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pub use crate::unicode::CharacterData;
use crate::unicode::{read_utf8, LinebreakData, Linebreaker, LINEBREAK_NONE};
use crate::Font;
use crate::{
platform::{ceil, floor},
Metrics,
};
use alloc::vec::*;
use core::borrow::Borrow;
use core::hash::{Hash, Hasher};
/// Horizontal alignment options for text when a max_width is provided.
#[derive(Copy, Clone, PartialEq)]
pub enum HorizontalAlign {
/// Aligns text to the left of the region defined by the max_width.
Left,
/// Aligns text to the center of the region defined by the max_width.
Center,
/// Aligns text to the right of the region defined by the max_width.
Right,
}
/// Vertical alignment options for text when a max_height is provided.
#[derive(Copy, Clone, PartialEq)]
pub enum VerticalAlign {
/// Aligns text to the top of the region defined by the max_height.
Top,
/// Aligns text to the middle of the region defined by the max_height.
Middle,
/// Aligns text to the bottom of the region defined by the max_height.
Bottom,
}
/// Wrap style is a hint for how strings of text should be wrapped to the next line. Line wrapping
/// can happen when the max width/height is reached.
#[derive(Copy, Clone, PartialEq)]
pub enum WrapStyle {
/// Word will break lines by the Unicode line breaking algorithm (Standard Annex #14) This will
/// generally break lines where you expect them to be broken at and will preserve words.
Word,
/// Letter will not preserve words, breaking into a new line after the nearest letter.
Letter,
}
/// The direction that the Y coordinate increases in. Layout needs to be aware of your coordinate
/// system to place the glyphs correctly.
#[derive(Copy, Clone, PartialEq)]
pub enum CoordinateSystem {
/// The Y coordinate increases up relative to the window or image. The higher up on the window,
/// the more positive Y becomes.
PositiveYUp,
/// The Y coordinate increases down relative to the window or image. The lower down on the
/// window, the more positive Y becomes.
PositiveYDown,
}
/// Settings to configure how text layout is constrained. Text layout is considered best effort and
/// layout may violate the constraints defined here if they prevent text from being laid out.
#[derive(Copy, Clone, PartialEq)]
pub struct LayoutSettings {
/// The leftmost boundary of the text region.
pub x: f32,
/// The topmost boundary of the text region.
pub y: f32,
/// An optional rightmost boundary on the text region. A line of text that exceeds the
/// max_width is wrapped to the line below. If the width of a glyph is larger than the
/// max_width, the glyph will overflow past the max_width. The application is responsible for
/// handling the overflow.
pub max_width: Option<f32>,
/// An optional bottom boundary on the text region. This is used for positioning the
/// vertical_align option. Text that exceeds the defined max_height will overflow past it. The
/// application is responsible for handling the overflow.
pub max_height: Option<f32>,
/// The default is Left. This option does nothing if the max_width isn't set.
pub horizontal_align: HorizontalAlign,
/// The default is Top. This option does nothing if the max_height isn't set.
pub vertical_align: VerticalAlign,
/// The height of each line as a multiplier of the default.
pub line_height: f32,
/// The default is Word. Wrap style is a hint for how strings of text should be wrapped to the
/// next line. Line wrapping can happen when the max width/height is reached.
pub wrap_style: WrapStyle,
/// The default is true. This option enables hard breaks, like new line characters, to
/// prematurely wrap lines. If false, hard breaks will not prematurely create a new line.
pub wrap_hard_breaks: bool,
}
impl Default for LayoutSettings {
fn default() -> LayoutSettings {
LayoutSettings {
x: 0.0,
y: 0.0,
max_width: None,
max_height: None,
horizontal_align: HorizontalAlign::Left,
vertical_align: VerticalAlign::Top,
line_height: 1.0,
wrap_style: WrapStyle::Word,
wrap_hard_breaks: true,
}
}
}
/// Configuration for rasterizing a glyph. This struct is also a hashable key that can be used to
/// uniquely identify a rasterized glyph for applications that want to cache glyphs.
#[derive(Debug, Copy, Clone)]
pub struct GlyphRasterConfig {
/// The glyph index represented by the glyph being positioned.
pub glyph_index: u16,
/// The scale of the glyph being positioned in px.
pub px: f32,
/// The hash of the font used in layout to raster the glyph.
pub font_hash: usize,
}
impl Hash for GlyphRasterConfig {
fn hash<H: Hasher>(&self, state: &mut H) {
self.glyph_index.hash(state);
self.px.to_bits().hash(state);
self.font_hash.hash(state);
}
}
impl PartialEq for GlyphRasterConfig {
fn eq(&self, other: &Self) -> bool {
self.glyph_index == other.glyph_index && self.px == other.px && self.font_hash == other.font_hash
}
}
impl Eq for GlyphRasterConfig {}
/// A positioned scaled glyph.
#[derive(Debug, Copy, Clone)]
pub struct GlyphPosition<U: Copy + Clone = ()> {
/// Hashable key that can be used to uniquely identify a rasterized glyph.
pub key: GlyphRasterConfig,
/// The index of the font used to generate this glyph position.
pub font_index: usize,
/// The associated character that generated this glyph. A character may generate multiple
/// glyphs.
pub parent: char,
/// The xmin of the glyph bounding box. This represents the left side of the glyph. Dimensions
/// are in pixels, and are always whole numbers.
pub x: f32,
/// The ymin of the glyph bounding box. If your coordinate system is PositiveYUp, this
/// represents the bottom side of the glyph. If your coordinate system is PositiveYDown, this
/// represents the top side of the glyph. This is like this so that (y + height) always produces
/// the other bound for the glyph.
pub y: f32,
/// The width of the glyph. Dimensions are in pixels.
pub width: usize,
/// The height of the glyph. Dimensions are in pixels.
pub height: usize,
/// The byte offset into the original string used in the append call which created
/// this glyph.
pub byte_offset: usize,
/// Additional metadata associated with the character used to generate this glyph.
pub char_data: CharacterData,
/// Custom user data associated with the text styled used to generate this glyph.
pub user_data: U,
}
/// A style description for a segment of text.
pub struct TextStyle<'a, U: Copy + Clone = ()> {
/// The text to layout.
pub text: &'a str,
/// The scale of the text in pixel units. The units of the scale are pixels per Em unit.
pub px: f32,
/// The font to layout the text in.
pub font_index: usize,
/// Additional user data to associate with glyphs produced by this text style.
pub user_data: U,
}
impl<'a> TextStyle<'a> {
pub fn new(text: &'a str, px: f32, font_index: usize) -> TextStyle<'a> {
TextStyle {
text,
px,
font_index,
user_data: (),
}
}
}
impl<'a, U: Copy + Clone> TextStyle<'a, U> {
pub fn with_user_data(text: &'a str, px: f32, font_index: usize, user_data: U) -> TextStyle<'a, U> {
TextStyle {
text,
px,
font_index,
user_data,
}
}
}
/// Metrics about a positioned line.
#[derive(Debug, Copy, Clone)]
pub struct LinePosition {
/// The y coordinate of the baseline of this line, in pixels.
pub baseline_y: f32,
/// How much empty space is left at the end of the line before any alignment. If no max width is
/// specified, f32::MAX is used.
pub padding: f32,
/// The highest point that any glyph in the font extends to above the baseline. Typically
/// positive. If there are multiple styles on this line, this is their max value.
pub max_ascent: f32,
/// The lowest point that any glyph in the font extends to below the baseline. Typically
/// negative. If there are multiple styles on this line, this is their min value.
pub min_descent: f32,
/// The gap to leave between the descent of one line and the ascent of the next. This is of
/// course only a guideline given by the font's designers. If there are multiple styles on this
/// line, this is their max value.
pub max_line_gap: f32,
/// A precalculated value for the of the line depending. It's calculated by: ascent - descent +
/// line_gap. If there are multiple styles on this line, this is their max value.
pub max_new_line_size: f32,
/// The GlyphPosition index of the first glyph in the line.
pub glyph_start: usize,
/// The GlyphPosition index of the last glyph in the line.
pub glyph_end: usize,
/// The x offset into the first layout pass.
tracking_x: f32,
}
impl Default for LinePosition {
fn default() -> Self {
LinePosition {
baseline_y: 0.0,
padding: 0.0,
max_ascent: 0.0,
min_descent: 0.0,
max_line_gap: 0.0,
max_new_line_size: 0.0,
glyph_start: 0,
glyph_end: 0,
tracking_x: 0.0,
}
}
}
/// Text layout requires a small amount of heap usage which is contained in the Layout struct. This
/// context is reused between layout calls. Reusing the Layout struct will greatly reduce memory
/// allocations and is advisable for performance.
pub struct Layout<U: Copy + Clone = ()> {
/// Marks if layout should be performed as if the Y axis is flipped (Positive Y incrementing
/// down instead of up).
flip: bool,
/// Origin position. Left side of the region text is being laid out in.
x: f32,
/// Origin position. Top side of the region text is being laid out in.
y: f32,
/// A mask to filter only linebreak types being requested.
wrap_mask: LinebreakData,
/// The max width of the region text is being laid out in.
max_width: f32,
/// The max height of the region text is being laid out in.
max_height: f32,
/// A multiplier for how text fills unused vertical space.
vertical_align: f32,
/// A multiplier for how text fills unused horizontal space.
horizontal_align: f32,
/// A multiplier for the amount of space between lines.
line_height: f32,
/// The current height of all laid out text.
height: f32,
/// Finalized glyph state.
output: Vec<GlyphPosition<U>>,
/// Intermediate glyph state.
glyphs: Vec<GlyphPosition<U>>,
/// Linebreak state. Used to derive linebreaks from past glyphs.
linebreaker: Linebreaker,
/// The current highest priority linebreak (Hard > Soft > None).
linebreak_prev: LinebreakData,
/// The x position that the glyph that has the current highest priority linebreak status starts
/// at.
linebreak_pos: f32,
/// The index of the glyph that has the current highest priority linebreak status. This glyph is
/// the last glyph on a line if a linebreak is required.
linebreak_idx: usize,
/// Layout state of each line currently laid out. This always has at least 1 element.
line_metrics: Vec<LinePosition>,
/// The x position the next glyph starts at.
current_pos: f32,
/// The ceil(ascent) of the current style.
current_ascent: f32,
/// The ceil(descent) of the current style.
current_descent: f32,
/// The ceil(line_gap) of the current style.
current_line_gap: f32,
/// The ceil(new_line_size) of the current style.
current_new_line: f32,
/// The x position the current line starts at.
start_pos: f32,
/// The settings currently being used for layout.
settings: LayoutSettings,
}
impl<'a, U: Copy + Clone> Layout<U> {
/// Creates a layout instance. This requires the direction that the Y coordinate increases in.
/// Layout needs to be aware of your coordinate system to place the glyphs correctly.
pub fn new(coordinate_system: CoordinateSystem) -> Layout<U> {
let settings = LayoutSettings::default();
let mut layout = Layout {
flip: coordinate_system == CoordinateSystem::PositiveYDown,
x: 0.0,
y: 0.0,
wrap_mask: LINEBREAK_NONE,
max_width: 0.0,
max_height: 0.0,
vertical_align: 0.0,
horizontal_align: 0.0,
line_height: 1.0,
output: Vec::new(),
glyphs: Vec::new(),
line_metrics: Vec::new(),
linebreaker: Linebreaker::new(),
linebreak_prev: LINEBREAK_NONE,
linebreak_pos: 0.0,
linebreak_idx: 0,
current_pos: 0.0,
current_ascent: 0.0,
current_descent: 0.0,
current_line_gap: 0.0,
current_new_line: 0.0,
start_pos: 0.0,
height: 0.0,
settings,
};
layout.reset(&settings);
layout
}
/// Resets the current layout settings and clears all appended text.
pub fn reset(&mut self, settings: &LayoutSettings) {
self.settings = *settings;
self.x = settings.x;
self.y = settings.y;
self.wrap_mask = LinebreakData::from_mask(
settings.wrap_style == WrapStyle::Word,
settings.wrap_hard_breaks,
settings.max_width.is_some(),
);
self.max_width = settings.max_width.unwrap_or(core::f32::MAX);
self.max_height = settings.max_height.unwrap_or(core::f32::MAX);
self.vertical_align = if settings.max_height.is_none() {
0.0
} else {
match settings.vertical_align {
VerticalAlign::Top => 0.0,
VerticalAlign::Middle => 0.5,
VerticalAlign::Bottom => 1.0,
}
};
self.horizontal_align = if settings.max_width.is_none() {
0.0
} else {
match settings.horizontal_align {
HorizontalAlign::Left => 0.0,
HorizontalAlign::Center => 0.5,
HorizontalAlign::Right => 1.0,
}
};
self.line_height = settings.line_height;
self.clear();
}
/// Keeps current layout settings but clears all appended text.
pub fn clear(&mut self) {
self.glyphs.clear();
self.output.clear();
self.line_metrics.clear();
self.line_metrics.push(LinePosition::default());
self.linebreaker.reset();
self.linebreak_prev = LINEBREAK_NONE;
self.linebreak_pos = 0.0;
self.linebreak_idx = 0;
self.current_pos = 0.0;
self.current_ascent = 0.0;
self.current_descent = 0.0;
self.current_line_gap = 0.0;
self.current_new_line = 0.0;
self.start_pos = 0.0;
self.height = 0.0;
}
/// Gets the current height of the appended text.
pub fn height(&self) -> f32 {
if let Some(line) = self.line_metrics.last() {
self.height + line.max_new_line_size
} else {
0.0
}
}
/// Gets the currently positioned lines. If there are no lines positioned, this returns none.
pub fn lines(&'a self) -> Option<&'a Vec<LinePosition>> {
if self.glyphs.is_empty() {
None
} else {
Some(&self.line_metrics)
}
}
/// Performs layout for text horizontally, and wrapping vertically. This makes a best effort
/// attempt at laying out the text defined in the given styles with the provided layout
/// settings. Text may overflow out of the bounds defined in the layout settings and it's up
/// to the application to decide how to deal with this.
///
/// Characters from the input string can only be omitted from the output, they are never
/// reordered. The output buffer will always contain characters in the order they were defined
/// in the styles.
pub fn append<T: Borrow<Font>>(&mut self, fonts: &[T], style: &TextStyle<U>) {
// The first layout pass requires some text.
if style.text.is_empty() {
return;
}
let font: &Font = &fonts[style.font_index].borrow();
if let Some(metrics) = font.horizontal_line_metrics(style.px) {
self.current_ascent = ceil(metrics.ascent);
self.current_new_line = ceil(metrics.new_line_size);
self.current_descent = ceil(metrics.descent);
self.current_line_gap = ceil(metrics.line_gap);
if let Some(line) = self.line_metrics.last_mut() {
if self.current_ascent > line.max_ascent {
line.max_ascent = self.current_ascent;
}
if self.current_descent < line.min_descent {
line.min_descent = self.current_descent;
}
if self.current_line_gap > line.max_line_gap {
line.max_line_gap = self.current_line_gap;
}
if self.current_new_line > line.max_new_line_size {
line.max_new_line_size = self.current_new_line;
}
}
}
let mut byte_offset = 0;
while byte_offset < style.text.len() {
let prev_byte_offset = byte_offset;
let character = read_utf8(style.text.as_bytes(), &mut byte_offset);
let linebreak = self.linebreaker.next(character).mask(self.wrap_mask);
let glyph_index = font.lookup_glyph_index(character);
let char_data = CharacterData::classify(character, glyph_index);
let metrics = if !char_data.is_control() {
font.metrics_indexed(glyph_index, style.px)
} else {
Metrics::default()
};
let advance = ceil(metrics.advance_width);
if linebreak >= self.linebreak_prev {
self.linebreak_prev = linebreak;
self.linebreak_pos = self.current_pos;
self.linebreak_idx = self.glyphs.len().saturating_sub(1); // Mark the previous glyph
}
// Perform a linebreak
if linebreak.is_hard() || (self.current_pos - self.start_pos + advance > self.max_width) {
self.linebreak_prev = LINEBREAK_NONE;
let mut next_glyph_start = self.glyphs().len();
if let Some(line) = self.line_metrics.last_mut() {
line.glyph_end = self.linebreak_idx;
line.padding = self.max_width - (self.linebreak_pos - self.start_pos);
self.height += line.max_new_line_size * self.line_height;
next_glyph_start = self.linebreak_idx + 1;
}
self.line_metrics.push(LinePosition {
baseline_y: 0.0,
padding: 0.0,
max_ascent: self.current_ascent,
min_descent: self.current_descent,
max_line_gap: self.current_line_gap,
max_new_line_size: self.current_new_line,
glyph_start: next_glyph_start,
glyph_end: 0,
tracking_x: self.linebreak_pos,
});
self.start_pos = self.linebreak_pos;
}
let y = if self.flip {
floor(-metrics.bounds.height - metrics.bounds.ymin) // PositiveYDown
} else {
floor(metrics.bounds.ymin) // PositiveYUp
};
self.glyphs.push(GlyphPosition {
key: GlyphRasterConfig {
glyph_index: glyph_index as u16,
px: style.px,
font_hash: font.file_hash(),
},
font_index: style.font_index,
parent: character,
byte_offset: prev_byte_offset,
x: floor(self.current_pos + metrics.bounds.xmin),
y,
width: metrics.width,
height: metrics.height,
char_data,
user_data: style.user_data,
});
self.current_pos += advance;
}
if let Some(line) = self.line_metrics.last_mut() {
line.padding = self.max_width - (self.current_pos - self.start_pos);
line.glyph_end = self.glyphs.len().saturating_sub(1);
}
self.finalize();
}
fn finalize(&mut self) {
// The second layout pass requires at least 1 glyph to layout.
if self.glyphs.is_empty() {
return;
}
unsafe { self.output.set_len(0) };
self.output.reserve(self.glyphs.len());
let dir = if self.flip {
-1.0 // PositiveYDown
} else {
1.0 // PositiveYUp
};
let mut baseline_y = self.y - dir * floor((self.max_height - self.height()) * self.vertical_align);
let mut idx = 0;
for line in &mut self.line_metrics {
let x_padding = self.x - line.tracking_x + floor(line.padding * self.horizontal_align);
baseline_y -= dir * line.max_ascent;
line.baseline_y = baseline_y;
while idx <= line.glyph_end {
let mut glyph = self.glyphs[idx];
glyph.x += x_padding;
glyph.y += baseline_y;
self.output.push(glyph);
idx += 1;
}
baseline_y -= dir * (line.max_new_line_size * self.line_height - line.max_ascent);
}
}
/// Gets the currently laid out glyphs.
pub fn glyphs(&'a self) -> &'a Vec<GlyphPosition<U>> {
&self.output
}
/// Gets the settings currently being used for layout.
pub fn settings(&self) -> &LayoutSettings {
&self.settings
}
}