How to make Scroller background transparent in NSScrollView? - swift

Question

I've used Storyboard to set up the NSScrollView and I cannot find any option where I can disable the scroller's background. Any ideas on how to make this happen?

Answer 1

Basically idea behind this is subclass the NSScroller and then make changes accordingly.
I had the same requirement so I subclassed it and did the changes as shown.
objective c code is converted with help of online tool so apologies for mistakes
and have look.
this may help.
// Converted to Swift 4 by Swiftify v4.1.6766 - https://objectivec2swift.com/
// GridScroller.h
// Created by Vikram on 08/09/16.
import Cocoa
class OpaqGridScroller: NSScroller {
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
NSColor.clear.setFill()
dirtyRect.fill()
// whatever style you want here for knob if you want
knobStyle = .dark
}
}

Answer 2

You can try override draw scroller rect
override func draw(_ dirtyRect: NSRect) {
NSDrawWindowBackground(bounds);
self.drawKnob()
}
You always can draw custom rect color by setting it before
override func draw(_ dirtyRect: NSRect) {
NSColor.clear.set()
__NSRectFill(dirtyRect)
self.drawKnob()
}

Answer 3

This solution worked for me.
class OpaqueGridScroller: NSScroller {
override func draw(_ dirtyRect: NSRect) {
// NSColor.clear.set()
// dirtyRect.fill()
self.drawKnob()
}
}

Answer 4

The foregoing answers that call self.drawKnob() are only partially correct. The problem is that the knob should usually not be drawn at all if there's nothing to scroll in that direction.
For my solution, I sub-classed the vertical NSScroller (scroll bar) in a scrolling NSTextView, in order to override the scroll bar's draw() method, as above. But when there was nothing to scroll, this draws a knob that has a length that's not correct.
So I added
#IBOutlet var myScroller : NSScrollView!
as a property of the sub-classed NSScroller and wired it up in the storyboard, so that the scroller bar can know the NSScrollView that uses it, and then draw the scroll bar with
override draw(_ dirtyRect: NSRect)
{
if myScroller.contentSize.height < myScroller.documentView!.bounds.height {
self.drawKnob()
}
}
The knob disappears when the NSScrollView is resized enough that there's nothing vertical to scroll, and re-appears when there is, while at the same time allowing whatever's in the background below it to show through.
I'm not sure if this is a hack, or the correct solution, but it seems to work as expected.