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Refactor text layout: fewer allocations

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This commit is contained in:
Emil Ernerfeldt 2020-05-16 17:28:15 +02:00
parent cdfd42eb3e
commit d3a3e4fa73
5 changed files with 115 additions and 75 deletions
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2
emigui/README.md
View file

@ -22,7 +22,7 @@ This is the core library crate Emigui. It is fully platform independent without
* [x] Scroll-wheel input
* [x] Drag background to scroll
* [ ] Kinetic scrolling
* [x] Add support for clicking links
* [x] Add support for clicking hyperlinks
* [x] Menu bar (File, Edit, etc)
* [ ] Sub-menus
* [ ] Keyboard shortcuts

5
emigui/src/containers/resize.rs
View file

@ -47,6 +47,11 @@ impl Default for Resize {
}
impl Resize {
pub fn default_width(mut self, width: f32) -> Self {
self.default_size.x = width;
self
}
pub fn default_height(mut self, height: f32) -> Self {
self.default_size.y = height;
self

6
emigui/src/examples/app.rs
View file

@ -120,9 +120,9 @@ impl OpenWindows {
fn show_menu_bar(ui: &mut Ui, windows: &mut OpenWindows) {
menu::bar(ui, |ui| {
menu::menu(ui, "File", |ui| {
ui.add(Button::new("Do nothing"));
ui.add(Button::new("Carry on"));
ui.add(Button::new("Don't Quit"));
if ui.add(Button::new("Clear memory")).clicked {
*ui.ctx().memory() = Default::default();
}
});
menu::menu(ui, "Windows", |ui| {
ui.add(Checkbox::new(&mut windows.examples, "Examples"));

175
emigui/src/font.rs
View file

@ -8,9 +8,12 @@ use crate::{
texture_atlas::TextureAtlas,
};
/// A typeset piece of text on a single line. Could be a whole line, or just a word.
/// A typeset piece of text on a single line.
pub struct Fragment {
/// The start of each character, starting at zero.
/// The start of each character, probably starting at zero.
/// The last element is the end of the last character.
/// x_offsets.len() == text.chars().count() + 1
/// This is never empty.
/// Unit: points.
pub x_offsets: Vec<f32>,
@ -18,7 +21,8 @@ pub struct Fragment {
/// Unit: points.
pub y_offset: f32,
/// The actual characters
// TODO: make this a str reference into a String owned by Galley
/// The actual characters.
pub text: String,
}
@ -41,7 +45,9 @@ impl Fragment {
// }
/// A collection of text locked into place.
#[derive(Default)]
pub struct Galley {
// TODO: maybe rename/refactor this as `lines`?
pub fragments: Vec<Fragment>,
pub size: Vec2,
}
@ -192,17 +198,13 @@ impl Font {
);
}
/// Returns the a single line of characters separated into words
/// Always returns at least one frament.
fn layout_words(&self, text: &str) -> Galley {
/// Typeset the given text onto one line.
/// Assumes there are no \n in the text.
/// Return x_offsets, one longer than the number of characters in the text.
fn layout_single_line_fragment(&self, text: &str) -> Vec<f32> {
let scale_in_pixels = Scale::uniform(self.scale_in_pixels);
let mut current_fragment = Fragment {
x_offsets: vec![0.0],
y_offset: 0.0,
text: String::new(),
};
let mut fragments = vec![];
let mut x_offsets = vec![0.0];
let mut cursor_x_in_points = 0.0f32;
let mut last_glyph_id = None;
@ -217,84 +219,118 @@ impl Font {
cursor_x_in_points += glyph.advance_width;
cursor_x_in_points = self.round_to_pixel(cursor_x_in_points);
last_glyph_id = Some(glyph.id);
let is_space = glyph.uv_rect.is_none();
if is_space {
// TODO: also break after hyphens etc
if !current_fragment.text.is_empty() {
fragments.push(current_fragment);
current_fragment = Fragment {
x_offsets: vec![cursor_x_in_points],
y_offset: 0.0,
text: String::new(),
}
}
// TODO: add a fragment for the space aswell
} else {
current_fragment.text.push(c);
current_fragment.x_offsets.push(cursor_x_in_points);
}
} else {
// Ignore unknown glyph
}
x_offsets.push(cursor_x_in_points);
}
if !current_fragment.text.is_empty() {
fragments.push(current_fragment)
}
let width = if fragments.is_empty() {
0.0
} else {
fragments.last().unwrap().max_x()
};
let size = vec2(width, self.height());
Galley { fragments, size }
x_offsets
}
/// Typeset the given text onto one line.
/// Always returns at least one frament.
/// Assumes there are no \n in the text.
/// Always returns exactly one frament.
pub fn layout_single_line(&self, text: &str) -> Galley {
// TODO: return a single Fragment instead of calling layout_words
// saves a lot of allocations
self.layout_words(text)
let x_offsets = self.layout_single_line_fragment(text);
let fragment = Fragment {
x_offsets,
y_offset: 0.0,
text: text.to_owned(),
};
assert_eq!(fragment.x_offsets.len(), fragment.text.chars().count() + 1);
let width = fragment.max_x();
let size = vec2(width, self.height());
Galley {
fragments: vec![fragment],
size,
}
}
/// A paragraph is text with no line break character in it.
/// The text will be linebreaked by the given max_width_in_points.
/// The text will be linebreaked by the given `max_width_in_points`.
/// TODO: return Galley ?
pub fn layout_paragraph_max_width(
&self,
text: &str,
max_width_in_points: f32,
) -> Vec<Fragment> {
let mut galley = self.layout_words(text);
if galley.fragments.is_empty() || galley.size.x <= max_width_in_points {
return galley.fragments; // Early-out
}
let full_x_offsets = self.layout_single_line_fragment(text);
let line_spacing = self.line_spacing();
// Break up lines:
let mut line_start_x = 0.0;
let mut line_start_x = full_x_offsets[0];
assert_eq!(line_start_x, 0.0);
let mut cursor_y = 0.0;
let mut line_start_idx = 0;
for word in galley.fragments.iter_mut().skip(1) {
if word.max_x() - line_start_x >= max_width_in_points {
// Time for a new line:
cursor_y += line_spacing;
line_start_x = word.min_x();
// start index of the last space. A candidate for a new line.
let mut last_space = None;
let mut out_fragments = vec![];
for (i, (x, chr)) in full_x_offsets.iter().skip(1).zip(text.chars()).enumerate() {
let line_width = x - line_start_x;
if line_width > max_width_in_points {
if let Some(last_space_idx) = last_space {
let include_trailing_space = true;
let fragment = if include_trailing_space {
Fragment {
x_offsets: full_x_offsets[line_start_idx..=last_space_idx + 1]
.iter()
.map(|x| x - line_start_x)
.collect(),
y_offset: cursor_y,
text: text
.chars()
.skip(line_start_idx)
.take(last_space_idx + 1 - line_start_idx)
.collect(),
}
} else {
Fragment {
x_offsets: full_x_offsets[line_start_idx..=last_space_idx]
.iter()
.map(|x| x - line_start_x)
.collect(),
y_offset: cursor_y,
text: text
.chars()
.skip(line_start_idx)
.take(last_space_idx - line_start_idx)
.collect(),
}
};
assert_eq!(fragment.x_offsets.len(), fragment.text.chars().count() + 1);
out_fragments.push(fragment);
line_start_idx = last_space_idx + 1;
line_start_x = full_x_offsets[line_start_idx];
last_space = None;
cursor_y += self.line_spacing();
cursor_y = self.round_to_pixel(cursor_y);
}
}
word.y_offset += cursor_y;
for x in &mut word.x_offsets {
*x -= line_start_x;
const NON_BREAKING_SPACE: char = '\u{A0}';
if chr.is_whitespace() && chr != NON_BREAKING_SPACE {
last_space = Some(i);
}
}
galley.fragments
if line_start_idx + 1 < full_x_offsets.len() {
let fragment = Fragment {
x_offsets: full_x_offsets[line_start_idx..]
.iter()
.map(|x| x - line_start_x)
.collect(),
y_offset: cursor_y,
text: text.chars().skip(line_start_idx).collect(),
};
assert_eq!(fragment.x_offsets.len(), fragment.text.chars().count() + 1);
out_fragments.push(fragment);
}
out_fragments
}
pub fn layout_multiline(&self, text: &str, max_width_in_points: f32) -> Galley {
@ -302,13 +338,14 @@ impl Font {
let mut cursor_y = 0.0;
let mut fragments = Vec::new();
for line in text.split('\n') {
let mut line_fragments = self.layout_paragraph_max_width(line, max_width_in_points);
if let Some(last_word) = line_fragments.last() {
let line_height = last_word.y_offset + line_spacing;
for fragment in &mut line_fragments {
let mut paragraph_fragments =
self.layout_paragraph_max_width(line, max_width_in_points);
if let Some(last_fragment) = paragraph_fragments.last() {
let line_height = last_fragment.y_offset + line_spacing;
for fragment in &mut paragraph_fragments {
fragment.y_offset += cursor_y;
}
fragments.append(&mut line_fragments);
fragments.append(&mut paragraph_fragments);
cursor_y += line_height; // TODO: add extra spacing between paragraphs
} else {
cursor_y += line_spacing;

2
emigui/src/widgets.rs
View file

@ -149,7 +149,6 @@ impl Widget for Hyperlink {
let id = ui.make_child_id(&self.url);
let font = &ui.fonts()[text_style];
let line_spacing = font.line_spacing();
// TODO: underline
let galley = font.layout_multiline(&self.text, ui.available().width());
let interact = ui.reserve_space(galley.size, Some(id));
if interact.hovered {
@ -161,7 +160,6 @@ impl Widget for Hyperlink {
if interact.hovered {
// Underline:
// TODO: underline spaces between words too.
for fragment in &galley.fragments {
let pos = interact.rect.min;
let y = pos.y + fragment.y_offset + line_spacing;