Creates a new GtkConstraintLayout layout manager.
Adds a constraint to the layout manager.
The [propertyGtk.Constraint:source] and [propertyGtk.Constraint:target]
properties of constraint can be:
NULL to indicate that the constraint refers to the
widget using layoutGtk.Widget] using layoutGtk.Widget] using layoutGtk.ConstraintGuide] that is part of layoutThe layout acquires the ownership of constraint after calling
this function.
a [classGtk.Constraint]
Creates a list of constraints from a VFL description.
The Visual Format Language, VFL, is based on Apple's AutoLayout VFL.
The views dictionary is used to match [ifaceGtk.ConstraintTarget]
instances to the symbolic view name inside the VFL.
The VFL grammar is:
<visualFormatString> = (<orientation>)?
(<superview><connection>)?
<view>(<connection><view>)*
(<connection><superview>)?
<orientation> = 'H' | 'V'
<superview> = '|'
<connection> = '' | '-' <predicateList> '-' | '-'
<predicateList> = <simplePredicate> | <predicateListWithParens>
<simplePredicate> = <metricName> | <positiveNumber>
<predicateListWithParens> = '(' <predicate> (',' <predicate>)* ')'
<predicate> = (<relation>)? <objectOfPredicate> (<operatorList>)? ('`'` <priority>)?
<relation> = '==' | '<=' | '>='
<objectOfPredicate> = <constant> | <viewName> | ('.' <attributeName>)?
<priority> = <positiveNumber> | 'required' | 'strong' | 'medium' | 'weak'
<constant> = <number>
<operatorList> = (<multiplyOperator>)? (<addOperator>)?
<multiplyOperator> = [ '*' | '/' ] <positiveNumber>
<addOperator> = [ '+' | '-' ] <positiveNumber>
<viewName> = [A-Za-z_]([A-Za-z0-9_]*) // A C identifier
<metricName> = [A-Za-z_]([A-Za-z0-9_]*) // A C identifier
<attributeName> = 'top' | 'bottom' | 'left' | 'right' | 'width' | 'height' |
'start' | 'end' | 'centerX' | 'centerY' | 'baseline'
<positiveNumber> // A positive real number parseable by g_ascii_strtod()
<number> // A real number parseable by g_ascii_strtod()
Note: The VFL grammar used by GTK is slightly different than the one defined by Apple, as it can use symbolic values for the constraint's strength instead of numeric values; additionally, GTK allows adding simple arithmetic operations inside predicates.
Examples of VFL descriptions are:
// Default spacing
[button]-[textField]
// Width constraint
[button(>=50)]
// Connection to super view
|-50-[purpleBox]-50-|
// Vertical layout
V:[topField]-10-[bottomField]
// Flush views
[maroonView][blueView]
// Priority
[button(100`strong)`]
// Equal widths
[button1(==button2)]
// Multiple predicates
[flexibleButton(>=70,<=100)]
// A complete line of layout
|-[find]-[findNext]-[findField(>=20)]-|
// Operators
[button1(button2 / 3 + 50)]
// Named attributes
[button1(==button2.height)]
an array of Visual Format Language lines defining a set of constraints
default horizontal spacing value, or -1 for the fallback value
default vertical spacing value, or -1 for the fallback value
a dictionary of [ name, target ] pairs; the name keys map to the view names in the VFL lines, while the target values map to children of the widget using a GtkConstraintLayout, or guides
Adds a guide to layout.
A guide can be used as the source or target of constraints, like a widget, but it is not visible.
The layout acquires the ownership of guide after calling
this function.
a [classGtk.ConstraintGuide] object
Assigns the given width, height, and baseline to
a widget, and computes the position and sizes of the children of
the widget using the layout management policy of manager.
the GtkWidget using manager
the new width of the widget
the new height of the widget
the baseline position of the widget, or -1
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:
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.
the property on source to bind
the target #GObject
the property on target to bind
flags to pass to #GBinding
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.
the property on source to bind
the target #GObject
the property on target to bind
flags to pass to #GBinding
a #GClosure wrapping the transformation function from the source to the target, or %NULL to use the default
a #GClosure wrapping the transformation function from the target to the source, or %NULL to use the default
This function is intended for #GObject implementations to re-enforce a [floating][floating-ref] object reference. Doing this is seldom required: all #GInitiallyUnowneds are created with a floating reference which usually just needs to be sunken by calling g_object_ref_sink().
Increases the freeze count on object. If the freeze count is
non-zero, the emission of "notify" signals on object is
stopped. The signals are queued until the freeze count is decreased
to zero. Duplicate notifications are squashed so that at most one
#GObject::notify signal is emitted for each property modified while the
object is frozen.
This is necessary for accessors that modify multiple properties to prevent premature notification while the object is still being modified.
Gets the ID of the buildable object.
GtkBuilder sets the name based on the ID attribute
of the
Gets a named field from the objects table of associations (see g_object_set_data()).
name of the key for that association
Retrieves a GtkLayoutChild instance for the GtkLayoutManager,
creating one if necessary.
The child widget must be a child of the widget using manager.
The GtkLayoutChild instance is owned by the GtkLayoutManager,
and is guaranteed to exist as long as child is a child of the
GtkWidget using the given GtkLayoutManager.
Gets a property of an object.
The value can be:
In general, a copy is made of the property contents and the caller is responsible for freeing the memory by calling g_value_unset().
Note that g_object_get_property() is really intended for language bindings, g_object_get() is much more convenient for C programming.
the name of the property to get
return location for the property value
This function gets back user data pointers stored via g_object_set_qdata().
A #GQuark, naming the user data pointer
Retrieves the request mode of manager.
Gets n_properties properties for an object.
Obtained properties will be set to values. All properties must be valid.
Warnings will be emitted and undefined behaviour may result if invalid
properties are passed in.
the names of each property to get
the values of each property to get
Checks whether object has a [floating][floating-ref] reference.
Queues a resize on the GtkWidget using manager, if any.
This function should be called by subclasses of GtkLayoutManager
in response to changes to their layout management policies.
Measures the size of the widget using manager, for the
given orientation and size.
See the [classGtk.Widget] documentation on layout management for
more details.
the GtkWidget using manager
the orientation to measure
Size for the opposite of orientation; for instance, if the orientation is %GTK_ORIENTATION_HORIZONTAL, this is the height of the widget; if the orientation is %GTK_ORIENTATION_VERTICAL, this is the width of the widget. This allows to measure the height for the given width, and the width for the given height. Use -1 if the size is not known
Emits a "notify" signal for the property property_name on object.
When possible, eg. when signaling a property change from within the class that registered the property, you should use g_object_notify_by_pspec() instead.
Note that emission of the notify signal may be blocked with g_object_freeze_notify(). In this case, the signal emissions are queued and will be emitted (in reverse order) when g_object_thaw_notify() is called.
the name of a property installed on the class of object.
Emits a "notify" signal for the property specified by pspec on object.
This function omits the property name lookup, hence it is faster than g_object_notify().
One way to avoid using g_object_notify() from within the class that registered the properties, and using g_object_notify_by_pspec() instead, is to store the GParamSpec used with g_object_class_install_property() inside a static array, e.g.:
enum
{
PROP_0,
PROP_FOO,
PROP_LAST
};
static GParamSpec *properties[PROP_LAST];
static void
my_object_class_init (MyObjectClass *klass)
{
properties[PROP_FOO] = g_param_spec_int ("foo", "Foo", "The foo",
0, 100,
50,
G_PARAM_READWRITE);
g_object_class_install_property (gobject_class,
PROP_FOO,
properties[PROP_FOO]);
}
and then notify a change on the "foo" property with:
g_object_notify_by_pspec (self, properties[PROP_FOO]);
the #GParamSpec of a property installed on the class of object.
Returns a GListModel to track the constraints that are
part of the layout.
Calling this function will enable extra internal bookkeeping to track constraints and emit signals on the returned listmodel. It may slow down operations a lot.
Applications should try hard to avoid calling this function because of the slowdowns.
Returns a GListModel to track the guides that are
part of the layout.
Calling this function will enable extra internal bookkeeping to track guides and emit signals on the returned listmodel. It may slow down operations a lot.
Applications should try hard to avoid calling this function because of the slowdowns.
Increase the reference count of object, and possibly remove the
[floating][floating-ref] reference, if object has a floating reference.
In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.
Since GLib 2.56, the type of object will be propagated to the return type
under the same conditions as for g_object_ref().
Removes all constraints from the layout manager.
Removes constraint from the layout manager,
so that it no longer influences the layout.
a [classGtk.Constraint]
Removes guide from the layout manager,
so that it no longer influences the layout.
a [classGtk.ConstraintGuide] object
Releases all references to other objects. This can be used to break reference cycles.
This function should only be called from object system implementations.
Each object carries around a table of associations from strings to pointers. This function lets you set an association.
If the object already had an association with that name, the old association will be destroyed.
Internally, the key is converted to a #GQuark using g_quark_from_string().
This means a copy of key is kept permanently (even after object has been
finalized) — so it is recommended to only use a small, bounded set of values
for key in your program, to avoid the #GQuark storage growing unbounded.
name of the key
data to associate with that key
Sets a property on an object.
the name of the property to set
the value
Remove a specified datum from the object's data associations, without invoking the association's destroy handler.
name of the key
This function gets back user data pointers stored via
g_object_set_qdata() and removes the data from object
without invoking its destroy() function (if any was
set).
Usually, calling this function is only required to update
user data pointers with a destroy notifier, for example:
void
object_add_to_user_list (GObject *object,
const gchar *new_string)
{
// the quark, naming the object data
GQuark quark_string_list = g_quark_from_static_string ("my-string-list");
// retrieve the old string list
GList *list = g_object_steal_qdata (object, quark_string_list);
// prepend new string
list = g_list_prepend (list, g_strdup (new_string));
// this changed 'list', so we need to set it again
g_object_set_qdata_full (object, quark_string_list, list, free_string_list);
}
static void
free_string_list (gpointer data)
{
GList *node, *list = data;
for (node = list; node; node = node->next)
g_free (node->data);
g_list_free (list);
}
Using g_object_get_qdata() in the above example, instead of g_object_steal_qdata() would have left the destroy function set, and thus the partial string list would have been freed upon g_object_set_qdata_full().
A #GQuark, naming the user data pointer
Reverts the effect of a previous call to
g_object_freeze_notify(). The freeze count is decreased on object
and when it reaches zero, queued "notify" signals are emitted.
Duplicate notifications for each property are squashed so that at most one #GObject::notify signal is emitted for each property, in the reverse order in which they have been queued.
It is an error to call this function when the freeze count is zero.
Decreases the reference count of object. When its reference count
drops to 0, the object is finalized (i.e. its memory is freed).
If the pointer to the #GObject may be reused in future (for example, if it is an instance variable of another object), it is recommended to clear the pointer to %NULL rather than retain a dangling pointer to a potentially invalid #GObject instance. Use g_clear_object() for this.
This function essentially limits the life time of the closure to
the life time of the object. That is, when the object is finalized,
the closure is invalidated by calling g_closure_invalidate() on
it, in order to prevent invocations of the closure with a finalized
(nonexisting) object. Also, g_object_ref() and g_object_unref() are
added as marshal guards to the closure, to ensure that an extra
reference count is held on object during invocation of the
closure. Usually, this function will be called on closures that
use this object as closure data.
#GClosure to watch
Find the #GParamSpec with the given name for an
interface. Generally, the interface vtable passed in as g_iface
will be the default vtable from g_type_default_interface_ref(), or,
if you know the interface has already been loaded,
g_type_default_interface_peek().
any interface vtable for the interface, or the default vtable for the interface
name of a property to look up.
Add a property to an interface; this is only useful for interfaces that are added to GObject-derived types. Adding a property to an interface forces all objects classes with that interface to have a compatible property. The compatible property could be a newly created #GParamSpec, but normally g_object_class_override_property() will be used so that the object class only needs to provide an implementation and inherits the property description, default value, bounds, and so forth from the interface property.
This function is meant to be called from the interface's default
vtable initialization function (the class_init member of
#GTypeInfo.) It must not be called after after class_init has
been called for any object types implementing this interface.
If pspec is a floating reference, it will be consumed.
any interface vtable for the interface, or the default vtable for the interface.
the #GParamSpec for the new property
Lists the properties of an interface.Generally, the interface
vtable passed in as g_iface will be the default vtable from
g_type_default_interface_ref(), or, if you know the interface has
already been loaded, g_type_default_interface_peek().
any interface vtable for the interface, or the default vtable for the interface
Creates a new GtkConstraintLayout layout manager.
Creates a new instance of a #GObject subtype and sets its properties.
Construction parameters (see %G_PARAM_CONSTRUCT, %G_PARAM_CONSTRUCT_ONLY) which are not explicitly specified are set to their default values.
the type id of the #GObject subtype to instantiate
an array of #GParameter
A layout manager using constraints to describe relations between widgets.
GtkConstraintLayoutis a layout manager that uses relations between widget attributes, expressed via [classGtk.Constraint] instances, to measure and allocate widgets.How do constraints work
Constraints are objects defining the relationship between attributes of a widget; you can read the description of the [class
Gtk.Constraint] class to have a more in depth definition.By taking multiple constraints and applying them to the children of a widget using
GtkConstraintLayout, it's possible to describe complex layout policies; each constraint applied to a child or to the parent widgets contributes to the full description of the layout, in terms of parameters for resolving the value of each attribute.It is important to note that a layout is defined by the totality of constraints; removing a child, or a constraint, from an existing layout without changing the remaining constraints may result in an unstable or unsolvable layout.
Constraints have an implicit "reading order"; you should start describing each edge of each child, as well as their relationship with the parent container, from the top left (or top right, in RTL languages), horizontally first, and then vertically.
A constraint-based layout with too few constraints can become "unstable", that is: have more than one solution. The behavior of an unstable layout is undefined.
A constraint-based layout with conflicting constraints may be unsolvable, and lead to an unstable layout. You can use the [property
Gtk.Constraint:strength] property of [classGtk.Constraint] to "nudge" the layout towards a solution.GtkConstraintLayout as GtkBuildable
GtkConstraintLayoutimplements the [ifaceGtk.Buildable] interface and has a custom "constraints" element which allows describing constraints in a [classGtk.Builder] UI file.An example of a UI definition fragment specifying a constraint:
The definition above will add two constraints to the GtkConstraintLayout:
The "target" and "target-attribute" attributes are required.
The "source" and "source-attribute" attributes of the "constraint" element are optional; if they are not specified, the constraint is assumed to be a constant.
The "relation" attribute is optional; if not specified, the constraint is assumed to be an equality.
The "strength" attribute is optional; if not specified, the constraint is assumed to be required.
The "source" and "target" attributes can be set to "super" to indicate that the constraint target is the widget using the GtkConstraintLayout.
There can be "constant" and "multiplier" attributes.
Additionally, the "constraints" element can also contain a description of the
GtkConstraintGuidesused by the layout:The "guide" element has the following optional attributes:
Using the Visual Format Language
Complex constraints can be described using a compact syntax called VFL, or Visual Format Language.
The Visual Format Language describes all the constraints on a row or column, typically starting from the leading edge towards the trailing one. Each element of the layout is composed by "views", which identify a [iface
Gtk.ConstraintTarget].For instance:
Describes a constraint that binds the trailing edge of "button" to the leading edge of "textField", leaving a default space between the two.
Using VFL is also possible to specify predicates that describe constraints on attributes like width and height:
The default orientation for a VFL description is horizontal, unless otherwise specified:
It's also possible to specify multiple predicates, as well as their strength:
Finally, it's also possible to use simple arithmetic operators: