1 files changed, 212 insertions, 0 deletions
diff --git a/core/src/text.rs b/core/src/text.rs
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+++ b/core/src/text.rs
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+//! Draw and interact with text.
+use crate::alignment;
+use crate::{Color, Pixels, Point, Rectangle, Size};
+
+use std::borrow::Cow;
+use std::hash::{Hash, Hasher};
+
+/// A paragraph.
+#[derive(Debug, Clone, Copy)]
+pub struct Text<'a, Font> {
+    /// The content of the paragraph.
+    pub content: &'a str,
+
+    /// The bounds of the paragraph.
+    pub bounds: Rectangle,
+
+    /// The size of the [`Text`] in logical pixels.
+    pub size: f32,
+
+    /// The line height of the [`Text`].
+    pub line_height: LineHeight,
+
+    /// The color of the [`Text`].
+    pub color: Color,
+
+    /// The font of the [`Text`].
+    pub font: Font,
+
+    /// The horizontal alignment of the [`Text`].
+    pub horizontal_alignment: alignment::Horizontal,
+
+    /// The vertical alignment of the [`Text`].
+    pub vertical_alignment: alignment::Vertical,
+
+    /// The [`Shaping`] strategy of the [`Text`].
+    pub shaping: Shaping,
+}
+
+/// The shaping strategy of some text.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
+pub enum Shaping {
+    /// No shaping and no font fallback.
+    ///
+    /// This shaping strategy is very cheap, but it will not display complex
+    /// scripts properly nor try to find missing glyphs in your system fonts.
+    ///
+    /// You should use this strategy when you have complete control of the text
+    /// and the font you are displaying in your application.
+    ///
+    /// This is the default.
+    #[default]
+    Basic,
+    /// Advanced text shaping and font fallback.
+    ///
+    /// You will need to enable this flag if the text contains a complex
+    /// script, the font used needs it, and/or multiple fonts in your system
+    /// may be needed to display all of the glyphs.
+    ///
+    /// Advanced shaping is expensive! You should only enable it when necessary.
+    Advanced,
+}
+
+/// The height of a line of text in a paragraph.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum LineHeight {
+    /// A factor of the size of the text.
+    Relative(f32),
+
+    /// An absolute height in logical pixels.
+    Absolute(Pixels),
+}
+
+impl LineHeight {
+    /// Returns the [`LineHeight`] in absolute logical pixels.
+    pub fn to_absolute(self, text_size: Pixels) -> Pixels {
+        match self {
+            Self::Relative(factor) => Pixels(factor * text_size.0),
+            Self::Absolute(pixels) => pixels,
+        }
+    }
+}
+
+impl Default for LineHeight {
+    fn default() -> Self {
+        Self::Relative(1.3)
+    }
+}
+
+impl From<f32> for LineHeight {
+    fn from(factor: f32) -> Self {
+        Self::Relative(factor)
+    }
+}
+
+impl From<Pixels> for LineHeight {
+    fn from(pixels: Pixels) -> Self {
+        Self::Absolute(pixels)
+    }
+}
+
+impl Hash for LineHeight {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        match self {
+            Self::Relative(factor) => {
+                state.write_u8(0);
+                factor.to_bits().hash(state);
+            }
+            Self::Absolute(pixels) => {
+                state.write_u8(1);
+                f32::from(*pixels).to_bits().hash(state);
+            }
+        }
+    }
+}
+
+/// The result of hit testing on text.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum Hit {
+    /// The point was within the bounds of the returned character index.
+    CharOffset(usize),
+}
+
+impl Hit {
+    /// Computes the cursor position of the [`Hit`] .
+    pub fn cursor(self) -> usize {
+        match self {
+            Self::CharOffset(i) => i,
+        }
+    }
+}
+
+/// A renderer capable of measuring and drawing [`Text`].
+pub trait Renderer: crate::Renderer {
+    /// The font type used.
+    type Font: Copy;
+
+    /// The icon font of the backend.
+    const ICON_FONT: Self::Font;
+
+    /// The `char` representing a ✔ icon in the [`ICON_FONT`].
+    ///
+    /// [`ICON_FONT`]: Self::ICON_FONT
+    const CHECKMARK_ICON: char;
+
+    /// The `char` representing a ▼ icon in the built-in [`ICON_FONT`].
+    ///
+    /// [`ICON_FONT`]: Self::ICON_FONT
+    const ARROW_DOWN_ICON: char;
+
+    /// Returns the default [`Self::Font`].
+    fn default_font(&self) -> Self::Font;
+
+    /// Returns the default size of [`Text`].
+    fn default_size(&self) -> f32;
+
+    /// Measures the text in the given bounds and returns the minimum boundaries
+    /// that can fit the contents.
+    fn measure(
+        &self,
+        content: &str,
+        size: f32,
+        line_height: LineHeight,
+        font: Self::Font,
+        bounds: Size,
+        shaping: Shaping,
+    ) -> Size;
+
+    /// Measures the width of the text as if it were laid out in a single line.
+    fn measure_width(
+        &self,
+        content: &str,
+        size: f32,
+        font: Self::Font,
+        shaping: Shaping,
+    ) -> f32 {
+        let bounds = self.measure(
+            content,
+            size,
+            LineHeight::Absolute(Pixels(size)),
+            font,
+            Size::INFINITY,
+            shaping,
+        );
+
+        bounds.width
+    }
+
+    /// Tests whether the provided point is within the boundaries of text
+    /// laid out with the given parameters, returning information about
+    /// the nearest character.
+    ///
+    /// If `nearest_only` is true, the hit test does not consider whether the
+    /// the point is interior to any glyph bounds, returning only the character
+    /// with the nearest centeroid.
+    fn hit_test(
+        &self,
+        contents: &str,
+        size: f32,
+        line_height: LineHeight,
+        font: Self::Font,
+        bounds: Size,
+        shaping: Shaping,
+        point: Point,
+        nearest_only: bool,
+    ) -> Option<Hit>;
+
+    /// Loads a [`Self::Font`] from its bytes.
+    fn load_font(&mut self, font: Cow<'static, [u8]>);
+
+    /// Draws the given [`Text`].
+    fn fill_text(&mut self, text: Text<'_, Self::Font>);
+}