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Excalidraw

Focused tour of drawing, rendering, history, and collaboration paths; not a whole-project map.

Snapshot readyCurated exploration

Upstream: excalidraw/excalidraw
Default branch: master
Revision: 5cf547650b70
Analysis date: 2026-07-20
Fixture version: v1.0.2
Coverage: Focused tour—not full-project coverage. Covers five selected flows through canvas input, element construction, rendering, history, and collaboration.

Architecture map

Trace responsibilities, not just imports.

Follow persisted relationships across interface, API, service, persistence, worker, and external boundaries.

15 nodes13 relationships

Canvas pointer controller

Editor interaction · ui

Builds shape attributes from the active tool and inserts a newly constructed element.

Collaboration portal

Realtime transport · external

Filters changed versions, encrypts the update, and emits it through the room socket.

Collaboration receive boundary

Collaboration orchestration · service

Handles a decrypted UPDATE message and routes remote elements through reconciliation before scene application.

Collaboration sync coordinator

Collaboration orchestration · service

Checks the scene version and forwards changed elements to the Portal for outbound transport.

Element factory

Element model · utility

Initializes a typed Excalidraw element with stable identity and default shape fields.

Element reconciler

Conflict resolution · utility

Deterministically merges remote and local versions while preserving fractional order.

Element renderer

Shape rendering · utility

Paints each element type, including rectangles, through cached RoughJS shapes.

History service

History · service

Pops inverse deltas, applies them to the current state, and maintains undo and redo stacks.

Remote scene apply

Collaboration orchestration · service

Applies reconciled remote elements without recording them as local undo history.

Scene model

Scene state · service

Maintains ordered scene elements and triggers subscribers when scene state changes.

Snapshot store

State capture · service

Queues durable state increments so restored changes can feed history and synchronization.

Static canvas

Canvas boundary · ui

Owns the static HTML canvas and invokes the scene renderer after React updates.

Static scene renderer

Scene rendering · service

Bootstraps the canvas and dispatches visible scene elements for painting.

Undo action

Editor actions · ui

Maps the undo command to history restoration when the editor is in a safe state.

Viewport renderer

Render selection · service

Derives the visible element set for the current viewport and editor state.

15 nodes · 13 relationships

Highlighted flow

7 steps

Draw a rectangle

Traces a rectangle from the canvas pointer handler through element construction, ordered scene insertion, viewport selection, and canvas painting.

Focus execution Clear

01
Handle the rectangle pointer down
The editor derives the new shape attributes from the pointer origin and active drawing style.
Locate Evidence
02
Construct the element
The shared element factory creates the typed rectangle record with its base fields.
Locate Evidence
03
Insert it into scene order
The Scene inserts the new element at the resolved index, repairs moved indices, and replaces its element set.
Locate Evidence
04
Select visible elements
The viewport renderer reads the scene and reduces it to the elements visible in the current viewport.
Locate Evidence
05
Enter the canvas boundary
The StaticCanvas effect forwards the visible element maps and editor state to the renderer.
Locate Evidence
06
Render the static scene
The scene renderer chooses the throttled or immediate canvas path for the prepared render configuration.
Locate Evidence
07
Paint the rectangle
The element renderer routes rectangles through the shared shape painting branch.
Locate Evidence

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