densa_chart/model.rs
1use densa_draw::Canvas;
2
3use crate::{Axis, AxisKind, ChartPalette, Plot};
4
5/// The data of a chart widget (`densa_widgets::Chart`): panes stacked top to bottom on one
6/// horizontal axis, each drawing its own series (candles over a line, volume bars below).
7///
8/// The widget decides what part of `x` shows (it follows the newest data until the user
9/// pans or zooms) and asks each pane for its vertical axis over that part, so panes scale to
10/// what is on screen. Painting goes through the series functions of this crate, which
11/// allocate nothing.
12pub trait ChartModel {
13 /// What the horizontal axis counts.
14 fn x_kind(&self) -> AxisKind {
15 AxisKind::Time
16 }
17
18 /// The lowest and highest `x` of the data, or `None` while there is none.
19 fn x_extent(&self) -> Option<(f64, f64)>;
20
21 /// The distance between two points (a candle's period), if the data has one: the
22 /// widget zooms in no further than a few of them.
23 fn x_step(&self) -> Option<f64> {
24 None
25 }
26
27 /// How many panes, top to bottom (one is drawn even for zero).
28 fn panes(&self) -> usize {
29 1
30 }
31
32 /// Pane `pane`'s share of the height, against the others' (above zero).
33 fn pane_weight(&self, pane: usize) -> f32 {
34 let _ = pane;
35 1.0
36 }
37
38 /// The vertical axis of pane `pane` while `x` shows: what its series need, with room
39 /// around them (see [`Axis::padded`]); `None` if it has nothing there.
40 fn y_axis(&self, pane: usize, x: &Axis) -> Option<Axis>;
41
42 /// Draws the series of pane `pane` onto `plot`, in `palette`'s colors.
43 fn paint(&self, pane: usize, plot: &Plot, canvas: &mut Canvas<'_>, palette: &ChartPalette);
44
45 /// Called before every frame is painted, to catch up with new data. Does nothing by
46 /// default.
47 fn prepare(&mut self) {}
48
49 /// What the chart shows, for screen readers ("ACME, one-minute candles, last 182.40").
50 /// Asked only while one is listening. Empty by default.
51 fn describe(&self) -> String {
52 String::new()
53 }
54}