Concepts

Four ideas compose the whole crate. Learn these and every example reads like prose.

Editor

Editor (in twrite-gpui) is the GPUI view and controller: it owns the EditorBuffer, the theme and config, the hook chain, and (since the prompt work) the shared PromptState plus the pending HookEffect queue. Its key handling has a fixed order:

1. Hooks run first via on_key; the first Consumed wins.
2. While a prompt is open, unconsumed keys never reach the buffer.
3. Otherwise the built-in editing keys apply (typing, undo, selection, ...).

Hooks

EditorHook (in twrite-core) is the only extension point, and it's GPUI-free. The methods you'll touch most:

• on_key: intercept input; return Consumed to halt the chain.
• before_insert: filter or rewrite typed text.
• after_edit: react to any buffer mutation.
• on_selection_change: track cursor/selection.
• status_text: feed the status bar.
• search_snapshot: expose search state to renderers (only search hooks).

HookContext hands every hook the same five handles: buffer, selection, cursor_style, prompt, and effects. If you can express it through those, it works on every frontend.

Prompt

PromptState is the headless input box behind the bottom bar and the F1 palette. Open one with a PromptSpec (your own id, prefix, placeholder, placement), route keys through handle_key, and read the Submitted input:

#![allow(unused)]
fn main() {
ctx.prompt.open(
    PromptSpec::new("goto-line", ":", "Line number", PromptPlacement::BottomBar, false),
    "",
);
// later, inside on_key while your spec is open:
match ctx.prompt.handle_key(event) {
    PromptAction::Editing => { /* live-update here */ }
    PromptAction::Submitted(input) => { /* interpret input, then close */ }
    PromptAction::Cancelled => { /* Esc already closed it */ }
    PromptAction::Ignored => { /* swallow while yours is open */ }
}
}

Typing, history, Tab completion, and Esc come free; PromptBar draws whatever is open with no per-client rendering code. See Command Palettes & Prompts for the full pattern.

Batteries

Batteries are optional feature-gated packs (twrite_core::batteries) built only on the public core API: the same surface you get. Markdown is the reference battery: Editor::enable_markdown() wires its highlighter plus hooks in one call. Writing a Battery documents the contract.