# VariableBox

> VariableBox is manim-dsa's MVariable with a label: name above a box with the variable's value, width by height pixels, widening to fit a longer value.…

Page: https://fframes-kit.pages.dev/docs/computer-science/variable-box/
Cargo feature: `cs` (`fframes-kit = { version = "..", features = ["cs"] }`)

`VariableBox` is manim-dsa's `MVariable` with a label: `name` above a box with the variable's
value, `width` by `height` pixels, widening to fit a longer value. `values` holds the value of
each step, the first at the start, and it changes every `step_time` seconds from `delay`, like
the steps of the other figures, so it can follow a trace step for step. On a change the old
value rises out of the box and the new one rises in, the box flashes `colors.compare` and
resizes. `value_at(seconds)` gives the value shown at a time of the video. Gallery scene:
`VariableBox` (the length and last value of an array as it grows and shrinks).

Gallery clip of `VariableBox`: https://fframes-kit.pages.dev/media/scenes/VariableBox-f6591dcb.mp4

```rust
use fframes_kit::prelude::*;

let sum = VariableBox {
    name: "sum",
    values: vec!["0".into(), "3".into(), "8".into()],
    delay: 1.0,
    step_time: 0.5,
    ..VariableBox::default()
};
assert_eq!((sum.value_at(0.0), sum.value_at(1.6)), (Some("0"), Some("3")));

fn variable<'a>(ui: &mut Ui<'a, '_, '_>, values: Vec<String>) -> Svgr<'a> {
    ui.show(VariableBox {
        name: "len(a)",
        values,
        step_time: 0.8,
        ..ui.defaults()
    })
}
```

## API

Components are plain structs. Set the fields you need and fill the rest with `..ui.defaults()`: the defaults below come from the current theme (`theme.` values are fields of `Theme`).

### VariableBox

| Field | Type | Default | Description |
| --- | --- | --- | --- |
| `name` | `&str` | `""` | Name written above the box. |
| `values` | `Vec<String>` | `Vec::new()` | The value at each step, as text; the first shows at the start. Empty draws nothing. |
| `delay` | `f32` | `0.0` | Seconds after the container's start before the value first changes. |
| `step_time` | `f32` | `0.8` | Seconds each value is shown before the next. |
| `center` | `(f64, f64)` | `(0.0, 0.0)` | The middle of the box, in units of `ui.space`. |
| `width` | `f32` | `120.0` | Smallest width of the box in pixels; it widens to fit a longer value. |
| `height` | `f32` | `80.0` | Height of the box in pixels. |
| `colors` | `CellColors` | `CellColors::themed(theme)` | Colours of the box; it flashes `colors.compare` when the value changes. |
| `name_color` | `Color` | `theme.colors.text` | Colour of the name above the box. |
| `value_style` | `TextStyle` | `value_style` | The font of the value in the box. |
| `name_style` | `TextStyle` | `theme.typography.caption` | The font of the name. |
| `enter` | `Option<FadeIn>` | `None` | Fade in at the start; `None` for none. |
| `exit` | `Option<FadeOut>` | `None` | Fade out before the end; `None` for none. |

Methods:

- `fn value_at(&self, seconds: f32) -> Option<&str>`: The value `seconds` into the video: the first value before `delay`, the last after the last step. `None` without values.

Feature `cs` · [Source](https://github.com/khanhthanhdev/fframes-kit/blob/main/fframes-kit/src/kits/cs/variable.rs#L29)