Testing GCO-to-BOX solution

graphicCellObjectBox.jsx

function graphicCellObjectBox(/*PageItem*/gco,  dup,t,lt,rb,xy,dx,dy)
//----------------------------------
// [DRAFT220802] Input: PageItem of a graphic cell.
{
	const AP_CC = +AnchorPoint.CENTER_ANCHOR;
	const AP_TL = +AnchorPoint.TOP_LEFT_ANCHOR;
	const AP_BR = +AnchorPoint.BOTTOM_RIGHT_ANCHOR;

	const CS_IN = +CoordinateSpaces.INNER_COORDINATES;
	const CS_PAR = +CoordinateSpaces.PARENT_COORDINATES;
	const CS_SPD = +CoordinateSpaces.SPREAD_COORDINATES;
	const CS_PB = +CoordinateSpaces.PASTEBOARD_COORDINATES;

	const BB_VIS = +BoundingBoxLimits.outerStrokeBounds;

	const MC = MatrixContent;
	const MC_SHR = [ MC.scaleValues, MC.shearValue, MC.rotationValue ];

	dup = gco.duplicate();                                           // Assert: dup is a Spread item (that's all we know!)
	(t=dup.pageItems).length && (t.everyItem().remove());            // Assert: dup has no inner stuff.
	dup.convertShape(+ConvertShapeOptions.CONVERT_TO_RECTANGLE);     // Assert: dup is a rectangular box (in its inner space!)
	dup.properties = { strokeColor:'None',fillColor:'Yellow' };      // Assert: visibleBounds == geoPath

	// 1. Reposition dup (in case of weird spread shift.)
	// ---
	xy = gco.resolve(AP_CC,CS_PB)[0];                                // Center point of gco in PB space.
	t = dup.resolve(AP_CC,CS_PB)[0];                                 // Center point of dup in PB space.
	dx = xy[0]-t[0];
	dy = xy[1]-t[1];
	(dx||dy) && dup.transform(CS_PB,[0,0],[1,0,0,1,dx,dy]);          // Reposition.

	// 2. Adjust the transform state of dup so that the
	// dup->Spread matrix matches the gcoParent->Spread matrix.
	// ---
	t = gco.transformValuesOf(CS_PAR)[0].invertMatrix()              // gcoParent -> gcoInner
		.catenateMatrix(gco.transformValuesOf(CS_SPD)[0]);           // gcoParent -> Spread
	dup.transform(CS_SPD, AP_CC, t, MC_SHR);                         // Assert: dup is now in good transform state!

	// 3. Reframe dup w.r.t the *visible in-parent* box of gco.
	// ---
	lt = gco.resolve([AP_TL,BB_VIS,CS_PAR],CS_PB)[0];                // Coordinates are returned in pasteboard space
	rb = gco.resolve([AP_BR,BB_VIS,CS_PAR],CS_PB)[0];                // because the *spread space is not reliable*.
	t = dup.transformValuesOf(CS_PB)[0].invertMatrix();              // Pasteboard -> dupInner
	lt = t.changeCoordinates(lt);
	rb = t.changeCoordinates(rb);
	dup.reframe(CS_IN, [lt,rb]);
};