Expresso.Steps (expresso v0.1.0)

Makes the list of each step of a deck for the presenter

The renderer writes the list into the document as JSON, in the element script#expresso-deck. The presenter script reads it at load. The script holds the index of the current step in the list, and it reads each other value from the list. It calculates nothing from the deck.

The JSON object has three keys:

"steps" - one entry for each step of each slide, in sequence. An entry is [slide, step, fraction, done, position]. entries/1 tells what each value is.
"slides" - one object for each slide, in sequence. slides/1 tells what each key is.
"duration_ms" - the length of the talk in milliseconds, or null. duration/1 gives it.

docs/research/elixir-presenter-report.md gives the reason for the list.

Summary

Types

entry()

One step of a deck

slide()

One slide of a deck

Functions

duration(deck)

Return the length of the talk in milliseconds, or nil

entries(deck)

Return one entry for each step of each slide, in sequence

json(deck)

Return the list of the steps as JSON for the script element

kind(transition)

Give the kind of a transition, as the presenter and the style sheet write it

slides(deck)

Return one map for each slide, in sequence

Types

entry()

@type entry() :: %{
  slide: pos_integer(),
  step: pos_integer(),
  fraction: float(),
  done: float(),
  position: String.t()
}

One step of a deck

slide()

@type slide() :: %{
  first: non_neg_integer(),
  steps: pos_integer(),
  transition: String.t()
}

One slide of a deck

Functions

duration(deck)

@spec duration(Expresso.Deck.t()) :: pos_integer() | nil

Return the length of the talk in milliseconds, or nil

The duration option of the deck gives the length in minutes. A value that is not a positive integer gives nil. The address parameter ?duration= replaces the length in the browser.

entries(deck)

@spec entries(Expresso.Deck.t()) :: [entry()]

Return one entry for each step of each slide, in sequence

The first slide is slide 1, and the first step is step 1. An entry holds:

fraction - the part of the deck before the step, from 0 at the first step to 1 at the last step. The progress bar shows it. A deck with one step gets 0.
done - the part of the steps before the step. The last step also has its part, so the value is less than 1. The speaker view compares it with the time of the talk.
position - the text of the speaker view, such as "Slide 4 of 13, step 2 of 3". A slide with one step gets no step part. A step with a label gets the label after a colon, such as "Slide 4 of 13, step 2 of 3: The restart".

The presenter adds ", black screen" or ", white screen" to the position while the screen is black or white.

json(deck)

@spec json(Expresso.Deck.t()) :: String.t()

Return the list of the steps as JSON for the script element

Expresso.Json.for_script/1 writes the text, so it has no <, and a value cannot close the script element.

The keys of each object are in alphabetical order, so each render of a deck gives the same text.

kind(transition)

@spec kind(atom()) :: String.t()

Give the kind of a transition, as the presenter and the style sheet write it

The kind is the name of the atom with a hyphen for each underscore, as for an effect. The style sheet then gives the rule for html[data-transition="wipe-down"].

iex> Expresso.Steps.kind(:wipe_down)
"wipe-down"

slides(deck)

@spec slides(Expresso.Deck.t()) :: [slide()]

Return one map for each slide, in sequence

A map holds:

first - the index of step 1 of the slide in the list of entries/1.
steps - the number of steps of the slide.
transition - the kind of the transition into the slide, such as "fade" or "wipe-down". The option of the slide comes first, then the option of the deck, then "fade". kind/1 gives the name.