Widget
The base class for all widgets.
GtkWidget is the base class all widgets in GTK derive from. 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:
vfunc@Gtk.Widget.get_request_mode
vfunc@Gtk.Widget.measure
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 vfunc@Gtk.Widget.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 its vfunc@Gtk.Widget.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 enum@Gtk.SizeRequestMode 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 id@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 id@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 method@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 GtkWidget 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 both GtkSizeRequestModes even if the widget in question only trades sizes in a single orientation.
For instance, a class@Gtk.Label that does height-for-width word wrapping will not expect to have vfunc@Gtk.Widget.measure with an orientation of %GTK_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 method@Gtk.Widget.measure inside your own vfunc@Gtk.Widget.size_allocate implementation. These return a request adjusted by class@Gtk.SizeGroup, 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 id@gtk_widget_measure; otherwise, you would not properly consider widget margins, class@Gtk.SizeGroup, 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 of %GTK_ALIGN_BASELINE, 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 the vfunc@Gtk.Widget.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 id@gtk_widget_get_allocated_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 class@Gtk.LayoutManager, GtkWidget supports a custom <layout> element, used to define layout properties:
<object class="GtkGrid" id="my_grid">
<child>
<object class="GtkLabel" id="label1">
<property name="label">Description</property>
<layout>
<property name="column">0</property>
<property name="row">0</property>
<property name="row-span">1</property>
<property name="column-span">1</property>
</layout>
</object>
</child>
<child>
<object class="GtkEntry" id="description_entry">
<layout>
<property name="column">1</property>
<property name="row">0</property>
<property name="row-span">1</property>
<property name="column-span">1</property>
</layout>
</object>
</child>
</object>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
GtkWidget exposes 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 method@Gtk.WidgetClass.set_template.
The interface description semantics expected in composite template descriptions is slightly different from regular class@Gtk.Builder XML.
Unlike regular interface descriptions, method@Gtk.WidgetClass.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 required for UI design tools like Glade 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.
An example of a template definition:
<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 method@Gtk.WidgetClass.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 method@Gtk.Widget.init_template from the instance initialization function:
static void
foo_widget_init (FooWidget *self)
{
// ...
gtk_widget_init_template (GTK_WIDGET (self));
}You can access widgets defined in the template using the id@gtk_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 call method@Gtk.WidgetClass.bind_template_child_full (or one of its wrapper macros func@Gtk.widget_class_bind_template_child and func@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_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_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)
{
}You can also use method@Gtk.WidgetClass.bind_template_callback_full (or is wrapper macro func@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);
}Skipped during bindings generation
method
create_pango_context: C function gtk_widget_create_pango_context is ignoredparameter
allocation: allocation: Out parameter is not supportedmethod
get_font_options: Return type cairo.FontOptions is unsupportedmethod
get_pango_context: C function gtk_widget_get_pango_context is ignoredparameter
width: width: Out parameter is not supportedparameter
minimum: minimum: Out parameter is not supportedparameter
options: cairo.FontOptionsparameter
allocation: Allocationmethod
snapshot_child: C function gtk_widget_snapshot_child is ignoredparameter
dest_x: dest_x: Out parameter is not supportedmethod
has-default: Property has no getter nor settermethod
has-focus: Property has no getter nor settermethod
height-request: Property has no getter nor settermethod
width-request: Property has no getter nor setter
Inheritors
Constructors
Properties
The accessible role of the given GtkAccessible implementation.
A list of css classes applied to this widget.
Whether the widget should grab focus when it is clicked with the mouse.
Enables or disables the emission of the ::query-tooltip signal on @widget.
Whether to use the hexpand property.
The GtkLayoutManager instance to use to compute the preferred size of the widget, and allocate its children.
Margin on bottom side of widget.
Margin on start of widget, horizontally.
Whether the widget will receive the default action when it is focused.
The scale factor of the widget.
Sets the text of tooltip to be the given string, which is marked up with Pango markup.
Sets the text of tooltip to be the given string.
Whether to use the vexpand property.
Functions
Enable or disable an action installed with gtk_widget_class_install_action().
Looks up the action in the action groups associated with
Activates the default.activate action from @widget.
Adds @controller to @widget so that it will receive events.
Adds a style class to @widget.
Adds a widget to the list of mnemonic labels for this widget.
Queues an animation frame update and adds a callback to be called before each frame.
Called by widgets as the user moves around the window using keyboard shortcuts.
Computes the bounds for @widget in the coordinate space of @target.
Computes whether a container should give this widget extra space when possible.
Translates the given @point in @widget's coordinates to coordinates relative to @target’s coordinate system.
Computes a matrix suitable to describe a transformation from
Signals that all holders of a reference to the widget should release the reference that they hold.
Emitted when the text direction of a widget changes.
Emitted when @widget is hidden.
Emitted if keyboard navigation fails.
Emitted when @widget is going to be mapped.
Emitted when a widget is activated via a mnemonic.
Emitted when the focus is moved.
Emitted when @widget is associated with a GdkSurface.
Emitted when @widget is shown.
Emitted when the widget state changes.
Emitted when @widget is going to be unmapped.
Emitted when the GdkSurface associated with @widget is destroyed.
Creates a new PangoLayout with the appropriate font map, font description, and base direction for drawing text for this widget.
Retrieves the GtkAccessibleRole for the given GtkAccessible.
Returns the baseline that has currently been allocated to @widget.
Returns the height that has currently been allocated to @widget.
Returns the width that has currently been allocated to @widget.
Gets the first ancestor of @widget with type @widget_type.
Gets the ID of the @buildable object.
Determines whether the input focus can enter @widget or any of its children.
Queries whether @widget can be the target of pointer events.
Gets the value set with gtk_widget_set_child_visible().
Gets the clipboard object for @widget.
Returns the list of style classes applied to @widget.
Returns the CSS name that is used for @self.
Gets the reading direction for a particular widget.
Get the GdkDisplay for the toplevel window associated with this widget.
Returns the widgets first child.
Determines whether @widget can own the input focus.
Returns the current focus child of @widget.
Returns whether the widget should grab focus when it is clicked with the mouse.
Gets the font map of @widget.
Obtains the frame clock for a widget.
Returns the current value of the has-tooltip property.
Gets whether the widget would like any available extra horizontal space.
Gets whether gtk_widget_set_hexpand() has been used to explicitly set the expand flag on this widget.
Returns the widgets last child.
Retrieves the layout manager used by @widget.
Gets the bottom margin of @widget.
Gets the end margin of @widget.
Gets the start margin of @widget.
Gets the top margin of @widget.
Returns the widgets next sibling.
#Fetches the requested opacity for this widget.
Returns the widgets overflow value.
Retrieves the minimum and natural size of a widget, taking into account the widget’s preference for height-for-width management.
Returns the widgets previous sibling.
Gets the primary clipboard of @widget.
Determines whether @widget is realized.
Determines whether @widget is always treated as the default widget within its toplevel when it has the focus, even if another widget is the default.
Gets whether the widget prefers a height-for-width layout or a width-for-height layout.
Retrieves the internal scale factor that maps from window coordinates to the actual device pixels.
Returns the widget’s sensitivity.
Gets the settings object holding the settings used for this widget.
Returns the content width or height of the widget.
Returns the widget state as a flag set.
Returns the style context associated to @widget.
Fetch an object build from the template XML for @widget_type in this @widget instance.
Gets the contents of the tooltip for @widget.
Gets the contents of the tooltip for @widget.
Gets whether the widget would like any available extra vertical space.
Gets whether gtk_widget_set_vexpand() has been used to explicitly set the expand flag on this widget.
Determines whether the widget is visible.
Returns whether @css_class is currently applied to @widget.
Determines whether @widget is the current default widget within its toplevel.
Determines if the widget should show a visible indication that it has the global input focus.
Returns whether the widget is currently being destroyed.
Creates and initializes child widgets defined in templates.
Inserts @group into @widget.
Inserts @widget into the child widget list of @parent.
Inserts @widget into the child widget list of @parent.
Determines whether @widget is somewhere inside @ancestor, possibly with intermediate containers.
Determines whether @widget can be drawn to.
Returns the widget’s effective sensitivity.
Emits the ::keynav-failed signal on the widget.
Returns the widgets for which this widget is the target of a mnemonic.
Emits the ::mnemonic-activate signal.
Returns a GListModel to track the children of @widget.
Returns a GListModel to track the class@Gtk.EventControllers of @widget.
Flags the widget for a rerun of the vfunc@Gtk.Widget.size_allocate function.
Flags a widget to have its size renegotiated.
Removes @controller from @widget, so that it doesn't process events anymore.
Removes a style from @widget.
Removes a widget from the list of mnemonic labels for this widget.
Removes a tick callback previously registered with gtk_widget_add_tick_callback().
Resets the accessible @property to its default value.
Resets the accessible @relation to its default value.
Resets the accessible @state to its default value.
Specifies whether the input focus can enter the widget or any of its children.
Sets whether @widget can be the target of pointer events.
Sets whether @widget should be mapped along with its parent.
Clear all style classes applied to @widget and replace them with @classes.
Sets a named cursor to be shown when pointer devices point towards @widget.
Sets the reading direction on a particular widget.
Specifies whether @widget can own the input focus.
Set @child as the current focus child of @widget.
Sets whether the widget should grab focus when it is clicked with the mouse.
Sets the font map to use for Pango rendering.
Sets the has-tooltip property on @widget to @has_tooltip.
Sets whether the widget would like any available extra horizontal space.
Sets whether the hexpand flag will be used.
Sets the layout manager delegate instance that provides an implementation for measuring and allocating the children of @widget.
Sets the bottom margin of @widget.
Sets the end margin of @widget.
Set all margins to the same value.
Set start and end margin to horizontal and top and bottom margin to vertical
Set margins.
Sets the start margin of @widget.
Sets the top margin of @widget.
Request the @widget to be rendered partially transparent.
Sets how @widget treats content that is drawn outside the widget's content area.
Specifies whether @widget will be treated as the default widget within its toplevel when it has the focus, even if another widget is the default.
Sets the sensitivity of a widget.
Sets the minimum size of a widget.
Turns on flag values in the current widget state.
Sets @markup as the contents of the tooltip, which is marked up with Pango markup.
Sets @text as the contents of the tooltip.
Sets whether the widget would like any available extra vertical space.
Sets whether the vexpand flag will be used.
Sets the visibility state of @widget.
Returns whether @widget should contribute to the measuring and allocation of its parent.
Triggers a tooltip query on the display where the toplevel of @widget is located.
Turns off flag values for the current widget state.