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5356fdcf89
* Run `cargo clippy --fix` * `BackendSelector` is easier to instantiate with auto `Default`
701 lines
25 KiB
Rust
701 lines
25 KiB
Rust
// Copyright © SixtyFPS GmbH <info@slint.dev>
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// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
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//! module for basic text layout
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//!
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//! The basic algorithm for breaking text into multiple lines:
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//! 1. First we determine the boundaries for text shaping. As shaping happens based on a single font and we know that different fonts cater different
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//! writing systems, we split up the text into chunks that maximize our chances of finding a font that covers all glyphs in the chunk. This way for
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//! example arabic text can be covered by a font that has excellent arabic coverage while latin text is rendered using a different font.
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//! Shaping boundaries are always also grapheme boundaries.
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//! 2. Then we shape the text at shaping boundaries, to determine the metrics of glyphs and glyph clusters
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//! 3. Loop over all glyph clusters as well as the line break opportunities produced by the unicode line break algorithm:
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//! Sum up the width of all glyph clusters until the next line break opportunity (encapsulated in FragmentIterator), record separately the width of
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//! trailing space within the fragment.
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//! If the width of the current line (including trailing whitespace) and the new fragment of glyph clusters (without trailing whitespace) is less or
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//! equal to the available width:
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//! Add fragment of glyph clusters to the current line
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//! Else:
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//! Emit current line as new line
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//! If encountering a mandatory line break opportunity:
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//! Emit current line as new line
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//!
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use alloc::vec::Vec;
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use euclid::num::{One, Zero};
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use crate::items::{TextHorizontalAlignment, TextOverflow, TextVerticalAlignment, TextWrap};
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#[cfg(feature = "unicode-linebreak")]
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mod linebreak_unicode;
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#[cfg(feature = "unicode-linebreak")]
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use linebreak_unicode::{BreakOpportunity, LineBreakIterator};
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#[cfg(not(feature = "unicode-linebreak"))]
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mod linebreak_simple;
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#[cfg(not(feature = "unicode-linebreak"))]
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use linebreak_simple::{BreakOpportunity, LineBreakIterator};
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mod fragments;
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mod glyphclusters;
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mod shaping;
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use shaping::ShapeBuffer;
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pub use shaping::{AbstractFont, FontMetrics, Glyph, TextShaper};
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mod linebreaker;
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pub use linebreaker::TextLine;
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pub use linebreaker::TextLineBreaker;
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pub struct TextLayout<'a, Font: AbstractFont> {
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pub font: &'a Font,
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pub letter_spacing: Option<<Font as TextShaper>::Length>,
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}
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impl<Font: AbstractFont> TextLayout<'_, Font> {
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// Measures the size of the given text when rendered with the specified font and optionally constrained
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// by the provided `max_width`.
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// Returns a tuple of the width of the longest line as well as height of all lines.
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pub fn text_size(
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&self,
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text: &str,
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max_width: Option<Font::Length>,
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text_wrap: TextWrap,
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) -> (Font::Length, Font::Length)
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where
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Font::Length: core::fmt::Debug,
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{
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let mut max_line_width = Font::Length::zero();
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let mut line_count: i16 = 0;
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let shape_buffer = ShapeBuffer::new(self, text);
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for line in TextLineBreaker::<Font>::new(text, &shape_buffer, max_width, None, text_wrap) {
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max_line_width = euclid::approxord::max(max_line_width, line.text_width);
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line_count += 1;
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}
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(max_line_width, self.font.height() * line_count.into())
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}
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}
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pub struct PositionedGlyph<Length> {
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pub x: Length,
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pub y: Length,
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pub advance: Length,
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pub glyph_id: core::num::NonZeroU16,
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pub text_byte_offset: usize,
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}
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pub struct TextParagraphLayout<'a, Font: AbstractFont> {
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pub string: &'a str,
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pub layout: TextLayout<'a, Font>,
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pub max_width: Font::Length,
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pub max_height: Font::Length,
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pub horizontal_alignment: TextHorizontalAlignment,
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pub vertical_alignment: TextVerticalAlignment,
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pub wrap: TextWrap,
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pub overflow: TextOverflow,
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pub single_line: bool,
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}
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impl<Font: AbstractFont> TextParagraphLayout<'_, Font> {
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/// Layout the given string in lines, and call the `layout_line` callback with the line to draw at position y.
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/// The signature of the `layout_line` function is: `(glyph_iterator, line_x, line_y, text_line, selection)`.
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/// Returns the baseline y coordinate as Ok, or the break value if `line_callback` returns `core::ops::ControlFlow::Break`.
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pub fn layout_lines<R>(
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&self,
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mut line_callback: impl FnMut(
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&mut dyn Iterator<Item = PositionedGlyph<Font::Length>>,
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Font::Length,
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Font::Length,
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&TextLine<Font::Length>,
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Option<core::ops::Range<Font::Length>>,
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) -> core::ops::ControlFlow<R>,
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selection: Option<core::ops::Range<usize>>,
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) -> Result<Font::Length, R> {
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let wrap = self.wrap != TextWrap::NoWrap;
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let elide = self.overflow == TextOverflow::Elide;
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let elide_glyph = if elide {
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self.layout.font.glyph_for_char('…').filter(|glyph| glyph.glyph_id.is_some())
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} else {
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None
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};
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let elide_width = elide_glyph.as_ref().map_or(Font::Length::zero(), |g| g.advance);
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let max_width_without_elision = self.max_width - elide_width;
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let shape_buffer = ShapeBuffer::new(&self.layout, self.string);
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let new_line_break_iter = || {
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TextLineBreaker::<Font>::new(
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self.string,
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&shape_buffer,
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if wrap { Some(self.max_width) } else { None },
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if elide { Some(self.layout.font.max_lines(self.max_height)) } else { None },
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self.wrap,
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)
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};
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let mut text_lines = None;
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let mut text_height = || {
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if self.single_line {
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self.layout.font.height()
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} else {
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text_lines = Some(new_line_break_iter().collect::<Vec<_>>());
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self.layout.font.height() * (text_lines.as_ref().unwrap().len() as i16).into()
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}
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};
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let two = Font::LengthPrimitive::one() + Font::LengthPrimitive::one();
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let baseline_y = match self.vertical_alignment {
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TextVerticalAlignment::Top => Font::Length::zero(),
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TextVerticalAlignment::Center => self.max_height / two - text_height() / two,
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TextVerticalAlignment::Bottom => self.max_height - text_height(),
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};
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let mut y = baseline_y;
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let mut process_line = |line: &TextLine<Font::Length>, glyphs: &[Glyph<Font::Length>]| {
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let elide_long_line =
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elide && (self.single_line || !wrap) && line.text_width > self.max_width;
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let elide_last_line = elide
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&& line.glyph_range.end < glyphs.len()
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&& y + self.layout.font.height() * two > self.max_height;
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let text_width = || {
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if elide_long_line || elide_last_line {
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let mut text_width = Font::Length::zero();
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for glyph in &glyphs[line.glyph_range.clone()] {
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if text_width + glyph.advance > max_width_without_elision {
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break;
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}
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text_width += glyph.advance;
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}
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return text_width + elide_width;
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}
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euclid::approxord::min(self.max_width, line.text_width)
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};
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let x = match self.horizontal_alignment {
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TextHorizontalAlignment::Left => Font::Length::zero(),
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TextHorizontalAlignment::Center => self.max_width / two - text_width() / two,
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TextHorizontalAlignment::Right => self.max_width - text_width(),
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};
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let mut elide_glyph = elide_glyph.as_ref();
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let selection = selection
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.as_ref()
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.filter(|selection| {
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line.byte_range.start < selection.end && selection.start < line.byte_range.end
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})
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.map(|selection| {
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let mut begin = Font::Length::zero();
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let mut end = Font::Length::zero();
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for glyph in glyphs[line.glyph_range.clone()].iter() {
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if glyph.text_byte_offset < selection.start {
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begin += glyph.advance;
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}
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if glyph.text_byte_offset >= selection.end {
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break;
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}
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end += glyph.advance;
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}
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begin..end
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});
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let glyph_it = glyphs[line.glyph_range.clone()].iter();
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let mut glyph_x = Font::Length::zero();
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let mut positioned_glyph_it = glyph_it.enumerate().filter_map(|(index, glyph)| {
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// TODO: cut off at grapheme boundaries
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if glyph_x > self.max_width {
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return None;
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}
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let elide_long_line = (elide_long_line || elide_last_line)
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&& x + glyph_x + glyph.advance > max_width_without_elision;
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let elide_last_line =
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elide_last_line && line.glyph_range.start + index == line.glyph_range.end - 1;
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if elide_long_line || elide_last_line {
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if let Some(elide_glyph) = elide_glyph.take() {
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let x = glyph_x;
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glyph_x += elide_glyph.advance;
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return Some(PositionedGlyph {
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x,
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y: Font::Length::zero(),
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advance: elide_glyph.advance,
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glyph_id: elide_glyph.glyph_id.unwrap(), // checked earlier when initializing elide_glyph
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text_byte_offset: glyph.text_byte_offset,
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});
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} else {
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return None;
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}
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}
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let x = glyph_x;
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glyph_x += glyph.advance;
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glyph.glyph_id.map(|existing_glyph_id| PositionedGlyph {
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x,
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y: Font::Length::zero(),
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advance: glyph.advance,
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glyph_id: existing_glyph_id,
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text_byte_offset: glyph.text_byte_offset,
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})
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});
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if let core::ops::ControlFlow::Break(break_val) =
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line_callback(&mut positioned_glyph_it, x, y, line, selection)
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{
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return core::ops::ControlFlow::Break(break_val);
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}
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y += self.layout.font.height();
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core::ops::ControlFlow::Continue(())
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};
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if let Some(lines_vec) = text_lines.take() {
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for line in lines_vec {
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if let core::ops::ControlFlow::Break(break_val) =
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process_line(&line, &shape_buffer.glyphs)
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{
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return Err(break_val);
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}
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}
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} else {
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for line in new_line_break_iter() {
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if let core::ops::ControlFlow::Break(break_val) =
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process_line(&line, &shape_buffer.glyphs)
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{
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return Err(break_val);
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}
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}
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}
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Ok(baseline_y)
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}
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/// Returns the leading edge of the glyph at the given byte offset
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pub fn cursor_pos_for_byte_offset(&self, byte_offset: usize) -> (Font::Length, Font::Length) {
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let mut last_glyph_right_edge = Font::Length::zero();
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let mut last_line_y = Font::Length::zero();
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match self.layout_lines(
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|glyphs, line_x, line_y, line, _| {
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last_glyph_right_edge = euclid::approxord::min(
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self.max_width,
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line_x + line.width_including_trailing_whitespace(),
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);
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last_line_y = line_y;
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if byte_offset >= line.byte_range.end + line.trailing_whitespace_bytes {
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return core::ops::ControlFlow::Continue(());
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}
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for positioned_glyph in glyphs {
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if positioned_glyph.text_byte_offset == byte_offset {
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return core::ops::ControlFlow::Break((
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euclid::approxord::min(self.max_width, line_x + positioned_glyph.x),
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last_line_y,
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));
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}
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}
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core::ops::ControlFlow::Break((last_glyph_right_edge, last_line_y))
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},
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None,
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) {
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Ok(_) => (last_glyph_right_edge, last_line_y),
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Err(position) => position,
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}
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}
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/// Returns the bytes offset for the given position
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pub fn byte_offset_for_position(&self, (pos_x, pos_y): (Font::Length, Font::Length)) -> usize {
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let mut byte_offset = 0;
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let two = Font::LengthPrimitive::one() + Font::LengthPrimitive::one();
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match self.layout_lines(
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|glyphs, line_x, line_y, line, _| {
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if pos_y >= line_y + self.layout.font.height() {
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byte_offset = line.byte_range.end;
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return core::ops::ControlFlow::Continue(());
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}
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if line.is_empty() {
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return core::ops::ControlFlow::Break(line.byte_range.start);
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}
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while let Some(positioned_glyph) = glyphs.next() {
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if pos_x >= line_x + positioned_glyph.x
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&& pos_x <= line_x + positioned_glyph.x + positioned_glyph.advance
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{
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if pos_x < line_x + positioned_glyph.x + positioned_glyph.advance / two {
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return core::ops::ControlFlow::Break(
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positioned_glyph.text_byte_offset,
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);
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} else if let Some(next_glyph) = glyphs.next() {
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return core::ops::ControlFlow::Break(next_glyph.text_byte_offset);
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}
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}
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}
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core::ops::ControlFlow::Break(line.byte_range.end)
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},
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None,
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) {
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Ok(_) => byte_offset,
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Err(position) => position,
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}
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}
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}
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#[test]
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fn test_no_linebreak_opportunity_at_eot() {
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let mut it = LineBreakIterator::new("Hello World");
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assert_eq!(it.next(), Some((6, BreakOpportunity::Allowed)));
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assert_eq!(it.next(), None);
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}
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// All glyphs are 10 pixels wide, break on ascii rules
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#[cfg(test)]
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pub struct FixedTestFont;
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#[cfg(test)]
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impl TextShaper for FixedTestFont {
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type LengthPrimitive = f32;
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type Length = f32;
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fn shape_text<GlyphStorage: std::iter::Extend<Glyph<f32>>>(
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&self,
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text: &str,
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glyphs: &mut GlyphStorage,
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) {
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let glyph_iter = text.char_indices().map(|(byte_offset, char)| {
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let mut utf16_buf = [0; 2];
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let utf16_char_as_glyph_id = char.encode_utf16(&mut utf16_buf)[0];
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Glyph {
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offset_x: 0.,
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offset_y: 0.,
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glyph_id: core::num::NonZeroU16::new(utf16_char_as_glyph_id),
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advance: 10.,
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text_byte_offset: byte_offset,
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}
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});
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glyphs.extend(glyph_iter);
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}
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fn glyph_for_char(&self, ch: char) -> Option<Glyph<f32>> {
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let mut utf16_buf = [0; 2];
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let utf16_char_as_glyph_id = ch.encode_utf16(&mut utf16_buf)[0];
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Glyph {
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offset_x: 0.,
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offset_y: 0.,
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glyph_id: core::num::NonZeroU16::new(utf16_char_as_glyph_id),
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advance: 10.,
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text_byte_offset: 0,
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}
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.into()
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}
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fn max_lines(&self, max_height: f32) -> usize {
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let height = self.ascent() - self.descent();
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(max_height / height).floor() as _
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}
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}
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#[cfg(test)]
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impl FontMetrics<f32> for FixedTestFont {
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fn ascent(&self) -> f32 {
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5.
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}
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fn descent(&self) -> f32 {
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-5.
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}
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fn x_height(&self) -> f32 {
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3.
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}
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fn cap_height(&self) -> f32 {
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4.
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}
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}
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#[test]
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fn test_elision() {
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let font = FixedTestFont;
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let text = "This is a longer piece of text";
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let mut lines = Vec::new();
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let paragraph = TextParagraphLayout {
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string: text,
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layout: TextLayout { font: &font, letter_spacing: None },
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max_width: 13. * 10.,
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max_height: 10.,
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horizontal_alignment: TextHorizontalAlignment::Left,
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vertical_alignment: TextVerticalAlignment::Top,
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wrap: TextWrap::NoWrap,
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overflow: TextOverflow::Elide,
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single_line: true,
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};
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paragraph
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.layout_lines::<()>(
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|glyphs, _, _, _, _| {
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lines.push(
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glyphs.map(|positioned_glyph| positioned_glyph.glyph_id).collect::<Vec<_>>(),
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);
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core::ops::ControlFlow::Continue(())
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},
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None,
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)
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.unwrap();
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assert_eq!(lines.len(), 1);
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let rendered_text = lines[0]
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.iter()
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.flat_map(|glyph_id| {
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core::char::decode_utf16(core::iter::once(glyph_id.get()))
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.map(|r| r.unwrap())
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.collect::<Vec<char>>()
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})
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.collect::<std::string::String>();
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debug_assert_eq!(rendered_text, "This is a lo…")
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}
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#[test]
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fn test_exact_fit() {
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let font = FixedTestFont;
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let text = "Fits";
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let mut lines = Vec::new();
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let paragraph = TextParagraphLayout {
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string: text,
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layout: TextLayout { font: &font, letter_spacing: None },
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max_width: 4. * 10.,
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max_height: 10.,
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horizontal_alignment: TextHorizontalAlignment::Left,
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vertical_alignment: TextVerticalAlignment::Top,
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wrap: TextWrap::NoWrap,
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overflow: TextOverflow::Elide,
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single_line: true,
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};
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paragraph
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.layout_lines::<()>(
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|glyphs, _, _, _, _| {
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lines.push(
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glyphs.map(|positioned_glyph| positioned_glyph.glyph_id).collect::<Vec<_>>(),
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);
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core::ops::ControlFlow::Continue(())
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},
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None,
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)
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.unwrap();
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assert_eq!(lines.len(), 1);
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let rendered_text = lines[0]
|
|
.iter()
|
|
.flat_map(|glyph_id| {
|
|
core::char::decode_utf16(core::iter::once(glyph_id.get()))
|
|
.map(|r| r.unwrap())
|
|
.collect::<Vec<char>>()
|
|
})
|
|
.collect::<std::string::String>();
|
|
debug_assert_eq!(rendered_text, "Fits")
|
|
}
|
|
|
|
#[test]
|
|
fn test_no_line_separators_characters_rendered() {
|
|
let font = FixedTestFont;
|
|
let text = "Hello\nWorld\n";
|
|
|
|
let mut lines = Vec::new();
|
|
|
|
let paragraph = TextParagraphLayout {
|
|
string: text,
|
|
layout: TextLayout { font: &font, letter_spacing: None },
|
|
max_width: 13. * 10.,
|
|
max_height: 10.,
|
|
horizontal_alignment: TextHorizontalAlignment::Left,
|
|
vertical_alignment: TextVerticalAlignment::Top,
|
|
wrap: TextWrap::NoWrap,
|
|
overflow: TextOverflow::Clip,
|
|
single_line: true,
|
|
};
|
|
paragraph
|
|
.layout_lines::<()>(
|
|
|glyphs, _, _, _, _| {
|
|
lines.push(
|
|
glyphs.map(|positioned_glyph| positioned_glyph.glyph_id).collect::<Vec<_>>(),
|
|
);
|
|
core::ops::ControlFlow::Continue(())
|
|
},
|
|
None,
|
|
)
|
|
.unwrap();
|
|
|
|
assert_eq!(lines.len(), 2);
|
|
let rendered_text = lines
|
|
.iter()
|
|
.map(|glyphs_per_line| {
|
|
glyphs_per_line
|
|
.iter()
|
|
.flat_map(|glyph_id| {
|
|
core::char::decode_utf16(core::iter::once(glyph_id.get()))
|
|
.map(|r| r.unwrap())
|
|
.collect::<Vec<char>>()
|
|
})
|
|
.collect::<std::string::String>()
|
|
})
|
|
.collect::<Vec<_>>();
|
|
debug_assert_eq!(rendered_text, std::vec!["Hello", "World"]);
|
|
}
|
|
|
|
#[test]
|
|
fn test_cursor_position() {
|
|
let font = FixedTestFont;
|
|
let text = "Hello World";
|
|
|
|
let paragraph = TextParagraphLayout {
|
|
string: text,
|
|
layout: TextLayout { font: &font, letter_spacing: None },
|
|
max_width: 10. * 10.,
|
|
max_height: 10.,
|
|
horizontal_alignment: TextHorizontalAlignment::Left,
|
|
vertical_alignment: TextVerticalAlignment::Top,
|
|
wrap: TextWrap::WordWrap,
|
|
overflow: TextOverflow::Clip,
|
|
single_line: false,
|
|
};
|
|
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(0), (0., 0.));
|
|
|
|
let e_offset = text
|
|
.char_indices()
|
|
.find_map(|(offset, ch)| if ch == 'e' { Some(offset) } else { None })
|
|
.unwrap();
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(e_offset), (10., 0.));
|
|
|
|
let w_offset = text
|
|
.char_indices()
|
|
.find_map(|(offset, ch)| if ch == 'W' { Some(offset) } else { None })
|
|
.unwrap();
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(w_offset + 1), (10., 10.));
|
|
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(text.len()), (10. * 5., 10.));
|
|
|
|
let first_space_offset =
|
|
text.char_indices().find_map(|(offset, ch)| ch.is_whitespace().then_some(offset)).unwrap();
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(first_space_offset), (5. * 10., 0.));
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(first_space_offset + 15), (10. * 10., 0.));
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(first_space_offset + 16), (10. * 10., 0.));
|
|
}
|
|
|
|
#[test]
|
|
fn test_cursor_position_with_newline() {
|
|
let font = FixedTestFont;
|
|
let text = "Hello\nWorld";
|
|
|
|
let paragraph = TextParagraphLayout {
|
|
string: text,
|
|
layout: TextLayout { font: &font, letter_spacing: None },
|
|
max_width: 100. * 10.,
|
|
max_height: 10.,
|
|
horizontal_alignment: TextHorizontalAlignment::Left,
|
|
vertical_alignment: TextVerticalAlignment::Top,
|
|
wrap: TextWrap::WordWrap,
|
|
overflow: TextOverflow::Clip,
|
|
single_line: false,
|
|
};
|
|
|
|
assert_eq!(paragraph.cursor_pos_for_byte_offset(5), (5. * 10., 0.));
|
|
}
|
|
|
|
#[test]
|
|
fn byte_offset_for_empty_line() {
|
|
let font = FixedTestFont;
|
|
let text = "Hello\n\nWorld";
|
|
|
|
let paragraph = TextParagraphLayout {
|
|
string: text,
|
|
layout: TextLayout { font: &font, letter_spacing: None },
|
|
max_width: 100. * 10.,
|
|
max_height: 10.,
|
|
horizontal_alignment: TextHorizontalAlignment::Left,
|
|
vertical_alignment: TextVerticalAlignment::Top,
|
|
wrap: TextWrap::WordWrap,
|
|
overflow: TextOverflow::Clip,
|
|
single_line: false,
|
|
};
|
|
|
|
assert_eq!(paragraph.byte_offset_for_position((0., 10.)), 6);
|
|
}
|
|
|
|
#[test]
|
|
fn test_byte_offset() {
|
|
let font = FixedTestFont;
|
|
let text = "Hello World";
|
|
let mut end_helper_text = std::string::String::from(text);
|
|
end_helper_text.push('!');
|
|
|
|
let paragraph = TextParagraphLayout {
|
|
string: text,
|
|
layout: TextLayout { font: &font, letter_spacing: None },
|
|
max_width: 10. * 10.,
|
|
max_height: 10.,
|
|
horizontal_alignment: TextHorizontalAlignment::Left,
|
|
vertical_alignment: TextVerticalAlignment::Top,
|
|
wrap: TextWrap::WordWrap,
|
|
overflow: TextOverflow::Clip,
|
|
single_line: false,
|
|
};
|
|
|
|
assert_eq!(paragraph.byte_offset_for_position((0., 0.)), 0);
|
|
|
|
let e_offset = text
|
|
.char_indices()
|
|
.find_map(|(offset, ch)| if ch == 'e' { Some(offset) } else { None })
|
|
.unwrap();
|
|
|
|
assert_eq!(paragraph.byte_offset_for_position((14., 0.)), e_offset);
|
|
|
|
let l_offset = text
|
|
.char_indices()
|
|
.find_map(|(offset, ch)| if ch == 'l' { Some(offset) } else { None })
|
|
.unwrap();
|
|
assert_eq!(paragraph.byte_offset_for_position((15., 0.)), l_offset);
|
|
|
|
let w_offset = text
|
|
.char_indices()
|
|
.find_map(|(offset, ch)| if ch == 'W' { Some(offset) } else { None })
|
|
.unwrap();
|
|
|
|
assert_eq!(paragraph.byte_offset_for_position((10., 10.)), w_offset + 1);
|
|
|
|
let o_offset = text
|
|
.char_indices()
|
|
.rev()
|
|
.find_map(|(offset, ch)| if ch == 'o' { Some(offset) } else { None })
|
|
.unwrap();
|
|
|
|
assert_eq!(paragraph.byte_offset_for_position((15., 10.)), o_offset + 1);
|
|
|
|
let d_offset = text
|
|
.char_indices()
|
|
.rev()
|
|
.find_map(|(offset, ch)| if ch == 'd' { Some(offset) } else { None })
|
|
.unwrap();
|
|
|
|
assert_eq!(paragraph.byte_offset_for_position((40., 10.)), d_offset);
|
|
|
|
let end_offset = end_helper_text
|
|
.char_indices()
|
|
.rev()
|
|
.find_map(|(offset, ch)| if ch == '!' { Some(offset) } else { None })
|
|
.unwrap();
|
|
|
|
assert_eq!(paragraph.byte_offset_for_position((45., 10.)), end_offset);
|
|
assert_eq!(paragraph.byte_offset_for_position((0., 20.)), end_offset);
|
|
}
|