (value);
canonicalize_key (name_copy);
name = name_copy;
}
if (prop_id == PROP_SOURCE_PROPERTY)
dest = &binding->source_property;
else
dest = &binding->target_property;
*dest = g_intern_string (name);
g_free (name_copy);
break;
}
case PROP_FLAGS:
binding->flags = g_value_get_flags (value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
break;
}
}
static void
g_binding_get_property (GObject *gobject,
guint prop_id,
GValue *value,
GParamSpec *pspec)
{
GBinding *binding = G_BINDING (gobject);
switch (prop_id)
{
case PROP_SOURCE:
g_value_take_object (value, g_weak_ref_get (&binding->context->source));
break;
case PROP_SOURCE_PROPERTY:
/* @source_property is interned, so we don’t need to take a copy */
g_value_set_interned_string (value, binding->source_property);
break;
case PROP_TARGET:
g_value_take_object (value, g_weak_ref_get (&binding->context->target));
break;
case PROP_TARGET_PROPERTY:
/* @target_property is interned, so we don’t need to take a copy */
g_value_set_interned_string (value, binding->target_property);
break;
case PROP_FLAGS:
g_value_set_flags (value, binding->flags);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
break;
}
}
static void
g_binding_constructed (GObject *gobject)
{
GBinding *binding = G_BINDING (gobject);
GBindingTransformFunc transform_func = default_transform;
GObject *source, *target;
GQuark source_property_detail;
GClosure *source_notify_closure;
/* assert that we were constructed correctly */
source = g_weak_ref_get (&binding->context->source);
target = g_weak_ref_get (&binding->context->target);
g_assert (source != NULL);
g_assert (target != NULL);
g_assert (binding->source_property != NULL);
g_assert (binding->target_property != NULL);
/* we assume a check was performed prior to construction - since
* g_object_bind_property_full() does it; we cannot fail construction
* anyway, so it would be hard for use to properly warn here
*/
binding->source_pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (source), binding->source_property);
binding->target_pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (target), binding->target_property);
g_assert (binding->source_pspec != NULL);
g_assert (binding->target_pspec != NULL);
/* switch to the invert boolean transform if needed */
if (binding->flags & G_BINDING_INVERT_BOOLEAN)
transform_func = default_invert_boolean_transform;
/* set the default transformation functions here */
binding->transform_func = transform_func_new (transform_func, transform_func, NULL, NULL);
source_property_detail = g_quark_from_string (binding->source_property);
source_notify_closure = g_cclosure_new (G_CALLBACK (on_source_notify),
binding_context_ref (binding->context),
(GClosureNotify) binding_context_unref);
binding->source_notify = g_signal_connect_closure_by_id (source,
gobject_notify_signal_id,
source_property_detail,
source_notify_closure,
FALSE);
g_object_weak_ref (source, weak_unbind, binding_context_ref (binding->context));
if (binding->flags & G_BINDING_BIDIRECTIONAL)
{
GQuark target_property_detail;
GClosure *target_notify_closure;
target_property_detail = g_quark_from_string (binding->target_property);
target_notify_closure = g_cclosure_new (G_CALLBACK (on_target_notify),
binding_context_ref (binding->context),
(GClosureNotify) binding_context_unref);
binding->target_notify = g_signal_connect_closure_by_id (target,
gobject_notify_signal_id,
target_property_detail,
target_notify_closure,
FALSE);
}
if (target != source)
{
g_object_weak_ref (target, weak_unbind, binding_context_ref (binding->context));
/* Need to remember separately if a target weak notify was installed as
* unlike for the source it can exist independently of the property
* notification callback */
binding->target_weak_notify_installed = TRUE;
}
g_object_unref (source);
g_object_unref (target);
}
static void
g_binding_class_init (GBindingClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_notify_signal_id = g_signal_lookup ("notify", G_TYPE_OBJECT);
g_assert (gobject_notify_signal_id != 0);
gobject_class->constructed = g_binding_constructed;
gobject_class->set_property = g_binding_set_property;
gobject_class->get_property = g_binding_get_property;
gobject_class->finalize = g_binding_finalize;
/**
* GBinding:source:
*
* The #GObject that should be used as the source of the binding
*
* Since: 2.26
*/
g_object_class_install_property (gobject_class, PROP_SOURCE,
g_param_spec_object ("source",
P_("Source"),
P_("The source of the binding"),
G_TYPE_OBJECT,
G_PARAM_CONSTRUCT_ONLY |
G_PARAM_READWRITE |
G_PARAM_STATIC_STRINGS));
/**
* GBinding:target:
*
* The #GObject that should be used as the target of the binding
*
* Since: 2.26
*/
g_object_class_install_property (gobject_class, PROP_TARGET,
g_param_spec_object ("target",
P_("Target"),
P_("The target of the binding"),
G_TYPE_OBJECT,
G_PARAM_CONSTRUCT_ONLY |
G_PARAM_READWRITE |
G_PARAM_STATIC_STRINGS));
/**
* GBinding:source-property:
*
* The name of the property of #GBinding:source that should be used
* as the source of the binding.
*
* This should be in [canonical form][canonical-parameter-names] to get the
* best performance.
*
* Since: 2.26
*/
g_object_class_install_property (gobject_class, PROP_SOURCE_PROPERTY,
g_param_spec_string ("source-property",
P_("Source Property"),
P_("The property on the source to bind"),
NULL,
G_PARAM_CONSTRUCT_ONLY |
G_PARAM_READWRITE |
G_PARAM_STATIC_STRINGS));
/**
* GBinding:target-property:
*
* The name of the property of #GBinding:target that should be used
* as the target of the binding.
*
* This should be in [canonical form][canonical-parameter-names] to get the
* best performance.
*
* Since: 2.26
*/
g_object_class_install_property (gobject_class, PROP_TARGET_PROPERTY,
g_param_spec_string ("target-property",
P_("Target Property"),
P_("The property on the target to bind"),
NULL,
G_PARAM_CONSTRUCT_ONLY |
G_PARAM_READWRITE |
G_PARAM_STATIC_STRINGS));
/**
* GBinding:flags:
*
* Flags to be used to control the #GBinding
*
* Since: 2.26
*/
g_object_class_install_property (gobject_class, PROP_FLAGS,
g_param_spec_flags ("flags",
P_("Flags"),
P_("The binding flags"),
G_TYPE_BINDING_FLAGS,
G_BINDING_DEFAULT,
G_PARAM_CONSTRUCT_ONLY |
G_PARAM_READWRITE |
G_PARAM_STATIC_STRINGS));
}
static void
g_binding_init (GBinding *binding)
{
g_mutex_init (&binding->unbind_lock);
binding->context = g_atomic_rc_box_new0 (BindingContext);
g_weak_ref_init (&binding->context->binding, binding);
g_weak_ref_init (&binding->context->source, NULL);
g_weak_ref_init (&binding->context->target, NULL);
}
/**
* g_binding_get_flags:
* @binding: a #GBinding
*
* Retrieves the flags passed when constructing the #GBinding.
*
* Returns: the #GBindingFlags used by the #GBinding
*
* Since: 2.26
*/
GBindingFlags
g_binding_get_flags (GBinding *binding)
{
g_return_val_if_fail (G_IS_BINDING (binding), G_BINDING_DEFAULT);
return binding->flags;
}
/**
* g_binding_get_source:
* @binding: a #GBinding
*
* Retrieves the #GObject instance used as the source of the binding.
*
* A #GBinding can outlive the source #GObject as the binding does not hold a
* strong reference to the source. If the source is destroyed before the
* binding then this function will return %NULL.
*
* Use g_binding_dup_source() if the source or binding are used from different
* threads as otherwise the pointer returned from this function might become
* invalid if the source is finalized from another thread in the meantime.
*
* Returns: (transfer none) (nullable): the source #GObject, or %NULL if the
* source does not exist any more.
*
* Deprecated: 2.68: Use g_binding_dup_source() for a safer version of this
* function.
*
* Since: 2.26
*/
GObject *
g_binding_get_source (GBinding *binding)
{
GObject *source;
g_return_val_if_fail (G_IS_BINDING (binding), NULL);
source = g_weak_ref_get (&binding->context->source);
/* Unref here, this API is not thread-safe
* FIXME: Remove this API when we next break API */
if (source)
g_object_unref (source);
return source;
}
/**
* g_binding_dup_source:
* @binding: a #GBinding
*
* Retrieves the #GObject instance used as the source of the binding.
*
* A #GBinding can outlive the source #GObject as the binding does not hold a
* strong reference to the source. If the source is destroyed before the
* binding then this function will return %NULL.
*
* Returns: (transfer full) (nullable): the source #GObject, or %NULL if the
* source does not exist any more.
*
* Since: 2.68
*/
GObject *
g_binding_dup_source (GBinding *binding)
{
g_return_val_if_fail (G_IS_BINDING (binding), NULL);
return g_weak_ref_get (&binding->context->source);
}
/**
* g_binding_get_target:
* @binding: a #GBinding
*
* Retrieves the #GObject instance used as the target of the binding.
*
* A #GBinding can outlive the target #GObject as the binding does not hold a
* strong reference to the target. If the target is destroyed before the
* binding then this function will return %NULL.
*
* Use g_binding_dup_target() if the target or binding are used from different
* threads as otherwise the pointer returned from this function might become
* invalid if the target is finalized from another thread in the meantime.
*
* Returns: (transfer none) (nullable): the target #GObject, or %NULL if the
* target does not exist any more.
*
* Deprecated: 2.68: Use g_binding_dup_target() for a safer version of this
* function.
*
* Since: 2.26
*/
GObject *
g_binding_get_target (GBinding *binding)
{
GObject *target;
g_return_val_if_fail (G_IS_BINDING (binding), NULL);
target = g_weak_ref_get (&binding->context->target);
/* Unref here, this API is not thread-safe
* FIXME: Remove this API when we next break API */
if (target)
g_object_unref (target);
return target;
}
/**
* g_binding_dup_target:
* @binding: a #GBinding
*
* Retrieves the #GObject instance used as the target of the binding.
*
* A #GBinding can outlive the target #GObject as the binding does not hold a
* strong reference to the target. If the target is destroyed before the
* binding then this function will return %NULL.
*
* Returns: (transfer full) (nullable): the target #GObject, or %NULL if the
* target does not exist any more.
*
* Since: 2.68
*/
GObject *
g_binding_dup_target (GBinding *binding)
{
g_return_val_if_fail (G_IS_BINDING (binding), NULL);
return g_weak_ref_get (&binding->context->target);
}
/**
* g_binding_get_source_property:
* @binding: a #GBinding
*
* Retrieves the name of the property of #GBinding:source used as the source
* of the binding.
*
* Returns: the name of the source property
*
* Since: 2.26
*/
const gchar *
g_binding_get_source_property (GBinding *binding)
{
g_return_val_if_fail (G_IS_BINDING (binding), NULL);
return binding->source_property;
}
/**
* g_binding_get_target_property:
* @binding: a #GBinding
*
* Retrieves the name of the property of #GBinding:target used as the target
* of the binding.
*
* Returns: the name of the target property
*
* Since: 2.26
*/
const gchar *
g_binding_get_target_property (GBinding *binding)
{
g_return_val_if_fail (G_IS_BINDING (binding), NULL);
return binding->target_property;
}
/**
* g_binding_unbind:
* @binding: a #GBinding
*
* Explicitly releases the binding between the source and the target
* property expressed by @binding.
*
* This function will release the reference that is being held on
* the @binding instance if the binding is still bound; if you want to hold on
* to the #GBinding instance after calling g_binding_unbind(), you will need
* to hold a reference to it.
*
* Note however that this function does not take ownership of @binding, it
* only unrefs the reference that was initially created by
* g_object_bind_property() and is owned by the binding.
*
* Since: 2.38
*/
void
g_binding_unbind (GBinding *binding)
{
g_return_if_fail (G_IS_BINDING (binding));
g_binding_unbind_internal (binding, TRUE);
}
/**
* g_object_bind_property_full:
* @source: (type GObject.Object): the source #GObject
* @source_property: the property on @source to bind
* @target: (type GObject.Object): the target #GObject
* @target_property: the property on @target to bind
* @flags: flags to pass to #GBinding
* @transform_to: (scope notified) (nullable): the transformation function
* from the @source to the @target, or %NULL to use the default
* @transform_from: (scope notified) (nullable): the transformation function
* from the @target to the @source, or %NULL to use the default
* @user_data: custom data to be passed to the transformation functions,
* or %NULL
* @notify: (nullable): a function to call when disposing the binding, to free
* resources used by the transformation functions, or %NULL if not required
*
* Complete version of g_object_bind_property().
*
* Creates a binding between @source_property on @source and @target_property
* on @target, allowing you to set the transformation functions to be used by
* the binding.
*
* If @flags contains %G_BINDING_BIDIRECTIONAL then the binding will be mutual:
* if @target_property on @target changes then the @source_property on @source
* will be updated as well. The @transform_from function is only used in case
* of bidirectional bindings, otherwise it will be ignored
*
* The binding will automatically be removed when either the @source or the
* @target instances are finalized. This will release the reference that is
* being held on the #GBinding instance; if you want to hold on to the
* #GBinding instance, you will need to hold a reference to it.
*
* To remove the binding, call g_binding_unbind().
*
* A #GObject can have multiple bindings.
*
* The same @user_data parameter will be used for both @transform_to
* and @transform_from transformation functions; the @notify function will
* be called once, when the binding is removed. If you need different data
* for each transformation function, please use
* g_object_bind_property_with_closures() instead.
*
* Returns: (transfer none): the #GBinding instance representing the
* binding between the two #GObject instances. The binding is released
* whenever the #GBinding reference count reaches zero.
*
* Since: 2.26
*/
GBinding *
g_object_bind_property_full (gpointer source,
const gchar *source_property,
gpointer target,
const gchar *target_property,
GBindingFlags flags,
GBindingTransformFunc transform_to,
GBindingTransformFunc transform_from,
gpointer user_data,
GDestroyNotify notify)
{
GParamSpec *pspec;
GBinding *binding;
g_return_val_if_fail (G_IS_OBJECT (source), NULL);
g_return_val_if_fail (source_property != NULL, NULL);
g_return_val_if_fail (g_param_spec_is_valid_name (source_property), NULL);
g_return_val_if_fail (G_IS_OBJECT (target), NULL);
g_return_val_if_fail (target_property != NULL, NULL);
g_return_val_if_fail (g_param_spec_is_valid_name (target_property), NULL);
if (source == target && g_strcmp0 (source_property, target_property) == 0)
{
g_critical ("Unable to bind the same property on the same instance");
return NULL;
}
/* remove the G_BINDING_INVERT_BOOLEAN flag in case we have
* custom transformation functions
*/
if ((flags & G_BINDING_INVERT_BOOLEAN) &&
(transform_to != NULL || transform_from != NULL))
{
flags &= ~G_BINDING_INVERT_BOOLEAN;
}
pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (source), source_property);
if (pspec == NULL)
{
g_critical ("%s: The source object of type %s has no property called '%s'",
G_STRLOC,
G_OBJECT_TYPE_NAME (source),
source_property);
return NULL;
}
if (!(pspec->flags & G_PARAM_READABLE))
{
g_critical ("%s: The source object of type %s has no readable property called '%s'",
G_STRLOC,
G_OBJECT_TYPE_NAME (source),
source_property);
return NULL;
}
if ((flags & G_BINDING_BIDIRECTIONAL) &&
((pspec->flags & G_PARAM_CONSTRUCT_ONLY) || !(pspec->flags & G_PARAM_WRITABLE)))
{
g_critical ("%s: The source object of type %s has no writable property called '%s'",
G_STRLOC,
G_OBJECT_TYPE_NAME (source),
source_property);
return NULL;
}
if ((flags & G_BINDING_INVERT_BOOLEAN) &&
!(G_PARAM_SPEC_VALUE_TYPE (pspec) == G_TYPE_BOOLEAN))
{
g_critical ("%s: The G_BINDING_INVERT_BOOLEAN flag can only be used "
"when binding boolean properties; the source property '%s' "
"is of type '%s'",
G_STRLOC,
source_property,
g_type_name (G_PARAM_SPEC_VALUE_TYPE (pspec)));
return NULL;
}
pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (target), target_property);
if (pspec == NULL)
{
g_critical ("%s: The target object of type %s has no property called '%s'",
G_STRLOC,
G_OBJECT_TYPE_NAME (target),
target_property);
return NULL;
}
if ((pspec->flags & G_PARAM_CONSTRUCT_ONLY) || !(pspec->flags & G_PARAM_WRITABLE))
{
g_critical ("%s: The target object of type %s has no writable property called '%s'",
G_STRLOC,
G_OBJECT_TYPE_NAME (target),
target_property);
return NULL;
}
if ((flags & G_BINDING_BIDIRECTIONAL) &&
!(pspec->flags & G_PARAM_READABLE))
{
g_critical ("%s: The target object of type %s has no readable property called '%s'",
G_STRLOC,
G_OBJECT_TYPE_NAME (target),
target_property);
return NULL;
}
if ((flags & G_BINDING_INVERT_BOOLEAN) &&
!(G_PARAM_SPEC_VALUE_TYPE (pspec) == G_TYPE_BOOLEAN))
{
g_critical ("%s: The G_BINDING_INVERT_BOOLEAN flag can only be used "
"when binding boolean properties; the target property '%s' "
"is of type '%s'",
G_STRLOC,
target_property,
g_type_name (G_PARAM_SPEC_VALUE_TYPE (pspec)));
return NULL;
}
binding = g_object_new (G_TYPE_BINDING,
"source", source,
"source-property", source_property,
"target", target,
"target-property", target_property,
"flags", flags,
NULL);
g_assert (binding->transform_func != NULL);
/* Use default functions if not provided here */
if (transform_to == NULL)
transform_to = binding->transform_func->transform_s2t;
if (transform_from == NULL)
transform_from = binding->transform_func->transform_t2s;
g_clear_pointer (&binding->transform_func, transform_func_unref);
binding->transform_func = transform_func_new (transform_to, transform_from, user_data, notify);
/* synchronize the target with the source by faking an emission of
* the ::notify signal for the source property; this will also take
* care of the bidirectional binding case because the eventual change
* will emit a notification on the target
*/
if (flags & G_BINDING_SYNC_CREATE)
on_source_notify (source, binding->source_pspec, binding->context);
return binding;
}
/**
* g_object_bind_property:
* @source: (type GObject.Object): the source #GObject
* @source_property: the property on @source to bind
* @target: (type GObject.Object): the target #GObject
* @target_property: the property on @target to bind
* @flags: flags to pass to #GBinding
*
* Creates a binding between @source_property on @source and @target_property
* on @target.
*
* Whenever the @source_property is changed the @target_property is
* updated using the same value. For instance:
*
* |[<!-- language="C" -->
* g_object_bind_property (action, "active", widget, "sensitive", 0);
* ]|
*
* Will result in the "sensitive" property of the widget #GObject instance to be
* updated with the same value of the "active" property of the action #GObject
* instance.
*
* If @flags contains %G_BINDING_BIDIRECTIONAL then the binding will be mutual:
* if @target_property on @target changes then the @source_property on @source
* will be updated as well.
*
* The binding will automatically be removed when either the @source or the
* @target instances are finalized. To remove the binding without affecting the
* @source and the @target you can just call g_object_unref() on the returned
* #GBinding instance.
*
* Removing the binding by calling g_object_unref() on it must only be done if
* the binding, @source and @target are only used from a single thread and it
* is clear that both @source and @target outlive the binding. Especially it
* is not safe to rely on this if the binding, @source or @target can be
* finalized from different threads. Keep another reference to the binding and
* use g_binding_unbind() instead to be on the safe side.
*
* A #GObject can have multiple bindings.
*
* Returns: (transfer none): the #GBinding instance representing the
* binding between the two #GObject instances. The binding is released
* whenever the #GBinding reference count reaches zero.
*
* Since: 2.26
*/
GBinding *
g_object_bind_property (gpointer source,
const gchar *source_property,
gpointer target,
const gchar *target_property,
GBindingFlags flags)
{
/* type checking is done in g_object_bind_property_full() */
return g_object_bind_property_full (source, source_property,
target, target_property,
flags,
NULL,
NULL,
NULL, NULL);
}
typedef struct _TransformData
{
GClosure *transform_to_closure;
GClosure *transform_from_closure;
} TransformData;
static gboolean
bind_with_closures_transform_to (GBinding *binding,
const GValue *source,
GValue *target,
gpointer data)
{
TransformData *t_data = data;
GValue params[3] = { G_VALUE_INIT, G_VALUE_INIT, G_VALUE_INIT };
GValue retval = G_VALUE_INIT;
gboolean res;
g_value_init (&params[0], G_TYPE_BINDING);
g_value_set_object (&params[0], binding);
g_value_init (&params[1], G_TYPE_VALUE);
g_value_set_boxed (&params[1], source);
g_value_init (&params[2], G_TYPE_VALUE);
g_value_set_boxed (&params[2], target);
g_value_init (&retval, G_TYPE_BOOLEAN);
g_value_set_boolean (&retval, FALSE);
g_closure_invoke (t_data->transform_to_closure, &retval, 3, params, NULL);
res = g_value_get_boolean (&retval);
if (res)
{
const GValue *out_value = g_value_get_boxed (&params[2]);
g_assert (out_value != NULL);
g_value_copy (out_value, target);
}
g_value_unset (&params[0]);
g_value_unset (&params[1]);
g_value_unset (&params[2]);
g_value_unset (&retval);
return res;
}
static gboolean
bind_with_closures_transform_from (GBinding *binding,
const GValue *source,
GValue *target,
gpointer data)
{
TransformData *t_data = data;
GValue params[3] = { G_VALUE_INIT, G_VALUE_INIT, G_VALUE_INIT };
GValue retval = G_VALUE_INIT;
gboolean res;
g_value_init (&params[0], G_TYPE_BINDING);
g_value_set_object (&params[0], binding);
g_value_init (&params[1], G_TYPE_VALUE);
g_value_set_boxed (&params[1], source);
g_value_init (&params[2], G_TYPE_VALUE);
g_value_set_boxed (&params[2], target);
g_value_init (&retval, G_TYPE_BOOLEAN);
g_value_set_boolean (&retval, FALSE);
g_closure_invoke (t_data->transform_from_closure, &retval, 3, params, NULL);
res = g_value_get_boolean (&retval);
if (res)
{
const GValue *out_value = g_value_get_boxed (&params[2]);
g_assert (out_value != NULL);
g_value_copy (out_value, target);
}
g_value_unset (&params[0]);
g_value_unset (&params[1]);
g_value_unset (&params[2]);
g_value_unset (&retval);
return res;
}
static void
bind_with_closures_free_func (gpointer data)
{
TransformData *t_data = data;
if (t_data->transform_to_closure != NULL)
g_closure_unref (t_data->transform_to_closure);
if (t_data->transform_from_closure != NULL)
g_closure_unref (t_data->transform_from_closure);
g_slice_free (TransformData, t_data);
}
/**
* g_object_bind_property_with_closures: (rename-to g_object_bind_property_full)
* @source: (type GObject.Object): the source #GObject
* @source_property: the property on @source to bind
* @target: (type GObject.Object): the target #GObject
* @target_property: the property on @target to bind
* @flags: flags to pass to #GBinding
* @transform_to: a #GClosure wrapping the transformation function
* from the @source to the @target, or %NULL to use the default
* @transform_from: a #GClosure wrapping the transformation function
* from the @target to the @source, or %NULL to use the default
*
* Creates a binding between @source_property on @source and @target_property
* on @target, allowing you to set the transformation functions to be used by
* the binding.
*
* This function is the language bindings friendly version of
* g_object_bind_property_full(), using #GClosures instead of
* function pointers.
*
* Returns: (transfer none): the #GBinding instance representing the
* binding between the two #GObject instances. The binding is released
* whenever the #GBinding reference count reaches zero.
*
* Since: 2.26
*/
GBinding *
g_object_bind_property_with_closures (gpointer source,
const gchar *source_property,
gpointer target,
const gchar *target_property,
GBindingFlags flags,
GClosure *transform_to,
GClosure *transform_from)
{
TransformData *data;
data = g_slice_new0 (TransformData);
if (transform_to != NULL)
{
if (G_CLOSURE_NEEDS_MARSHAL (transform_to))
g_closure_set_marshal (transform_to, g_cclosure_marshal_BOOLEAN__BOXED_BOXED);
data->transform_to_closure = g_closure_ref (transform_to);
g_closure_sink (data->transform_to_closure);
}
if (transform_from != NULL)
{
if (G_CLOSURE_NEEDS_MARSHAL (transform_from))
g_closure_set_marshal (transform_from, g_cclosure_marshal_BOOLEAN__BOXED_BOXED);
data->transform_from_closure = g_closure_ref (transform_from);
g_closure_sink (data->transform_from_closure);
}
return g_object_bind_property_full (source, source_property,
target, target_property,
flags,
transform_to != NULL ? bind_with_closures_transform_to : NULL,
transform_from != NULL ? bind_with_closures_transform_from : NULL,
data,
bind_with_closures_free_func);
}
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