Inspired by an oiginal design of Hans-Martin Mosner, this ScrollBar is intended to exercise the handling of input events in Morphic. With sufficient flexibility in this area, all particular behavior can be concentrated in this single class with no need to specialize any other morphs to achieve button, slider and menu-button behavior.

Once we have this working, put in logic for horizontal operation as well.

CachedImages was added to reduce the number of forms created and thrown away. This will be helpful for Nebraska and others as well.

	as yet unclassified
	cachedImageAt:ifAbsentPut:

	geometry
	buttonExtent computeSlider expandSlider extent: sliderExtent totalSliderArea

	initialize
	initialize initializeDownButton initializeMenuButton initializePagingArea initializeSlider initializeUpButton upArrow8Bit

	other events
	menuButtonMouseDown: mouseDownInSlider:

	scroll timing
	resetTimer waitForDelay1:delay2:

	scrolling
	doScrollByPage doScrollDown doScrollUp finishedScrolling scrollBarAction scrollBarAction: scrollDown scrollDown: scrollDownInit scrollPageInit: scrollUp scrollUp: scrollUpInit setNextDirectionFromEvent: setValue:

	stepping
	step stepTime wantsSteps

	access	top
	interval: Supply an optional floating fraction so slider can expand to indicate range
	pagingArea
	scrollDelta
	scrollDelta:pageDelta: Supply optional increments for better scrolling of, eg, text

	as yet unclassified	top
	cachedImageAt:ifAbsentPut:

	geometry	top
	buttonExtent
	computeSlider interval ifNotNil: [self expandSlider].
	expandSlider Compute the new size of the slider (use the old sliderThickness as a minimum).
	extent:
	sliderExtent The sliderExtent is now stored in the slider itself, not hardcoded as it is in the superclass.
	totalSliderArea

	initialize	top
	initialize
	initializeDownButton
	initializeMenuButton Preferences disable: #scrollBarsWithoutMenuButton
	initializePagingArea
	initializeSlider
	initializeUpButton
	upArrow8Bit convert to 8-bit and convert white to transparent to avoid gratuitous conversion every time we put one in an ImageMorph

	other events	top
	menuButtonMouseDown:
	mouseDownInSlider:

	scroll timing	top
	resetTimer
	waitForDelay1:delay2: Return true if an appropriate delay has passed since the last scroll operation. The delay decreases exponentially from delay1 to delay2.

	scrolling	top
	doScrollByPage Scroll automatically while mouse is down
	doScrollDown Scroll automatically while mouse is down
	doScrollUp Scroll automatically while mouse is down
	finishedScrolling
	scrollBarAction
	scrollBarAction:
	scrollDown
	scrollDown:
	scrollDownInit
	scrollPageInit:
	scrollUp
	scrollUp:
	scrollUpInit
	setNextDirectionFromEvent:
	setValue: Using roundTo: instead of truncateTo: ensures that scrollUp will scroll the same distance as scrollDown.

	stepping	top
	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.

	class initialization	top
	initialize ScrollBar initialize