Story templating improvements.

[gmajoulet]

The goals of this project are to:

1. Provide an API to write media queries for a Story.

As of today, media queries don’t work for Stories, since the story element doesn’t always fit the viewport. Fixing this would make designing for stories and selecting assets a lot easier.

2. Provide a way to configure different assets (videos, images) depending on the story dimensions and orientation.

Having to pick assets that work for both landscape and portrait when designing a story is too restrictive.
Allowing publishers to write media queries enables them to show different versions of the same assets, based on the screen dimensions or orientation. However, we need to make sure we only preload what’s necessary, and fix how our code reacts to orientation or dimensions changes while media elements are playing.
We need to change the way we preload assets so we have better control over it.

3. Provide an API to control how assets (videos, images) are cropped.

Today, we force publishers to pick assets where the point of interest is perfectly centered, which is very restrictive. They need to be able to provide cropping information for their assets, so the interesting part of the asset stays visible, no matter the screen dimensions or orientation.

4. Design an API to start allowing pre-templated UIs

We want to design an API that lets us introduce many pre-templated UIs, starting with the “landscape half-half” - that we believe makes it easier to design for the immersive landscape experience.