If text begins with a zero-width space fragment, CannotFit exception is thrown

[mojavelinux]

If a string of text begins with a discrete zero-width space fragment, the line wrap logic incorrectly concludes that the text cannot fit. This happens even when the "wrap by char" option is active.

Here's a scenario that reproduces this problem:

require 'prawn'
Prawn::Document.generate 'cannot-fit-bug.pdf' do
  font %(#{Prawn::DATADIR}/fonts/DejaVuSans.ttf)
  bounding_box [0, cursor], width: 50 do
    text %(\u200b<color rgb="0000FF">stringofchars</color>), inline_format: true
  end
end

If the leading zero-width space character (\u200b) is taken away, the text is rendered without exception.

The problematic line is line_wrap.rb#L199 called from line_wrap.rb#L112.

A zero-width space fragment is often used as a placeholder for adding non-visible objects such as an anchor point.