chore: establish learning module baseline

OpenMAIC/components/edit/surfaces/slide/editing-state.ts

@@ -0,0 +1,35 @@
+import type { PPTElement } from '@openmaic/dsl';
+
+/**
+ * The single selected slide element — `undefined` unless exactly one element is
+ * selected and it resolves in the content. The basis for the surface's
+ * selection-anchored chrome (the text format bar, the image action bar).
+ */
+export function resolveSelectedElement(
+  activeElementIdList: readonly string[],
+  elements: readonly PPTElement[],
+): PPTElement | undefined {
+  if (activeElementIdList.length !== 1) return undefined;
+  return elements.find((el) => el.id === activeElementIdList[0]);
+}
+
+/**
+ * The slide surface's text-editing policy: a single selected text element is,
+ * by definition, the element being edited (there is no separate
+ * "selected-not-editing" state for text). Anything else resolves to "".
+ *
+ * This is the value the surface writes into the canvas store's
+ * `editingElementId`, which the renderer's `TextElementOperate` reads to swap
+ * its dashed select frame for a clean solid editing frame.
+ */
+export function resolveEditingElementId(
+  activeElementIdList: readonly string[],
+  elements: readonly PPTElement[],
+  requestedId?: string,
+  editableTypes: readonly PPTElement['type'][] = ['text'],
+): string {
+  const el = resolveSelectedElement(activeElementIdList, elements);
+  const editable = Boolean(el && editableTypes.includes(el.type));
+  if (requestedId === undefined) return editable ? (el?.id ?? '') : '';
+  return editable && !el?.lock && el?.id === requestedId ? requestedId : '';
+}