# dev_menu [](https://travis-ci.org/PistonDevelopers/dev_menu)
In-game developer menu for Piston and [gfx-rs](https://github.com/gfx-rs/gfx-rs)
[Documentation](http://www.piston.rs/docs/dev_menu/dev_menu/)
## Usage
A `Menu` instance can be intitialized to operate on some particular type, for example a "Settings" struct:
```Rust
pub struct Settings {
setting_a: bool,
setting_b: f32,
// ... etc
}
...
let mut menu = dev_menu::Menu<Settings>::new();
```
Menu items display in a vertical list, and the selection can be changed with the up and down arrow keys.
Items can be added to the menu with `add_item`. An `ActionItem`, when selected, executes a given closure when the spacebar or left or right arrow keys are hit. For example, it can be used to toggle a boolean setting as follows:
```Rust
menu.add_item(dev_menu::MenuItem::action_item(
"Toggle Setting A", // Label for the item
Box::new(|ref mut settings| { settings.setting_a = !settings.setting_a; }) // Closure to execute
));
```
A `SliderItem`, when selected, can be used to increment or decrement a particular value while the right or left arrow keys are held down, using a pair of accessor closures to get or set the value within the settings object. It will also display the current value to the right of the label. For example:
```Rust
menu.add_item(dev_menu::MenuItem::slider_item(
"Setting B = ", // Label for the item. Value will show to the right
[-5.0, 5.0], // Valid range for the value
0.01, // Value to increment / decrement by on each update, while key is held down
Box::new(|ref settings| { settings.setting_b }), // Closure for retrieving value
Box::new(|ref mut settings, value| { settings.setting_b = value }), // Closure for setting value
));
```
To update and render the menu, using the Piston event loop:
```Rust
for e in window.events() {
// Send event to menu, with the settings object that should be accessed and/or modified
menu.event(&e, &mut settings);
...
e.render(|args| {
...
// Draw the menu with gfx_debug_draw::DebugRenderer
menu.draw(&settings, &mut debug_renderer);
...
}
}
```