Device Info and App Events

Alloy exposes information about the watch and screen through the watch, screen, and device globals, delivers app lifecycle events through watch, and lets you control the backlight with watch.light().

Platform Support: These APIs are available on Emery (Pebble Time 2) and Gabbro (Pebble Time 2 round).

Watch Information

The watch global describes the device and the user's preferences:

console.log(`watch.model ${watch.model}`);
console.log(`firmware ${watch.firmwareVersion.major}.${watch.firmwareVersion.minor}.${watch.firmwareVersion.patch}`);
console.log(`user prefers ${watch.hour12 ? "12" : "24"} hour display`);

Property	Description
`watch.model`	The watch model identifier.
`watch.firmwareVersion`	Object with `major`, `minor`, and `patch` numbers.
`watch.hour12`	`true` if the user prefers a 12-hour clock, `false` for 24-hour.
`watch.launch`	How the app was launched: `reason` and `arguments`.
`watch.wake`	Present when launched by a wakeup; see Wakeups.

Screen Properties

The screen global describes the display:

console.log(`screen ${screen.width} x ${screen.height}`);
console.log(`round ${screen.round}, color ${screen.color}`);

Property	Description
`screen.width`	Display width in pixels.
`screen.height`	Display height in pixels.
`screen.round`	`true` on round displays (Gabbro).
`screen.color`	`true` on color displays.

Device Sensors

The device.sensor object reports which sensors are available, so you can feature-detect before using one:

const hasTouch = device.sensor.Touch ? true : false;
console.log(`touch available ${hasTouch}`);

App Lifecycle and Display Events

Subscribe to app events on watch with addEventListener:

watch.addEventListener("willFocus", inFocus => {
    console.log(`willFocus with inFocus ${inFocus}`);
});

watch.addEventListener("didFocus", inFocus => {
    console.log(`didFocus with inFocus ${inFocus}`);
});

watch.addEventListener("resize", progress => {
    console.log(`screen resized to ${screen.width} x ${screen.height} at progress ${progress}`);
});

Event	Description
`"willFocus"`	The app is about to gain or lose focus. The handler receives `inFocus`.
`"didFocus"`	The app has gained or lost focus. The handler receives `inFocus`.
`"resize"`	The drawable area is changing size (for example during an animation). The handler receives the animation `progress`.

Controlling the Backlight

Use watch.light() to control the backlight:

watch.light(true);   // force the backlight on
watch.light(false);  // turn the backlight off

watch.light();       // turn on temporarily, as if the user interacted

Calling watch.light() with no argument turns the backlight on for the standard auto-off interval, just like a button press or shake would. Passing a boolean forces the backlight on or off.

Note: Holding the backlight on draws significantly more power than letting it auto-off. Only force it on for short, deliberate interactions.

See the helloinfo, helloappevents, and hellolight examples for complete projects.

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