Struct AlphaMask 

pub struct AlphaMask { /* private fields */ }

The alpha mask of an element: a CompositionSurfaceBrush that shows the alpha of what the element draws, for a DropShadow.Mask and other composition effects.

The element embeds one and forwards to it: get from its get_alpha_mask, update_if_available at the end of its render (WinUI’s NotifyRenderContent).

As in WinUI the brush is created on the first request and stays the same object for the life of the element; its surface is an image of the element’s own drawing at the scale of its transform to the window and of the scaling of the window (WinUI’s realization scale), with the colour dropped (black with the alpha, as an alpha-only texture is sampled). The image is drawn again each time the element draws its content again, so it follows the text, the geometry, the source and the size; while the element has no size, is not visible or is not in a tree, the brush has no surface and paints nothing. Its Stretch is Fill, so a visual of the size of the element shows the mask over itself.

Implementations

impl AlphaMask

pub fn new() -> Self

pub fn get(&self, element: &Visual) -> Option<Rc<CompositionBrush>>

GetAlphaMask: the brush of the mask of element, created on the first call and drawn at once when the element can be drawn (WinUI’s AlphaMask::Ensure). None when no compositor is available for the element.

pub fn is_present(&self) -> bool

Whether the brush was created.

pub fn is_connected(&self) -> bool

Whether the brush shows an image of the element.

pub fn update_if_available(&self, element: &Visual)

Draws the mask of element again when the brush was created (WinUI’s AlphaMask::UpdateIfAvailable, called by the render walk for an element whose content is drawn again): an element with a size, in a tree and visible gets a new image; otherwise the brush loses its surface.

pub fn hide(&self)

Takes the surface from the brush (WinUI’s AlphaMask::Hide): the element is not drawn, so its mask is empty.

Trait Implementations

impl Default for AlphaMask

fn default() -> Self

Returns the “default value” for a type.

impl Drop for AlphaMask

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.