The walks over a tree of elements
A container, such as a text box, a column or a list, holds its children
under the key :elements. Each function of this module reads the children
of an element with children/1, so each walk reads them in the same way.
An element without the key, such as a pause, has no children, and nil
is an empty list.
Each function visits the elements in document order: an element comes before its children, and its children come before the next element. A function that changes the elements calls the function of the caller on an element first, and then it walks the children of the result.
The overlay expansion, the overlay check, Expresso.Overlay.Render.identify/1
and Expresso.Placement keep their own walks, because they carry the
context of the parent or they have their own rules. The first three read
the children with children/1 too. Expresso.Placement also reads the
key :timeline of a chart.
Summary
Functions
Return the children of an element
Return each element of a list and each element under it, in document order
Change each element of a list and each element under it
Change each element of each slide of a deck, as map/2 does
Change each element of a list and each element under it, and stop at the first error
Change each element of a list and each element under it, with a value that goes from one element to the next
Change each element of each slide of a deck, with a value that goes from
one element to the next, as map_reduce/3 does
Types
@type element() :: map()
An element struct, or a different map with the key :elements
Functions
Return the children of an element
The function returns [] for an element without the key :elements, and
for the value nil.
iex> Expresso.Element.Tree.children(%{elements: [%{text: "a"}]})
[%{text: "a"}]
iex> Expresso.Element.Tree.children(%{elements: nil})
[]
iex> Expresso.Element.Tree.children(%{text: "a"})
[]Return each element of a list and each element under it, in document order
iex> tree = [%{name: "a", elements: [%{name: "b"}]}, %{name: "c"}]
iex> tree |> Expresso.Element.Tree.descendants() |> Enum.map(& &1.name)
["a", "b", "c"]Change each element of a list and each element under it
The function calls fun on an element, and then it changes the children
of the result. An element without the key :elements stays without it.
Change each element of each slide of a deck, as map/2 does
The function takes a deck or a different map with the key :slides.
@spec map_ok([element()] | nil, (element() -> {:ok, element()} | {:error, reason})) :: {:ok, [element()]} | {:error, reason} when reason: term()
Change each element of a list and each element under it, and stop at the first error
fun returns {:ok, element} or {:error, reason}. The function returns
{:ok, elements}, or the first error in document order.
@spec map_reduce([element()] | nil, acc, (element(), acc -> {element(), acc})) :: {[element()], acc} when acc: term()
Change each element of a list and each element under it, with a value that goes from one element to the next
fun takes an element and the value, and it returns the changed element
and the next value, as for Enum.map_reduce/3.
@spec map_reduce_deck(deck, acc, (element(), acc -> {element(), acc})) :: {deck, acc} when deck: map(), acc: term()
Change each element of each slide of a deck, with a value that goes from
one element to the next, as map_reduce/3 does
The value goes from the last element of a slide to the first element of the next slide.