Fix image dimming stuck after modal dismiss

tintColorDidChange could overwrite originalImage with an already
desaturated version on repeated calls while dimmed, so restoring
the "original" on undim produced a grey icon.

Split write/read paths: only cell providers save the original image,
tintColorDidChange only reads it. Keep originalImage alive across
dimmed/normal transitions until prepareForReuse.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ivanvorobei

Sources/DiffableKit/Table/Cells/DiffableButtonTableViewCell.swift

@@ -16,15 +16,15 @@ open class DiffableButtonTableViewCell: DiffableTableViewCell {
         super.init(coder: coder)
     }
 
-    override func updateImageDimming() {
+    override func updateImageDimming(saveOriginal: Bool = false) {
         guard var content = contentConfiguration as? UIListContentConfiguration else { return }
         let dimmed = tintAdjustmentMode == .dimmed
         let color: UIColor = dimmed ? .secondaryLabel : tintColor
         if content.textProperties.color != color {
             content.textProperties.color = color
             contentConfiguration = content
         }
-        super.updateImageDimming()
+        super.updateImageDimming(saveOriginal: saveOriginal)
     }
 
     open override func setHighlighted(_ highlighted: Bool, animated: Bool) {

Sources/DiffableKit/Table/Cells/DiffableTableViewCell.swift

@@ -30,18 +30,16 @@ open class DiffableTableViewCell: UITableViewCell {
         updateImageDimming()
     }
 
-    func updateImageDimming() {
+    func updateImageDimming(saveOriginal: Bool = false) {
         guard var content = contentConfiguration as? UIListContentConfiguration else { return }
+        if saveOriginal { originalImage = content.image }
         let dimmed = tintAdjustmentMode == .dimmed
         if dimmed {
-            let currentImage = content.image
-            if currentImage !== originalImage { originalImage = currentImage }
             guard let desaturated = originalImage?.desaturated() else { return }
             content.image = desaturated
         } else {
             guard let original = originalImage else { return }
             content.image = original
-            originalImage = nil
         }
         contentConfiguration = content
     }

Sources/DiffableKit/Table/DataSource/DiffableTableDataSource+CellProvider.swift

@@ -51,7 +51,7 @@ extension DiffableTableDataSource {
                 content.image = item.icon
                 applyImageLayout(&content)
                 cell.contentConfiguration = content
-                cell.updateImageDimming()
+                cell.updateImageDimming(saveOriginal: true)
                 cell.accessoryType = item.accessoryType
                 cell.selectionStyle = item.selectionStyle
                 return cell
@@ -68,7 +68,7 @@ extension DiffableTableDataSource {
                 content.image = item.icon
                 applyImageLayout(&content)
                 cell.contentConfiguration = content
-                cell.updateImageDimming()
+                cell.updateImageDimming(saveOriginal: true)
                 cell.accessoryType = item.accessoryType
                 cell.selectionStyle = item.selectionStyle
                 return cell
@@ -87,7 +87,7 @@ extension DiffableTableDataSource {
                 let descriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: .body)
                 content.textProperties.font = UIFont.systemFont(ofSize: descriptor.pointSize, weight: .medium)
                 cell.contentConfiguration = content
-                cell.updateImageDimming()
+                cell.updateImageDimming(saveOriginal: true)
                 cell.accessoryType = item.accessoryType
                 return cell
             }
@@ -102,7 +102,7 @@ extension DiffableTableDataSource {
                 content.image = item.icon
                 applyImageLayout(&content)
                 cell.contentConfiguration = content
-                cell.updateImageDimming()
+                cell.updateImageDimming(saveOriginal: true)
 
                 if let control = cell.accessoryView as? DiffableSwitch {
                     control.action = item.action
@@ -127,7 +127,7 @@ extension DiffableTableDataSource {
                 content.image = item.icon
                 applyImageLayout(&content)
                 cell.contentConfiguration = content
-                cell.updateImageDimming()
+                cell.updateImageDimming(saveOriginal: true)
 
                 if let control = cell.accessoryView as? DiffableStepper {
                     control.action = item.action