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use crate::{paragraph::TextStyle, prelude::*, FontMetrics};
use skia_bindings::{self as sb, skia_textlayout_LineMetrics, skia_textlayout_StyleMetrics};
use std::{marker::PhantomData, ops::Range, ptr};
#[repr(C)]
#[derive(Clone, Debug)]
pub struct StyleMetrics<'a> {
pub text_style: &'a TextStyle,
/// [`FontMetrics`] contains the following metrics:
///
/// * Top distance to reserve above baseline
/// * Ascent distance to reserve below baseline
/// * Descent extent below baseline
/// * Bottom extent below baseline
/// * Leading distance to add between lines
/// * AvgCharWidth average character width
/// * MaxCharWidth maximum character width
/// * XMin minimum x
/// * XMax maximum x
/// * XHeight height of lower-case 'x'
/// * CapHeight height of an upper-case letter
/// * UnderlineThickness underline thickness
/// * UnderlinePosition underline position relative to baseline
/// * StrikeoutThickness strikeout thickness
/// * StrikeoutPosition strikeout position relative to baseline
pub font_metrics: FontMetrics,
}
native_transmutable!(skia_textlayout_StyleMetrics, StyleMetrics<'_>);
impl<'a> StyleMetrics<'a> {
pub fn new(style: &'a TextStyle, metrics: impl Into<Option<FontMetrics>>) -> Self {
Self {
text_style: style,
font_metrics: metrics.into().unwrap_or_default(),
}
}
}
#[derive(Clone, Debug)]
pub struct LineMetrics<'a> {
// The following fields are used in the layout process itself.
/// The index in the text buffer the line begins.
pub start_index: usize,
/// The index in the text buffer the line ends.
pub end_index: usize,
pub end_excluding_whitespaces: usize,
pub end_including_newline: usize,
pub hard_break: bool,
// The following fields are tracked after or during layout to provide to
// the user as well as for computing bounding boxes.
/// The final computed ascent and descent for the line. This can be impacted by
/// the strut, height, scaling, as well as outlying runs that are very tall.
///
/// The top edge is `baseline - ascent` and the bottom edge is `baseline +
/// descent`. Ascent and descent are provided as positive numbers. Raw numbers
/// for specific runs of text can be obtained in run_metrics_map. These values
/// are the cumulative metrics for the entire line.
pub ascent: f64,
pub descent: f64,
pub unscaled_ascent: f64,
/// Total height of the paragraph including the current line.
///
/// The height of the current line is `round(ascent + descent)`.
pub height: f64,
/// Width of the line.
pub width: f64,
/// The left edge of the line. The right edge can be obtained with `left +
/// width`
pub left: f64,
/// The y position of the baseline for this line from the top of the paragraph.
pub baseline: f64,
/// Zero indexed line number
pub line_number: usize,
/// Mapping between text index ranges and the FontMetrics associated with
/// them. The first run will be keyed under start_index. The metrics here
/// are before layout and are the base values we calculate from.
style_metrics: Vec<sb::IndexedStyleMetrics>,
pd: PhantomData<&'a StyleMetrics<'a>>,
}
impl<'a> LineMetrics<'a> {
// TODO: may support constructors (but what about the lifetime bounds?).
/// Returns the number of style metrics in the given index range.
pub fn get_style_metrics_count(&self, range: Range<usize>) -> usize {
let lower = self
.style_metrics
.partition_point(|ism| ism.index < range.start);
let upper = self
.style_metrics
.partition_point(|ism| ism.index < range.end);
upper - lower
}
/// Returns indices and references to style metrics in the given range.
pub fn get_style_metrics(&'a self, range: Range<usize>) -> Vec<(usize, &'a StyleMetrics<'a>)> {
let lower = self
.style_metrics
.partition_point(|ism| ism.index < range.start);
let upper = self
.style_metrics
.partition_point(|ism| ism.index < range.end);
self.style_metrics[lower..upper]
.iter()
.map(|ism| (ism.index, StyleMetrics::from_native_ref(&ism.metrics)))
.collect()
}
// We can't use a `std::map` in rust, it does not seem to be safe to move. So we copy it into a
// sorted Vec.
pub(crate) fn from_native_ref<'b>(lm: &skia_textlayout_LineMetrics) -> LineMetrics<'b> {
let sm_count = unsafe { sb::C_LineMetrics_styleMetricsCount(lm) };
let mut style_metrics = vec![
sb::IndexedStyleMetrics {
index: 0,
metrics: sb::skia_textlayout_StyleMetrics {
text_style: ptr::null(),
font_metrics: sb::SkFontMetrics {
fFlags: 0,
fTop: 0.0,
fAscent: 0.0,
fDescent: 0.0,
fBottom: 0.0,
fLeading: 0.0,
fAvgCharWidth: 0.0,
fMaxCharWidth: 0.0,
fXMin: 0.0,
fXMax: 0.0,
fXHeight: 0.0,
fCapHeight: 0.0,
fUnderlineThickness: 0.0,
fUnderlinePosition: 0.0,
fStrikeoutThickness: 0.0,
fStrikeoutPosition: 0.0
}
}
};
sm_count
];
unsafe { sb::C_LineMetrics_getAllStyleMetrics(lm, style_metrics.as_mut_ptr()) }
LineMetrics {
start_index: lm.fStartIndex,
end_index: lm.fEndIndex,
end_excluding_whitespaces: lm.fEndExcludingWhitespaces,
end_including_newline: lm.fEndIncludingNewline,
hard_break: lm.fHardBreak,
ascent: lm.fAscent,
descent: lm.fDescent,
unscaled_ascent: lm.fUnscaledAscent,
height: lm.fHeight,
width: lm.fWidth,
left: lm.fLeft,
baseline: lm.fBaseline,
line_number: lm.fLineNumber,
style_metrics,
pd: PhantomData,
}
}
}