Add an option to display single image on the first reader page. Close #244

lib/foundation/appdata.dart

@@ -185,6 +185,7 @@ class Settings with ChangeNotifier {
     'initialPage': '0',
     'comicListDisplayMode': 'paging', // paging, continuous
     'showPageNumberInReader': true,
+    'showSingleImageOnFirstPage': false,
   };
 
   operator [](String key) {

lib/pages/reader/images.dart

@@ -118,7 +118,14 @@ class _GalleryModeState extends State<_GalleryMode>
 
   /// [totalPages] is the total number of pages in the current chapter.
   /// More than one images can be displayed on one page.
-  int get totalPages => (reader.images!.length / reader.imagesPerPage).ceil();
+  int get totalPages {
+    if (!showSingleImageOnFirstPage) {
+      return (reader.images!.length / reader.imagesPerPage).ceil();
+    } else {
+      return 1 +
+          ((reader.images!.length - 1) / reader.imagesPerPage).ceil();
+    }
+  }
 
   var imageStates = <State<ComicImage>>{};
 
@@ -137,6 +144,27 @@ class _GalleryModeState extends State<_GalleryMode>
     super.initState();
   }
 
+  bool get showSingleImageOnFirstPage => appdata.settings["showSingleImageOnFirstPage"];
+
+  /// Get the range of images for the given page. [page] is 1-based.
+  (int start, int end) getPageImagesRange(int page) {
+    if (showSingleImageOnFirstPage) {
+      if (page == 1) {
+        return (0, 1);
+      } else {
+        int startIndex = (page - 2) * reader.imagesPerPage + 1;
+        int endIndex = math.min(
+            startIndex + reader.imagesPerPage, reader.images!.length);
+        return (startIndex, endIndex);
+      }
+    } else {
+      int startIndex = (page - 1) * reader.imagesPerPage;
+      int endIndex = math.min(
+          startIndex + reader.imagesPerPage, reader.images!.length);
+      return (startIndex, endIndex);
+    }
+  }
+
   /// [cache] is used to cache the images.
   /// The count of images to cache is determined by the [preCacheCount] setting.
   /// For previous page and next page, it will do a memory cache.
@@ -151,9 +179,7 @@ class _GalleryModeState extends State<_GalleryMode>
   }
 
   void _cachePage(int page, bool shouldPreCache) {
-    int startIndex = (page - 1) * reader.imagesPerPage;
-    int endIndex =
-    math.min(startIndex + reader.imagesPerPage, reader.images!.length);
+    var (startIndex, endIndex) = getPageImagesRange(page);
     for (int i = startIndex; i < endIndex; i++) {
       if (shouldPreCache) {
         _precacheImage(i+1, context);
@@ -201,10 +227,7 @@ class _GalleryModeState extends State<_GalleryMode>
               child: const SizedBox(),
             );
           } else {
-            int pageIndex = index - 1;
-            int startIndex = pageIndex * reader.imagesPerPage;
-            int endIndex = math.min(
-                startIndex + reader.imagesPerPage, reader.images!.length);
+            var (startIndex, endIndex) = getPageImagesRange(index);
             List<String> pageImages =
                 reader.images!.sublist(startIndex, endIndex);
 
@@ -1081,6 +1104,9 @@ void _preDownloadImage(int page, BuildContext context) {
   }
   var reader = context.reader;
   var imageKey = reader.images![page - 1];
+  if (imageKey.startsWith("file://")) {
+    return;
+  }
   var cid = reader.cid;
   var eid = reader.eid;
   var sourceKey = reader.type.comicSource?.key;

lib/pages/settings/reader.dart

@@ -66,6 +66,7 @@ class _ReaderSettingsState extends State<ReaderSettings> {
           min: 1,
           max: 20,
           onChanged: () {
+            setState(() {});
             widget.onChanged?.call("autoPageTurningInterval");
           },
         ).toSliver(),
@@ -80,6 +81,7 @@ class _ReaderSettingsState extends State<ReaderSettings> {
             min: 1,
             max: 5,
             onChanged: () {
+              setState(() {});
               widget.onChanged?.call("readerScreenPicNumberForLandscape");
             },
           ),
@@ -99,6 +101,18 @@ class _ReaderSettingsState extends State<ReaderSettings> {
             },
           ),
         ),
+        SliverAnimatedVisibility(
+          visible: appdata.settings['readerMode']!.startsWith('gallery') &&
+              (appdata.settings['readerScreenPicNumberForLandscape'] > 1 ||
+                  appdata.settings['readerScreenPicNumberForPortrait'] > 1),
+          child: _SwitchSetting(
+            title: "Show single image on first page".tl,
+            settingKey: "showSingleImageOnFirstPage",
+            onChanged: () {
+              widget.onChanged?.call("showSingleImageOnFirstPage");
+            },
+          ),
+        ),
         _SwitchSetting(
           title: 'Long press to zoom'.tl,
           settingKey: 'enableLongPressToZoom',