crates/plotters/src/chart/state.rs

use std::sync::Arc;

use super::ChartContext;
use crate::coord::{CoordTranslate, Shift};
use crate::drawing::DrawingArea;
use plotters_backend::DrawingBackend;

/// A chart context state - This is the data that is needed to reconstruct the chart context
/// without actually drawing the chart. This is useful when we want to do realtime rendering and
/// want to incrementally update the chart.
///
/// For each frame, instead of updating the entire backend, we are able to keep the keep the figure
/// component like axis, labels untouched and make updates only in the plotting drawing area.
/// This is very useful for incremental render.
/// ```rust
///   use plotters::prelude::*;
///    let mut buffer = vec![0u8;1024*768*3];
///    let area = BitMapBackend::with_buffer(&mut buffer[..], (1024, 768))
///        .into_drawing_area()
///        .split_evenly((1,2));
///    let chart = ChartBuilder::on(&area[0])
///        .caption("Incremental Example", ("sans-serif", 20))
///        .set_all_label_area_size(30)
///        .build_cartesian_2d(0..10, 0..10)
///        .expect("Unable to build ChartContext");
///    // Draw the first frame at this point
///    area[0].present().expect("Present");
///    let state = chart.into_chart_state();
///    // Let's draw the second frame
///    let chart = state.restore(&area[0]);
///    chart.plotting_area().fill(&WHITE).unwrap(); // Clear the previously drawn graph
///    // At this point, you are able to draw next frame
///```
#[derive(Clone)]
pub struct ChartState<CT: CoordTranslate> {
    drawing_area_pos: (i32, i32),
    drawing_area_size: (u32, u32),
    coord: CT,
}

impl<'a, DB: DrawingBackend, CT: CoordTranslate> From<ChartContext<'a, DB, CT>> for ChartState<CT> {
    fn from(chart: ChartContext<'a, DB, CT>) -> ChartState<CT> {
        ChartState {
            drawing_area_pos: chart.drawing_area_pos,
            drawing_area_size: chart.drawing_area.dim_in_pixel(),
            coord: chart.drawing_area.into_coord_spec(),
        }
    }
}

impl<'a, DB: DrawingBackend, CT: CoordTranslate> ChartContext<'a, DB, CT> {
    /// Convert a chart context into a chart state, by doing so, the chart context is consumed and
    /// a saved chart state is created for later use. This is typically used in incrmental rendering. See documentation of `ChartState` for more detailed example.
    pub fn into_chart_state(self) -> ChartState<CT> {
        self.into()
    }

    /// Convert the chart context into a sharable chart state.
    /// Normally a chart state can not be clone, since the coordinate spec may not be able to be
    /// cloned. In this case, we can use an `Arc` get the coordinate wrapped thus the state can be
    /// cloned and shared by multiple chart context
    pub fn into_shared_chart_state(self) -> ChartState<Arc<CT>> {
        ChartState {
            drawing_area_pos: self.drawing_area_pos,
            drawing_area_size: self.drawing_area.dim_in_pixel(),
            coord: Arc::new(self.drawing_area.into_coord_spec()),
        }
    }
}

impl<'a, DB, CT> From<&ChartContext<'a, DB, CT>> for ChartState<CT>
where
    DB: DrawingBackend,
    CT: CoordTranslate + Clone,
{
    fn from(chart: &ChartContext<'a, DB, CT>) -> ChartState<CT> {
        ChartState {
            drawing_area_pos: chart.drawing_area_pos,
            drawing_area_size: chart.drawing_area.dim_in_pixel(),
            coord: chart.drawing_area.as_coord_spec().clone(),
        }
    }
}

impl<'a, DB: DrawingBackend, CT: CoordTranslate + Clone> ChartContext<'a, DB, CT> {
    /// Make the chart context, do not consume the chart context and clone the coordinate spec
    pub fn to_chart_state(&self) -> ChartState<CT> {
        self.into()
    }
}

impl<CT: CoordTranslate> ChartState<CT> {
    /// Restore the chart context on the given drawing area
    ///
    /// - `area`: The given drawing area where we want to restore the chart context
    /// - **returns** The newly created chart context
    pub fn restore<'a, DB: DrawingBackend>(
        self,
        area: &DrawingArea<DB, Shift>,
    ) -> ChartContext<'a, DB, CT> {
        let area = area
            .clone()
            .shrink(self.drawing_area_pos, self.drawing_area_size);
        ChartContext {
            x_label_area: [None, None],
            y_label_area: [None, None],
            drawing_area: area.apply_coord_spec(self.coord),
            series_anno: vec![],
            drawing_area_pos: self.drawing_area_pos,
        }
    }
}