Fixes #169. Text::Box :valign option.

[jessedoyle]

Please see the comments in issue #169 for demonstrated changes.

[jessedoyle]

This pull requests adds a :final_gap option to Prawn::Text::Formatted::Box.

This option defaults to true to match the current existing behaviour.

Vertical align centering is also changed slightly to calculate the top/bottom gaps based on the distance between the bottom of the box and the baseline of the text (as opposed to the descender).

Here's some output with the various options:

[jessedoyle]

@sandal: I removed the :final_gap option as you suggested.

This patch should make all text_boxes with :valign => :bottom render correctly without any padding on the bottom of the box.

I agree with your previous comments about fine-grained control over the location of rendered text.

As a Prawn user, I'd like to see padding options added with a format like:

 ... padding: { top: 10, bottom: 10, left: 5, right: 15 }, ...

Or:

 ... padding: 10, ...

to set the padding equally in all directions.

I would be willing to help implement these features, but I'll likely require assistance from someone more familiar with the codebase to do so.

[practicingruby]

@jessedoyle: I'm trying to decide whether to add the padding options directly to text_box or to provide a higher level layout tool that is capable of doing this sort of thing.

I'm going to think on that for a few days, but if it becomes a big rats nest of a problem, we can think about merging your patch for a temporary solution.

[practicingruby]

@jessedoyle: I decided to merge this, because the concern about "how do we give better control over padding" seems to be orthogonal to the question of "how do we vertically align our text". Prawn's existing behavior was flawed for the latter, and your patch fixes that.

You already have commit access to Prawn, so in the future, please use a feature branch off of our main repository rather than your fork. That makes it easier for us to make revisions to a pull request if needed before merging while preserving the full history.

[practicingruby]

@jessedoyle Thanks for this fix!

[jessedoyle]

@sandal: I'll do that.

Thanks for being awesome and making Prawn!