draw_text and text_box have different coordinates origin

[paniko0]

Hey guys, I am having a weird behaviour after moving from draw_text to text_box. We needed to make that change because draw_text doesn't support fallback fonts.

If you run the following code, you will notice that the rendered PDF plots the text in different positions:

Prawn::Document.generate("a.pdf") do |document|
  document.stroke_axis
  document.text_box 'text', at: [200, 400]
  document.draw_text 'draw', at: [200, 400]
end

Apparently, they use different origins, which cause them to render the text in different positions. If I adjust the y of the text_box by 70%, then it would render in the right position:

Prawn::Document.generate("a.pdf") do |document|
  document.stroke_axis
  document.text_box 'text', at: [200, 400 + (0.7 * document.font_size)]
  document.draw_text 'draw', at: [200, 400]
end

Any ideas on how to elegantly fix this? Or just adjusting it by 70% would suffice?

[gettalong]

Haven't looked at the code but I guess the difference is because of different text origins.

With #draw_text you define the lower-left corner where drawing should be done since this method is basically a one-to-one mapping of the PDF text drawing command. Therefore the word "draw" appears above the 400 line.

With #text_box you use a high-level method that defines a box into which text should be drawn. And the at option defines the upper-left corner of this box (see the API spec, therefore the text appears below the 400 line.

[paniko0]

Thanks for getting back @gettalong

Any specific reason on why those two methods use two different origins? It seems confusing to me that one uses top-down and the other bottom-up. Do you think it's worth to add an option that specifies the origin so we can have both methods behaving the same way?

Or do you think it's possible to add support to fallback fonts in the draw-text method? I'm opened to implement that if you think that's feasible.

Cheers,

[gettalong]

The reason is that these two methods do different things. As I mentioned #draw_text is a low-level drawing method, doing nothing more than outputting the PDF code needed. The #text_box method, however, is a high-level drawing method, providing, among other things, automatic line wrapping and limiting the drawn text to a rectangular area.

Therefore it doesn't really make sense for the :at option to behave exactly the same for these two methods.

As for fallback fonts in #draw_text: This may be a solution for your problem.