Struct ViewportKeyMap 

pub struct ViewportKeyMap {
    pub page_down: Binding,
    pub page_up: Binding,
    pub half_page_up: Binding,
    pub half_page_down: Binding,
    pub down: Binding,
    pub up: Binding,
    pub left: Binding,
    pub right: Binding,
}

Keyboard binding configuration for viewport navigation.

This struct defines all key combinations that control viewport scrolling, including line-by-line movement, page scrolling, and horizontal navigation. Each binding supports multiple key combinations and includes help text for documentation generation.

Default Key Bindings

The default configuration provides both traditional navigation keys and Vim-style alternatives for maximum compatibility:

• Line Movement: Arrow keys (↑↓) and Vim keys (kj)
• Page Movement: Page Up/Down and Vim keys (bf)
• Half Page: Vim-style u (up) and d (down)
• Horizontal: Arrow keys (←→) and Vim keys (hl)

Examples

use bubbletea_widgets::viewport::{ViewportKeyMap, Model};
use bubbletea_widgets::key;
use crossterm::event::KeyCode;

// Use default key bindings
let mut viewport = Model::new(80, 24);
let keymap = viewport.keymap.clone(); // Uses ViewportKeyMap::default()

// Customize key bindings
let mut custom_keymap = ViewportKeyMap::default();
custom_keymap.page_down = key::Binding::new(vec![KeyCode::Char('n')])
    .with_help("n", "next page");
custom_keymap.page_up = key::Binding::new(vec![KeyCode::Char('p')])
    .with_help("p", "previous page");

viewport.keymap = custom_keymap;

Integration with help system:

use bubbletea_widgets::viewport::ViewportKeyMap;
use bubbletea_widgets::key::KeyMap as KeyMapTrait;

let keymap = ViewportKeyMap::default();

// Get essential bindings for compact help
let short_help = keymap.short_help();
assert_eq!(short_help.len(), 4); // up, down, page_up, page_down

// Get all bindings organized by category
let full_help = keymap.full_help();
assert_eq!(full_help.len(), 4); // 4 categories of bindings

Customization Patterns

Common customization scenarios:

use bubbletea_widgets::viewport::ViewportKeyMap;
use bubbletea_widgets::key;
use crossterm::event::KeyCode;

let mut keymap = ViewportKeyMap::default();

// Add additional keys for page navigation
keymap.page_down = key::Binding::new(vec![
    KeyCode::PageDown,
    KeyCode::Char(' '),    // Space bar (default)
    KeyCode::Char('f'),    // Vim style (default)
    KeyCode::Enter,        // Custom addition
]).with_help("space/f/enter", "next page");

// Game-style WASD navigation
keymap.up = key::Binding::new(vec![KeyCode::Char('w')])
    .with_help("w", "move up");
keymap.down = key::Binding::new(vec![KeyCode::Char('s')])
    .with_help("s", "move down");
keymap.left = key::Binding::new(vec![KeyCode::Char('a')])
    .with_help("a", "move left");
keymap.right = key::Binding::new(vec![KeyCode::Char('d')])
    .with_help("d", "move right");

Fields

page_down: Binding

Key binding for scrolling down one full page.

Default keys: Page Down, Space, f (Vim-style “forward”)

page_up: Binding

Key binding for scrolling up one full page.

Default keys: Page Up, b (Vim-style “backward”)

half_page_up: Binding

Key binding for scrolling up half a page.

Default key: u (Vim-style “up half page”)

half_page_down: Binding

Key binding for scrolling down half a page.

Default key: d (Vim-style “down half page”)

down: Binding

Key binding for scrolling down one line.

Default keys: Down arrow (↓), j (Vim-style)

up: Binding

Key binding for scrolling up one line.

Default keys: Up arrow (↑), k (Vim-style)

left: Binding

Key binding for horizontal scrolling to the left.

Default keys: Left arrow (←), h (Vim-style)

right: Binding

Key binding for horizontal scrolling to the right.

Default keys: Right arrow (→), l (Vim-style)

Trait Implementations

impl Clone for ViewportKeyMap

fn clone(&self) -> ViewportKeyMap

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ViewportKeyMap

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ViewportKeyMap

fn default() -> Self

Creates default viewport key bindings with Vim-style alternatives.

The default configuration provides comprehensive navigation options that accommodate both traditional arrow key users and Vim enthusiasts. Each binding includes multiple key combinations for flexibility.

Default Key Mappings

Binding	Keys	Description
page_down	PgDn, Space, f	Scroll down one page
page_up	PgUp, b	Scroll up one page
half_page_down	d	Scroll down half page
half_page_up	u	Scroll up half page
down	↓, j	Scroll down one line
up	↑, k	Scroll up one line
left	←, h	Scroll left horizontally
right	→, l	Scroll right horizontally

Examples

use bubbletea_widgets::viewport::ViewportKeyMap;

// Create with default bindings
let keymap = ViewportKeyMap::default();

// Verify some default key combinations
assert!(!keymap.page_down.keys().is_empty());
assert!(!keymap.up.keys().is_empty());

Design Philosophy

• Accessibility: Arrow keys work for all users
• Efficiency: Vim keys provide rapid navigation for power users
• Consistency: Key choices match common terminal application patterns
• Discoverability: Help text explains each binding clearly

impl KeyMap for ViewportKeyMap

fn short_help(&self) -> Vec<&Binding>

Returns the most essential key bindings for compact help display.

This method provides a concise list of the most frequently used navigation keys, suitable for brief help displays or status bars.

Returns

A vector containing bindings for: up, down, page up, page down

Examples

use bubbletea_widgets::viewport::ViewportKeyMap;
use bubbletea_widgets::key::KeyMap as KeyMapTrait;

let keymap = ViewportKeyMap::default();
let essential_keys = keymap.short_help();

assert_eq!(essential_keys.len(), 4);
// Contains: up, down, page_up, page_down

fn full_help(&self) -> Vec<Vec<&Binding>>

Returns all key bindings organized by navigation category.

This method groups related navigation keys together for comprehensive help displays. Each group represents a logical category of movement.

Returns

A vector of binding groups:

1. Line navigation: up, down
2. Horizontal navigation: left, right
3. Page navigation: page up, page down
4. Half-page navigation: half page up, half page down

Examples

use bubbletea_widgets::viewport::ViewportKeyMap;
use bubbletea_widgets::key::KeyMap as KeyMapTrait;

let keymap = ViewportKeyMap::default();
let all_keys = keymap.full_help();

assert_eq!(all_keys.len(), 4); // 4 categories
assert_eq!(all_keys[0].len(), 2); // Line navigation: up, down
assert_eq!(all_keys[1].len(), 2); // Horizontal: left, right
assert_eq!(all_keys[2].len(), 2); // Page: page_up, page_down
assert_eq!(all_keys[3].len(), 2); // Half-page: half_page_up, half_page_down

Help Display Integration

This organization enables structured help displays:

Navigation:
  ↑/k, ↓/j     line up, line down
  ←/h, →/l     scroll left, scroll right
   
  b/pgup, f/pgdn/space    page up, page down
  u, d                     half page up, half page down