# Quantity

Used to record a single non-negative integer value. For example, the width of the display in pixels.

Quantities are only available for metrics that come from Gecko.

## Configuration

Say you're adding a new quantity for the width of the display in pixels. First you need to add an entry for the quantity to the metrics.yaml file:

gfx:
display_width:
type: quantity
description: >
The width of the display, in pixels.
unit: pixels
gecko_datapoint: DISPLAY_W_PIXELS
...


Note that quantities have a required unit parameter, which is a free-form string for documentation purposes.

## API

import org.mozilla.yourApplication.GleanMetrics.Gfx

Gfx.displayWidth.set(width)


There are test APIs available too:

import org.mozilla.yourApplication.GleanMetrics.Gfx

// Was anything recorded?
assertTrue(Gfx.displayWidth.testHasValue())
// Does the quantity have the expected value?
assertEquals(6, Gfx.displayWidth.testGetValue())
// Did it record an error due to a negative value?
assertEquals(1, Gfx.displayWidth.testGetNumRecordedErrors(ErrorType.InvalidValue))


## Limits

• Quantities must be non-negative integers.

• Quantities are only available for metrics that come from Gecko.

## Examples

• What is the width of the display, in pixels?

## Recorded errors

• invalid_value: If a negative value is passed in.