@@ -28,34 +28,121 @@ open class AutoScrollView: UIScrollView {
2828 }
2929 didSet {
3030 if let contentView = contentView {
31+ contentView. translatesAutoresizingMaskIntoConstraints = false
3132 addSubview ( contentView)
3233 updateContentViewConstraints ( )
3334 }
3435 }
3536 }
3637 fileprivate var contentViewConstraints : [ NSLayoutConstraint ] ?
3738
39+ /// This layout guide follows the `contentView` and honors the `horizontallyCompactContentWidth`
40+ /// and `horizontallyRegularContentWidth` values.
41+ public var contentViewLayoutGuide = UILayoutGuide ( )
42+ private var contentViewLayoutGuideConstraints : [ NSLayoutConstraint ] = [ ]
43+
44+ /// This setting determines how the content should be laid out in a horizontally compact environment.
45+ public var horizontallyCompactContentWidth : ContentWidth = . matchScrollViewWidth {
46+ didSet {
47+ guard horizontallyCompactContentWidth != oldValue else { return }
48+
49+ switch traitCollection. horizontalSizeClass {
50+ case . compact: updateContentViewConstraints ( )
51+ case . regular, . unspecified: break // no-op
52+ @unknown default : break
53+ }
54+ }
55+ }
56+
57+ /// This setting determines how the content should be laid out in a horizontally regular environment.
58+ public var horizontallyRegularContentWidth : ContentWidth = . matchScrollViewWidth {
59+ didSet {
60+ guard horizontallyRegularContentWidth != oldValue else { return }
61+
62+ switch traitCollection. horizontalSizeClass {
63+ case . regular: updateContentViewConstraints ( )
64+ case . compact, . unspecified: break // no-op
65+ @unknown default : break
66+ }
67+ }
68+ }
69+
3870 override open var contentInset : UIEdgeInsets {
3971 didSet {
4072 updateContentViewConstraints ( )
4173 }
4274 }
4375
4476 fileprivate func updateContentViewConstraints( ) {
77+ let contentViewFollowsReadableWidth : Bool
78+ switch traitCollection. horizontalSizeClass {
79+ case . compact:
80+ switch horizontallyCompactContentWidth {
81+ case . matchScrollViewWidth:
82+ contentViewFollowsReadableWidth = false
83+ case . matchReadableContentGuideWidth:
84+ contentViewFollowsReadableWidth = true
85+ }
86+
87+ case . regular:
88+ switch horizontallyRegularContentWidth {
89+ case . matchScrollViewWidth:
90+ contentViewFollowsReadableWidth = false
91+ case . matchReadableContentGuideWidth:
92+ contentViewFollowsReadableWidth = true
93+ }
94+
95+ case . unspecified:
96+ return // abort early
97+
98+ @unknown default :
99+ contentViewFollowsReadableWidth = false
100+ }
101+
45102 if let constraints = contentViewConstraints {
46103 NSLayoutConstraint . deactivate ( constraints)
47104 }
48- if let contentView = contentView {
49- contentViewConstraints = contentView. activateSuperviewHuggingConstraints ( insets: contentInset)
105+ NSLayoutConstraint . deactivate ( contentViewLayoutGuideConstraints)
106+
107+ let newLayoutGuide : UILayoutGuide
108+ if contentViewFollowsReadableWidth, let contentView = contentView {
109+ let newConstraints = [
110+ contentView. leadingAnchor. constraint (
111+ equalTo: readableContentGuide. leadingAnchor,
112+ constant: contentInset. left
113+ ) ,
114+ contentView. trailingAnchor. constraint (
115+ equalTo: readableContentGuide. trailingAnchor,
116+ constant: - contentInset. right
117+ ) ,
118+ contentView. topAnchor. constraint ( equalTo: topAnchor, constant: contentInset. top) ,
119+ contentView. bottomAnchor. constraint ( equalTo: bottomAnchor, constant: - contentInset. bottom) ,
120+ ]
121+ NSLayoutConstraint . activate ( newConstraints)
122+ contentViewConstraints = newConstraints
123+
124+ newLayoutGuide = readableContentGuide
50125 } else {
51- contentViewConstraints = nil
126+ contentViewConstraints = contentView? . activateSuperviewHuggingConstraints ( insets: contentInset)
127+
128+ newLayoutGuide = frameLayoutGuide
52129 }
130+
131+ contentViewLayoutGuideConstraints = [
132+ contentViewLayoutGuide. leadingAnchor. constraint ( equalTo: newLayoutGuide. leadingAnchor) ,
133+ contentViewLayoutGuide. topAnchor. constraint ( equalTo: newLayoutGuide. topAnchor) ,
134+ contentViewLayoutGuide. trailingAnchor. constraint ( equalTo: newLayoutGuide. trailingAnchor) ,
135+ contentViewLayoutGuide. bottomAnchor. constraint ( equalTo: newLayoutGuide. bottomAnchor) ,
136+ ]
137+ NSLayoutConstraint . activate ( contentViewLayoutGuideConstraints)
53138 }
54139
55140 fileprivate func commonInit( ) {
56141 let nc = NotificationCenter . default
57142 nc. addObserver ( self , selector: #selector( AutoScrollView . keyboardWillShow ( _: ) ) , name: UIResponder . keyboardWillShowNotification, object: nil )
58143 nc. addObserver ( self , selector: #selector( AutoScrollView . keyboardWillHide ( _: ) ) , name: UIResponder . keyboardWillHideNotification, object: nil )
144+
145+ addLayoutGuide ( contentViewLayoutGuide)
59146 }
60147
61148 public override init ( frame: CGRect ) {
@@ -77,6 +164,14 @@ open class AutoScrollView: UIScrollView {
77164 return true
78165 }
79166
167+ open override func traitCollectionDidChange( _ previousTraitCollection: UITraitCollection ? ) {
168+ guard traitCollection. horizontalSizeClass != previousTraitCollection? . horizontalSizeClass else {
169+ return
170+ }
171+
172+ updateContentViewConstraints ( )
173+ }
174+
80175 // MARK: Notifications
81176
82177 // Implementation based on code from Apple documentation
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