.title
Pie Menu Distance

.synonyms
distance
distance.

.definition
How pie menus use distance.

.contents

	The other important characteristic of a pie menu is the way in which
	the cursor distance effects the menu selection.
	
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.tab 0 .line SELECTION SPEED
	To select any item, the cursor has only to move out of radius of the
	small inactive region in the menu center, where the menu was invoked.
	An item is selected by moving the cursor into its pie slice shaped
	active region, outside of the inactive region.  They are all equally
	distant from the cursor's initial position, but in different
	directions.  The active regions actually extend past the menu window
	edge, to the edge of the screen.
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	In an experiment comparing pie menus with traditional linear menus,
	Jack Callahan has shown that novice users could make selection from
	eight item pie menus faster, and with fewer errors, than from
	traditional linear menus. (Callahan, et all, 1988)
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	Fitt's law (Card, 1983) states that positioning time is dependant on
	the distance and target size.  Pie menus are fast because the distance
	to each target region is small, and the size of each target area is
	large.
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.tab 0 .line INCREASED ANGULAR PRECISION
	As the cursor moves farther away from the menu center, to the wider
	regions of the slices, cursor motion has less effect on the direction
	from the menu center. The target regions extend out past the edges of
	the menu window to the screen edge, so the user can move the cursor
	out as far as needed to get the angular precision desired.
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.tab 0 .line DISTANCE AS AN ARGUMENT
	The cursor's distance from the menu center can also be used as an
	additional input. It can serve as a continuous numeric argument to the
	menu selection, or it can select between one of several discrete
	sub-items of the selected slice.

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	==> .~ Application Examples~