Feature - zooming callbacks

ImageSlideshow/Classes/Core/ImageSlideshow.swift

@@ -153,6 +153,15 @@ open class ImageSlideshow: UIView {
 
     /// Image Slideshow Items loaded to slideshow
     open fileprivate(set) var slideshowItems = [ImageSlideshowItem]()
+
+    /// Called on zoom of item.
+    open var onZoom: ((CGFloat) -> Void)?
+
+    /// Called on end of zoom.
+    open var onDidEndZooming: (() -> Void)?
+
+    /// Called on scroll of the scroll view
+    open var onDidScroll: ((_ contentOffset: CGPoint, _ contentSize: CGSize) -> Void)?
 
     // MARK: - Preferences
 
@@ -320,7 +329,7 @@ open class ImageSlideshow: UIView {
 
         var i = 0
         for image in scrollViewImages {
-            let item = ImageSlideshowItem(image: image, zoomEnabled: zoomEnabled, activityIndicator: activityIndicator?.create(), maximumScale: maximumScale)
+            let item = ImageSlideshowItem(image: image, zoomEnabled: zoomEnabled, activityIndicator: activityIndicator?.create(), maximumScale: maximumScale, onZoom: onZoom, onDidEndZooming: onDidEndZooming)
             item.imageView.contentMode = contentScaleMode
             slideshowItems.append(item)
             scrollView.addSubview(item)
@@ -590,9 +599,28 @@ extension ImageSlideshow: UIScrollViewDelegate {
         if scrollView.isDragging {
             pageIndicator?.page = currentPageForScrollViewPage(primaryVisiblePage)
         }
+
+        self.onDidScroll?(scrollView.contentOffset, scrollView.contentSizePlusInsets)
     }
 
     public func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
         isAnimating = false
     }
 }
+
+extension UIScrollView
+{
+    var contentSizePlusInsets: CGSize
+    {
+        CGSize(
+            width: contentSize.width + adjustedContentInset.left + adjustedContentInset.right,
+            height: contentSize.height + adjustedContentInset.bottom + contentInset.top) // NOTE: the adjusted top inset intentionally left out, as SwiftUI uses a negative contentOffset to display the nav bar (doesn't affect content size)
+    }
+
+    var maxContentOffset: CGPoint
+    {
+        CGPoint(
+            x: max(0, contentSizePlusInsets.width - bounds.width),
+            y: max(0, contentSizePlusInsets.height + safeAreaInsets.top - bounds.height))
+    }
+}

ImageSlideshow/Classes/Core/ImageSlideshowItem.swift

@@ -45,6 +45,12 @@ open class ImageSlideshowItem: UIScrollView, UIScrollViewDelegate {
 
     /// Wraps around ImageView so RTL transformation on it doesn't interfere with UIScrollView zooming
     private let imageViewWrapper = UIView()
+
+    /// Called when item is zoomed.
+    private let onZoom: ((CGFloat) -> Void)?
+
+    /// Called when item is zoom ends.
+    private let onDidEndZooming: (() -> Void)?
 
     // MARK: - Life cycle
 
@@ -53,11 +59,13 @@ open class ImageSlideshowItem: UIScrollView, UIScrollViewDelegate {
         - parameter image: Input Source to load the image
         - parameter zoomEnabled: holds if it should be possible to zoom-in the image
     */
-    init(image: InputSource, zoomEnabled: Bool, activityIndicator: ActivityIndicatorView? = nil, maximumScale: CGFloat = 2.0) {
+    init(image: InputSource, zoomEnabled: Bool, activityIndicator: ActivityIndicatorView? = nil, maximumScale: CGFloat = 2.0, onZoom: ((CGFloat) -> Void)? = nil, onDidEndZooming: (() -> Void)? = nil) {
         self.zoomEnabled = zoomEnabled
         self.image = image
         self.activityIndicator = activityIndicator
         self.maximumScale = maximumScale
+        self.onZoom = onZoom
+        self.onDidEndZooming = onDidEndZooming
 
         super.init(frame: CGRect.null)
 
@@ -175,8 +183,8 @@ open class ImageSlideshowItem: UIScrollView, UIScrollViewDelegate {
         return self.zoomScale != self.minimumZoomScale
     }
 
-    func zoomOut() {
-        self.setZoomScale(minimumZoomScale, animated: false)
+    public func zoomOut(_ animated: Bool = false) {
+        self.setZoomScale(minimumZoomScale, animated: animated)
     }
 
     func tapZoom() {
@@ -230,8 +238,13 @@ open class ImageSlideshowItem: UIScrollView, UIScrollViewDelegate {
     // MARK: UIScrollViewDelegate
 
     open func scrollViewDidZoom(_ scrollView: UIScrollView) {
+        self.onZoom?(scrollView.zoomScale)
         setPictoCenter()
     }
+
+    open func scrollViewDidEndZooming(_ scrollView: UIScrollView, with view: UIView?, atScale scale: CGFloat) {
+        self.onDidEndZooming?()
+    }
 
     open func viewForZooming(in scrollView: UIScrollView) -> UIView? {
         return zoomEnabled ? imageViewWrapper : nil

Package.swift

@@ -5,7 +5,7 @@ import PackageDescription
 let package = Package(
     name: "ImageSlideshow",
     platforms: [
-        .iOS(.v10),
+        .iOS(.v11),
     ],
     products: [
         .library(