Show Keyboard Shortcut Hints While a Modifier Is Held in Angular

Some apps show each button's shortcut only while the user holds a modifier, so the hints are there when the user reaches for the keyboard, and out of the way otherwise. injectHotkeyHint returns a signal that's true while the user holds modifiers that belong to a hotkey. It's an optional helper, and it doesn't register anything, so use it alongside injectHotkey.

Show a hint next to a button#

import { Component } from '@angular/core'
import {
  formatForDisplay,
  injectHotkey,
  injectHotkeyHint,
} from '@tanstack/angular-hotkeys'

const saveHotkey = 'Mod+S'

@Component({
  selector: 'app-save-button',
  template: `
    <button (click)="save()">
      Save
      @if (showHint()) {
        <kbd>{{ label }}</kbd>
      }
    </button>
  `,
})
export class SaveButtonComponent {
  readonly label = formatForDisplay(saveHotkey)
  readonly showHint = injectHotkeyHint(saveHotkey)

  constructor() {
    injectHotkey(saveHotkey, () => this.save())
  }

  save() {
    /* ... */
  }
}

While the user holds Command on macOS, or Control elsewhere, the button reads "Save ⌘ S" or "Save Ctrl+S". Formatting & Display covers labels and keycaps.

When a hint shows#

• Holding any of the hotkey's modifiers shows the hint. For Alt+Shift+[KeyK], holding Alt, Shift, or both shows it.
• Holding a modifier the hotkey doesn't use hides the hint, so holding Control and Alt shows only the hints for hotkeys that use both.
• Releasing every modifier, or the window losing focus, hides the hint.
• Other held keys don't matter. AltGr never shows hints, because it types characters.
• A hotkey without modifiers, such as Escape or G, never shows a hint.

To show a hint only while every modifier is held, pass exact:

readonly showHint = injectHotkeyHint('Alt+Shift+[KeyK]', { exact: true }) // Needs Alt and Shift

If the hotkey sets platform, pass the same platform to injectHotkeyHint, so Mod resolves the same way. The hotkey and the options can also be getters.

Hints for sequences#

A sequence shows its hint while the user holds the modifiers of its first step:

readonly showHint = injectHotkeyHint(['Mod+K', 'Mod+C']) // true while Mod is held

Hints for app hotkeys#

Pass an app hotkey to show the user's current hotkey, including one they changed. An app hotkey with no hotkey assigned shows no hint. A small component keeps every button's hint the same:

import { Component, computed, input } from '@angular/core'
import {
  formatForDisplay,
  injectAppHotkeys,
  injectHotkeyHint,
} from '@tanstack/angular-hotkeys'
import type { AppHotkeyId } from '@tanstack/angular-hotkeys'

@Component({
  selector: 'app-hint',
  template: `
    @if (showHint() && appHotkey().hotkey; as hotkey) {
      <kbd>{{ format(hotkey) }}</kbd>
    }
  `,
})
export class HintComponent {
  readonly id = input.required<AppHotkeyId>()
  readonly appHotkeys = injectAppHotkeys()
  readonly appHotkey = computed(() => this.appHotkeys()[this.id()])
  readonly showHint = injectHotkeyHint(() => this.appHotkey())
  readonly format = formatForDisplay
}

<button (click)="save()">Save <app-hint id="doc.save" /></button>

Hide hints for hotkeys that can't fire#

injectHotkeyHint only looks at held keys. It doesn't know whether the hotkey is enabled, its scope is active, or its target has focus. When a hotkey can be off, combine the hint with the same state:

readonly isDirty = signal(false)
private readonly hint = injectHotkeyHint(saveHotkey)
readonly showHint = computed(() => this.hint() && this.isDirty())

constructor() {
  injectHotkey(saveHotkey, () => this.save(), () => ({ enabled: this.isDirty() }))
}

Check held modifiers without the helper#

To check outside a component, such as while drawing on a canvas, pass the held keys to matchesHeldModifiers. It takes the same options:

import { getKeyStateTracker, matchesHeldModifiers } from '@tanstack/angular-hotkeys'

const tracker = getKeyStateTracker()

matchesHeldModifiers('Mod+S', tracker.getHeldKeys()) // true while Mod is held

Held Key State Helpers covers the tracker and the other held-key functions.

The Kitchen Sink example shows hints next to its navigation links and buttons while Alt or Option is held.