This class combines the old Polygon and Curve classes.

The 1-bit fillForm to make display and containment tests reasonably fast. However, this functionality is in the process of being supplanted by balloon capabilities, which should eventually provide anti-aliasing as well.

	dashes
	borderDashOffset dashedBorder: step stepTime wantsSteps

	drawing
	areasRemainingToFill: drawArrowOn:at:from: drawArrowsOn: drawBorderOn: drawBorderOn:usingEnds: drawClippedBorderOn:usingEnds: drawDashedBorderOn: drawDashedBorderOn:usingEnds: drawOn: drawOnFormCanvas: drawPostscriptOn:

	editing
	addHandles dragVertex:event:fromHandle: dragVertex:fromHandle:vertIndex: dropVertex:event:fromHandle: dropVertex:fromHandle:vertIndex: fillStyle fillStyle: handlesMouseDown: justDroppedInto:event: mouseDown: newVertex:event:fromHandle: newVertex:fromHandle:afterVert: updateHandles verticesAt:put:

	geometry
	closestPointTo: containsPoint: couldHaveRoundedCorners extent: flipHAroundX: flipVAroundY: inset: merge: mergeDropThird:in:from:

	halo control
	addFlexShellIfNecessary heading: referencePosition rotationCenter rotationCenter: rotationDegrees rotationDegrees: setRotationCenterFrom: transformedBy:

	initialization
	beSmoothCurve beStraightSegments initialize initializeToStandAlone installModelIn: vertices:color:borderWidth:borderColor:

	menu
	addCustomMenuItems:hand: arrowSpec: customizeArrows: handlesShowingPhrase makeBackArrow makeBothArrows makeClosed makeForwardArrow makeNoArrows makeOpen quickFill: removeHandles showOrHideHandles showingHandles specifyDashedLine standardArrows toggleHandles toggleSmoothing

	object fileIn
	convertToCurrentVersion:refStream:

	private
	arrowBoundsAt:from: arrowForms borderForm computeArrowFormAt:from: computeBounds curveBounds filledForm getVertices includesHandle: lineSegments loadCachedState privateMoveBy: releaseCachedState setVertices:

	smoothing
	coefficients computeNextToEndPoints derivs:first:second:third: lineSegmentsDo: nextToFirstPoint nextToLastPoint

	visual properties
	canHaveFillStyles defaultColor

	parts bin
	descriptionForPartsBin

	access	top
	borderColor:
	borderWidth:
	isClosed
	isCurve
	isOpen
	makeOpenOrClosed toggle the open/closed status of the receiver
	openOrClosePhrase
	vertices

	dashes	top
	borderDashOffset
	dashedBorder: A dash spec is a 3- or 5-element array with { length of normal border color. length of alternate border color. alternate border color. starting offset. amount to add to offset at each step } Starting offset is usually = 0, but changing it moves the dashes along the curve.
	step Do some periodic activity. Use startStepping/stopStepping to start and stop getting sent this message. The time between steps is specified by this morph's answer to the stepTime message. The generic version dispatches control to the player, if any. The nasty circumlocation about owner's transformation is necessitated by the flexing problem that the player remains in the properties dictionary both of the flex and the real morph. In the current architecture, only the top renderer's pointer to the player should actually be honored for the purpose of firing.
	stepTime Answer the desired time between steps in milliseconds. This default implementation requests that the 'step' method be called once every second.
	wantsSteps Return true if the receiver overrides the default Morph step method.

	drawing	top
	areasRemainingToFill: Could be improved by quick check of inner rectangle
	drawArrowOn:at:from: Draw a triangle oriented along the line from priorPoint to endPoint. Answer the wingBase.
	drawArrowsOn: Answer (possibly modified) endpoints for border drawing
	drawBorderOn:
	drawBorderOn:usingEnds: Display my border on the canvas.
	drawClippedBorderOn:usingEnds:
	drawDashedBorderOn:
	drawDashedBorderOn:usingEnds: Display my border on the canvas. NOTE: mostly copied from drawBorderOn:
	drawOn: Display the receiver, a spline curve, approximated by straight line segments.
	drawOnFormCanvas: Display the receiver, a spline curve, approximated by straight line segments.
	drawPostscriptOn: Display the receiver, a spline curve, approximated by straight line segments.

	editing	top
	addHandles
	dragVertex:event:fromHandle:
	dragVertex:fromHandle:vertIndex: Reorder the arguments for existing event handlers
	dropVertex:event:fromHandle:
	dropVertex:fromHandle:vertIndex: Reorder the arguments for existing event handlers
	fillStyle Return the current fillStyle of the receiver.
	fillStyle: Set the current fillStyle of the receiver.
	handlesMouseDown: Do I want to receive mouseDown events (mouseDown:, mouseMove:, mouseUp:)?
	justDroppedInto:event: This message is sent to a dropped morph after it has been dropped on -- and been accepted by -- a drop-sensitive morph
	mouseDown: Handle a mouse down event. The default response is to let my eventHandler, if any, handle it.
	newVertex:event:fromHandle: Insert a new vertex and fix everything up! Install the drag-handle of the new vertex as recipient of further mouse events.
	newVertex:fromHandle:afterVert: Reorder the arguments for existing event handlers
	updateHandles
	verticesAt:put:

	geometry	top
	closestPointTo:
	containsPoint:
	couldHaveRoundedCorners subclases unhappy with rounded corners reimplement
	extent: Not really advisable, but we can preserve most of the geometry if we don't shrink things too small.
	flipHAroundX: Flip me horizontally around the center. If centerX is nil, compute my center of gravity.
	flipVAroundY: Flip me vertically around the center. If centerY is nil, compute my center of gravity.
	inset: Only works if I am made of rectangles (every segment of me is horizontal or vertical). Inset each vertex by amt. Uses containsPoint.
	merge: Expand myself to enclose the other polygon. (Later merge overlapping or disjoint in a smart way.) For now, the two polygons must share at least two vertices. Shared vertices must come one after the other in each polygon. Polygons must not overlap.
	mergeDropThird:in:from: We are merging two polygons. In this case, they have at least three identical shared vertices. Make sure they are sequential in each, and drop the middle one from vertex lists mv, hv, and shared. First vertices on lists are identical already.

	halo control	top
	addFlexShellIfNecessary When scaling or rotating from a halo, I can do this without a flex shell
	heading: Set the receiver's heading (in eToy terms). Note that polygons never use flex shells.
	referencePosition Return the current reference position of the receiver
	rotationCenter Return the rotation center of the receiver. The rotation center defines the relative offset inside the receiver's bounds for locating the reference position.
	rotationCenter: Set the new rotation center of the receiver. The rotation center defines the relative offset inside the receiver's bounds for locating the reference position.
	rotationDegrees Default implementation.
	rotationDegrees:
	setRotationCenterFrom: Polygons store their referencePosition.
	transformedBy:

	initialization	top
	beSmoothCurve
	beStraightSegments
	initialize
	initializeToStandAlone Set up the receiver, created by a #basicNew and now ready to be initialized, as a fully-formed morph suitable for providing a graphic for a parts bin surrogate, and, when such a parts-bin surrogate is clicked on, for attaching to the hand as a viable stand-alone morph. Because of historical precedent, #initialize has been expected to handle this burden, though a great number of morphs actually cannot stand alone. In any case, by default we call the historical #initialize, though unhappily, so that all existing morphs will work no worse than before when using this protocol.
	installModelIn: Simple morphs have no model
	vertices:color:borderWidth:borderColor:

	menu	top
	addCustomMenuItems:hand: Add morph-specific items to the given menu which was invoked by the given hand. This method provides is invoked both from the halo-menu and from the control-menu regimes.
	arrowSpec: Specify a custom arrow for this line. specPt x abs gives the length of the arrow (point to base) in terms of borderWidth. If specPt x is negative, then the base of the arrow will be concave. specPt y abs gives the width of the arrow. The standard arrow is equivalent to arrowSpec: 5@4. See arrowBoundsAt:From: for details.
	customizeArrows:
	handlesShowingPhrase
	makeBackArrow
	makeBothArrows
	makeClosed
	makeForwardArrow
	makeNoArrows
	makeOpen
	quickFill:
	removeHandles tk 9/2/97 allow it to be called twice (when nil already)
	showOrHideHandles
	showingHandles
	specifyDashedLine
	standardArrows
	toggleHandles
	toggleSmoothing

	object fileIn	top
	convertToCurrentVersion:refStream: subclasses should implement if they wish to convert old instances to modern ones

	private	top
	arrowBoundsAt:from: Answer a triangle oriented along the line from priorPoint to endPoint.
	arrowForms ArrowForms are computed only upon demand
	borderForm A form must be created for drawing the border whenever the borderColor is translucent.
	computeArrowFormAt:from: Compute a triangle oriented along the line from priorPoint to endPoint. Then draw those lines in a form and return that form, with appropriate offset
	computeBounds
	curveBounds
	filledForm Note: The filled form is actually 2 pixels bigger than bounds, and the point corresponding to this morphs' position is at 1@1 in the form. This is due to the details of the fillig routines, at least one of which requires an extra 1-pixel margin around the outside. Computation of the filled form is done only on demand.
	getVertices
	includesHandle:
	lineSegments
	loadCachedState Prepare for fast response -- next page of a book?
	privateMoveBy: Private! Use 'position:' instead.
	releaseCachedState Release any state that can be recomputed on demand, such as the pixel values for a color gradient or the editor state for a TextMorph. This method may be called to save space when a morph becomes inaccessible. Implementations of this method should do 'super releaseCachedState'.
	setVertices:

	smoothing	top
	coefficients Compute an array for the coefficients. This is copied from Flegal's old code in the Spline class.
	computeNextToEndPoints
	derivs:first:second:third: Compute the first, second and third derivitives (in coeffs) from the Points in this Path (coeffs at: 1 and coeffs at: 5).
	lineSegmentsDo: Emit a sequence of segment endpoints into endPointsBlock.
	nextToFirstPoint For arrow direction
	nextToLastPoint For arrow direction

	visual properties	top
	canHaveFillStyles Return true if the receiver can have general fill styles; not just colors. This method is for gradually converting old morphs.
	defaultColor Return the default fill style for the receiver

	instance creation	top
	arrowPrototype
	fromHand: Let the user draw a polygon, clicking at each vertex, and ending by clicking within 5 of the first point...
	fromHandFreehand: Let the user draw a polygon, holding the mouse down, and ending by clicking within 5 of the first point...
	shapeFromPen:color:borderWidth:borderColor: World addMorph: (PolygonMorph shapeFromPen: [:p | p hilbert: 4 side: 5. p go: 5. p hilbert: 4 side: 5. p go: 5] color: Color red borderWidth: 1 borderColor: Color black)
	supplementaryPartsDescriptions Answer a list of DescriptionForPartsBin objects that characterize objects that this class wishes to contribute to Stationery bins *other* than by the standard default #newStandAlone protocol
	vertices:color:borderWidth:borderColor:

	parts bin	top
	descriptionForPartsBin If the receiver is a member of a class that would like to be represented in a parts bin, answer the name by which it should be known, and a documentation string to be provided, for example, as balloon help. When the 'nativitySelector' is sent to the 'globalReceiver', it is expected that some kind of Morph will result. The parameters used in the implementation below are for documentation purposes only!