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//! Traits for fonts and text handling. use std::ops::{Range, RangeBounds}; use crate::kurbo::{Point, Rect, Size}; use crate::{Color, Error, FontFamily, FontStyle, FontWeight}; /// The Piet text API. /// /// This trait is the interface for text-related functionality, such as font /// management and text layout. pub trait Text: Clone { /// A concrete type that implements the [`TextLayoutBuilder`] trait. /// /// [`TextLayoutBuilder`]: trait.TextLayoutBuilder.html type TextLayoutBuilder: TextLayoutBuilder<Out = Self::TextLayout>; /// A concrete type that implements the [`TextLayout`] trait. /// /// [`TextLayout`]: trait.TextLayout.html type TextLayout: TextLayout; /// Query the platform for a font with a given name, and return a [`FontFamily`] /// object corresponding to that font, if it is found. /// /// # Examples /// /// Trying a preferred font, falling back if it isn't found. /// /// ``` /// # use piet::*; /// # let mut ctx = NullRenderContext::new(); /// # let text = ctx.text(); /// let text_font = text.font_family("Charter") /// .or_else(|| text.font_family("Garamond")) /// .unwrap_or(FontFamily::SERIF); /// ``` /// /// [`FontFamily`]: struct.FontFamily.html fn font_family(&mut self, family_name: &str) -> Option<FontFamily>; /// Load the provided font data and make it available for use. /// /// This method takes font data (such as the contents of a file on disk) and /// attempts to load it, making it subsequently available for use. /// /// If loading is successful, this method will return a [`FontFamily`] handle /// that can be used to select this font when constructing a [`TextLayout`]. /// /// # Notes /// /// ## font families and styles: /// /// If you wish to use multiple fonts in a given family, you will need to /// load them individually. This method will return the same handle for /// each font in the same family; the handle **does not refer to a specific /// font**. This means that if you load bold and regular fonts from the /// same family, to *use* the bold version you must, when constructing your /// [`TextLayout`], pass the family as well as the correct weight. /// /// *If you wish to use custom fonts, load each concrete instance of the /// font-family that you wish to use; that is, if you are using regular, /// bold, italic, and bold-italic, you should be loading four distinct fonts.* /// /// ## family name masking /// /// If you load a custom font, the family name of your custom font will take /// precedence over system families of the same name; so your 'Helvetica' will /// potentially interfere with the use of the platform 'Helvetica'. /// /// # Examples /// /// ``` /// # use piet::*; /// # let mut ctx = NullRenderContext::new(); /// # let text = ctx.text(); /// # fn get_font_data(name: &str) -> Vec<u8> { Vec::new() } /// let helvetica_regular = get_font_data("Helvetica-Regular"); /// let helvetica_bold = get_font_data("Helvetica-Bold"); /// /// let regular = text.load_font(&helvetica_regular).unwrap(); /// let bold = text.load_font(&helvetica_bold).unwrap(); /// assert_eq!(regular, bold); /// /// let layout = text.new_text_layout("Custom Fonts") /// .font(regular, 12.0) /// .range_attribute(6.., FontWeight::BOLD); /// /// ``` /// /// [`TextLayout`]: trait.TextLayout.html /// [`FontFamily`]: struct.FontFamily.html fn load_font(&mut self, data: &[u8]) -> Result<FontFamily, Error>; /// Create a new layout object to display the provided `text`. /// /// The returned object is a [`TextLayoutBuilder`]; methods on that type /// can be used to customize the layout. /// /// The text is a type that impls `Into<Arc<str>>`. This is an optimization; /// because the layout object needs to retain the text, if the caller wants /// to avoid duplicate data they can use an `Arc`. If this doesn't matter, /// they can pass a `&str`, which the layout will retain. /// /// [`TextLayoutBuilder`]: trait.TextLayoutBuilder.html fn new_text_layout(&mut self, text: impl TextStorage) -> Self::TextLayoutBuilder; } /// A type that stores text. /// /// This allows the client to more completely control how text is stored. /// If you do not care about this, implementations are provided for `String`, /// `Arc<str>`, and `Rc<str>`. /// /// This has a `'static` bound because the inner type will be behind a shared /// pointer. /// /// # Implementors /// /// This trait expects immutable data. Mutating the data (using interior mutability) /// May cause any [`TextLayout`] objects using this [`TextStorage`] to become /// inconsistent. pub trait TextStorage: 'static { /// Return the underlying text as a contiguous buffer. /// /// Types that do not store their text as a contiguous buffer (such as ropes /// or gap buffers) will need to use a wrapper to maintain a separate /// contiguous buffer as required. /// /// In practice, these types should be using a [`TextLayout`] object /// per paragraph, and in general a separate buffer will be unnecessary. /// /// [`TextLayout`]: trait.TextLayout.html fn as_str(&self) -> &str; } impl std::ops::Deref for dyn TextStorage { type Target = str; fn deref(&self) -> &Self::Target { self.as_str() } } /// Attributes that can be applied to text. pub enum TextAttribute { /// The font family. FontFamily(FontFamily), /// The font size, in points. FontSize(f64), /// The [`FontWeight`](struct.FontWeight.html). Weight(FontWeight), /// The foreground color of the text. TextColor(crate::Color), /// The [`FontStyle`]; either regular or italic. /// /// [`FontStyle`]: enum.FontStyle.html Style(FontStyle), /// Underline. Underline(bool), /// Strikethrough. Strikethrough(bool), } /// A trait for laying out text. pub trait TextLayoutBuilder: Sized { type Out: TextLayout; /// Set a max width for this layout. /// /// You may pass an `f64` to this method to indicate a width (in display points) /// that will be used for word-wrapping. /// /// If you pass `f64::INFINITY`, words will not be wrapped; this is the /// default behaviour. fn max_width(self, width: f64) -> Self; /// Set the [`TextAlignment`] to be used for this layout. /// /// [`TextAlignment`]: enum.TextAlignment.html fn alignment(self, alignment: TextAlignment) -> Self; /// A convenience method for setting the default font family and size. /// /// # Examples /// /// ``` /// # use piet::*; /// # let mut ctx = NullRenderContext::new(); /// # let mut text = ctx.text(); /// /// let times = text.font_family("Times New Roman").unwrap(); /// /// // the following are equivalent /// let layout_one = text.new_text_layout("hello everyone!") /// .font(times.clone(), 12.0) /// .build(); /// /// let layout_two = text.new_text_layout("hello everyone!") /// .default_attribute(TextAttribute::FontFamily(times.clone())) /// .default_attribute(TextAttribute::FontSize(12.0)) /// .build(); /// ``` fn font(self, font: FontFamily, font_size: f64) -> Self { self.default_attribute(TextAttribute::FontFamily(font)) .default_attribute(TextAttribute::FontSize(font_size)) } /// A convenience method for setting the default text color. /// /// This is equivalent to passing `TextAttribute::TextColor` to the /// `default_attribute` method. fn text_color(self, color: Color) -> Self { self.default_attribute(TextAttribute::TextColor(color)) } /// Add a default [`TextAttribute`] for this layout. /// /// Default attributes will be used for regions of the layout that do not /// have explicit attributes added via [`range_attribute`]. /// /// You must set default attributes before setting range attributes, /// or the implementation is free to ignore them. /// /// [`TextAttribute`]: enum.TextAttribute.html /// [`range_attribute`]: #tymethod.range_attribute fn default_attribute(self, attribute: impl Into<TextAttribute>) -> Self; /// Add a [`TextAttribute`] to a range of this layout. /// /// The `range` argument is can be any of the range forms accepted by /// slice indexing, such as `..`, `..n`, `n..`, `n..m`, etcetera. /// /// The `attribute` argument is a [`TextAttribute`] or any type that can be /// converted to such an attribute; for instance you may pass a [`FontWeight`] /// directly. /// /// ## Notes /// /// This is a low-level API; what this means in particular is that it is designed /// to be efficiently implemented, not necessarily ergonomic to use, and there /// may be a few gotchas. /// /// **ranges of added attributes should be added in non-decreasing start order**. /// This is to say that attributes should be added in the order of the start /// of their ranges. Attributes added out of order may be skipped. /// /// **attributes do not stack**. Setting the range `0..100` to `FontWeight::BOLD` /// and then setting the range `20..50` to `FontWeight::THIN` will result in /// the range `50..100` being reset to the default font weight; we will not /// remember that you had earlier set it to `BOLD`. /// /// ## Examples /// /// ``` /// # use piet::*; /// # let mut ctx = NullRenderContext::new(); /// # let mut text = ctx.text(); /// /// let times = text.font_family("Times New Roman").unwrap(); /// let layout = text.new_text_layout("This API is okay, I guess?") /// .font(FontFamily::MONOSPACE, 12.0) /// .default_attribute(FontStyle::Italic) /// .range_attribute(..5, FontWeight::BOLD) /// .range_attribute(5..14, times) /// .range_attribute(20.., TextAttribute::TextColor(Color::rgb(1.0, 0., 0.,))) /// .build(); /// ``` /// /// [`TextAttribute`]: enum.TextAttribute.html /// [`FontWeight`]: struct.FontWeight.html fn range_attribute( self, range: impl RangeBounds<usize>, attribute: impl Into<TextAttribute>, ) -> Self; fn build(self) -> Result<Self::Out, Error>; } /// The alignment of text in a [`TextLayout`]. /// /// [`TextLayout`]: trait.TextLayout.html #[derive(Debug, Clone, Copy, PartialEq, Eq)] pub enum TextAlignment { /// Text is aligned to the left edge in left-to-right scripts, and the /// right edge in right-to-left scripts. Start, /// Text is aligned to the right edge in left-to-right scripts, and the /// left edge in right-to-left scripts. End, Center, Justified, } /// A drawable text object. /// /// ## Line Breaks /// /// A text layout may be broken into multiple lines in order to fit within a given width. /// Line breaking is generally done between words (whitespace-separated). /// /// A line's text and [`LineMetric`][]s can be accessed by 0-indexed line number. /// /// ## Text Position /// /// A text position is the offset in the underlying string, defined in utf-8 /// code units, as is standard for Rust strings. /// /// However, text position is also related to valid cursor positions. Therefore: /// - The beginning of a line has text position `0`. /// - The end of a line is a valid text position. e.g. `text.len()` is a valid text position. /// - If the text position is not at a code point or grapheme boundary, undesirable behavior may /// occur. /// /// [`LineMetric`]: struct.LineMetric.html pub trait TextLayout: Clone { /// The total size of this `TextLayout`. /// /// This is the size required to draw this `TextLayout`, as provided by the /// platform text system. /// /// If the layout is empty (the text is the empty string) the returned /// `Size` will have the height required to draw a cursor in the layout's /// default font. /// /// # Note /// /// This is not currently defined very rigorously; in particular we do not /// specify whether this should include half-leading or paragraph spacing /// above or below the text. /// /// We would ultimately like to review and attempt to standardize this /// behaviour, but it is out of scope for the time being. fn size(&self) -> Size; /// The width of this layout, including the width of any trailing whitespace. /// /// In many situations you do not want to include the width of trailing /// whitespace when measuring width; for instance when word-wrap is enabled, /// trailing whitespace is ignored. In other circumstances, however, this /// width is important, such as when editing a single line of text; in these /// cases you want to use this method to ensure you account for the actual /// size of any trailing whitespace. fn trailing_whitespace_width(&self) -> f64; /// Returns a `Rect` representing the bounding box of the glyphs in this layout, /// relative to the top-left of the layout object. /// /// This is sometimes called the bounding box or the inking rect, and is /// used to determine when the layout has become visible (for instance, /// during scrolling) and thus needs to be drawn. fn image_bounds(&self) -> Rect; /// The text used to create this layout. fn text(&self) -> &str; /// Given a line number, return a reference to that line's underlying string. /// /// This will include any trailing whitespace. fn line_text(&self, line_number: usize) -> Option<&str>; /// Given a line number, return a reference to that line's metrics, if the line exists. /// /// If this layout's text is the empty string, calling this method with `0` /// returns some [`LineMetric`]; this will use the layout's default font to /// determine what the expected height of the first line would be, which is /// necessary for things like cursor drawing. /// /// [`LineMetric`]: struct.LineMetric.html fn line_metric(&self, line_number: usize) -> Option<LineMetric>; /// Returns total number of lines in the text layout. /// /// The return value will always be greater than 0; a layout of the empty /// string is considered to have a single line. fn line_count(&self) -> usize; /// Given a `Point`, return a [`HitTestPoint`] describing the corresponding /// text position. /// /// This is used for things like mapping a mouse click to a cursor position. /// /// The point should be in the coordinate space of the layout object. /// /// ## Notes: /// /// This will always return *some* text position. If the point is outside of /// the bounds of the layout, it will return the nearest text position. /// /// For more on text positions, see docs for the [`TextLayout`] trait. /// /// [`HitTestPoint`]: struct.HitTestPoint.html /// [`TextLayout`]: ../piet/trait.TextLayout.html fn hit_test_point(&self, point: Point) -> HitTestPoint; /// Given a grapheme boundary in the string used to create this [`TextLayout`], /// return a [`HitTestPosition`] object describing the location of that boundary /// within the layout. /// /// For more on text positions, see docs for the [`TextLayout`] trait. /// /// ## Panics: /// /// This method will panic if the text position is not a character boundary, /// /// [`HitTestPosition`]: struct.HitTestPosition.html /// [`TextLayout`]: ../piet/trait.TextLayout.html fn hit_test_text_position(&self, idx: usize) -> HitTestPosition; /// Returns a vector of `Rect`s that cover the region of the text indicated /// by `range`. /// /// The returned rectangles are suitable for things like drawing selection /// regions or highlights. /// /// `range` will be clamped to the length of the text if necessary. /// /// Note: this implementation is not currently BiDi aware; it will be updated /// when BiDi support is added. fn rects_for_range(&self, range: impl RangeBounds<usize>) -> Vec<Rect> { let text_len = self.text().len(); let mut range = crate::util::resolve_range(range, text_len); range.start = range.start.min(text_len); range.end = range.end.min(text_len); if range.start >= range.end { return Vec::new(); } let first_line = self.hit_test_text_position(range.start).line; let last_line = self.hit_test_text_position(range.end).line; let mut result = Vec::new(); for line in first_line..=last_line { let metrics = self.line_metric(line).unwrap(); let y0 = metrics.y_offset; let y1 = y0 + metrics.height; let line_range_start = if line == first_line { range.start } else { metrics.start_offset }; let line_range_end = if line == last_line { range.end } else { metrics.end_offset - metrics.trailing_whitespace }; let start_point = self.hit_test_text_position(line_range_start); let end_point = self.hit_test_text_position(line_range_end); result.push(Rect::new(start_point.point.x, y0, end_point.point.x, y1)); } result } } /// Metadata about each line in a text layout. #[derive(Clone, Debug, Default, PartialEq)] pub struct LineMetric { /// The start index of this line in the underlying `String` used to create the /// [`TextLayout`] to which this line belongs. /// /// [`TextLayout`]: trait.TextLayout.html pub start_offset: usize, /// The end index of this line in the underlying `String` used to create the /// [`TextLayout`] to which this line belongs. /// /// This is the end of an exclusive range; this index is not part of the line. /// /// Includes trailing whitespace. /// /// [`TextLayout`]: trait.TextLayout.html pub end_offset: usize, /// The length of the trailing whitespace at the end of this line, in utf-8 /// code units. /// /// When lines are broken on whitespace (as is common), the whitespace /// is assigned to the end of the preceding line. Reporting the size of /// the trailing whitespace section lets an API consumer measure and render /// only the trimmed line up to the whitespace. pub trailing_whitespace: usize, /// The distance from the top of the line (`y_offset`) to the baseline. pub baseline: f64, /// The height of the line. /// /// This value is intended to be used to determine the height of features /// such as cursors and selection regions. Although it is generally the case /// that `y_offset + height` for line `n` is equal to the `y_offset` of /// line `n + 1`, this is not strictly enforced, and should not be counted on. pub height: f64, /// The y position of the top of this line, relative to the top of the layout. /// /// It should be possible to use this position, in conjunction with `height`, /// to determine the region that would be used for things like text selection. pub y_offset: f64, } impl LineMetric { /// The utf-8 range in the underlying `String` used to create the /// [`TextLayout`] to which this line belongs. /// /// [`TextLayout`]: trait.TextLayout.html #[inline] pub fn range(&self) -> Range<usize> { self.start_offset..self.end_offset } } /// Result of hit testing a point in a [`TextLayout`]. /// /// This type is returned by [`TextLayout::hit_test_point`]. /// /// [`TextLayout`]: ../piet/trait.TextLayout.html /// [`TextLayout::hit_test_point`]: ../piet/trait.TextLayout.html#tymethod.hit_test_point #[derive(Debug, Default, PartialEq)] #[non_exhaustive] pub struct HitTestPoint { /// The index representing the grapheme boundary closest to the `Point`. pub idx: usize, /// Whether or not the point was inside the bounds of the layout object. /// /// A click outside the layout object will still resolve to a position in the /// text; for instance a click to the right edge of a line will resolve to the /// end of that line, and a click below the last line will resolve to a /// position in that line. pub is_inside: bool, } /// Result of hit testing a text position in a [`TextLayout`]. /// /// This type is returned by [`TextLayout::hit_test_text_position`]. /// /// [`TextLayout`]: ../piet/trait.TextLayout.html /// [`TextLayout::hit_test_text_position`]: ../piet/trait.TextLayout.html#tymethod.hit_test_text_position #[derive(Debug, Default)] #[non_exhaustive] pub struct HitTestPosition { /// the `point`'s `x` value is the position of the leading edge of the /// grapheme cluster containing the text position. The `y` value corresponds /// to the baseline of the line containing that grapheme cluster. //FIXME: maybe we should communicate more about this position? for instance //instead of returning an x/y point, we could return the x offset, the line's y_offset, //and the line height (everything tou would need to draw a cursor) pub point: Point, /// The number of the line containing this position. /// /// This value can be used to retrieve the [`LineMetric`] for this line, /// via the [`TextLayout::line_metric`] method. /// /// [`LineMetric`]: struct.LineMetric.html /// [`TextLayout::line_metric`]: trait.TextLayout.html#tymethod.line_metric pub line: usize, } impl HitTestPoint { /// Only for use by backends #[doc(hidden)] pub fn new(idx: usize, is_inside: bool) -> HitTestPoint { HitTestPoint { idx, is_inside } } } impl HitTestPosition { /// Only for use by backends #[doc(hidden)] pub fn new(point: Point, line: usize) -> HitTestPosition { HitTestPosition { point, line } } } impl From<FontFamily> for TextAttribute { fn from(t: FontFamily) -> TextAttribute { TextAttribute::FontFamily(t) } } impl From<FontWeight> for TextAttribute { fn from(src: FontWeight) -> TextAttribute { TextAttribute::Weight(src) } } impl From<FontStyle> for TextAttribute { fn from(src: FontStyle) -> TextAttribute { TextAttribute::Style(src) } } impl Default for TextAlignment { fn default() -> Self { TextAlignment::Start } } impl TextStorage for std::sync::Arc<str> { fn as_str(&self) -> &str { self } } impl TextStorage for std::rc::Rc<str> { fn as_str(&self) -> &str { self } } impl TextStorage for String { fn as_str(&self) -> &str { self.as_str() } } impl TextStorage for std::sync::Arc<String> { fn as_str(&self) -> &str { self } } impl TextStorage for std::rc::Rc<String> { fn as_str(&self) -> &str { self } } impl TextStorage for &'static str { fn as_str(&self) -> &str { self } }