Breeze.Implicit behaviour (Breeze v0.4.0)

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Behaviour implemented by stateful renderer extensions.

An implicit owns state for an element without requiring the parent view to handle every interaction itself. It must implement init/3 and handle_modifiers/3. Event handling and animation are optional.

Initialization

children is a list of attribute maps for elements owned by the implicit. root_attrs is the implicit root's attribute map with :id included. last_state is the state from the preceding render; once layout is known it also contains the previous Breeze.Viewport under :__element__.

An initializer can return the state directly, {:ok, state}, or {:ok, state, options}. The options are:

  • :rerender_every - a positive interval in milliseconds for asynchronous animate/5 calls. It has no effect unless animate/5 is implemented.
  • :active_when_pending - run periodic animation only while an input event is pending. If this and :active_when_focused are both true, pending state takes precedence.
  • :active_when_focused - run periodic animation only while the implicit root is focused.
  • :captures_keys - true to capture every key, or a list of key names to capture selectively.
  • :captures_printable_keys - capture printable input and supported text editing keys.
  • :captures_control_keys - capture control-modified key input.
  • :captures_focus_keys - capture Tab and Shift-Tab input.
  • :requires_layout_rerender - rerender after the implicit's dimensions change so layout-dependent state can settle.
  • :state_change_requires_rerender - set to false when changing only the implicit state does not require another render. The default is true.

Events

handle_event/3 receives a reserved event-kind argument, the event payload, and the current implicit state. Breeze adds the target's Breeze.Viewport to the payload as "element" when one is available.

Every reply stores the returned state. {:noreply, state} stops there. {{:change, event}, state} and {{:submit, event}, state} route event through the root element's br-change or br-submit handler. A change reply may also contain focus: id (or focus: nil) as its third element. Finally, {{:delegate, id}, state} sends the original event to another implicit.

Render modifiers

handle_modifiers/3 runs for the implicit root and each owned child during rendering. Its first argument is :root or :child; its second is the element's attribute keyword list, with :layout_element added when a previous Breeze.Viewport is available.

It returns a keyword list. style: value adds a binary, map, or list of style modifiers. scroll_y: top, scroll_x: left, and scroll: {top, left} control the viewport offset. Any other atom/value pair becomes a renderer flag; common examples include selected: true, default_focus: true, and focus_scope: :trap.

Animation

animate/5 receives the element type, its rendered BackBreeze.Box, the element flags, implicit state, and a context map. It may return a box directly, {:ok, box}, or {:ok, box, options}. The only animation option is overlays: overlays; overlays are applied during asynchronous animation passes.

Breeze calls animate/5 for roots and children during a normal render. :rerender_every additionally schedules lightweight asynchronous calls for the root. The context contains :phase, :frame, :now, :pending?, :focused?, :last_render_at, :last_interaction_at, :theme, :id, and :layout.

Summary

Types

animation_context()

Runtime context supplied to animate/5.

animation_option()

An option returned from an animation pass.

animation_reply()

A valid return value from animate/5.

attributes()

Attributes collected from an implicit element.

element_type()

The implicit root or one of its child elements.

event_option()

An option returned with an implicit event action.

event_reply()

A valid return value from handle_event/3.

flags()

Renderer flags attached to an implicit element.

init_option()

An option returned while initializing implicit state.

init_result()

A valid return value from init/3.

key_name()

A decoded terminal key name.

modifier()

A style, scroll, or state modifier returned during rendering.

state()

State owned by an implicit implementation.

Callbacks

animate(element_type, %BackBreeze.Box{}, flags, state, animation_context)

Transforms a rendered box during the normal render or a periodic animation pass.

handle_event(term, map, state)

Handles an event captured by the implicit and returns its next state and action.

handle_modifiers(element_type, flags, state)

Returns renderer modifiers for the implicit root or one of its children.

init(list, attributes, state)

Initializes state from the owned children, root attributes, and previous state.

Types

animation_context()

@type animation_context() :: %{
  phase: :base | :async,
  frame: non_neg_integer(),
  now: integer() | nil,
  pending?: boolean(),
  focused?: boolean(),
  last_render_at: integer() | nil,
  last_interaction_at: integer() | nil,
  theme: Breeze.Theme.t(),
  id: String.t() | nil,
  layout: Breeze.Viewport.t() | nil
}

Runtime context supplied to animate/5.

animation_option()

@type animation_option() :: {:overlays, [map()]}

An option returned from an animation pass.

animation_reply()

@type animation_reply() ::
  %BackBreeze.Box{
    bottom: term(),
    children: term(),
    content: term(),
    display: term(),
    fixed_layer_map: term(),
    height: term(),
    layer: term(),
    layer_map: term(),
    left: term(),
    overlay?: term(),
    position: term(),
    right: term(),
    scroll: term(),
    state: term(),
    style: term(),
    top: term(),
    width: term()
  }
  | {:ok,
     %BackBreeze.Box{
       bottom: term(),
       children: term(),
       content: term(),
       display: term(),
       fixed_layer_map: term(),
       height: term(),
       layer: term(),
       layer_map: term(),
       left: term(),
       overlay?: term(),
       position: term(),
       right: term(),
       scroll: term(),
       state: term(),
       style: term(),
       top: term(),
       width: term()
     }}
  | {:ok,
     %BackBreeze.Box{
       bottom: term(),
       children: term(),
       content: term(),
       display: term(),
       fixed_layer_map: term(),
       height: term(),
       layer: term(),
       layer_map: term(),
       left: term(),
       overlay?: term(),
       position: term(),
       right: term(),
       scroll: term(),
       state: term(),
       style: term(),
       top: term(),
       width: term()
     }, [animation_option()]}

A valid return value from animate/5.

attributes()

@type attributes() :: map()

Attributes collected from an implicit element.

element_type()

@type element_type() :: :root | :child

The implicit root or one of its child elements.

event_option()

@type event_option() :: {:focus, String.t() | nil}

An option returned with an implicit event action.

event_reply()

@type event_reply() ::
  {:noreply, state()}
  | {{:change, map()}, state()}
  | {{:change, map()}, state(), [event_option()]}
  | {{:submit, map()}, state()}
  | {{:delegate, String.t()}, state()}

A valid return value from handle_event/3.

flags()

@type flags() :: keyword()

Renderer flags attached to an implicit element.

init_option()

@type init_option() ::
  {:rerender_every, pos_integer()}
  | {:active_when_pending, boolean()}
  | {:active_when_focused, boolean()}
  | {:captures_keys, boolean() | [key_name()]}
  | {:captures_printable_keys, boolean()}
  | {:captures_control_keys, boolean()}
  | {:captures_focus_keys, boolean()}
  | {:requires_layout_rerender, boolean()}
  | {:state_change_requires_rerender, boolean()}

An option returned while initializing implicit state.

init_result()

@type init_result() :: state() | {:ok, state()} | {:ok, state(), [init_option()]}

A valid return value from init/3.

key_name()

@type key_name() :: String.t()

A decoded terminal key name.

modifier()

@type modifier() ::
  {:style, binary() | map() | list()}
  | {:scroll_y, integer()}
  | {:scroll_x, integer()}
  | {:scroll, {integer(), integer()}}
  | {atom(), term()}

A style, scroll, or state modifier returned during rendering.

state()

@type state() :: term()

State owned by an implicit implementation.

Callbacks

animate(element_type, %BackBreeze.Box{}, flags, state, animation_context)

(optional) 
@callback animate(
  element_type(),
  %BackBreeze.Box{
    bottom: term(),
    children: term(),
    content: term(),
    display: term(),
    fixed_layer_map: term(),
    height: term(),
    layer: term(),
    layer_map: term(),
    left: term(),
    overlay?: term(),
    position: term(),
    right: term(),
    scroll: term(),
    state: term(),
    style: term(),
    top: term(),
    width: term()
  },
  flags(),
  state(),
  animation_context()
) :: animation_reply()

Transforms a rendered box during the normal render or a periodic animation pass.

handle_event(term, map, state)

(optional) 
@callback handle_event(term(), map(), state()) :: event_reply()

Handles an event captured by the implicit and returns its next state and action.

handle_modifiers(element_type, flags, state)

@callback handle_modifiers(element_type(), flags(), state()) :: [modifier()]

Returns renderer modifiers for the implicit root or one of its children.

init(list, attributes, state)

@callback init([attributes()], attributes(), state()) :: init_result()

Initializes state from the owned children, root attributes, and previous state.