buildScene abstract method
Builds the neutral contract scene: MaterialApp (Material 3) with an
AppBar(title: 'Contract scene'), a ListView of 12 rows (row 5 =
element B, the anchor), a 1200 px scroll margin after the rows, and a
fixed FloatingActionButton (element A). Keys and geometry are the
package's constants (scene.dart); spec.listScroll must drive the
ListView and element A must increment SceneSpec.aTaps.
withLibrary selects between two mounts of the same scene:
false — the base scene, the solution is absent from the tree (S1);
true — the scene as the solution is really used, nothing shown (idle).
Implementation
Widget buildScene({required bool withLibrary, required SceneSpec spec});