From 2ab4433c65ec006d7c63a2d825d54aa3ffa45c29 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eddy=20Leli=C3=A8vre-Berna?= <eddy@lelievre-berna.net>
Date: Tue, 18 Jul 2023 22:42:58 +0200
Subject: [PATCH] Fixes #544 second suggestion: scrollView management modified
 so that pinching with two fingers triggers a return to the album view when
 the image is zoomed out

---
 piwigo/Album/ImageAnimatedTransitioning.swift |  2 +-
 piwigo/Image/ImagePreviewViewController.swift | 28 +++++++++++++++++--
 piwigo/Image/ImageViewController.swift        |  4 +--
 3 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/piwigo/Album/ImageAnimatedTransitioning.swift b/piwigo/Album/ImageAnimatedTransitioning.swift
index 3790ee380..aa30c5f66 100644
--- a/piwigo/Album/ImageAnimatedTransitioning.swift
+++ b/piwigo/Album/ImageAnimatedTransitioning.swift
@@ -21,7 +21,7 @@ enum PresentationType {
 // See https://medium.com/@tungfam/custom-uiviewcontroller-transitions-in-swift-d1677e5aa0bf
 final class ImageAnimatedTransitioning: NSObject, UIViewControllerAnimatedTransitioning {
 
-    static let duration: TimeInterval = 0.5
+    static let duration: TimeInterval = 0.2
 
     private let type: PresentationType
     private let albumViewController: AlbumViewController
diff --git a/piwigo/Image/ImagePreviewViewController.swift b/piwigo/Image/ImagePreviewViewController.swift
index 412da4124..cfcefeaad 100644
--- a/piwigo/Image/ImagePreviewViewController.swift
+++ b/piwigo/Image/ImagePreviewViewController.swift
@@ -31,7 +31,7 @@ class ImagePreviewViewController: UIViewController
     private let placeHolder = UIImage(named: "placeholderImage")!
     private var userDidTapOnce: Bool = false        // True if the user did tap the view
     private var userDidRotateDevice: Bool = false   // True if the user did rotate the device
-
+    private var startingZoomScale = CGFloat(1)      // To remember the scale before starting zooming
 
     // MARK: - View Lifecycle
     override func viewDidLoad() {
@@ -169,6 +169,10 @@ class ImagePreviewViewController: UIViewController
         scrollView.bounds = view.bounds
         scrollView.contentSize = image.size
         
+        // Prevents scrolling image at minimum scale
+        // Will be unlocked when starting zooming
+        scrollView.isScrollEnabled = false
+        
         // Don't adjust the insets when showing or hiding the navigation bar/toolbar
         scrollView.contentInset = .zero
         scrollView.contentInsetAdjustmentBehavior = .never
@@ -340,14 +344,32 @@ extension ImagePreviewViewController: UIScrollViewDelegate
     func viewForZooming(in scrollView: UIScrollView) -> UIView? {
         return imageView
     }
+    
+    // Zooming of the content in the scroll view is about to commence
+    func scrollViewWillBeginZooming(_ scrollView: UIScrollView, with view: UIView?) {
+        // Allows scrolling zoomed image
+        scrollView.isScrollEnabled = true
+        // Store zoom scale value before starting zooming
+        startingZoomScale = scrollView.zoomScale
+    }
 
+    // The scroll view’s zoom factor changed
     func scrollViewDidZoom(_ scrollView: UIScrollView) {
-        centerImageView()
+        if scrollView.zoomScale < 0.9 * scrollView.minimumZoomScale,
+            startingZoomScale < 1.1 * scrollView.minimumZoomScale {
+            dismiss(animated: true)
+        } else {
+            centerImageView()
+        }
     }
 
+    // Zooming of the content in the scroll view completed
     func scrollViewDidEndZooming(_ scrollView: UIScrollView, with view: UIView?, atScale scale: CGFloat) {
         // Limit the zoom scale
-        if scale < scrollView.minimumZoomScale {
+        if scrollView.zoomScale < 0.9 * scrollView.minimumZoomScale,
+           startingZoomScale < 1.1 * scrollView.minimumZoomScale {
+            dismiss(animated: true)
+        } else if scale <= scrollView.minimumZoomScale {
             scrollView.zoomScale = scrollView.minimumZoomScale
             centerImageView()
         } else if scale > scrollView.maximumZoomScale {
diff --git a/piwigo/Image/ImageViewController.swift b/piwigo/Image/ImageViewController.swift
index db44388a7..a41de82e2 100644
--- a/piwigo/Image/ImageViewController.swift
+++ b/piwigo/Image/ImageViewController.swift
@@ -105,7 +105,7 @@ class ImageViewController: UIViewController {
         tapOnce.require(toFail: tapTwice)
 
         // Down swipes return to album view
-        let swipeDown = UISwipeGestureRecognizer(target: self, action: #selector(swipeDown(_:)))
+        let swipeDown = UISwipeGestureRecognizer(target: self, action: #selector(didSwipeDown(_:)))
         swipeDown.numberOfTouchesRequired = 1
         swipeDown.direction = .down
         tapOnce.require(toFail: swipeDown)
@@ -578,7 +578,7 @@ class ImageViewController: UIViewController {
         }
     }
 
-    @objc func swipeDown(_ gestureRecognizer: UIGestureRecognizer) {
+    @objc func didSwipeDown(_ gestureRecognizer: UIGestureRecognizer) {
         // Return to the album view
         returnToAlbum()
     }