[UX] Add inverse reading order to gesture manager (#5423)

Also fixes #5354.

frontend/apps/reader/modules/readergesture.lua

@@ -80,6 +80,7 @@ local action_strings = {
     toggle_bookmark = _("Toggle bookmark"),
     toggle_page_flipping = _("Toggle page flipping"),
     toggle_reflow = _("Toggle reflow"),
+    toggle_inverse_reading_order = _("Toggle page turn direction"),
 
     zoom_contentwidth = _("Zoom to fit content width"),
     zoom_contentheight = _("Zoom to fit content height"),
@@ -723,6 +724,7 @@ function ReaderGesture:buildMenu(ges, default)
         {"toggle_bookmark", not self.is_docless, true},
         {"toggle_page_flipping", not self.is_docless, true},
         {"toggle_reflow", not self.is_docless, true},
+        {"toggle_inverse_reading_order", not self.is_docless, true},
         {"zoom_contentwidth", not self.is_docless},
         {"zoom_contentheight", not self.is_docless},
         {"zoom_pagewidth", not self.is_docless},
@@ -1357,6 +1359,8 @@ function ReaderGesture:gestureAction(action, ges)
         end
     elseif action == "toggle_bookmark" then
         self.ui:handleEvent(Event:new("ToggleBookmark"))
+    elseif action == "toggle_inverse_reading_order" then
+        self:onToggleReadingOrder()
     elseif action == "toggle_frontlight" then
         -- when using frontlight system settings
         if lightFrontlight() then
@@ -1564,4 +1568,20 @@ function ReaderGesture:onGSensorToggle()
     return true
 end
 
+function ReaderGesture:onToggleReadingOrder()
+    local document_module = self.ui.document.info.has_pages and self.ui.paging or self.ui.rolling
+    document_module.inverse_reading_order = not document_module.inverse_reading_order
+    document_module:setupTouchZones()
+    -- Needed to reset the touch zone overrides
+    local gesture_manager = G_reader_settings:readSetting(self.ges_mode)
+    for gesture, action in pairs(gesture_manager) do
+        self:setupGesture(gesture, action)
+    end
+    UIManager:show(Notification:new{
+        text = document_module.inverse_reading_order and _("RTL page turning.") or _("LTR page turning."),
+        timeout = 2.5,
+    })
+    return true
+end
+
 return ReaderGesture