prawnpdf/prawn

# frozen_string_literal: true

require 'prawn/manual_builder'

Prawn::ManualBuilder::Chapter.new do
  title 'Origin'

  text do
    prose <<~TEXT
      This is the most important concept you need to learn about Prawn:

      PDF documents have the origin <code>[0,0]</code> at the bottom-left corner
      of the page.

      A bounding box is a structure which provides boundaries for inserting
      content. A bounding box also has the property of relocating the origin to
      its relative bottom-left corner. However, be aware that the location
      specified when creating a bounding box is its top-left corner, not
      bottom-left (hence the <code>[100, 300]</code> coordinates below).

      Even if you never create a bounding box explicitly, each document already
      comes with one called the margin box. This initial bounding box is the
      one responsible for the document margins.

      So practically speaking the origin of a page on a default generated
      document isn't the absolute bottom left corner but the bottom left corner
      of the margin box.

      The following snippet strokes a circle on the margin box origin. Then
      strokes the boundaries of a bounding box and a circle on its origin.
    TEXT
  end

  example axes: true do
    stroke_circle [0, 0], 10

    bounding_box([100, 200], width: 300, height: 100) do
      stroke_bounds
      stroke_circle [0, 0], 10
    end
  end
end