From 77a99f30afcc89715ef5510d78e20c3a12b56e18 Mon Sep 17 00:00:00 2001
From: Ming Ming <nkming2@gmail.com>
Date: Thu, 9 Dec 2021 04:18:48 +0800
Subject: [PATCH] Swipe down to dismiss viewer

---
 lib/widget/viewer.dart | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/lib/widget/viewer.dart b/lib/widget/viewer.dart
index 23f16766..00d7df10 100644
--- a/lib/widget/viewer.dart
+++ b/lib/widget/viewer.dart
@@ -326,7 +326,12 @@ class _ViewerState extends State<Viewer>
     if (!_canOpenDetailPane()) {
       return false;
     }
+    if (notification is ScrollStartNotification) {
+      _scrollStartPosition =
+          _pageStates[index]?.scrollController.position.pixels;
+    }
     if (notification is ScrollEndNotification) {
+      _scrollStartPosition = null;
       final scrollPos = _pageStates[index]!.scrollController.position;
       if (scrollPos.pixels == 0) {
         setState(() {
@@ -360,6 +365,19 @@ class _ViewerState extends State<Viewer>
         });
       }
     }
+
+    if (notification is OverscrollNotification) {
+      if (_scrollStartPosition == 0) {
+        // start at top
+        _overscrollSum += notification.overscroll;
+        if (_overscrollSum < -176) {
+          // and scroll downwards
+          Navigator.of(context).pop();
+        }
+      }
+    } else {
+      _overscrollSum = 0;
+    }
     return false;
   }
 
@@ -578,6 +596,9 @@ class _ViewerState extends State<Viewer>
   bool _isViewerLoaded = false;
   final _pageStates = <int, _PageState>{};
 
+  double? _scrollStartPosition;
+  var _overscrollSum = 0.0;
+
   static final _log = Logger("widget.viewer._ViewerState");
 
   static const _viewportFraction = 1.05;