UIScrollView category usable for scrollbar dragging detection.

UIScrollView+ScrollbarDraggingDetect.m

@interface UIScrollView ()
- (BOOL)_isScrubbing;
@end

@implementation UIScrollView (ScrollbarDraggingDetect)

/// A bit complicated and sophisticated subview introspection to detect whether
/// the vertical scroll indicator is “expanded for direct manipulation” (= being
/// dragged) using private accessors reads and some clang diagnostics pushing.

- (BOOL)isScrollingByDraggingVerticalIndicator
{
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
#pragma clang diagnostic ignored "-Wdeprecated-objc-pointer-introspection"
	if (isIOS13) {
		SEL sel = NSSelectorFromString([@[@"_", @"verticalScroll", @"Indicator"] componentsJoinedByString:@""]);
		UIView *indy = nil;
		if ([self respondsToSelector:sel])
			indy = [self performSelector:sel];
		NSUInteger expanded = 0;
		sel = NSSelectorFromString([@[ @"expandedFor", @"Direct", @"Manipulation" ] componentsJoinedByString:@""]);
		if ([indy respondsToSelector:sel])
			expanded = (NSUInteger)[indy performSelector:sel] & 0x1;
		return expanded > 0;
	}
#pragma clang diagnostic pop

	return NO;
}

/// This method states scroll bar dragging (scrubbing) in general. It's a private method though.

- (BOOL)isScrubbing
{
	if ([self respondsToSelector:@selector(_isScrubbing)])
		return [self _isScrubbing];

	return NO;
}

@end