zed/crates/gpui/docs/key_dispatch.md
2024-01-09 11:36:36 +02:00

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# Key Dispatch
GPUI is designed for keyboard-first interactivity.
To expose functionality to the mouse, you render a button with a click handler.
To expose functionality to the keyboard, you bind an *action* in a *key context*.
Actions are similar to framework-level events like `MouseDown`, `KeyDown`, etc, but you can define them yourself:
```rust
mod menu {
#[gpui::action]
struct MoveUp;
#[gpui::action]
struct MoveDown;
}
```
Actions are frequently unit structs, for which we have a macro. The above could also be written:
```rust
mod menu {
actions!(gpui, [MoveUp, MoveDown]);
}
```
Actions can also be more complex types:
```rust
mod menu {
#[gpui::action]
struct Move {
direction: Direction,
select: bool,
}
}
```
To bind actions, chain `on_action` on to your element:
```rust
impl Render for Menu {
fn render(&mut self, cx: &mut ViewContext<Self>) -> impl Component {
div()
.on_action(|this: &mut Menu, move: &MoveUp, cx: &mut ViewContext<Menu>| {
// ...
})
.on_action(|this, move: &MoveDown, cx| {
// ...
})
.children(unimplemented!())
}
}
```
In order to bind keys to actions, you need to declare a *key context* for part of the element tree by calling `key_context`.
```rust
impl Render for Menu {
fn render(&mut self, cx: &mut ViewContext<Self>) -> impl Component {
div()
.key_context("menu")
.on_action(|this: &mut Menu, move: &MoveUp, cx: &mut ViewContext<Menu>| {
// ...
})
.on_action(|this, move: &MoveDown, cx| {
// ...
})
.children(unimplemented!())
}
}
```
Now you can target your context in the keymap. Note how actions are identified in the keymap by their fully-qualified type name.
```json
{
"context": "menu",
"bindings": {
"up": "menu::MoveUp",
"down": "menu::MoveDown"
}
}
```
If you had opted for the more complex type definition, you'd provide the serialized representation of the action alongside the name:
```json
{
"context": "menu",
"bindings": {
"up": ["menu::Move", {direction: "up", select: false}]
"down": ["menu::Move", {direction: "down", select: false}]
"shift-up": ["menu::Move", {direction: "up", select: true}]
"shift-down": ["menu::Move", {direction: "down", select: true}]
}
}
```