[ttml2] Include better positioning example in Introduction (#1204)

nigelmegitt has just created a new issue for https://github.com/w3c/ttml2:

== Include better positioning example in Introduction ==
From implementor feedback: the examples in the introduction at [1.2 Document Example](https://www.w3.org/TR/ttml2/#example) seem to suggest that specifying a `region` attribute on the `body` element is a good idea. 

However as we know from [[construct intermediate document]](https://www.w3.org/TR/ttml2/#procedure-construct-intermediate-document) step 3d, the effect of this is that if any descendant specifies a different region, then that descendant gets pruned. This is non-obvious to the casual reader, but the effect is that, except in simple cases, setting `@region` on `body` is probably a bad idea.

Another data point: setting `region` on `body` is prohibited in the EBU-TT-D profile.

I propose that we:

1. Change the TTML Body example fragment from:

```xml
<body region="subtitleArea">
  <div>
```

to:

```xml
<body>
  <div region="subtitleArea">
```

and

2. Add additional examples demonstrating positioning, perhaps with two regions defined, one at the top and one at the bottom, with content in both regions.


Please view or discuss this issue at https://github.com/w3c/ttml2/issues/1204 using your GitHub account

Received on Thursday, 16 April 2020 09:19:10 UTC