TouchMenu: show checkboxes in grey for disabled menu items

frontend/ui/widget/checkmark.lua

@@ -14,6 +14,7 @@ Example:
 
 ]]
 
+local Blitbuffer = require("ffi/blitbuffer")
 local Font = require("ui/font")
 local InputContainer = require("ui/widget/container/inputcontainer")
 local OverlapGroup = require("ui/widget/overlapgroup")
@@ -22,6 +23,7 @@ local TextWidget = require("ui/widget/textwidget")
 local CheckMark = InputContainer:new{
     checkable = true,
     checked = false,
+    enabled = true,
     face = Font:getFace("smallinfofont"),
     width = 0,
     height = 0,
@@ -36,16 +38,37 @@ function CheckMark:init()
         text = "▢ ",
         face = self.face,
     }
+    local disabled_checked_widget = TextWidget:new{
+        text = " ✓", -- preceded by thin space for better alignment
+        face = self.face,
+        fgcolor = Blitbuffer.COLOR_GREY,
+    }
+    local disabled_unchecked_widget = TextWidget:new{
+        text = "▢ ",
+        face = self.face,
+        fgcolor = Blitbuffer.COLOR_GREY,
+    }
     local empty_widget = TextWidget:new{
         text = "",
         face = self.face,
     }
-    self[1] = self.checkable and OverlapGroup:new{
-        (self.checked and checked_widget or empty_widget),
-        unchecked_widget
-    }
-    or empty_widget
-
+    local widget
+    if self.checkable then
+        if self.enabled then
+            widget = OverlapGroup:new{
+                (self.checked and checked_widget or empty_widget),
+                unchecked_widget
+            }
+        else
+            widget = OverlapGroup:new{
+                (self.checked and disabled_checked_widget or empty_widget),
+                disabled_unchecked_widget
+            }
+        end
+    else
+        widget = empty_widget
+    end
+    self[1] = widget
     self.dimen = unchecked_widget:getSize()
 end
 

frontend/ui/widget/touchmenu.lua

@@ -73,14 +73,14 @@ function TouchMenuItem:init()
         item_checkable = true
         item_checked = self.item.checked_func()
     end
-    local checked_widget = CheckMark:new{
-        checked = true,
-    }
-    local unchecked_widget = CheckMark:new{
-        checked = false,
+    local checkmark_widget = CheckMark:new{
+        checkable = item_checkable,
+        checked = item_checked,
+        enabled = item_enabled,
     }
-    local empty_widget = CheckMark:new{
-        checkable = false,
+
+    local checked_widget = CheckMark:new{ -- for layout, to :getSize()
+        checked = true,
     }
 
     -- text_max_width should be the TouchMenuItem width minus the below
@@ -98,11 +98,7 @@ function TouchMenuItem:init()
             align = "center",
             CenterContainer:new{
                 dimen = Geom:new{ w = checked_widget:getSize().w },
-                item_checkable and (
-                    item_checked and checked_widget
-                    or unchecked_widget
-                )
-                or empty_widget
+                checkmark_widget,
             },
             TextWidget:new{
                 text = text,