`height` here is how much vertical space we have before we want the text to flow under the elements preceding us in this line. The first layout we attempt set the exact width we have, `Swt::TextLayout` does its own text fitting, then this checks whether that resulting text runs further down than we're allowed (i.e. past `height`).

Attempt at a text diagram to make that clearer:

```
-----------------------   <---
|   tall     |   text  |     |
|  elem      |   more  |   height
-------------   text   |  <----
| should flow under... |
```

Hopefully that helps a bit. If not, please let me know and I'll see if I can explain it better. My head's pretty deep into this, so I want to make sure I can make clear what it's doing.