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581 lines
18 KiB
581 lines
18 KiB
use super::iter::GlyphMetrics;
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use crate::ui::{
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display,
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display::{Color, Font},
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geometry::{Offset, Point, Rect},
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};
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#[derive(Copy, Clone)]
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pub enum LineBreaking {
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/// Break line only at whitespace, if possible. If we don't find any
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/// whitespace, break words.
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BreakAtWhitespace,
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/// Break words, adding a hyphen before the line-break. Does not use any
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/// smart algorithm, just char-by-char.
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BreakWordsAndInsertHyphen,
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}
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#[derive(Copy, Clone)]
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pub enum PageBreaking {
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/// Stop after hitting the bottom-right edge of the bounds.
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Cut,
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/// Before stopping at the bottom-right edge, insert ellipsis to signify
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/// more content is available, but only if no hyphen has been inserted yet.
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CutAndInsertEllipsis,
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}
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/// Visual instructions for laying out a formatted block of text.
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#[derive(Copy, Clone)]
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pub struct TextLayout {
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/// Bounding box restricting the layout dimensions.
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pub bounds: Rect,
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/// Additional space before beginning of text, can be negative to shift text
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/// upwards.
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pub padding_top: i32,
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/// Additional space between end of text and bottom of bounding box, can be
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/// negative.
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pub padding_bottom: i32,
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/// Background color.
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pub background_color: Color,
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/// Text color. Can be overridden by `Op::Color`.
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pub text_color: Color,
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/// Text font ID. Can be overridden by `Op::Font`.
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pub text_font: Font,
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/// Specifies which line-breaking strategy to use.
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pub line_breaking: LineBreaking,
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/// Font used for drawing the word-breaking hyphen.
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pub hyphen_font: Font,
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/// Foreground color used for drawing the hyphen.
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pub hyphen_color: Color,
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/// Specifies what to do at the end of the page.
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pub page_breaking: PageBreaking,
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/// Font used for drawing the ellipsis.
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pub ellipsis_font: Font,
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/// Foreground color used for drawing the ellipsis.
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pub ellipsis_color: Color,
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/// Font used to format `{normal}`.
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pub normal_font: Font,
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/// Font used to format `{medium}`.
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pub medium_font: Font,
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/// Font used to format `{bold}`.
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pub bold_font: Font,
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/// Font used to format `{mono}`.
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pub mono_font: Font,
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}
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pub trait DefaultTextTheme {
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const BACKGROUND_COLOR: Color;
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const TEXT_FONT: Font;
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const TEXT_COLOR: Color;
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const HYPHEN_FONT: Font;
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const HYPHEN_COLOR: Color;
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const ELLIPSIS_FONT: Font;
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const ELLIPSIS_COLOR: Color;
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const NORMAL_FONT: Font;
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const MEDIUM_FONT: Font;
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const BOLD_FONT: Font;
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const MONO_FONT: Font;
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}
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impl TextLayout {
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/// Create a new text layout, with empty size and default text parameters
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/// filled from `T`.
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pub fn new<T: DefaultTextTheme>() -> Self {
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Self {
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bounds: Rect::zero(),
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padding_top: 0,
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padding_bottom: 0,
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background_color: T::BACKGROUND_COLOR,
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text_color: T::TEXT_COLOR,
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text_font: T::TEXT_FONT,
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line_breaking: LineBreaking::BreakAtWhitespace,
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hyphen_font: T::HYPHEN_FONT,
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hyphen_color: T::HYPHEN_COLOR,
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page_breaking: PageBreaking::CutAndInsertEllipsis,
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ellipsis_font: T::ELLIPSIS_FONT,
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ellipsis_color: T::ELLIPSIS_COLOR,
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normal_font: T::NORMAL_FONT,
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medium_font: T::MEDIUM_FONT,
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bold_font: T::BOLD_FONT,
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mono_font: T::MONO_FONT,
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}
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}
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pub fn with_bounds(mut self, bounds: Rect) -> Self {
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self.bounds = bounds;
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self
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}
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pub fn initial_cursor(&self) -> Point {
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self.bounds.top_left() + Offset::y(self.text_font.text_height() + self.padding_top)
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}
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pub fn fit_text(&self, text: &str) -> LayoutFit {
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self.layout_text(text, &mut self.initial_cursor(), &mut TextNoOp)
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}
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pub fn render_text(&self, text: &str) {
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self.layout_text(text, &mut self.initial_cursor(), &mut TextRenderer);
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}
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pub fn layout_ops<'o>(
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mut self,
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ops: &mut dyn Iterator<Item = Op<'o>>,
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cursor: &mut Point,
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sink: &mut dyn LayoutSink,
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) -> LayoutFit {
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let init_cursor = *cursor;
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let mut total_processed_chars = 0;
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for op in ops {
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match op {
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Op::Color(color) => {
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self.text_color = color;
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}
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Op::Font(font) => {
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self.text_font = font;
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}
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Op::Text(text) => match self.layout_text(text, cursor, sink) {
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LayoutFit::Fitting {
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processed_chars, ..
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} => {
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total_processed_chars += processed_chars;
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}
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LayoutFit::OutOfBounds {
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processed_chars, ..
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} => {
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total_processed_chars += processed_chars;
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return LayoutFit::OutOfBounds {
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processed_chars: total_processed_chars,
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height: self.layout_height(init_cursor, *cursor),
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};
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}
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},
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}
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}
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LayoutFit::Fitting {
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processed_chars: total_processed_chars,
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height: self.layout_height(init_cursor, *cursor),
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}
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}
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pub fn layout_text(
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&self,
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text: &str,
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cursor: &mut Point,
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sink: &mut dyn LayoutSink,
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) -> LayoutFit {
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let init_cursor = *cursor;
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let bottom = (self.bounds.y1 - self.padding_bottom).max(self.bounds.y0);
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let mut remaining_text = text;
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// Check if bounding box is high enough for at least one line.
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if cursor.y > bottom {
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sink.out_of_bounds();
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return LayoutFit::OutOfBounds {
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processed_chars: 0,
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height: 0,
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};
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}
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while !remaining_text.is_empty() {
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let span = Span::fit_horizontally(
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remaining_text,
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self.bounds.x1 - cursor.x,
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self.text_font,
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self.hyphen_font,
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self.line_breaking,
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);
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// Report the span at the cursor position.
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sink.text(*cursor, self, &remaining_text[..span.length]);
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// Continue with the rest of the remaining_text.
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remaining_text = &remaining_text[span.length + span.skip_next_chars..];
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// Advance the cursor horizontally.
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cursor.x += span.advance.x;
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if span.advance.y > 0 {
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// We're advancing to the next line.
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// Check if we should be appending a hyphen at this point.
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if span.insert_hyphen_before_line_break {
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sink.hyphen(*cursor, self);
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}
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// Check the amount of vertical space we have left.
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if cursor.y + span.advance.y > bottom {
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if !remaining_text.is_empty() {
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// Append ellipsis to indicate more content is available, but only if we
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// haven't already appended a hyphen.
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let should_append_ellipsis =
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matches!(self.page_breaking, PageBreaking::CutAndInsertEllipsis)
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&& !span.insert_hyphen_before_line_break;
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if should_append_ellipsis {
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sink.ellipsis(*cursor, self);
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}
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// TODO: This does not work in case we are the last
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// fitting text token on the line, with more text tokens
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// following and `text.is_empty() == true`.
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}
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// Report we are out of bounds and quit.
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sink.out_of_bounds();
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return LayoutFit::OutOfBounds {
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processed_chars: text.len() - remaining_text.len(),
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height: self.layout_height(init_cursor, *cursor),
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};
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} else {
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// Advance the cursor to the beginning of the next line.
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cursor.x = self.bounds.x0;
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cursor.y += span.advance.y;
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// Report a line break. While rendering works using the cursor coordinates, we
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// use explicit line-break reporting in the `Trace` impl.
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sink.line_break(*cursor);
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}
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}
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}
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LayoutFit::Fitting {
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processed_chars: text.len(),
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height: self.layout_height(init_cursor, *cursor),
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}
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}
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fn layout_height(&self, init_cursor: Point, end_cursor: Point) -> i32 {
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self.padding_top
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+ self.text_font.text_height()
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+ (end_cursor.y - init_cursor.y)
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+ self.padding_bottom
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}
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}
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pub enum LayoutFit {
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/// Entire content fits. Vertical size is returned in `height`.
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Fitting { processed_chars: usize, height: i32 },
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/// Content fits partially or not at all.
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OutOfBounds { processed_chars: usize, height: i32 },
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}
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impl LayoutFit {
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pub fn height(&self) -> i32 {
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match self {
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LayoutFit::Fitting { height, .. } => *height,
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LayoutFit::OutOfBounds { height, .. } => *height,
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}
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}
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}
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/// Visitor for text segment operations.
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pub trait LayoutSink {
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fn text(&mut self, _cursor: Point, _layout: &TextLayout, _text: &str) {}
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fn hyphen(&mut self, _cursor: Point, _layout: &TextLayout) {}
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fn ellipsis(&mut self, _cursor: Point, _layout: &TextLayout) {}
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fn line_break(&mut self, _cursor: Point) {}
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fn out_of_bounds(&mut self) {}
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}
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pub struct TextNoOp;
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impl LayoutSink for TextNoOp {}
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pub struct TextRenderer;
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impl LayoutSink for TextRenderer {
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fn text(&mut self, cursor: Point, layout: &TextLayout, text: &str) {
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display::text(
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cursor,
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text,
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layout.text_font,
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layout.text_color,
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layout.background_color,
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);
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}
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fn hyphen(&mut self, cursor: Point, layout: &TextLayout) {
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display::text(
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cursor,
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"-",
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layout.hyphen_font,
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layout.hyphen_color,
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layout.background_color,
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);
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}
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fn ellipsis(&mut self, cursor: Point, layout: &TextLayout) {
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display::text(
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cursor,
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"...",
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layout.ellipsis_font,
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layout.ellipsis_color,
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layout.background_color,
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);
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}
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}
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#[cfg(feature = "ui_debug")]
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pub mod trace {
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use crate::ui::geometry::Point;
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use super::*;
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pub struct TraceSink<'a>(pub &'a mut dyn crate::trace::Tracer);
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impl<'a> LayoutSink for TraceSink<'a> {
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fn text(&mut self, _cursor: Point, _layout: &TextLayout, text: &str) {
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self.0.string(text);
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}
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fn hyphen(&mut self, _cursor: Point, _layout: &TextLayout) {
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self.0.string("-");
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}
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fn ellipsis(&mut self, _cursor: Point, _layout: &TextLayout) {
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self.0.string("...");
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}
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fn line_break(&mut self, _cursor: Point) {
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self.0.string("\n");
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}
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}
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}
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#[derive(Copy, Clone, PartialEq, Eq)]
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pub enum Op<'a> {
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/// Render text with current color and font.
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Text(&'a str),
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/// Set current text color.
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Color(Color),
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/// Set currently used font.
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Font(Font),
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}
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impl<'a> Op<'a> {
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pub fn skip_n_text_bytes(
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ops: impl Iterator<Item = Op<'a>>,
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skip_bytes: usize,
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) -> impl Iterator<Item = Op<'a>> {
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let mut skipped = 0;
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ops.filter_map(move |op| match op {
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Op::Text(text) if skipped < skip_bytes => {
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skipped = skipped.saturating_add(text.len());
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if skipped > skip_bytes {
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let leave_bytes = skipped - skip_bytes;
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Some(Op::Text(&text[text.len() - leave_bytes..]))
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} else {
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None
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}
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}
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op_to_pass_through => Some(op_to_pass_through),
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})
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}
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}
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#[derive(Debug, PartialEq, Eq)]
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struct Span {
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/// How many characters from the input text this span is laying out.
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length: usize,
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/// How many chars from the input text should we skip before fitting the
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/// next span?
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skip_next_chars: usize,
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/// By how much to offset the cursor after this span. If the vertical offset
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/// is bigger than zero, it means we are breaking the line.
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advance: Offset,
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/// If we are breaking the line, should we insert a hyphen right after this
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/// span to indicate a word-break?
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insert_hyphen_before_line_break: bool,
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}
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impl Span {
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fn fit_horizontally(
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text: &str,
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max_width: i32,
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text_font: impl GlyphMetrics,
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hyphen_font: impl GlyphMetrics,
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breaking: LineBreaking,
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) -> Self {
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const ASCII_LF: char = '\n';
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const ASCII_CR: char = '\r';
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const ASCII_SPACE: char = ' ';
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const ASCII_HYPHEN: char = '-';
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fn is_whitespace(ch: char) -> bool {
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ch == ASCII_SPACE || ch == ASCII_LF || ch == ASCII_CR
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}
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let hyphen_width = hyphen_font.char_width(ASCII_HYPHEN);
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// The span we return in case the line has to break. We mutate it in the
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// possible break points, and its initial value is returned in case no text
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// at all is fitting the constraints: zero length, zero width, full line
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// break.
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let mut line = Self {
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length: 0,
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advance: Offset::y(text_font.line_height()),
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insert_hyphen_before_line_break: false,
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skip_next_chars: 0,
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};
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let mut span_width = 0;
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let mut found_any_whitespace = false;
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let mut char_indices_iter = text.char_indices().peekable();
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// Iterating manually because we need a reference to the iterator inside the
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// loop.
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while let Some((i, ch)) = char_indices_iter.next() {
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let char_width = text_font.char_width(ch);
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// Consider if we could be breaking the line at this position.
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if is_whitespace(ch) {
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// Break before the whitespace, without hyphen.
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line.length = i;
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line.advance.x = span_width;
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line.insert_hyphen_before_line_break = false;
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line.skip_next_chars = 1;
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if ch == ASCII_CR {
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// We'll be breaking the line, but advancing the cursor only by a half of the
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// regular line height.
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line.advance.y = text_font.line_height() / 2;
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}
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if ch == ASCII_LF || ch == ASCII_CR {
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// End of line, break immediately.
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return line;
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}
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found_any_whitespace = true;
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} else if span_width + char_width > max_width {
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// Return the last breakpoint.
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return line;
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} else {
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let have_space_for_break = span_width + char_width + hyphen_width <= max_width;
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let can_break_word = matches!(breaking, LineBreaking::BreakWordsAndInsertHyphen)
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|| !found_any_whitespace;
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if have_space_for_break && can_break_word {
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// Break after this character, append hyphen.
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line.length = match char_indices_iter.peek() {
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Some((idx, _)) => *idx,
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None => text.len(),
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};
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line.advance.x = span_width + char_width;
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line.insert_hyphen_before_line_break = true;
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line.skip_next_chars = 0;
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}
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}
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|
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span_width += char_width;
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}
|
|
|
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// The whole text is fitting.
|
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Self {
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length: text.len(),
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advance: Offset::x(span_width),
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insert_hyphen_before_line_break: false,
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skip_next_chars: 0,
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}
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
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|
use super::*;
|
|
|
|
pub struct Fixed {
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|
pub width: i32,
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|
pub height: i32,
|
|
}
|
|
|
|
impl GlyphMetrics for Fixed {
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|
fn char_width(&self, _ch: char) -> i32 {
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self.width
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}
|
|
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fn line_height(&self) -> i32 {
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self.height
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}
|
|
}
|
|
|
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const FIXED_FONT: Fixed = Fixed {
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width: 1,
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height: 1,
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};
|
|
|
|
#[test]
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|
fn test_span() {
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assert_eq!(spans_from("hello", 5), vec![("hello", false)]);
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assert_eq!(spans_from("", 5), vec![("", false)]);
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assert_eq!(
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spans_from("hello world", 5),
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vec![("hello", false), ("world", false)]
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);
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|
assert_eq!(
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spans_from("hello\nworld", 5),
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|
vec![("hello", false), ("world", false)]
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|
);
|
|
}
|
|
|
|
#[test]
|
|
#[ignore]
|
|
fn test_leading_trailing() {
|
|
assert_eq!(
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|
spans_from("\nhello\nworld\n", 5),
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|
vec![("", false), ("hello", false), ("world", false), ("", false)]
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|
);
|
|
}
|
|
|
|
#[test]
|
|
fn test_long_word() {
|
|
assert_eq!(
|
|
spans_from("Down with the establishment!", 5),
|
|
vec![
|
|
("Down", false),
|
|
("with", false),
|
|
("the", false),
|
|
("esta", true),
|
|
("blis", true),
|
|
("hmen", true),
|
|
("t!", false),
|
|
]
|
|
);
|
|
}
|
|
|
|
#[test]
|
|
fn test_char_boundary() {
|
|
assert_eq!(
|
|
spans_from("+ěščřžýáíé", 5),
|
|
vec![("+ěšč", true), ("řžýá", true), ("íé", false)]
|
|
);
|
|
}
|
|
|
|
fn spans_from(text: &str, max_width: i32) -> Vec<(&str, bool)> {
|
|
let mut spans = vec![];
|
|
let mut remaining_text = text;
|
|
loop {
|
|
let span = Span::fit_horizontally(
|
|
remaining_text,
|
|
max_width,
|
|
FIXED_FONT,
|
|
FIXED_FONT,
|
|
LineBreaking::BreakAtWhitespace,
|
|
);
|
|
spans.push((
|
|
&remaining_text[..span.length],
|
|
span.insert_hyphen_before_line_break,
|
|
));
|
|
remaining_text = &remaining_text[span.length + span.skip_next_chars..];
|
|
if remaining_text.is_empty() {
|
|
break;
|
|
}
|
|
}
|
|
spans
|
|
}
|
|
}
|