Struct atk::Value

source · []
#[repr(transparent)]
pub struct Value { /* private fields */ }
Expand description

The ATK interface implemented by valuators and components which display or select a value from a bounded range of values.

Value should be implemented for components which either display a value from a bounded range, or which allow the user to specify a value from a bounded range, or both. For instance, most sliders and range controls, as well as dials, should have Object representations which implement Value on the component’s behalf. AtKValues may be read-only, in which case attempts to alter the value return would fail.

``On the subject of current value text`` `` In addition to providing the current value, implementors can optionally provide an end-user-consumable textual description associated with this value. This description should be included when the numeric value fails to convey the full, on-screen representation seen by users. ``

<example> <title>Password strength</title> A password strength meter whose value changes as the user types their new password. Red is used for values less than 4.0, yellow for values between 4.0 and 7.0, and green for values greater than 7.0. In this instance, value text should be provided by the implementor. Appropriate value text would be “weak”, “acceptable,” and “strong” respectively. </example>

A level bar whose value changes to reflect the battery charge. The color remains the same regardless of the charge and there is no on-screen text reflecting the fullness of the battery. In this case, because the position within the bar is the only indication the user has of the current charge, value text should not be provided by the implementor.

``Implementor Notes`` `` Implementors should bear in mind that assistive technologies will likely prefer the value text provided over the numeric value when presenting a widget's value. As a result, strings not intended for end users should not be exposed in the value text, and strings which are exposed should be localized. In the case of widgets which display value text on screen, for instance through a separate label in close proximity to the value-displaying widget, it is still expected that implementors will expose the value text using the above API. ``

<para> Value should NOT be implemented for widgets whose displayed value is not reflective of a meaningful amount. For instance, a progress pulse indicator whose value alternates between 0.0 and 1.0 to indicate that some process is still taking place should not implement Value because the current value does not reflect progress towards completion. </para> </refsect2> </refsect1>

``On the subject of ranges`` `` In addition to providing the minimum and maximum values, implementors can optionally provide details about subranges associated with the widget. These details should be provided by the implementor when both of the following are communicated visually to the end user: `` `` ``The existence of distinct ranges such as "weak", "acceptable", and "strong" indicated by color, bar tick marks, and/or on-screen text.`` ``Where the current value stands within a given subrange, for instance illustrating progression from very "weak" towards nearly "acceptable" through changes in shade and/or position on the bar within the "weak" subrange.`` `` `` If both of the above do not apply to the widget, it should be sufficient to expose the numeric value, along with the value text if appropriate, to make the widget accessible. `` ``Implementor Notes`` `` If providing subrange details is deemed necessary, all possible values of the widget are expected to fall within one of the subranges defined by the implementor. `` `` `` ``On the subject of localization of end-user-consumable text values`` `` Because value text and subrange descriptors are human-consumable, implementors are expected to provide localized strings which can be directly presented to end users via their assistive technology. In order to simplify this for implementors, implementors can use [`ValueType::localized_name()`][crate::ValueType::localized_name()] with the following already-localized constants for commonly-needed values can be used: ``

<itemizedlist> <listitem>ATK_VALUE_VERY_WEAK</listitem> <listitem>ATK_VALUE_WEAK</listitem> <listitem>ATK_VALUE_ACCEPTABLE</listitem> <listitem>ATK_VALUE_STRONG</listitem> <listitem>ATK_VALUE_VERY_STRONG</listitem> <listitem>ATK_VALUE_VERY_LOW</listitem> <listitem>ATK_VALUE_LOW</listitem> <listitem>ATK_VALUE_MEDIUM</listitem> <listitem>ATK_VALUE_HIGH</listitem> <listitem>ATK_VALUE_VERY_HIGH</listitem> <listitem>ATK_VALUE_VERY_BAD</listitem> <listitem>ATK_VALUE_BAD</listitem> <listitem>ATK_VALUE_GOOD</listitem> <listitem>ATK_VALUE_VERY_GOOD</listitem> <listitem>ATK_VALUE_BEST</listitem> <listitem>ATK_VALUE_SUBSUBOPTIMAL</listitem> <listitem>ATK_VALUE_SUBOPTIMAL</listitem> <listitem>ATK_VALUE_OPTIMAL</listitem> </itemizedlist> <para> Proposals for additional constants, along with their use cases, should be submitted to the GNOME Accessibility Team. </para> </refsect1>

``On the subject of changes`` `` Note that if there is a textual description associated with the new numeric value, that description should be included regardless of whether or not it has also changed. `` ``

Implements

ValueExt

Implementations

Trait Implementations

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Formats the value using the given formatter. Read more
Feeds this value into the given Hasher. Read more
Feeds a slice of this type into the given Hasher. Read more
This method returns an Ordering between self and other. Read more
Compares and returns the maximum of two values. Read more
Compares and returns the minimum of two values. Read more
Restrict a value to a certain interval. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
This method returns an ordering between self and other values if one exists. Read more
This method tests less than (for self and other) and is used by the < operator. Read more
This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
This method tests greater than (for self and other) and is used by the > operator. Read more
This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
Returns the type identifier of Self.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
Upcasts an object to a superclass or interface T. Read more
Upcasts an object to a reference of its superclass or interface T. Read more
Tries to downcast to a subclass or interface implementor T. Read more
Tries to downcast to a reference of its subclass or interface implementor T. Read more
Tries to cast to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more
Tries to cast to reference to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more
Casts to T unconditionally. Read more
Casts to &T unconditionally. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

Returns true if the object is an instance of (can be cast to) T.
Returns the type of the object.
Returns the ObjectClass of the object. Read more
Returns the class of the object.
Returns the class of the object in the given type T. Read more
Returns the interface T of the object. Read more
Sets the property property_name of the object to value value. Read more
Sets the property property_name of the object to value value. Read more
Sets multiple properties of the object at once. Read more
Sets multiple properties of the object at once. Read more
Gets the property property_name of the object and cast it to the type V. Read more
Gets the property property_name of the object. Read more
Check if the object has a property property_name of the given type_. Read more
Get the type of the property property_name of this object. Read more
Get the ParamSpec of the property property_name of this object.
Return all ParamSpec of the properties of this object.
Freeze all property notifications until the return guard object is dropped. Read more
Set arbitrary data on this object with the given key. Read more
Return previously set arbitrary data of this object with the given key. Read more
Retrieve previously set arbitrary data of this object with the given key. Read more
Set arbitrary data on this object with the given key. Read more
Return previously set arbitrary data of this object with the given key. Read more
Retrieve previously set arbitrary data of this object with the given key. Read more
Block a given signal handler. Read more
Unblock a given signal handler.
Stop emission of the currently emitted signal.
Stop emission of the currently emitted signal by the (possibly detailed) signal name.
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect a closure to the signal signal_name on this object. Read more
Connect a closure to the signal signal_id on this object. Read more
Limits the lifetime of closure to the lifetime of the object. When the object’s reference count drops to zero, the closure will be invalidated. An invalidated closure will ignore any calls to invoke_with_values, or invoke when using Rust closures. Read more
Emit signal by signal id. Read more
Same as Self::emit but takes Value for the arguments.
Emit signal by its name. Read more
Emit signal by its name. Read more
Emit signal by its name with details. Read more
Emit signal by its name with details. Read more
Emit signal by signal id with details. Read more
Emit signal by signal id with details. Read more
Disconnect a previously connected signal handler.
Connect to the notify signal of the object. Read more
Connect to the notify signal of the object. Read more
Connect to the notify signal of the object. Read more
Notify that the given property has changed its value. Read more
Notify that the given property has changed its value. Read more
Downgrade this object to a weak reference.
Add a callback to be notified when the Object is disposed.
Add a callback to be notified when the Object is disposed. Read more
Bind property source_property on this object to the target_property on the target object. Read more
Returns the strong reference count of this object.
Ensures that the type has been registered with the type system.
The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
Converts the given value to a String. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.