UILabel has internal padding from programmatic constraints

Question

So, I don't know why this is happening, but here is a pic depicting it.

If you look at the UILabel with green background, there is padding above and below it, but I don't know why that is.

This is how I create it:

var bodyLabel: ActiveLabel = {
    let label = ActiveLabel()
    label.translatesAutoresizingMaskIntoConstraints = false
    label.isUserInteractionEnabled = false
    label.backgroundColor = .green
    label.numberOfLines = 0
    label.textColor = .darkGray
    label.font = UIFont.systemFont(ofSize: MessageTableViewCell.defaultFontSize())

    label.enabledTypes = [.mention]
    label.mentionColor = .gray //Figure this out

    return label
}()

The fact that it is an ActiveLabel is not the reason why this is happening.

Here are all the constraints it is involved in:

self.contentView.addSubview(self.thumbnailView)
self.contentView.addSubview(self.titleLabel)
self.contentView.addSubview(self.bodyLabel)
self.contentView.addSubview(self.likeView)

let views = ["thumbnailView" : self.thumbnailView,
                 "titleLabel" : self.titleLabel,
                 "bodyLabel" : self.bodyLabel,
                 "likeView"  : self.likeView] as [String : Any]

let metrics = ["tumbSize" : Constants.kMessageTableViewCellAvatarHeight,
                   "padding" : 15,
                   "right" : 10,
                   "left" : 5]

self.contentView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-left-[thumbnailView(tumbSize)]-right-[titleLabel(>=0)]-right-|", options: [], metrics: metrics, views: views))
self.contentView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-left-[thumbnailView(tumbSize)]-right-[bodyLabel(>=0)]-right-|", options: [], metrics: metrics, views: views))
self.contentView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-right-[thumbnailView(tumbSize)]-(>=0)-|", options: [], metrics: metrics, views: views))

if self.reuseIdentifier == Constants.MessageCellIdentifier {
    self.contentView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-right-[titleLabel(20)]-left-[bodyLabel(>=0@999)]-left-|", options: [], metrics: metrics, views: views))
} else {
    self.contentView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[titleLabel]|", options: [], metrics: metrics, views: views))
}

I noticed that when I remove the constraint in the if statement, that obviously the views get into awkward positions, but I do notice that it no longer has that green padding. I'm really not sure what is causing this padding.

This is what the code is based on.

Answer 1

Well, you're adding that padding by wrapping that body label with the left value.

So instead of: V:|-right-[titleLabel(20)]-left-[bodyLabel(>=0@999)]-left-|

Do something like: V:|-right-[titleLabel(20)][bodyLabel(>=0@999)]|

That will remove both top and bottom padding. I hope that helps!