package mosaic

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Module Mosaic_ui.RendererSource

Layout, drawing, hit testing, and event dispatch pipeline.

Renderer: layout, drawing, hit testing, and event dispatch.

The renderer drives a three-pass pipeline over a Renderable.t tree:

  • Lifecycle: runs per-frame and resize hooks on registered nodes.
  • Layout and command generation: computes layout via Toffee, walks the tree depth-first to extract absolute positions, and builds a flat render command list (opacity, scissors, draw calls).
  • Execution: replays the command list to populate the grid and hit grid.

After the pipeline, render diffs the grid against the previous frame and returns minimal ANSI output.

The renderer owns the root Renderable.t, the Screen.t, and all pipeline state. Widget code builds the tree under root; the event loop calls render_frame and render, then dispatches input events.

Types

Sourcetype t

The type for renderer state. Owns the root renderable, layout tree, screen, and all render pipeline state.

Constructors

Sourceval create : ?glyph_pool:Glyph.Pool.t -> ?width_method:Glyph.width_method -> ?style:Toffee.Style.t -> unit -> t

create () is a renderer with a root renderable and an empty screen. The optional parameters are:

  • glyph_pool: the shared glyph pool for text rendering. Defaults to a fresh Glyph.Pool.t.
  • width_method: the glyph width computation method. Defaults to the Glyph.width_method default.
  • style: the root node's initial style. Defaults to Toffee.Style.default.

Accessors

Sourceval root : t -> Renderable.t

root t is the root renderable. Build the UI tree under this node.

Sourceval screen : t -> Screen.t

screen t is the underlying screen.

Sourceval glyph_pool : t -> Glyph.Pool.t

glyph_pool t is the shared glyph pool for text rendering.

Rendering

Sourceval render_frame : t -> width:int -> height:int -> delta:float -> unit

render_frame t ~width ~height ~delta builds the next frame.

The pipeline runs in order:

  • Runs lifecycle passes (on_frame and resize hooks).
  • Runs frame callbacks (see add_frame_callback).
  • Computes layout via Toffee.
  • Walks the tree: extracts layout and builds the render command list.
  • Executes render commands: draws to the grid and populates the hit grid.
  • Rechecks hover state against the updated hit grid.

width and height are the frame dimensions in terminal cells. delta is elapsed milliseconds since the last frame.

Sourceval render : ?full:bool -> t -> string

render t diffs the current frame against the previous one and returns the minimal ANSI output string. Call after render_frame.

When full is true, all cells are emitted regardless of changes. full defaults to false.

Sourceval needs_render : t -> bool

needs_render t is true iff a renderable has requested a re-render or live nodes are active.

Event dispatch

Sourceval dispatch_key : t -> Input.Key.event -> Event.key

dispatch_key t key sends key to the focused renderable and returns the resulting event.

If the focused node does not prevent default, the default key handler runs. The returned event carries the default_prevented flag set by the focused node's handler; callers can inspect it to determine whether the key was consumed.

Sourceval dispatch_mouse : t -> Input.Mouse.event -> unit

dispatch_mouse t mouse runs the full mouse dispatch pipeline:

  • Updates pointer state.
  • Hit-tests the mouse position.
  • Advances the selection state machine (start, update, or finish).
  • Tracks hover state and fires Over/Out events on target change.
  • Redirects events to the drag-captured node when active.
  • Dispatches with bubbling to the hit-tested node.
  • Auto-focuses on left click.
  • Clears stale selection if not prevented.
Sourceval dispatch_paste : t -> string -> unit

dispatch_paste t text sends text as a paste event to the focused renderable.

Sourceval dispatch_scroll : t -> x:int -> y:int -> direction:Event.Mouse.scroll_direction -> delta:int -> modifiers:Input.Key.modifier -> unit

dispatch_scroll t ~x ~y ~direction ~delta ~modifiers dispatches a scroll event at terminal cell position (x, y).

Focus

Sourceval focused : t -> Renderable.t option

focused t is the currently focused renderable, if any.

Sourceval focus : t -> Renderable.t -> bool

focus t node focuses node and is true iff node is focusable.

Sourceval blur : t -> unit

blur t removes focus from the currently focused renderable.

Selection

Sourceval selection : t -> Selection.t option

selection t is the active text selection, if any.

Sourceval clear_selection : t -> unit

clear_selection t clears the active text selection, notifying all selectable renderables under the selection container.

Drag capture

Sourceval captured : t -> Renderable.t option

captured t is the renderable currently capturing all mouse events during a drag gesture, if any.

Hover

Sourceval hover : t -> Renderable.t option

hover t is the renderable currently under the mouse pointer, if any.

Frame callbacks

Sourceval add_frame_callback : t -> (float -> unit) -> unit

add_frame_callback t f registers f to run at the start of each frame with delta time in milliseconds. Callbacks run after lifecycle passes and before layout computation.

See also remove_frame_callback and clear_frame_callbacks.

Sourceval remove_frame_callback : t -> (float -> unit) -> unit

remove_frame_callback t f unregisters f using physical equality.

See also add_frame_callback.

Sourceval clear_frame_callbacks : t -> unit

clear_frame_callbacks t removes all registered frame callbacks.

See also add_frame_callback.

Post-processing

Sourceval add_post_process : t -> (Grid.t -> delta:float -> unit) -> Screen.effect_id

add_post_process t f registers f as a persistent post-processing transform on the underlying screen. f receives the rendered Grid.t and the frame delta in milliseconds; it runs after frame building and before diffing. Returns a Screen.effect_id for later removal.

See also remove_post_process and clear_post_processes.

Sourceval remove_post_process : t -> Screen.effect_id -> unit

remove_post_process t id unregisters the post-processor identified by id.

See also add_post_process.

Sourceval clear_post_processes : t -> unit

clear_post_processes t removes all registered post-processing functions.

See also add_post_process.