112 lines
3.5 KiB
Rust
112 lines
3.5 KiB
Rust
//! Linear gradient builder & definition.
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use crate::gradient::{ColorStop, Gradient, Position};
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use crate::{Color, Point};
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/// A linear gradient that can be used in the style of [`Fill`] or [`Stroke`].
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///
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/// [`Fill`]: crate::widget::canvas::Fill
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/// [`Stroke`]: crate::widget::canvas::Stroke
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#[derive(Debug, Clone, PartialEq)]
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pub struct Linear {
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/// The point where the linear gradient begins.
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pub start: Point,
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/// The point where the linear gradient ends.
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pub end: Point,
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/// [`ColorStop`]s along the linear gradient path.
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pub color_stops: Vec<ColorStop>,
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}
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/// A [`Linear`] builder.
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#[derive(Debug)]
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pub struct Builder {
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start: Point,
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end: Point,
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stops: Vec<ColorStop>,
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error: Option<BuilderError>,
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}
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impl Builder {
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/// Creates a new [`Builder`].
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pub fn new(position: Position) -> Self {
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let (start, end) = match position {
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Position::Absolute { start, end } => (start, end),
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Position::Relative {
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top_left,
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size,
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start,
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end,
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} => (
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start.to_absolute(top_left, size),
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end.to_absolute(top_left, size),
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),
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};
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Self {
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start,
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end,
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stops: vec![],
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error: None,
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}
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}
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/// Adds a new stop, defined by an offset and a color, to the gradient.
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///
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/// `offset` must be between `0.0` and `1.0` or the gradient cannot be built.
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///
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/// Note: when using the [`glow`] backend, any color stop added after the 16th
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/// will not be displayed.
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///
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/// On the [`wgpu`] backend this limitation does not exist (technical limit is 524,288 stops).
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///
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/// [`glow`]: https://docs.rs/iced_glow
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/// [`wgpu`]: https://docs.rs/iced_wgpu
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pub fn add_stop(mut self, offset: f32, color: Color) -> Self {
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if offset.is_finite() && (0.0..=1.0).contains(&offset) {
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match self.stops.binary_search_by(|stop| {
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stop.offset.partial_cmp(&offset).unwrap()
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}) {
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Ok(_) => {
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self.error = Some(BuilderError::DuplicateOffset(offset))
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}
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Err(index) => {
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self.stops.insert(index, ColorStop { offset, color });
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}
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}
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} else {
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self.error = Some(BuilderError::InvalidOffset(offset))
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};
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self
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}
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/// Builds the linear [`Gradient`] of this [`Builder`].
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///
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/// Returns `BuilderError` if gradient in invalid.
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pub fn build(self) -> Result<Gradient, BuilderError> {
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if self.stops.is_empty() {
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Err(BuilderError::MissingColorStop)
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} else if let Some(error) = self.error {
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Err(error)
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} else {
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Ok(Gradient::Linear(Linear {
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start: self.start,
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end: self.end,
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color_stops: self.stops,
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}))
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}
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}
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}
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/// An error that happened when building a [`Linear`] gradient.
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#[derive(Debug, thiserror::Error)]
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pub enum BuilderError {
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#[error("Gradients must contain at least one color stop.")]
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/// Gradients must contain at least one color stop.
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MissingColorStop,
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#[error("Offset {0} must be a unique, finite number.")]
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/// Offsets in a gradient must all be unique & finite.
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DuplicateOffset(f32),
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#[error("Offset {0} must be between 0.0..=1.0.")]
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/// Offsets in a gradient must be between 0.0..=1.0.
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InvalidOffset(f32),
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}
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