Swipe up to open detail pane in viewer

lib/widget/image_viewer.dart

@@ -50,7 +50,7 @@ class _ImageViewerState extends State<ImageViewer>
       minScale: 1.0,
       maxScale: 3.0,
       transformationController: _transformationController,
-      panEnabled: widget.canZoom,
+      panEnabled: widget.canZoom && _isZoomed,
       scaleEnabled: widget.canZoom,
       // allow the image to be zoomed to fill the whole screen
       child: Container(

lib/widget/viewer.dart

@@ -233,13 +233,12 @@ class _ViewerState extends State<Viewer>
         onNotification: (notif) => _onPageContentScrolled(notif, index),
         child: SingleChildScrollView(
           controller: _pageStates[index]!.scrollController,
-          physics:
+          physics: !_isZoomed ? null : const NeverScrollableScrollPhysics(),
-              _isDetailPaneActive ? null : const NeverScrollableScrollPhysics(),
           child: Stack(
             children: [
               _buildItemView(context, index),
               Visibility(
-                visible: _isDetailPaneActive,
+                visible: !_isZoomed,
                 child: AnimatedOpacity(
                   opacity: _isShowDetailPane ? 1 : 0,
                   duration: k.animationDurationNormal,
@@ -260,6 +259,11 @@ class _ViewerState extends State<Viewer>
                           const BorderRadius.vertical(top: Radius.circular(4)),
                     ),
                     margin: EdgeInsets.only(top: _calcDetailPaneOffset(index)),
+                    // this visibility widget avoids loading the detail pane
+                    // until it's actually opened, otherwise swiping between
+                    // photos will slow down severely
+                    child: Visibility(
+                      visible: _isShowDetailPane,
                       child: ViewerDetailPane(
                         account: widget.account,
                         file: widget.streamFiles[index],
@@ -269,6 +273,7 @@ class _ViewerState extends State<Viewer>
                     ),
                   ),
                 ),
+              ),
             ],
           ),
         ),
@@ -350,6 +355,14 @@ class _ViewerState extends State<Viewer>
           });
         }
       }
+    } else if (notification is ScrollUpdateNotification) {
+      if (!_isShowDetailPane) {
+        Future.delayed(Duration.zero, () {
+          setState(() {
+            _isShowDetailPane = true;
+          });
+        });
+      }
     }
     return false;
   }

lib/widget/viewer_detail_pane.dart

@@ -30,6 +30,7 @@ import 'package:nc_photos/theme.dart';
 import 'package:nc_photos/use_case/remove_from_album.dart';
 import 'package:nc_photos/use_case/update_album.dart';
 import 'package:nc_photos/use_case/update_property.dart';
+import 'package:nc_photos/widget/animated_visibility.dart';
 import 'package:nc_photos/widget/gps_map.dart';
 import 'package:nc_photos/widget/handler/add_selection_to_album_handler.dart';
 import 'package:nc_photos/widget/photo_date_time_edit_dialog.dart';
@@ -71,6 +72,15 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
         _initMetadata();
       }
     }
+
+    // postpone loading map to improve responsiveness
+    Future.delayed(const Duration(milliseconds: 750)).then((_) {
+      if (mounted) {
+        setState(() {
+          _shouldBlockGpsMap = false;
+        });
+      }
+    });
   }
 
   @override
@@ -239,7 +249,11 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
               subtitle: cameraSubStr.isNotEmpty ? Text(cameraSubStr) : null,
             ),
           if (features.isSupportMapView && _gps != null)
-            SizedBox(
+            AnimatedVisibility(
+              opacity: _shouldBlockGpsMap ? 0 : 1,
+              curve: Curves.easeInOut,
+              duration: k.animationDurationNormal,
+              child: SizedBox(
                 height: 256,
                 child: GpsMap(
                   center: _gps!,
@@ -247,6 +261,7 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
                   onTap: _onMapTap,
                 ),
               ),
+            ),
         ],
       ),
     );
@@ -489,6 +504,8 @@ class _ViewerDetailPaneState extends State<ViewerDetailPane> {
 
   late final bool _canRemoveFromAlbum = _checkCanRemoveFromAlbum();
 
+  var _shouldBlockGpsMap = true;
+
   static final _log =
       Logger("widget.viewer_detail_pane._ViewerDetailPaneState");
 }