Gtk.Widget (original) (raw)

Class

GtkWidget

Description [src]

abstract class Gtk.Widget : GObject.InitiallyUnowned
  implements Gtk.Accessible, Gtk.Buildable, Gtk.ConstraintTarget {
  /* No available fields */
}

The base class for all widgets.

It manages the widget lifecycle, layout, states and style.

Height-for-width Geometry Management

GTK uses a height-for-width (and width-for-height) geometry management system. Height-for-width means that a widget can change how much vertical space it needs, depending on the amount of horizontal space that it is given (and similar for width-for-height). The most common example is a label that reflows to fill up the available width, wraps to fewer lines, and therefore needs less height.

Height-for-width geometry management is implemented in GTK by way of two virtual methods:

There are some important things to keep in mind when implementing height-for-width and when using it in widget implementations.

If you implement a direct GtkWidget subclass that supports height-for-width or width-for-height geometry management for itself or its child widgets, the Gtk.WidgetClass.get_request_mode virtual function must be implemented as well and return the widget’s preferred request mode. The default implementation of this virtual function returns GTK_SIZE_REQUEST_CONSTANT_SIZE, which means that the widget will only ever get -1 passed as the for_size value to itsGtk.WidgetClass.measure implementation.

The geometry management system will query a widget hierarchy in only one orientation at a time. When widgets are initially queried for their minimum sizes it is generally done in two initial passes in the GtkSizeRequestMode chosen by the toplevel.

For example, when queried in the normal GTK_SIZE_REQUEST_HEIGHT_FOR_WIDTH mode:

First, the default minimum and natural width for each widget in the interface will be computed using gtk_widget_measure() with an orientation of GTK_ORIENTATION_HORIZONTAL and a for_size of -1. Because the preferred widths for each widget depend on the preferred widths of their children, this information propagates up the hierarchy, and finally a minimum and natural width is determined for the entire toplevel. Next, the toplevel will use the minimum width to query for the minimum height contextual to that width using gtk_widget_measure() with an orientation of GTK_ORIENTATION_VERTICAL and a for_size of the just computed width. This will also be a highly recursive operation. The minimum height for the minimum width is normally used to set the minimum size constraint on the toplevel.

After the toplevel window has initially requested its size in both dimensions it can go on to allocate itself a reasonable size (or a size previously specified with gtk_window_set_default_size()). During the recursive allocation process it’s important to note that request cycles will be recursively executed while widgets allocate their children. Each widget, once allocated a size, will go on to first share the space in one orientation among its children and then request each child’s height for its target allocated width or its width for allocated height, depending. In this way a widget will typically be requested its size a number of times before actually being allocated a size. The size a widget is finally allocated can of course differ from the size it has requested. For this reason, GtkWidget caches a small number of results to avoid re-querying for the same sizes in one allocation cycle.

If a widget does move content around to intelligently use up the allocated size then it must support the request in bothGtkSizeRequestModes even if the widget in question only trades sizes in a single orientation.

For instance, a GtkLabel that does height-for-width word wrapping will not expect to have Gtk.WidgetClass.measure with an orientation ofGTK_ORIENTATION_VERTICAL called because that call is specific to a width-for-height request. In this case the label must return the height required for its own minimum possible width. By following this rule any widget that handles height-for-width or width-for-height requests will always be allocated at least enough space to fit its own content.

Here are some examples of how a GTK_SIZE_REQUEST_HEIGHT_FOR_WIDTH widget generally deals with width-for-height requests:

`static void foo_widget_measure (GtkWidget *widget, GtkOrientation orientation, int for_size, int *minimum_size, int *natural_size, int *minimum_baseline, int *natural_baseline) { if (orientation == GTK_ORIENTATION_HORIZONTAL) { // Calculate minimum and natural width } else // VERTICAL { if (i_am_in_height_for_width_mode) { int min_width, dummy;

      // First, get the minimum width of our widget
      GTK_WIDGET_GET_CLASS (widget)->measure (widget, GTK_ORIENTATION_HORIZONTAL, -1,
                                              &min_width, &dummy, &dummy, &dummy);

      // Now use the minimum width to retrieve the minimum and natural height to display
      // that width.
      GTK_WIDGET_GET_CLASS (widget)->measure (widget, GTK_ORIENTATION_VERTICAL, min_width,
                                              minimum_size, natural_size, &dummy, &dummy);
    }
  else
    {
      // ... some widgets do both.
    }
}

} `

Often a widget needs to get its own request during size request or allocation. For example, when computing height it may need to also compute width. Or when deciding how to use an allocation, the widget may need to know its natural size. In these cases, the widget should be careful to call its virtual methods directly, like in the code example above.

It will not work to use the wrapper function gtk_widget_measure()inside your own Gtk.WidgetClass.size_allocate implementation. These return a request adjusted by GtkSizeGroup, the widget’s align and expand flags, as well as its CSS style.

If a widget used the wrappers inside its virtual method implementations, then the adjustments (such as widget margins) would be applied twice. GTK therefore does not allow this and will warn if you try to do it.

Of course if you are getting the size request for another widget, such as a child widget, you must use gtk_widget_measure(); otherwise, you would not properly consider widget margins, GtkSizeGroup, and so forth.

GTK also supports baseline vertical alignment of widgets. This means that widgets are positioned such that the typographical baseline of widgets in the same row are aligned. This happens if a widget supports baselines, has a vertical alignment using baselines, and is inside a widget that supports baselines and has a natural “row” that it aligns to the baseline, or a baseline assigned to it by the grandparent.

Baseline alignment support for a widget is also done by theGtk.WidgetClass.measure virtual function. It allows you to report both a minimum and natural size.

If a widget ends up baseline aligned it will be allocated all the space in the parent as if it was GTK_ALIGN_FILL, but the selected baseline can be found via gtk_widget_get_baseline(). If the baseline has a value other than -1 you need to align the widget such that the baseline appears at the position.

GtkWidget as GtkBuildable

The GtkWidget implementation of the GtkBuildable interface supports various custom elements to specify additional aspects of widgets that are not directly expressed as properties.

If the widget uses a GtkLayoutManager, GtkWidget supports a custom <layout> element, used to define layout properties:

GtkWidget allows style information such as style classes to be associated with widgets, using the custom <style> element:

<object class="GtkButton" id="button1"> <style> <class name="my-special-button-class"/> <class name="dark-button"/> </style> </object>

GtkWidget allows defining accessibility information, such as properties, relations, and states, using the custom <accessibility> element:

<object class="GtkButton" id="button1"> <accessibility> <property name="label">Download</property> <relation name="labelled-by">label1</relation> </accessibility> </object>

Building composite widgets from template XML

GtkWidgetexposes some facilities to automate the procedure of creating composite widgets using “templates”.

To create composite widgets with GtkBuilder XML, one must associate the interface description with the widget class at class initialization time using gtk_widget_class_set_template().

The interface description semantics expected in composite template descriptions is slightly different from regular GtkBuilder XML.

Unlike regular interface descriptions, gtk_widget_class_set_template()will expect a <template> tag as a direct child of the toplevel<interface> tag. The <template> tag must specify the “class” attribute which must be the type name of the widget. Optionally, the “parent” attribute may be specified to specify the direct parent type of the widget type; this is ignored by GtkBuilder but can be used by UI design tools to introspect what kind of properties and internal children exist for a given type when the actual type does not exist.

The XML which is contained inside the <template> tag behaves as if it were added to the <object> tag defining the widget itself. You may set properties on a widget by inserting <property> tags into the <template> tag, and also add <child> tags to add children and extend a widget in the normal way you would with <object> tags.

Additionally, <object> tags can also be added before and after the initial<template> tag in the normal way, allowing one to define auxiliary objects which might be referenced by other widgets declared as children of the<template> tag.

Since, unlike the <object> tag, the <template> tag does not contain an “id” attribute, if you need to refer to the instance of the object itself that the template will create, simply refer to the template class name in an applicable element content.

Here is an example of a template definition, which includes an example of this in the <signal> tag:

<interface> <template class="FooWidget" parent="GtkBox"> <property name="orientation">horizontal</property> <property name="spacing">4</property> <child> <object class="GtkButton" id="hello_button"> <property name="label">Hello World</property> <signal name="clicked" handler="hello_button_clicked" object="FooWidget" swapped="yes"/> </object> </child> <child> <object class="GtkButton" id="goodbye_button"> <property name="label">Goodbye World</property> </object> </child> </template> </interface>

Typically, you’ll place the template fragment into a file that is bundled with your project, using GResource. In order to load the template, you need to call gtk_widget_class_set_template_from_resource()from the class initialization of your GtkWidget type:

`static void foo_widget_class_init (FooWidgetClass *klass) { // ...

gtk_widget_class_set_template_from_resource (GTK_WIDGET_CLASS (klass), "/com/example/ui/foowidget.ui"); } `

You will also need to call gtk_widget_init_template() from the instance initialization function:

`static void foo_widget_init (FooWidget *self) { gtk_widget_init_template (GTK_WIDGET (self));

// Initialize the rest of the widget... } `

as well as calling gtk_widget_dispose_template() from the dispose function:

`static void foo_widget_dispose (GObject *gobject) { FooWidget *self = FOO_WIDGET (gobject);

// Dispose objects for which you have a reference...

// Clear the template children for this widget type gtk_widget_dispose_template (GTK_WIDGET (self), FOO_TYPE_WIDGET);

G_OBJECT_CLASS (foo_widget_parent_class)->dispose (gobject); } `

You can access widgets defined in the template using thegtk_widget_get_template_child() function, but you will typically declare a pointer in the instance private data structure of your type using the same name as the widget in the template definition, and callgtk_widget_class_bind_template_child_full() (or one of its wrapper macrosgtk_widget_class_bind_template_child() and gtk_widget_class_bind_template_child_private()) with that name, e.g.

`typedef struct { GtkWidget *hello_button; GtkWidget *goodbye_button; } FooWidgetPrivate;

G_DEFINE_TYPE_WITH_PRIVATE (FooWidget, foo_widget, GTK_TYPE_BOX)

static void foo_widget_dispose (GObject *gobject) { gtk_widget_dispose_template (GTK_WIDGET (gobject), FOO_TYPE_WIDGET);

G_OBJECT_CLASS (foo_widget_parent_class)->dispose (gobject); }

static void foo_widget_class_init (FooWidgetClass *klass) { // ... G_OBJECT_CLASS (klass)->dispose = foo_widget_dispose;

gtk_widget_class_set_template_from_resource (GTK_WIDGET_CLASS (klass), "/com/example/ui/foowidget.ui"); gtk_widget_class_bind_template_child_private (GTK_WIDGET_CLASS (klass), FooWidget, hello_button); gtk_widget_class_bind_template_child_private (GTK_WIDGET_CLASS (klass), FooWidget, goodbye_button); }

static void foo_widget_init (FooWidget *widget) { gtk_widget_init_template (GTK_WIDGET (widget)); } `

You can also use gtk_widget_class_bind_template_callback_full() (or is wrapper macro gtk_widget_class_bind_template_callback()) to connect a signal callback defined in the template with a function visible in the scope of the class, e.g.

`// the signal handler has the instance and user data swapped // because of the swapped="yes" attribute in the template XML static void hello_button_clicked (FooWidget *self, GtkButton *button) { g_print ("Hello, world!\n"); }

static void foo_widget_class_init (FooWidgetClass *klass) { // ... gtk_widget_class_set_template_from_resource (GTK_WIDGET_CLASS (klass), "/com/example/ui/foowidget.ui"); gtk_widget_class_bind_template_callback (GTK_WIDGET_CLASS (klass), hello_button_clicked); } `

Descendants

Functions

Instance methods

gtk_widget_allocate

Assigns size, position, (optionally) a baseline and transform to a child widget.

gtk_widget_compute_point

Translates the given point in widget‘s coordinates to coordinates in target’s coordinate system.

gtk_widget_compute_transform

Computes a matrix suitable to describe a transformation fromwidget‘s coordinate system into target‘s coordinate system.

gtk_widget_get_preferred_size

Retrieves the minimum and natural size of a widget, taking into account the widget’s preference for height-for-width management.

gtk_widget_get_receives_default

Determines whether the widget is always treated as the default widget within its toplevel when it has the focus, even if another widget is the default.

gtk_widget_hide

Reverses the effects of [method.Gtk.Widget.show].

deprecated: 4.10

gtk_widget_measure

Measures widget in the orientation orientation and for the given for_size.

gtk_widget_set_receives_default

Sets whether the widget will be treated as the default widget within its toplevel when it has the focus, even if another widget is the default.

gtk_widget_size_allocate

Allocates widget with a transformation that translates the origin to the position in allocation.

gtk_widget_translate_coordinates

Translates coordinates relative to src_widget’s allocation to coordinates relative to dest_widget’s allocations.

deprecated: 4.12

Methods inherited from GObject (43)

Please see GObject for a full list of methods.

Properties

Gtk.Widget:layout-manager

The GtkLayoutManager instance to use to compute the preferred size of the widget, and allocate its children.

Gtk.Widget:root

The GtkRoot widget of the widget tree containing this widget.

Signals

Gtk.Widget::destroy

Signals that all holders of a reference to the widget should release the reference that they hold.

Signals inherited from GObject (1)

GObject::notify

The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.

Class structure

struct GtkWidgetClass {
  GInitiallyUnownedClass parent_class;
  void (* show) (
    GtkWidget* widget
  );
  void (* hide) (
    GtkWidget* widget
  );
  void (* map) (
    GtkWidget* widget
  );
  void (* unmap) (
    GtkWidget* widget
  );
  void (* realize) (
    GtkWidget* widget
  );
  void (* unrealize) (
    GtkWidget* widget
  );
  void (* root) (
    GtkWidget* widget
  );
  void (* unroot) (
    GtkWidget* widget
  );
  void (* size_allocate) (
    GtkWidget* widget,
    int width,
    int height,
    int baseline
  );
  void (* state_flags_changed) (
    GtkWidget* widget,
    GtkStateFlags previous_state_flags
  );
  void (* direction_changed) (
    GtkWidget* widget,
    GtkTextDirection previous_direction
  );
  GtkSizeRequestMode (* get_request_mode) (
    GtkWidget* widget
  );
  void (* measure) (
    GtkWidget* widget,
    GtkOrientation orientation,
    int for_size,
    int* minimum,
    int* natural,
    int* minimum_baseline,
    int* natural_baseline
  );
  gboolean (* mnemonic_activate) (
    GtkWidget* widget,
    gboolean group_cycling
  );
  gboolean (* grab_focus) (
    GtkWidget* widget
  );
  gboolean (* focus) (
    GtkWidget* widget,
    GtkDirectionType direction
  );
  void (* set_focus_child) (
    GtkWidget* widget,
    GtkWidget* child
  );
  void (* move_focus) (
    GtkWidget* widget,
    GtkDirectionType direction
  );
  gboolean (* keynav_failed) (
    GtkWidget* widget,
    GtkDirectionType direction
  );
  gboolean (* query_tooltip) (
    GtkWidget* widget,
    int x,
    int y,
    gboolean keyboard_tooltip,
    GtkTooltip* tooltip
  );
  void (* compute_expand) (
    GtkWidget* widget,
    gboolean* hexpand_p,
    gboolean* vexpand_p
  );
  void (* css_changed) (
    GtkWidget* widget,
    GtkCssStyleChange* change
  );
  void (* system_setting_changed) (
    GtkWidget* widget,
    GtkSystemSetting settings
  );
  void (* snapshot) (
    GtkWidget* widget,
    GtkSnapshot* snapshot
  );
  gboolean (* contains) (
    GtkWidget* widget,
    double x,
    double y
  );
  
}

No description available.

Class members

parent_class: GInitiallyUnownedClass

The object class structure needs to be the first element in the widget class structure in order for the class mechanism to work correctly. This allows a GtkWidgetClass pointer to be cast to a GObjectClass pointer.

show: void (* show) ( GtkWidget* widget )

Signal emitted when widget is shown.

hide: void (* hide) ( GtkWidget* widget )

Signal emitted when widget is hidden.

map: void (* map) ( GtkWidget* widget )

Signal emitted when widget is going to be mapped, that is when the widget is visible (which is controlled with gtk_widget_set_visible()) and all its parents up to the toplevel widget are also visible.

unmap: void (* unmap) ( GtkWidget* widget )

Signal emitted when widget is going to be unmapped, which means that either it or any of its parents up to the toplevel widget have been set as hidden.

realize: void (* realize) ( GtkWidget* widget )

Signal emitted when widget is associated with aGdkSurface, which means that gtk_widget_realize() has been called or the widget has been mapped (that is, it is going to be drawn).

unrealize: void (* unrealize) ( GtkWidget* widget )

Signal emitted when the GdkSurface associated with widget is destroyed, which means that gtk_widget_unrealize() has been called or the widget has been unmapped (that is, it is going to be hidden).

root: void (* root) ( GtkWidget* widget )

Called when the widget gets added to a GtkRoot widget. Must chain up.

unroot: void (* unroot) ( GtkWidget* widget )

Called when the widget is about to be removed from itsGtkRoot widget. Must chain up.

size_allocate: void (* size_allocate) ( GtkWidget* widget, int width, int height, int baseline )

Called to set the allocation, if the widget does not have a layout manager.

state_flags_changed: void (* state_flags_changed) ( GtkWidget* widget, GtkStateFlags previous_state_flags )

Signal emitted when the widget state changes, see gtk_widget_get_state_flags().

direction_changed: void (* direction_changed) ( GtkWidget* widget, GtkTextDirection previous_direction )

Signal emitted when the text direction of a widget changes.

get_request_mode: GtkSizeRequestMode (* get_request_mode) ( GtkWidget* widget )

Called to get the request mode, if the widget does not have a layout manager. This allows a widget to tell its parent container whether it prefers to be allocated in GTK_SIZE_REQUEST_HEIGHT_FOR_WIDTH orGTK_SIZE_REQUEST_WIDTH_FOR_HEIGHT mode.GTK_SIZE_REQUEST_HEIGHT_FOR_WIDTH means the widget prefers to haveGtkWidgetClass.measure() called first to get the default width (passing a for_size of -1), then again to get the height for said default width.GTK_SIZE_REQUEST_CONSTANT_SIZE disables any height-for-width or width-for-height geometry management for said widget and is the default return. It’s important to note that any widget which trades height-for-width or width-for-height must respond properly to a for_size value >= -1 passed to GtkWidgetClass.measure, for both possible orientations.

measure: void (* measure) ( GtkWidget* widget, GtkOrientation orientation, int for_size, int* minimum, int* natural, int* minimum_baseline, int* natural_baseline )

Called to obtain the minimum and natural size of the widget, if the widget does not have a layout manager. Depending on the orientation parameter, the passed for_size can be interpreted as width or height. A widget will never be allocated less than its minimum size.

mnemonic_activate: gboolean (* mnemonic_activate) ( GtkWidget* widget, gboolean group_cycling )

Activates the widget if group_cycling isFALSE, and just grabs the focus if group_cycling is TRUE.

grab_focus: gboolean (* grab_focus) ( GtkWidget* widget )

Causes widget to have the keyboard focus for theGtkWindow it’s inside.

focus: gboolean (* focus) ( GtkWidget* widget, GtkDirectionType direction )

Vfunc for gtk_widget_child_focus().

set_focus_child: void (* set_focus_child) ( GtkWidget* widget, GtkWidget* child )

Sets the focused child of a widget. Must chain up.

move_focus: void (* move_focus) ( GtkWidget* widget, GtkDirectionType direction )

Signal emitted when a change of focus is requested.

keynav_failed: gboolean (* keynav_failed) ( GtkWidget* widget, GtkDirectionType direction )

Signal emitted if keyboard navigation fails.

query_tooltip: gboolean (* query_tooltip) ( GtkWidget* widget, int x, int y, gboolean keyboard_tooltip, GtkTooltip* tooltip )

Signal emitted when “has-tooltip” is TRUE and the hover timeout has expired with the cursor hovering “above” widget; or emitted when widget got focus in keyboard mode.

compute_expand: void (* compute_expand) ( GtkWidget* widget, gboolean* hexpand_p, gboolean* vexpand_p )

Computes whether a container should give this widget extra space when possible.

css_changed: void (* css_changed) ( GtkWidget* widget, GtkCssStyleChange* change )

Vfunc called when the CSS used by widget was changed. Widgets should then discard their caches that depend on CSS and queue resizes or redraws accordingly. The default implementation will take care of this for all the default CSS properties, so implementations must chain up.

system_setting_changed: void (* system_setting_changed) ( GtkWidget* widget, GtkSystemSetting settings )

Emitted when a system setting was changed. Must chain up.

snapshot: void (* snapshot) ( GtkWidget* widget, GtkSnapshot* snapshot )

Vfunc called when a new snapshot of the widget has to be taken.

contains: gboolean (* contains) ( GtkWidget* widget, double x, double y )

Vfunc for gtk_widget_contains().

Virtual methods

Gtk.WidgetClass.css_changed

Signal emitted when “has-tooltip” is TRUE and the hover timeout has expired with the cursor hovering “above” widget; or emitted when widget got focus in keyboard mode.

Class methods

gtk_widget_class_add_binding

Creates a new shortcut for widget_class that calls the given callbackwith arguments according to format_string.

gtk_widget_class_bind_template_child_full

Assigns an object declared in the class template XML to be set to a location on a freshly built instance’s private data, or alternatively accessible via gtk_widget_get_template_child().