menu: keyboard_layout: add ability for layout-specific settings

A layout might want to make some specific feature configurable, so
create an addToMainMenu-like system for allowing layouts to add their
own configuration sub-menu to the keyboard configuration menu.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

frontend/ui/elements/menu_keyboard_layout.lua

@@ -3,6 +3,7 @@ local FFIUtil = require("ffi/util")
 local Language = require("ui/language")
 local UIManager = require("ui/uimanager")
 local VirtualKeyboard = require("ui/widget/virtualkeyboard")
+local dbg = require("dbg")
 local util = require("util")
 local _ = require("gettext")
 
@@ -94,29 +95,33 @@ local sub_item_table = {
             input_dialog:onShowKeyboard()
         end,
     },
+    {
+        text = _("Layout-specific keyboard settings"),
+        sub_item_table = {},
+    }
 }
 
-for k, __ in FFIUtil.orderedPairs(VirtualKeyboard.lang_to_keyboard_layout) do
+for lang, keyboard_layout in FFIUtil.orderedPairs(VirtualKeyboard.lang_to_keyboard_layout) do
     table.insert(sub_item_table[1].sub_item_table, {
         text_func = function()
-            local text = Language:getLanguageName(k)
-            if G_reader_settings:readSetting("keyboard_layout_default") == k then
+            local text = Language:getLanguageName(lang)
+            if G_reader_settings:readSetting("keyboard_layout_default") == lang then
                 text = text .. "   ★"
             end
             return text
         end,
         checked_func = function()
             local keyboard_layouts = G_reader_settings:readSetting("keyboard_layouts") or {}
-            return util.arrayContains(keyboard_layouts, k)
+            return util.arrayContains(keyboard_layouts, lang)
         end,
         callback = function()
             local keyboard_layouts = G_reader_settings:readSetting("keyboard_layouts") or {}
-            local layout_index = util.arrayContains(keyboard_layouts, k)
+            local layout_index = util.arrayContains(keyboard_layouts, lang)
             if layout_index then
                 table.remove(keyboard_layouts, layout_index)
             else
                 if #keyboard_layouts < 4 then
-                    table.insert(keyboard_layouts, k)
+                    table.insert(keyboard_layouts, lang)
                 else -- no more space in the 'globe' popup
                     UIManager:show(require("ui/widget/infomessage"):new{
                         text = _("Up to four layouts can be enabled."),
@@ -128,10 +133,19 @@ for k, __ in FFIUtil.orderedPairs(VirtualKeyboard.lang_to_keyboard_layout) do
             G_reader_settings:saveSetting("keyboard_layouts", keyboard_layouts)
         end,
         hold_callback = function(touchmenu_instance)
-            G_reader_settings:saveSetting("keyboard_layout_default", k)
+            G_reader_settings:saveSetting("keyboard_layout_default", lang)
             if touchmenu_instance then touchmenu_instance:updateItems() end
         end,
     })
+    if VirtualKeyboard.lang_has_submenu[lang] then
+        local keyboard = require("ui/data/keyboardlayouts/" .. keyboard_layout)
+        if dbg.dassert(keyboard.genMenuItems ~= nil) then
+            table.insert(sub_item_table[4].sub_item_table, {
+                text = Language:getLanguageName(lang),
+                sub_item_table = keyboard:genMenuItems(),
+            })
+        end
+    end
 end
 
 return sub_item_table

frontend/ui/widget/virtualkeyboard.lua

@@ -761,6 +761,10 @@ local VirtualKeyboard = FocusManager:new{
         ru = "ru_keyboard",
         tr = "tr_keyboard",
     },
+
+    lang_has_submenu = {
+        ja = true,
+    },
 }
 
 function VirtualKeyboard:init()