dynamic height

[ollym]

I'm trying to use rghost to generate a order receipt. The width of the receipt is fixed but the height varies depending on how many items were purchased.

Is there a way to have a flexible page height?

[shairontoledo]

Yeap you can use width and height programatically https://github.com/shairontoledo/rghost/wiki/Paper-and-Page-Layout#custom-paper keep in mind that you need to know the size before the document creating.

[ollym]

Yea that's my problem, is It's going to be incredibly difficult to work that out by hand. Is there no way to do a dry–run render, and work out the height first?

UPDATE:
Or maybe set the height to 10000 and then crop it to the final cursor position when rendering?

[shairontoledo]

That could work, do you need a precise height for this receipt? If you have a sample of what you're expecting would help me help you.

[ollym]

Say for example:

The height obviously changes with the more tickets being purchased. At the moment I have a dynamic height calculation done in prawnpdf which looks a bit like:

class ReceiptPdf < Prawn::Document
  include Prawn::Measurements

  def initialize(order, width = nil)
    margin = 20
    super page_size: [mm2pt(width || 80), 10000], margin: margin
    y_before = self.y

    transaction do
      draw_content(order)
      rollback
    end

    height = (y_before - self.y) + (margin * 2)

    self.page_height = height
    self.y = height - margin
    draw_content(order)
  end

  def page_height=(value)
    page.dictionary.data[:MediaBox][3] = value.to_f
  end

I just wondered if there was a similar or easier way to do it using rghost?

[shairontoledo]

Understood, there is not way to do that in rghost since the variables to define paper/page is defined in the beginning of the document.

[ollym]

@shairontoledo you have to do that with prawn too. But the physical height variables obviously aren't written until you render the document. The page_height= method you see is a hack to achieve that.

The same will be possible with rghost, the difficulty comes with calculating heights for individual elements, like when generating a QR Code etc. then adding them all together to work out the total height of the document.

I'll have a play with this tomorrow and see what I come up with and will report back here. Thanks anyway for checking this over.

[ollym]

Edit: A version that actually works correctly:

margin_top, margin_bottom = paper.instance_variable_get(:@options)
  .values_at :margin_top, :margin_bottom

variables[:rows_per_page] = @rows + 1
default_variables

page_height = ((variables[:row_height] * @rows + 1) + margin_top + margin_bottom) * 72 / 2.545
head.instance_variable_get(:@body).gsub!(/\/pagesize \[(\d+) \d+\]/, "/pagesize [\\1 #{page_height}]")

PS. I'll leave this issue open so that eventually I (or someone) can produce a proper fix.