Access to typesetting info #239

Currently, troika-three doesn't support scrolling the text within a fixed area. If the lines calculated by the typesetting could be exposed, it should be possible to pass in a block of text, get back the array of lines that would be rendered. Instead of rendering all the lines, I could pass in just the lines that would fit in the area. Scrolling would involve just changing the index of the first line to be rendered.

Imagine I passed in the following text.

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book.

Based on the width, the typesetter might break it into the following lines of text

Lorem Ipsum is simply dummy text 
of the printing and typesetting industry. 
Lorem Ipsum has been the industry's 
standard dummy text ever since the 1500s,
when an unknown printer took a galley of 
type and scrambled it to make a type 
specimen book.

However, I want to limit the height of the text being rendered to only the first 3 lines. Now that I know how the typesetter will render the lines, I can just pass in the text for the first three lines.

Lorem Ipsum is simply dummy text 
of the printing and typesetting industry. 
Lorem Ipsum has been the industry's 

To scroll, I would change the index of the first of the three lines

of the printing and typesetting industry. 
Lorem Ipsum has been the industry's 
standard dummy text ever since the 1500s,

Does this sound reasonable? Can this capability be added?