Refactor symmetryGroups to a structure level property

src/mol-geo/representation/structure/index.ts

@@ -43,7 +43,7 @@ export function StructureRepresentation<P extends StructureProps>(unitsVisualCto
 
         return Task.create('Creating StructureRepresentation', async ctx => {
             if (!_structure) {
-                _groups = StructureSymmetry.getTransformGroups(structure);
+                _groups = structure.symmetryGroups;
                 for (let i = 0; i < _groups.length; i++) {
                     const group = _groups[i];
                     const visual = unitsVisualCtor()
@@ -59,7 +59,7 @@ export function StructureRepresentation<P extends StructureProps>(unitsVisualCto
                 if (_structure.hashCode === structure.hashCode) {
                     await update(_props)
                 } else {
-                    _groups = StructureSymmetry.getTransformGroups(structure);
+                    _groups = structure.symmetryGroups;
                     const newGroups: Unit.SymmetryGroup[] = []
                     const oldUnitsVisuals = unitsVisuals
                     unitsVisuals = new Map()

src/mol-model/structure/structure/structure.ts

@@ -16,6 +16,7 @@ import { CoarseElements } from '../model/properties/coarse';
 import { StructureSubsetBuilder } from './util/subset-builder';
 import { Queries } from '../query';
 import { InterUnitBonds, computeInterUnitBonds } from './unit/links';
+import StructureSymmetry from './symmetry';
 
 class Structure {
     readonly unitMap: IntMap<Unit>;
@@ -68,6 +69,13 @@ class Structure {
         return this._links;
     }
 
+    private _symmetryGroups?: ReadonlyArray<Unit.SymmetryGroup> = void 0;
+    get symmetryGroups(): ReadonlyArray<Unit.SymmetryGroup> {
+        if (this._symmetryGroups) return this._symmetryGroups;
+        this._symmetryGroups = StructureSymmetry.computeTransformGroups(this);
+        return this._symmetryGroups;
+    }
+
     constructor(units: ArrayLike<Unit>) {
         const map = IntMap.Mutable<Unit>();
         let elementCount = 0;

src/mol-model/structure/structure/symmetry.ts

@@ -68,7 +68,7 @@ namespace StructureSymmetry {
         return EquivalenceClasses<number, Unit>(hashUnit, areUnitsEquivalent);
     }
 
-    export function getTransformGroups(s: Structure): ReadonlyArray<Unit.SymmetryGroup> {
+    export function computeTransformGroups(s: Structure): ReadonlyArray<Unit.SymmetryGroup> {
         const groups = UnitEquivalenceBuilder();
         for (const u of s.units) groups.add(u.id, u);