Prevent audio from other apps pausing when showing gifv attachments

Fixes #101

Tusker.xcodeproj/project.pbxproj

@@ -234,6 +234,8 @@
 		D6C7D27D22B6EBF800071952 /* AttachmentsContainerView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C7D27C22B6EBF800071952 /* AttachmentsContainerView.swift */; };
 		D6C94D872139E62700CB5196 /* LargeImageViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C94D862139E62700CB5196 /* LargeImageViewController.swift */; };
 		D6C94D892139E6EC00CB5196 /* AttachmentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C94D882139E6EC00CB5196 /* AttachmentView.swift */; };
+		D6CA6A92249FAD8900AD45C1 /* AudioSessionHelper.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6CA6A91249FAD8900AD45C1 /* AudioSessionHelper.swift */; };
+		D6CA6A94249FADE700AD45C1 /* GalleryPlayerViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6CA6A93249FADE700AD45C1 /* GalleryPlayerViewController.swift */; };
 		D6D4DDD0212518A000E1C4BB /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D4DDCF212518A000E1C4BB /* AppDelegate.swift */; };
 		D6D4DDD7212518A200E1C4BB /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = D6D4DDD6212518A200E1C4BB /* Assets.xcassets */; };
 		D6D4DDDA212518A200E1C4BB /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = D6D4DDD8212518A200E1C4BB /* LaunchScreen.storyboard */; };
@@ -536,6 +538,8 @@
 		D6C7D27C22B6EBF800071952 /* AttachmentsContainerView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AttachmentsContainerView.swift; sourceTree = "<group>"; };
 		D6C94D862139E62700CB5196 /* LargeImageViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LargeImageViewController.swift; sourceTree = "<group>"; };
 		D6C94D882139E6EC00CB5196 /* AttachmentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AttachmentView.swift; sourceTree = "<group>"; };
+		D6CA6A91249FAD8900AD45C1 /* AudioSessionHelper.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AudioSessionHelper.swift; sourceTree = "<group>"; };
+		D6CA6A93249FADE700AD45C1 /* GalleryPlayerViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GalleryPlayerViewController.swift; sourceTree = "<group>"; };
 		D6D4DDCC212518A000E1C4BB /* Tusker.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Tusker.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		D6D4DDCF212518A000E1C4BB /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		D6D4DDD6212518A200E1C4BB /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
@@ -618,6 +622,7 @@
 				04D14BAE22B34A2800642648 /* GalleryViewController.swift */,
 				D647D92724257BEB0005044F /* AttachmentPreviewViewController.swift */,
 				D6531DEF246B867E000F9538 /* GifvAttachmentViewController.swift */,
+				D6CA6A93249FADE700AD45C1 /* GalleryPlayerViewController.swift */,
 			);
 			path = "Attachment Gallery";
 			sourceTree = "<group>";
@@ -1289,6 +1294,7 @@
 				D6DFC69F242C4CCC00ACC392 /* WeakArray.swift */,
 				D64D8CA82463B494006B0BAA /* CachedDictionary.swift */,
 				D60E2F2B24423EAD005F8713 /* LazilyDecoding.swift */,
+				D6CA6A91249FAD8900AD45C1 /* AudioSessionHelper.swift */,
 				D6F1F84E2193B9BE00F5FE67 /* Caching */,
 				D6757A7A2157E00100721E32 /* XCallbackURL */,
 				D62D241E217AA46B005076CC /* Shortcuts */,
@@ -1725,11 +1731,13 @@
 				D60E2F2E244248BF005F8713 /* MastodonCachePersistentStore.swift in Sources */,
 				D620483623D38075008A63EF /* ContentTextView.swift in Sources */,
 				D6F2E965249E8BFD005846BB /* CrashReporterViewController.swift in Sources */,
+				D6CA6A94249FADE700AD45C1 /* GalleryPlayerViewController.swift in Sources */,
 				D6A3BC802321B7E600FD64D5 /* FollowNotificationGroupTableViewCell.swift in Sources */,
 				D627944D23A9A03D00D38C68 /* ListTimelineViewController.swift in Sources */,
 				D6945C3823AC739F005C403C /* InstanceTimelineViewController.swift in Sources */,
 				D60309B52419D4F100A465FF /* ComposeAttachmentsViewController.swift in Sources */,
 				D62D2422217AA7E1005076CC /* UserActivityManager.swift in Sources */,
+				D6CA6A92249FAD8900AD45C1 /* AudioSessionHelper.swift in Sources */,
 				D60D2B8223844C71001B87A3 /* BaseStatusTableViewCell.swift in Sources */,
 				D60E2F272442372B005F8713 /* StatusMO.swift in Sources */,
 				D60E2F2C24423EAD005F8713 /* LazilyDecoding.swift in Sources */,

Tusker/AppDelegate.swift

@@ -8,7 +8,6 @@
 
 import UIKit
 import CrashReporter
-import MessageUI
 
 @UIApplicationMain
 class AppDelegate: UIResponder, UIApplicationDelegate {
@@ -20,7 +19,14 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
         #if !DEBUG
         setupCrashReporter()
         #endif
+        
         AppShortcutItem.createItems(for: application)
+        
+        DispatchQueue.global(qos: .userInitiated).async {
+            AudioSessionHelper.disable()
+            AudioSessionHelper.setDefault()
+        }
+
         return true
     }
     

Tusker/AudioSessionHelper.swift

@@ -0,0 +1,28 @@
+//
+//  AudioSessionHelper.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 6/21/20.
+//  Copyright © 2020 Shadowfacts. All rights reserved.
+//
+
+import Foundation
+import AVFoundation
+
+struct AudioSessionHelper {
+    static func enable() {
+        try? AVAudioSession.sharedInstance().setActive(true, options: [])
+    }
+    
+    static func disable() {
+        try? AVAudioSession.sharedInstance().setActive(false, options: .notifyOthersOnDeactivation)
+    }
+
+    static func setDefault() {
+        try? AVAudioSession.sharedInstance().setCategory(.playback, options: .mixWithOthers)
+    }
+    
+    static func setVideoPlayback() {
+        try? AVAudioSession.sharedInstance().setCategory(.playback, options: [])
+    }
+}

Tusker/Screens/Attachment Gallery/GalleryPlayerViewController.swift

@@ -0,0 +1,36 @@
+//
+//  GalleryPlayerViewController.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 6/21/20.
+//  Copyright © 2020 Shadowfacts. All rights reserved.
+//
+
+import UIKit
+import AVKit
+
+class GalleryPlayerViewController: AVPlayerViewController {
+
+    override func viewDidAppear(_ animated: Bool) {
+        super.viewDidAppear(animated)
+        
+        // starting while audio is already playing from another app often takes nearly a second,
+        // so do it on a background thread as to not block the UI
+        DispatchQueue.global(qos: .userInitiated).async {
+            AudioSessionHelper.enable()
+            AudioSessionHelper.setVideoPlayback()
+        }
+    }
+
+    override func viewWillDisappear(_ animated: Bool) {
+        super.viewWillDisappear(animated)
+        
+        // starting often takes around half a second,
+        // so do it on a background thread as to not block the UI
+        DispatchQueue.global(qos: .userInitiated).async {
+            AudioSessionHelper.setDefault()
+            AudioSessionHelper.disable()
+        }
+    }
+
+}

Tusker/Screens/Attachment Gallery/GalleryViewController.swift

@@ -72,7 +72,7 @@ class GalleryViewController: UIPageViewController, UIPageViewControllerDataSourc
                 vc.shrinkGestureEnabled = false
                 return vc
             case .video, .audio:
-                let vc = AVPlayerViewController()
+                let vc = GalleryPlayerViewController()
                 vc.player = AVPlayer(url: attachment.url)
                 return vc
             case .gifv:

Tusker/Views/Attachments/GifvAttachmentView.swift

@@ -30,6 +30,7 @@ class GifvAttachmentView: UIView {
         
         playerLayer.player = player
         playerLayer.videoGravity = gravity
+        player.isMuted = true
         player.play()
 
         NotificationCenter.default.addObserver(self, selector: #selector(restartItem), name: .AVPlayerItemDidPlayToEndTime, object: item)