Useful to draw whitespaces with alternate characters and colors
without slowing down the text rendering.
A new API is implemented. A renderer.replacements object can be created
to list the replacements.
In turns the function renderer.draw_text and draw_text_subpixel now accept
two optional arguments for replacements.
In order to fix the issue with cursor positioning a subpixel-aware draw
text operation within rencache was required.
With this modification the cursor positioning problem is completely
resolved.
A new function renderer.draw_text_subpixel is introduced to perform
consecutive, inline, text drawings with subpixel accuracy.
In order to get right the cursor position on text on mouse clicks it is
needed to take into account text's subpixel positioning.
This fix mostly corrects the problem but cursor positioning is still
somewhat inaccurate for long lines due to repeated commands to draw a text
along a line. Repeated draw text calls make the subpixel information
lost and small errors will add-up.
Francesco Abbate
rxi