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GObject Reference Manual | |
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| Top | Description | Object Hierarchy | Properties | ||||
#include <glib-object.h>
GBinding;
enum GBindingFlags;
GObject * g_binding_get_source (GBinding *binding);
const gchar * g_binding_get_source_property (GBinding *binding);
GObject * g_binding_get_target (GBinding *binding);
const gchar * g_binding_get_target_property (GBinding *binding);
GBindingFlags g_binding_get_flags (GBinding *binding);
GBinding * g_object_bind_property (gpointer source,
const gchar *source_property,
gpointer target,
const gchar *target_property,
GBindingFlags flags);
gboolean (*GBindingTransformFunc) (GBinding *binding,
const GValue *source_value,
GValue *target_value,
gpointer user_data);
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);
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);
"flags" GBindingFlags : Read / Write / Construct Only "source" GObject* : Read / Write / Construct Only "source-property" gchar* : Read / Write / Construct Only "target" GObject* : Read / Write / Construct Only "target-property" gchar* : Read / Write / Construct Only
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:
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g_object_bind_property (object1, "property-a", object2, "property-b", G_BINDING_DEFAULT); |
will cause object2:property-b to be updated every
time g_object_set() or the specific accessor changes the value of
object1:property-a.
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:
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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:
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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 adjustment1:value property changes
and will transform the current value of the property before applying it
to the adjustment2:value property; vice versa, the
fahrenheit_to_celsius function will be called whenever
the adjustment2:value property changes, and will
transform the current value of the property before applying it to the
adjustment1:value.
Note that GBinding does not resolve cycles by itself; a cycle like
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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 "notify" signal only
if the value has effectively been changed. A binding is implemented
using the "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.
GBinding is available since GObject 2.26
typedef struct _GBinding GBinding;
GBinding is an opaque structure whose members cannot be accessed directly.
Since 2.26
typedef enum { /*< prefix=G_BINDING >*/
G_BINDING_DEFAULT = 0,
G_BINDING_BIDIRECTIONAL = 1 << 0,
G_BINDING_SYNC_CREATE = 1 << 1,
G_BINDING_INVERT_BOOLEAN = 1 << 2
} GBindingFlags;
Flags to be passed to g_object_bind_property() or
g_object_bind_property_full().
This enumeration can be extended at later date.
| The default binding; if the source property changes, the target property is updated with its value. | |
| Bidirectional binding; if either the property of the source or the property of the target changes, the other is updated. | |
| Synchronize the values of the source and target properties when creating the binding; the direction of the synchronization is always from the source to the target. | |
If the two properties being bound are
booleans, setting one to TRUE will result in the other being
set to FALSE and vice versa. This flag will only work for
boolean properties, and cannot be used when passing custom
transformation functions to g_object_bind_property_full().
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Since 2.26
GObject * g_binding_get_source (GBinding *binding);
Retrieves the GObject instance used as the source of the binding
Since 2.26
const gchar * g_binding_get_source_property (GBinding *binding);
Retrieves the name of the property of "source" used as the source of the binding
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a GBinding |
Returns : |
the name of the source property |
Since 2.26
GObject * g_binding_get_target (GBinding *binding);
Retrieves the GObject instance used as the target of the binding
Since 2.26
const gchar * g_binding_get_target_property (GBinding *binding);
Retrieves the name of the property of "target" used as the target of the binding
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a GBinding |
Returns : |
the name of the target property |
Since 2.26
GBindingFlags g_binding_get_flags (GBinding *binding);
Retrieves the flags passed when constructing the GBinding
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a GBinding |
Returns : |
the GBindingFlags used by the GBinding |
Since 2.26
GBinding * g_object_bind_property (gpointer source,const gchar *source_property,gpointer target,const gchar *target_property,GBindingFlags flags);
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:
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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.
A GObject can have multiple bindings.
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the source GObject |
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the property on source to bind |
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the target GObject |
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the property on target to bind |
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flags to pass to GBinding |
Returns : |
the GBinding instance representing the binding between the two GObject instances. The binding is released whenever the GBinding reference count reaches zero. [transfer none] |
Since 2.26
gboolean (*GBindingTransformFunc) (GBinding *binding,const GValue *source_value,GValue *target_value,gpointer user_data);
A function to be called to transform the source property of source
from source_value into the target property of target
using target_value.
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a GBinding |
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the value of the source property |
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the value of the target property |
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data passed to the transform function |
Returns : |
TRUE if the transformation was successful, and FALSE
otherwise |
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);
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. To remove the binding without affecting the
source and the target you can just call g_object_unref() on the returned
GBinding instance.
A GObject can have multiple bindings.
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.
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the source GObject |
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the property on source to bind |
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the target GObject |
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the property on target to bind |
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flags to pass to GBinding |
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the transformation function
from the source to the target, or NULL to use the default. [scope notified][allow-none]
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the transformation function
from the target to the source, or NULL to use the default. [scope notified][allow-none]
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custom data to be passed to the transformation functions,
or NULL
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function to be called when disposing the binding, to free the resources used by the transformation functions |
Returns : |
the GBinding instance representing the binding between the two GObject instances. The binding is released whenever the GBinding reference count reaches zero. [transfer none] |
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);
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.
Rename to: g_object_bind_property_full
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the source GObject |
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the property on source to bind |
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the target GObject |
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the property on target to bind |
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flags to pass to GBinding |
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a GClosure wrapping the transformation function
from the source to the target, or NULL to use the default |
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a GClosure wrapping the transformation function
from the target to the source, or NULL to use the default |
Returns : |
the GBinding instance representing the binding between the two GObject instances. The binding is released whenever the GBinding reference count reaches zero. [transfer none] |
Since 2.26
"flags" property"flags" GBindingFlags : Read / Write / Construct Only
Flags to be used to control the GBinding
Since 2.26
"source" property"source" GObject* : Read / Write / Construct Only
The GObject that should be used as the source of the binding
Since 2.26
"source-property" property"source-property" gchar* : Read / Write / Construct Only
The name of the property of "source" that should be used as the source of the binding
Default value: NULL
Since 2.26
"target" property"target" GObject* : Read / Write / Construct Only
The GObject that should be used as the target of the binding
Since 2.26