[RTL UI] update widgets and apps for UI mirroring

Small tweaks all around to handle UI mirroring:
- swap existing symbols like arrows, or use alternative ones
- rotate some images, like chevrons and dogear icons
- flip some left and right swipe handling
- flip some geometry arithmetic like tap on left or right
  side of page or dict window
- use new ProgressWidget:getPercentageFromPosition() instead
  of geometry arithmetic
- BD.wrap() some concatenated string bits, like in reader
  and menu footers
- flip inverse_reading_order when UI is mirrored

More specific tweaks:
- ReaderGesture: reset some specific gestures when UI direction
  has changed (tap on top/bottom left/right corners, for
  bookmarks and FileManager "Plus menu").
- ReaderRolling: show markers on the correct side of page,
  in single or dual page mode.
- KoptOptions: swap left and right icons in Alignment toggle
- CheckMark: proper rendering in all 4 mirroring/rtl combinations.
- VirtualKeyboard: forbid any mirroring
- Move util.getMenuText into Menu.lua

frontend/apps/reader/modules/readertoc.lua

@@ -1,3 +1,4 @@
+local BD = require("ui/bidi")
 local Button = require("ui/widget/button")
 local CenterContainer = require("ui/widget/container/centercontainer")
 local ConfirmBox = require("ui/widget/confirmbox")
@@ -285,6 +286,7 @@ function ReaderToc:onShowToc()
     -- update collapsible state
     self.expand_button = Button:new{
         icon = "resources/icons/appbar.control.expand.png",
+        icon_rotation_angle = BD.mirroredUILayout() and 180 or 0,
         width = Screen:scaleBySize(30),
         bordersize = 0,
         show_parent = self,
@@ -338,7 +340,7 @@ function ReaderToc:onShowToc()
                     w = Screen:getWidth(),
                     h = Screen:getHeight(),
                 },
-                direction = "west"
+                direction = BD.flipDirectionIfMirroredUILayout("west")
             }
         }
     }
@@ -352,7 +354,15 @@ function ReaderToc:onShowToc()
     function toc_menu:onMenuSelect(item, pos)
         -- if toc item has expand/collapse state and tap select on the left side
         -- the state switch action is triggered, otherwise goto the linked page
-        if item.state and pos and pos.x < 0.3 then
+        local do_toggle_state = false
+        if item.state and pos and pos.x then
+            if BD.mirroredUILayout() then
+                do_toggle_state = pos.x > 0.7
+            else
+                do_toggle_state = pos.x < 0.3
+            end
+        end
+        if do_toggle_state then
             item.state.callback()
         else
             toc_menu:close_callback()