Fix skeletons interfering with attributed strings in text-based views (#520)

When enabling skeleton mode in a text-based view (`UILabel`,
`UITextView`, `UITextField`), it sets the `textColor` to `.clear`,
which is fine when `text` is used, but causes problems when
`attributedText` is used, as it effectively "resets" the string to have
a single color.

Additionally, when a `UILabel` is nested inside a `UIStackView` a
dummy string `" "` was set on the label's `text` so that it didn't have
a 0 height content size. However, this workaround didn't consider the
case where the label already had a non-empty text, meaning that this
(intrusive) `text = " "` broke existing code by clearing the label's
contents.

By improving the corresponding `RecoverableXState` structs, we are able
to preserve each element's contents and state as skeleton is disabled.

Fixes #518.

## Changes

- Create new `RecoverableLabelState` containing a `attributedText` and
`text`, and use it on `UILabel`.

- Update `RecoverableTextViewState` and `RecoverableTextFieldState` to
have a `attributedText`.

- Check if `UILabel`'s `text` is empty before setting dummy value when
enabling skeleton mode in a label nested inside a `UIStackView`.

Author: p4checo

SkeletonViewCore/Sources/Internal/Models/RecoverableViewState.swift

@@ -24,23 +24,38 @@ struct RecoverableViewState {
 
 }
 
-struct RecoverableTextViewState {
+struct RecoverableLabelState {
+    var attributedText: NSAttributedString? // we mess with `textColor`, which impacts attributed string if defined
+    var text: String? // we mess with `text` if the label is within a `UIStackView`
     var textColor: UIColor?
-    
+
     init(view: UILabel) {
+        if let attributedText = view.attributedText {
+            self.attributedText = attributedText
+        } else {
+            self.text = view.text
+        }
         self.textColor = view.textColor
     }
+}
+
+struct RecoverableTextViewState {
+    var attributedText: NSAttributedString? // we mess with `textColor`, which impacts attributed string if defined
+    var textColor: UIColor?
 
     init(view: UITextView) {
+        self.attributedText = view.attributedText
         self.textColor = view.textColor
     }
 }
 
 struct RecoverableTextFieldState {
+    var attributedText: NSAttributedString? // we mess with `textColor`, which impacts attributed string if defined
     var textColor: UIColor?
     var placeholder: String?
 
     init(view: UITextField) {
+        self.attributedText = view.attributedText
         self.textColor = view.textColor
         self.placeholder = view.placeholder
     }

SkeletonViewCore/Sources/Internal/SkeletonExtensions/Recoverable.swift

@@ -47,14 +47,14 @@ extension UIView: Recoverable {
 
 extension UILabel {
 
-    var labelState: RecoverableTextViewState? {
-        get { return ao_get(pkey: &ViewAssociatedKeys.labelViewState) as? RecoverableTextViewState }
+    var labelState: RecoverableLabelState? {
+        get { return ao_get(pkey: &ViewAssociatedKeys.labelViewState) as? RecoverableLabelState }
         set { ao_setOptional(newValue, pkey: &ViewAssociatedKeys.labelViewState) }
     }
 
     override func saveViewState() {
         super.saveViewState()
-        labelState = RecoverableTextViewState(view: self)
+        labelState = RecoverableLabelState(view: self)
     }
 
     override func recoverViewState(forced: Bool) {
@@ -70,6 +70,11 @@ extension UILabel {
 
             if self.textColor == .clear || forced {
                 self.textColor = storedLabelState.textColor
+                if let attributedText = storedLabelState.attributedText {
+                    self.attributedText = attributedText
+                } else {
+                    self.text = storedLabelState.text
+                }
             }
         }
     }
@@ -95,6 +100,9 @@ extension UITextView {
 
             if self?.textColor == .clear || forced {
                 self?.textColor = storedLabelState.textColor
+                if let attributedText = storedLabelState.attributedText {
+                    self?.attributedText = attributedText
+                }
             }
         }
     }
@@ -120,6 +128,9 @@ extension UITextField {
 
             if self?.textColor == .clear || forced {
                 self?.textColor = storedLabelState.textColor
+                if let attributedText = storedLabelState.attributedText {
+                    self?.attributedText = attributedText
+                }
             }
 
             if self?.placeholder == nil || forced {

SkeletonViewCore/Sources/Internal/UIKitExtensions/UILabel+Extensions.swift

@@ -27,7 +27,7 @@ extension UILabel {
         guard estimatedNumberOfLines > 1 || estimatedNumberOfLines == 0 else { return }
 
         // Workaround to simulate content when the label is contained in a `UIStackView`.
-        if isSuperviewAStackView, bounds.height == 0 {
+        if isSuperviewAStackView, bounds.height == 0, (text?.isEmpty ?? true) {
             // This is a placeholder text to simulate content because it's contained in a stack view in order to prevent that the content size will be zero.
             text = " "
         }