Implement swipe up/down gestures tto move between sections

src/pyj/read_book/goto.pyj

@@ -25,6 +25,13 @@ def create_goto_list(onclick):
     return ans
 
 
+def get_next_section(forward):
+    toc = current_book().manifest.toc
+    id_map = get_toc_maps(toc)[1]
+    before, after = get_border_nodes(toc, id_map)
+    return after if forward else before
+
+
 def create_goto_panel(book, container, onclick):
     panel = create_goto_list(onclick)
     set_css(container, display='flex', flex_direction='column')

src/pyj/read_book/paged_mode.pyj

@@ -505,7 +505,7 @@ def onkeydown(evt):
 def handle_gesture(gesture):
     if gesture.type is 'swipe':
         if gesture.axis is 'vertical':
-            pass  # TODO: next/prev section
+            get_boss().send_message('next_section', forward=gesture.direction is 'up')
         else:
             if not gesture.active or gesture.is_held:
                 scroll_by_page(gesture.direction is 'right', True)

src/pyj/read_book/view.pyj

@@ -15,6 +15,7 @@
 from read_book.prefs.font_size import change_font_size_by
 from read_book.touch import set_left_margin_handler, set_right_margin_handler
 from read_book.toc import update_visible_toc_nodes
+from read_book.goto import get_next_section
 from book_list.theme import get_color
 from utils import parse_url_params, username_key
 
@@ -82,6 +83,7 @@ def __init__(self, container, ui):
             'ready': self.on_iframe_ready,
             'error': self.on_iframe_error,
             'next_spine_item': self.on_next_spine_item,
+            'next_section': self.on_next_section,
             'goto_doc_boundary': self.goto_doc_boundary,
             'scroll_to_anchor': self.on_scroll_to_anchor,
             'update_cfi': self.on_update_cfi,
@@ -310,6 +312,11 @@ def on_next_spine_item(self, data):
             idx = max(0, min(spine.length - 1, idx + 1))
             self.show_name(spine[idx], initial_position={'type':'frac', 'frac':0, 'replace_history':True})
 
+    def on_next_section(self, data):
+        toc_node = get_next_section(data.forward)
+        if toc_node:
+            self.goto_named_destination(toc_node.dest, toc_node.frag)
+
     def on_update_cfi(self, data):
         self.currently_showing.bookpos = data.cfi
         get_boss().push_state(replace=data.replace_history)