HasBuiltInScrollArrows

DirtyScrollArrows DotInWhichScrollArrow Draw DrawScrollArrows HandleTouchInScrollArrows ScrollArrowImage ScrollArrowPositions Touch

Attributes

CanDrawIn ScrollsHorizontally UseBuiltInScrollArrows

Fields

Define Class HasBuiltInScrollArrows;
    mixes in with Viewable, HasScrolling;
    
    operation DirtyScrollArrows(), noFail;
        // calls DirtyBox on the enclosing box of each scroll arrow
        // call to force a redraw of the scroll arrow area without redrawing entire content
        // override rarely
        
    operation DotInWhichScrollArrow(probe: Dot): ScrollArrowType;
        // returns which scroll arrow (or none) probe is in
        // possible values are scrollBackArrow, scrollForwardArrow, and noScrollArrow   
    
    operation DrawScrollArrows(), noFail;
        // draws scroll arrows
        // called from Draw
        // sometimes call from overrides of Draw if not calling inherited Draw for other reasons
        // override rarely
    
    operation HandleTouchInScrollArrows(touchInput: TouchInput): Boolean;
        // if UseBuiltInScrollArrows is false, returns false
        // if start point of <touchInput> was in back or forward arrow, handles the touch and returns true
        // else returns false
        // called from HasBuiltInScrollArrows_Touch, and from touch methods of subclasses that override touch
        // override rarely
        
    operation ScrollArrowImage(backArrow: Boolean): Image;
        // call to get image of scroll arrow from scroll direction
        // returns iScrollUpArrow if <backArrow> is true, iDownScrollArrow otherwise
        // override rarely to use different images; the two images should be the same size
        
    operation ScrollArrowPositions(var backArrowPosition: Dot; var forwardArrowPosition: Dot);
        // fills in position parameters with dots in upper right and lower right of self's content box
        // override sometimes to position scroll arrows elsewhere
    
    attribute ScrollsHorizontally: Boolean, readOnly;
        // distinguishes between up-and-down scrolling and left-and-right scrolling
        // returns false
        // override sometimes to return true for subclasses that scroll horizontally
        // overriders should also override ScrollArrowImage and probably ScrollArrowPositions since
        // default implementations are designed for vertical scrolling
    
    attribute UseBuiltInScrollArrows: Boolean, readOnly;
        // returns true
        // override sometimes to let subclass use built-in scroll arrows on an instance-by-instance basis
    
    overrides CanDrawIn;
        // returns kDontDrawHere if current touch is in built-in scroll arrows,
        // otherwise returns result of inherited method
    overrides Draw;
        // draws scroll arrows after calling inherited method
    overrides Touch;
        // calls HandleTouchInScrollArrows. If it returns false, calls inherited method.
    
end class;