Struct BackendCaps 

#[non_exhaustive]
pub struct BackendCaps {
    pub reports_cancel: bool,
    pub reports_pressure: bool,
    pub reports_tilt: bool,
    pub reports_twist: bool,
    pub reports_pen_kind: bool,
    pub reports_palm: bool,
    pub reports_scroll_phase: bool,
    pub reports_os_momentum: bool,
    pub reports_os_pinch: bool,
    pub synthesises_mouse_from_touch: bool,
    pub touch_window_drag: bool,
    pub osk: SoftKeyboardSupport,
}

What a backend can actually report.

Every field is a platform fact established by reading the backend, not an aspiration. The per-OS matrix and its citations are in docs/touch-and-pen.md, “Platform capabilities”; the machine-readable version is BackendCaps::for_platform.

#[non_exhaustive]: construct one with for_platform and adjust, so a later capability cannot break a call site.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

reports_cancel: bool

The backend reports a cancel distinct from a lift. When false, a revoked contact arrives as an ordinary Ended (or as nothing at all) and the framework has to infer revocation from focus loss.

reports_pressure: bool

Contacts carry a tip pressure.

reports_tilt: bool

Stylus tilt is reported.

reports_twist: bool

Stylus barrel rotation is reported.

reports_pen_kind: bool

The backend distinguishes a pen tip from an eraser.

reports_palm: bool

The backend flags a contact the digitizer classified as a palm.

reports_scroll_phase: bool

Scroll samples carry a begin/change/end structure rather than being bare notches.

reports_os_momentum: bool

The OS produces the momentum (inertial) part of a scroll itself, so the framework must not add a fling of its own on top.

reports_os_pinch: bool

The OS recognises pinch/rotate on the trackpad and hands over the result.

synthesises_mouse_from_touch: bool

The OS also synthesises a mouse stream from touch, so the translator must suppress one of the two.

touch_window_drag: bool

A finger can start an OS window move/resize.

osk: SoftKeyboardSupport

How the on-screen keyboard can be reached.

Implementations

impl BackendCaps

pub const fn for_platform( platform: PlatformKind, window_system: WindowSystem, ) -> Self

The capability row for one platform, and — on Unix — one window system.

window_system is ignored off Unix: WindowSystem only ever resolves to Wayland or X11 from a live Linux/BSD display handle, and WindowSystem::Unknown is precisely the set {Windows, macOS, headless}. That is what makes Unknown a safe default for the mouse-promotion suppressors — none of those three platforms promote.

Every value here is cited in docs/touch-and-pen.md.

Trait Implementations

impl Clone for BackendCaps

fn clone(&self) -> BackendCaps

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for BackendCaps

impl Debug for BackendCaps

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for BackendCaps

fn default() -> BackendCaps

Returns the “default value” for a type.

impl Eq for BackendCaps

impl Hash for BackendCaps

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for BackendCaps

fn eq(&self, other: &BackendCaps) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for BackendCaps