[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/readerhighlight.lua

@@ -1,3 +1,4 @@
+local BD = require("ui/bidi")
 local ButtonDialog = require("ui/widget/buttondialog")
 local Device = require("device")
 local Event = require("ui/event")
@@ -350,9 +351,19 @@ function ReaderHighlight:onShowHighlightDialog(page, index)
     }
 
     if not self.ui.document.info.has_pages then
+        local start_prev = "◁⇱"
+        local start_next = "⇱▷"
+        local end_prev = "◁⇲"
+        local end_next = "⇲▷"
+        if BD.mirroredUILayout() then
+            -- Sadly, there's only north west & south east arrow to corner,
+            -- north east and south west do not exist in Unicode.
+            start_prev, start_next = BD.ltr(start_next), BD.ltr(start_prev)
+            end_prev, end_next = BD.ltr(end_next), BD.ltr(end_prev)
+        end
         table.insert(buttons, {
             {
-                text = "◁⇱",
+                text = start_prev,
                 callback = function()
                     self:updateHighlight(page, index, 0, -1, false)
                 end,
@@ -362,7 +373,7 @@ function ReaderHighlight:onShowHighlightDialog(page, index)
                 end
             },
             {
-                text = "⇱▷",
+                text = start_next,
                 callback = function()
                     self:updateHighlight(page, index, 0, 1, false)
                 end,
@@ -372,7 +383,7 @@ function ReaderHighlight:onShowHighlightDialog(page, index)
                 end
             },
             {
-                text = "◁⇲",
+                text = end_prev,
                 callback = function()
                     self:updateHighlight(page, index, 1, -1, false)
                 end,
@@ -381,7 +392,7 @@ function ReaderHighlight:onShowHighlightDialog(page, index)
                 end
             },
             {
-                text = "⇲▷",
+                text = end_next,
                 callback = function()
                     self:updateHighlight(page, index, 1, 1, false)
                 end,
@@ -577,6 +588,14 @@ function ReaderHighlight:onHoldPan(_, ges)
                                   and self.holdpan_pos.x < 1/8*Screen:getWidth()
         local is_in_bottom_right_corner = self.holdpan_pos.y > 7/8*Screen:getHeight()
                                       and self.holdpan_pos.x > 7/8*Screen:getWidth()
+        if BD.mirroredUILayout() then
+            -- Note: this might not be really usable, as crengine native selection
+            -- is not adapted to RTL text
+            is_in_top_left_corner = self.holdpan_pos.y < 1/8*Screen:getHeight()
+                                      and self.holdpan_pos.x > 7/8*Screen:getWidth()
+            is_in_bottom_right_corner = self.holdpan_pos.y > 7/8*Screen:getHeight()
+                                          and self.holdpan_pos.x < 1/8*Screen:getWidth()
+        end
         if is_in_top_left_corner or is_in_bottom_right_corner then
             if self.was_in_some_corner then
                 -- Do nothing, wait for the user to move his finger out of that corner