amp-font

Introduction

Learn how to use the amp-font component to trigger and monitor the loading of custom fonts on AMP pages.

Setup

Import the amp-font component.

<script async custom-element="amp-font" src="https://cdn.ampproject.org/v0/amp-font-0.1.js"></script>

Define custom CSS rules to style your document depending on whether a font was loaded successfully or not. Find out about all the supported css classes here.

<style amp-custom>
:root {
  --color-error: #B00020;
  --color-primary: #005AF0;
}
@font-face {
  font-family: 'UnavailableFont';
  font-style: normal;
  font-weight: 400;
  src: url(fonts/UnavailableFont.ttf) format('truetype');
}
@font-face {
  font-family: 'Comic AMP';
  font-style: normal;
  font-weight: 400;
  src: local('Comic AMP'), url(/static/samples/fonts/ComicAMP.ttf) format('truetype');
}
@font-face {
  font-family: 'Comic AMP 2';
  font-style: normal;
  font-weight: 400;
  src: local('Comic AMP'), url(/static/samples/fonts/ComicAMP2.ttf) format('truetype');
}

.unavailable-font-loaded .unavailable-font {
  font-family: 'UnavailableFont';
}
.comicamp-loaded .comicamp {
  font-family: 'Comic AMP';
}
.comicamp2-loaded .comicamp2 {
  font-family: 'Comic AMP 2';
}
.comicamp-loading .comicamp,
.comicamp2-loading .comicamp2,
.unavailable-font-loading .unavailable-font {
  color: var(--color-primary);
}
.comicamp-missing .comicamp,
.comicamp2-missing .comicamp2,
.unavailable-font-missing .unavailable-font {
  color: var(--color-error);
}
</style>

Existing font

The amp-font components needs to be embedded inside the body or the head. Use the attribute timeout to specify the time in milliseconds to wait until the font becomes available. This attribute is optional and it's default value is 3000. Use on-error-remove-class, on-error-add-class, on-load-remove-class, on-load-add-class to specify the CSS classes to be used if the font loads correctly or not. This sample demonstrates that amp-font will add the class comicamp-loaded to the root element if the font is downloaded.

This text is displayed in red if the font `Comic AMP` is not available.

<amp-font layout="nodisplay" font-family="Comic AMP" timeout="2000" on-error-remove-class="comicamp-loading" on-error-add-class="comicamp-missing" on-load-remove-class="comicamp-loading" on-load-add-class="comicamp-loaded">
</amp-font>
<p class="comicamp">
  This text is displayed in red if the font `Comic AMP` is not available.
</p>

Unavailable font

amp-font will add a class unvailable-font-missing to the root element in this sample.

This text is displayed in red if the font `UnavailableFont` is not available.

<amp-font layout="nodisplay" font-family="UnavailableFont" timeout="2000" on-error-remove-class="unavailable-font-loading" on-error-add-class="unavailable-font-missing" on-load-remove-class="unavailable-font-loading" on-load-add-class="unavailable-font-loaded">
</amp-font>
<p class="unavailable-font">
  This text is displayed in red if the font `UnavailableFont` is not available.
</p>

Using only cached fonts

Set timeout="0" to load the font only if already in cache.

This text is displayed in red if the font `Comic AMP 2` is not cached.

<amp-font layout="nodisplay" font-family="Comic AMP 2" timeout="0" on-error-remove-class="comicamp2-loading" on-error-add-class="comicamp2-missing" on-load-remove-class="comicamp2-loading" on-load-add-class="comicamp2-loaded">
</amp-font>
<p class="comicamp2">
  This text is displayed in red if the font `Comic AMP 2` is not cached.
</p>

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Written by @kul3r4