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Adjuster(3I) InterViews Reference Manual Adjuster(3I)


Adjuster - button-like interactors for incremental scrolling and zooming


#include <InterViews/adjuster.h>


Adjuster objects manipulate a perspective using a pushbutton-like interface. Adjusters also provide an auto-repeat capability. Depressing and holding down any mouse button on an adjuster for a specified time causes it to repeatedly perform its operation. The auto-repeat terminates when the button is released.

Predefined subclasses of Adjuster include Zoomer and Mover. Zoomers adjust the perspective's curwidth and curheight members to suggest magnification. The user clicks on a zoomer to magnify or reduce the contents of the interactor through its perspective. The Enlarger zoomer subclass halves the perspective values while the Reducer class doubles them. Movers provide an incremental movement of the perspective in one of four directions; left, right, down, or up. The user clicks on a mover to move the perspective.


Adjuster constructors take a pointer to the interactor whose perspective will be adjusted and a delay (in tenths of a second) after which auto-repeat will begin once the adjuster is ``pressed''.
These functions define how the adjuster draws itself when it is pressed. The adjuster is highlighted when it is pressed with any mouse button and unhighlighted when the button is released. The default is to invert the adjuster when highlighted.


This function defines how the adjuster adjusts the interactor's perspective. It is called after the adjuster is pressed and released, or repeatedly during auto-repeat. Derived classes should redefine this function to implement the desired behavior.


Enlargers and reducers adjust an interactor's perspective to enlarge and reduce the visible area by factors of one half and two, respectively. This suggests to an interactor to enlarge or reduce its contents. Auto-repeat is disabled on these adjusters.
These subclasses of Mover adjust the current origin of the interactor's perspective by an amount in the corresponding direction. If the shift key is down while the mover is pressed, the amount corresponds to the perspective's lx or ly member variables; otherwise, the sx or sy values are used.


Interactor(3I), Perspective(3I)

15 January 1988 InterViews