Native graph implementation history

This historical implementation note records the migration from the bespoke SWbpAnimStateMachineGraph canvas to a native Unreal graph-editor stack built on UEdGraph, schema classes, graph nodes, and SGraphEditor.

This page preserves the existing engineering history; it is not the current product roadmap or a release promise. See Animation state machines for the current feature overview and In development for additions still being implemented and validated.

Goal

Move the state machine editor toward the same underlying editor architecture used by Unreal’s native graph tooling, so the module can eventually inherit more of the engine’s built-in graph behavior, visuals, extensibility, and interaction model.

Migration Strategy

The migration was staged. The native graph is now the only graph tab, and the custom SWbpAnimStateMachineGraph canvas has been removed.

Slice 1: Native Graph Foundation

Status: implemented

Added a native graph tab to the state machine definition editor.
Introduced a transient editor graph model:
UWbpAnimStateMachineEdGraph
UWbpAnimStateMachineEdGraphNode
UWbpAnimStateMachineEdGraphSchema
Added a native SGraphEditor surface wired to the definition editor.
Added custom graph node visuals for the new editor graph.
Added one-way synchronization from the definition asset into the transient editor graph.
Added selection/focus handoff for the native graph tab.

Slice 2: Native Graph Parity

Status: implemented

Add richer node metadata presentation in native nodes:
play mode
animation name
sub-machine state indication
clip/state bridge cues
Add native graph selection parity with the current details/debugger/status surfaces.
Improve connection presentation with a custom connection drawing policy.
Represent wildcard transitions and special transition cases more faithfully.

Implemented in this slice so far:

native nodes now surface more authored semantics:
play mode badges
re-entry badges
child-definition and auto-transition summary text
missing-clip warning text
bridge-target emphasis
native connections now use a custom connection drawing policy instead of the default generic graph styling
native bidirectional transitions now render as separated parallel lanes
native endpoints now distribute across each node edge, keeping dense incoming/outgoing connection points readable instead of stacking them on one pixel
native connection routing now stays farther outside the state cards and mirrors bidirectional pairs with matching curvature
native connector anchors now choose and space a sensible state edge from relative node positions instead of visually forcing all incoming links onto the left side
native pin presentation is now quieter so state-to-state flow reads more clearly than explicit socket chrome
native transition wires now use metadata-aware color and weight cues for breakpoint, condition/rule, and blend/curve state without adding extra mid-wire decoration
native graph rebuild now tracks details-panel edits live, so the graph tab stays synchronized while authoring
native node movement and connection edits now sync back into the definition for:
EditorNodePositions
InitialState
transition wiring (while preserving existing transition metadata for unchanged edges)
native graph now supports basic graph-first authoring:
add state from empty-graph context menu
create and autowire a new state from a dragged pin
connect to existing states from node context menus
rename authored states in-place
delete authored states
edit linked transitions from pin context menus:
remove a connected transition
add the reverse transition
toggle breakpoint metadata
explicitly author special-node semantics:
Make Initial State
Add Any-State Transition
Remove Any-State Transition
Clear Initial State Link

Slice 3: Native Editing

Status: implemented

Added schema-driven editing actions:
add state
delete state
connect states
rename state
drag node positions
Persisted native graph edits back into:
States
Transitions
EditorNodePositions
Added transaction-aware edits for graph-to-definition synchronization.

Slice 4: Native-first Editor

Status: implemented

Made the native graph the default Graph tab.
Removed the custom canvas fallback.
Added standard graph comments for production notes and callouts.
Added Backspace/Delete deletion for selected states and comments.
Added auto-layout modes for compact, flow-first, wide, and selected-only graph reshaping.
Added edge-wide smart anchors, endpoint spacing, and matched bidirectional lanes.
Ported the remaining everyday graph conveniences to the native editor path.

Slice 5: Full Replacement / Cleanup

Status: implemented

Removed the legacy bespoke graph after native graph feature parity was reached.
Consolidated graph-related editor entry points around the native graph stack.
Retired duplicate graph affordances that only existed to support the migration period.
Keep the definition asset as the single serialized source of truth.

Remaining Parity Risks

The native graph is now the single visual authoring path.

Remaining areas to keep validating:

dense graphs with dozens or hundreds of transitions on one state
selected-wire deletion and other subtle SGraphEditor command expectations
visual parity for any legacy-only debugging overlays
long-duration editor sessions with repeated graph rebuilds and details-panel edits
project-specific workflows that relied on legacy collapse/expand behavior

Design Notes

The native graph is editor-only and transient.
The source of truth remains UWbpAnimStateMachineDefinition.
The native graph is a synchronized editor representation, not a second serialized runtime format.
This keeps runtime data stable while allowing the editor experience to become much more native over time.