Struct TextAnchor 

pub struct TextAnchor {
    pub h: TextAlign,
    pub v: TextVAlign,
}

How canvas text hangs on its at point: one placement per axis (docs/canvas.md “Text”).

Two axes rather than a list of named positions, because that is the shape of the problem and of every native API underneath: NSAttributedString drawing, Pango extents, QFontMetricsF, Paint.Align, Canvas2D’s textAlign/textBaseline. The alignment is done by the backend, which is both cheaper and more accurate than doing it in app code: it already has the laid-out metrics, where an app has to ask for them through Toolkit::measure_text first.

TextAnchor::LEADING and TextAnchor::CENTERED name the two placements that used to be this type’s only variants.

Fields

h: TextAlign

The horizontal placement: the same three-way leading/center/trailing a wrapped label’s lines take (props::TextAlign), because it is the same question with the same RTL rule. Trailing is what an axis label right-aligned against its axis wants, and the reason the horizontal axis is settable at all: emulating it in app code costs a Toolkit::measure_text call per label, where the backend already holds the width it is about to draw with.

v: TextVAlign

Implementations

impl TextAnchor

pub const LEADING: TextAnchor

The top-leading corner of the line box, the default.

pub const CENTERED: TextAnchor

The center of the line box, both ways.

pub const TRAILING: TextAnchor

The top-trailing corner of the line box.

pub fn offset(self, width: f64, height: f64, ascent: f64) -> (f64, f64)

Where the text’s top-leading corner goes, as an offset from at, given the line box this text measures to. The single definition of what an anchor means: every backend that draws in Rust calls this, and the C++/Java/JS shims repeat exactly this arithmetic.

height is the line box (ascent + descent) and ascent the baseline’s offset from its top, the two numbers TextMetrics carries.

pub fn pack(self) -> f64

The anchor as one number, for the numeric op stream the serializing backends share: h * 4 + v, so it still occupies the single slot the two-variant enum did.

pub fn unpack(code: f64) -> TextAnchor

Inverse of TextAnchor::pack. An unrecognized code answers the default rather than failing: a stream is only ever written by a matching encoder, and a drawing with text in the wrong corner beats one that panics inside a native draw callback.

Trait Implementations

impl Clone for TextAnchor

fn clone(&self) -> TextAnchor

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for TextAnchor

impl Debug for TextAnchor

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

Formats the value using the given formatter.

impl Default for TextAnchor

fn default() -> TextAnchor

Returns the “default value” for a type.

impl Eq for TextAnchor

impl PartialEq for TextAnchor

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for TextAnchor