Struct LayoutFontMetrics 

pub struct LayoutFontMetrics {
    pub ascent: f32,
    pub descent: f32,
    pub line_gap: f32,
    pub units_per_em: u16,
    pub x_height: Option<f32>,
    pub cap_height: Option<f32>,
}

Layout-specific font metrics extracted from FontMetrics Contains only the metrics needed for text layout and rendering

Fields

ascent: f32

descent: f32

line_gap: f32

units_per_em: u16

x_height: Option<f32>

OS/2 sxHeight: distance from baseline to top of lowercase ‘x’ (in font units). Used for vertical-align: middle per CSS Inline 3 §4.1.

cap_height: Option<f32>

OS/2 sCapHeight: height of capital letters from baseline (in font units). Used for drop cap / initial-letter alignment per CSS Inline 3 §7.1.1.

Implementations

impl LayoutFontMetrics

pub fn baseline_scaled(&self, font_size: f32) -> f32

pub fn x_height_scaled(&self, font_size: f32) -> f32

Returns the x-height scaled to the given font size in px. Falls back to 0.5em when the font doesn’t provide sxHeight.

pub fn cap_height_scaled(&self, font_size: f32) -> f32

Returns the cap height scaled to the given font size in px. Falls back to ascent when the font doesn’t provide sCapHeight.

pub fn from_font_metrics(metrics: &FontMetrics) -> Self

Convert from full FontMetrics to layout-specific metrics.

Per CSS 2.2 §10.8.1: prefer OS/2 sTypoAscender/sTypoDescender, fall back to HHEA Ascent/Descent if OS/2 metrics are absent.

pub fn em_over(&self) -> f32

Synthesize em-over baseline offset (in font units). Per CSS Inline 3 Appendix A.1: em-over = central baseline + 0.5em. Central baseline is synthesized as midpoint of ascent and descent.

pub fn em_under(&self) -> f32

Synthesize em-under baseline offset (in font units). Per CSS Inline 3 Appendix A.1: em-under = central baseline - 0.5em.

pub fn central_baseline(&self) -> f32

Synthesize central baseline (in font units). Midpoint between ascent and descent when not provided by the font.

Trait Implementations

impl Clone for LayoutFontMetrics

fn clone(&self) -> LayoutFontMetrics

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for LayoutFontMetrics

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

Formats the value using the given formatter.