molstar-structure-editor-dev

name	molstar-structure-editor-dev
description	Use when modifying the molstar-structure-editor plugin, extending edit behavior, changing gizmo interaction, or working on Mol* coordinate-driven structure editing in this repository.

Molstar Structure Editor Dev

Overview

This plugin edits structures by continuously replacing selected atom coordinates and letting Mol* redraw from the updated model. It does not mutate the original trajectory frame in place.

When to Use

• Adding move, rotate, commit, or cancel behavior
• Extending selection handling
• Changing how edited structures are shown in Mol*
• Modifying gizmo rendering or input flow

Architecture

• src/helpers.ts Public entrypoints: register plugin, enter move/rotate, commit, cancel.
• src/behavior.ts Main controller. Owns state machine, toolbar, pointer handling, gizmo placement, and edit-mode structure swapping.
• src/session.ts Edit math. Freezes selected atom indices, stores base/current frames, applies rigid translation/rotation.
• src/coordinate-updater.ts Inserts or reuses ModelWithCoordinates, then updates atomicCoordinateFrame.
• src/gizmo-representation.ts Builds the visible axes/rings mesh.
• src/gizmo-hit-test.ts Screen-space picking for axes and rings.
• src/selection-target.ts Resolves the active Mol* selection to a single editable structure target.

Core Data Flow

1. User selects atoms or residues in Mol*.
2. enterMode() in src/behavior.ts creates an EditSession.
3. CoordinateUpdater ensures a ModelWithCoordinates node exists under the selected model.
4. A temporary structure branch is built from that coordinate-backed model and shown while the source structure is hidden.
5. Pointer drag updates the session transform.
6. Session rebuilds currentFrame for selected atoms only.
7. CoordinateUpdater pushes the new frame into Mol*.
8. Mol* redraws the edited structure branch.

Rules for Safe Changes

• Keep v1 scoped to one structure and one model.
• Treat selection as rigid-body editing unless you are explicitly adding internal deformation support.
• When changing screen-space math, keep behavior.ts projection logic and gizmo-hit-test.ts thresholds in sync.
• When changing coordinate updates, verify the visible structure branch still comes from the coordinate-backed model, not the hidden source branch.

Common Extension Points

• Add hover feedback: start in src/behavior.ts and pass activeHandle into the gizmo transform.
• Add new edit modes: extend EditKind, session math, and toolbar commands together.
• Support better chemical editing: add a new post-transform relaxation or topology-aware layer above session.ts. Do not overload ModelWithCoordinates with chemistry logic.

Fast References

• Public API: src/index.ts, src/helpers.ts
• Edit session math: src/session.ts
• Mol* coordinate bridge: src/coordinate-updater.ts
• Pointer bugs: src/behavior.ts, src/gizmo-hit-test.ts