Subclass of NSScroller not drawing

Question

I have an NSScrollView and I'd like to know when the user mouseDown's on it's NSScroller. When subclassed NSScroller (to override mouseDown), my NSScrollView's horizontal scroller is no longer drawn/visible. If I override the my NSScroller's drawRect (and use it's superview to do the drawing), it gets called with the expected NSRect, but nothing is being drawn. What am I missing?

Actually, there appears to be a 15x15 segment of a vertical scroller track on the right side of the expected HScroller area. Maybe I need to specify setFrameRotation or something...although if I call NSFillRect in MyHScroller's drawRect, it draws the expected rect - if I rotate by 90 degrees, my fill is only 15x15 on the left side of the expected HScroller area.

Here's my NSScrollView creation code:

MyHScroller  *pMyHScroller  = [[MyHScroller  alloc] init];
MyScrollView *pMyScrollView = [[MyScrollView alloc] initWithFrame:nsrcFrame];
// pMyHScroller = nil;  // With this line uncommented, the HScroller is drawn perfectly
if (pMyHScroller)
{
    [pMyScrollView setHorizontalScroller:pMyHScroller];
}
[pMyScrollView setHasVerticalScroller:    NO];
[pMyScrollView setHasHorizontalScroller: YES];
[pMyScrollView setAutohidesScrollers:     NO];
[pMyScrollView setBorderType:  NSBezelBorder];
[pMyScrollView setAutoresizingMask:0|NSViewMinYMargin];

[pMyScrollView setHorizontalLineScroll:  10];
[pMyScrollView setHorizontalPageScroll: 100];
[pMyScrollView setScrollsDynamically:   YES];

Here is the NSScroller subclass:

@interface MyHScroller : NSScroller
{
}
- (void)mouseDown:(NSEvent *)eventInfo;
- (void)drawRect:(NSRect)nsrcDirty;
@end 

@implementation MyHScroller // NSScroller
- (void)mouseDown:(NSEvent *)eventInfo
{
   [super mouseDown:eventInfo];
}


- (void)drawRect:(NSRect)nsrcDirty
{
    // This fills the expected HScoller area with yellow
    [[NSColor yellowColor] set];
    NSRectFill(nsrcDirty);

    // This verifies the ends of the rect are visible
    {
        [[NSColor cyanColor] set];
        NSBezierPath* aPath = [NSBezierPath bezierPath];
        [aPath moveToPoint:NSMakePoint(bounds.origin.x     , bounds.origin.y                       )];
        [aPath lineToPoint:NSMakePoint(bounds.origin.x+20.0, bounds.origin.y+bounds.size.height/2.0)];
        [aPath lineToPoint:NSMakePoint(bounds.origin.x     , bounds.origin.y+bounds.size.height    )];
        [aPath stroke];
    }
    {
        [[NSColor cyanColor] set];
        NSBezierPath* aPath = [NSBezierPath bezierPath];
        [aPath moveToPoint:NSMakePoint(bounds.origin.x+bounds.size.width     , bounds.origin.y                       )];
        [aPath lineToPoint:NSMakePoint(bounds.origin.x+bounds.size.width-20.0, bounds.origin.y+bounds.size.height/2.0)];
        [aPath lineToPoint:NSMakePoint(bounds.origin.x+bounds.size.width     , bounds.origin.y+bounds.size.height    )];
        [aPath stroke];
    }

    // This draws what appears to be a 15x15 Vertical Scroller track segment
    // over the right size of the yellow rect
    [super drawRect:nsrcDirty];
}

@end

The MyScrollView is just an NSScrollView override with functions added for scrolling synchronization.

nubee nubee · Accepted Answer · 2011-06-29T16:43:17

Simple Solution...there's an undocumented bitflag that controls the orientation and behavior: sFlags.isHorz needs to be set to YES or NO in the NSScroller subclass.

Here's a not-necessarily-recommended example using the setFrame: override:

-(void)setFrame:(NSRect)nsrcFrame
{
    [super setFrame:nsrcFrame];
    sFlags.isHoriz = (nsrcFrame.size.width > nsrcFrame.size.height); // otherwise always draws vertically
}

Subclass of NSScroller not drawing

1 Answers