Expresso.Overlay.Check (expresso v0.1.0)

Copy Markdown View Source

The checks of the overlay steps of one slide

slide/1 does the work of the verifier, and it is a pure function on an Expresso.Slide struct that Expresso.Overlay.Expand.slide/1 expanded. It reads the steps field of each element and of each on entity.

docs/overlays.md gives the conditions.

Summary

Functions

slide(slide)

Give an error for a slide that breaks a rule of the overlays

Functions

slide(slide)

@spec slide(Expresso.Slide.t()) :: :ok | {:error, String.t()}

Give an error for a slide that breaks a rule of the overlays

The function reports the first of these conditions:

  • A pause entity is inside an element.
  • A step number is less than 1.
  • An on entity has a step at which its element does not show.
  • An on entity with move_to is not in a part, or it also sets x or y.
  • An on entity with copy_to is not in a part of a diagram.
  • A child element has a step at which its nearest ancestor with steps does not show.
  • A group of the highlight option of a chart has a step at which the chart does not show.
  • A frame of a chart starts at a step at which the chart does not show.

An element without an at option shows at each step of its parent. Therefore its nearest ancestor with steps limits the steps of its descendants and of its on entities. An element without such an ancestor shows at each step, and the function accepts each step for it. The transformer reports a step that is more than the maximum, because the expansion needs the maximum.