keygrabber: Do not try to guess the modifiers name

There is no an API to query the correct value

Fixes #2515

lib/awful/key.lua

@@ -9,15 +9,12 @@
 -- Grab environment we need
 local setmetatable = setmetatable
 local ipairs = ipairs
-local capi = { key = key, root = root }
+local capi = { key = key, root = root, awesome = awesome }
 local gmath = require("gears.math")
 local gtable = require("gears.table")
 
-
-
 local key = { mt = {}, hotkeys = {} }
 
-
 --- Modifiers to ignore.
 -- By default this is initialized as { "Lock", "Mod2" }
 -- so the Caps Lock or Num Lock modifier are not taking into account by awesome
@@ -27,23 +24,53 @@ local key = { mt = {}, hotkeys = {} }
 key.ignore_modifiers = { "Lock", "Mod2" }
 
 --- Convert the modifiers into pc105 key names
-local conversion = {
-    mod4    = "Super_L",
-    control = "Control_L",
-    shift   = "Shift_L",
-    mod1    = "Alt_L",
-}
+local conversion = nil
+
+local function generate_conversion_map()
+    if conversion then return conversion end
+
+    local mods = capi.awesome._modifiers
+    assert(mods)
+
+    conversion = {}
+
+    for mod, keysyms in pairs(mods) do
+        for _, keysym in ipairs(keysyms) do
+            assert(keysym.keysym)
+            conversion[mod] = conversion[mod] or keysym.keysym
+            conversion[keysym.keysym] = mod
+        end
+    end
+
+    return conversion
+end
+
+capi.awesome.connect_signal("xkb::map_changed"  , function() conversion = nil end)
 
 --- Execute a key combination.
 -- If an awesome keybinding is assigned to the combination, it should be
 -- executed.
+--
+-- To limit the chances of accidentally leaving a modifier key locked when
+-- calling this function from a keybinding, make sure is attached to the
+-- release event and not the press event.
+--
 -- @see root.fake_input
 -- @tparam table mod A modified table. Valid modifiers are: Any, Mod1,
 --   Mod2, Mod3, Mod4, Mod5, Shift, Lock and Control.
 -- @tparam string k The key
 function key.execute(mod, k)
+    local modmap = generate_conversion_map()
+    local active = capi.awesome._active_modifiers
+
+    -- Release all modifiers
+    for _, m in ipairs(active) do
+        assert(modmap[m])
+        root.fake_input("key_release", modmap[m])
+    end
+
     for _, v in ipairs(mod) do
-        local m = conversion[v:lower()]
+        local m = modmap[v]
         if m then
             root.fake_input("key_press", m)
         end
@@ -53,11 +80,18 @@ function key.execute(mod, k)
     root.fake_input("key_release", k)
 
     for _, v in ipairs(mod) do
-        local m = conversion[v:lower()]
+        local m = modmap[v]
         if m then
             root.fake_input("key_release", m)
         end
     end
+
+    -- Restore the previous modifiers all modifiers. Please note that yes,
+    -- there is a race condition if the user was fast enough to release the
+    -- key during this operation.
+    for _, m in ipairs(active) do
+        root.fake_input("key_press", modmap[m])
+    end
 end
 
 --- Create a new key to use as binding.

lib/awful/keygrabber.lua

@@ -72,7 +72,7 @@ local gtable = require("gears.table")
 local gobject = require("gears.object")
 local gtimer = require("gears.timer")
 local glib = require("lgi").GLib
-local capi = { keygrabber = keygrabber, root = root }
+local capi = { keygrabber = keygrabber, root = root, awesome = awesome }
 
 local keygrab = {}
 
@@ -85,17 +85,7 @@ local keygrabber = {
 }
 
 -- Instead of checking for every modifiers, check the key directly.
---FIXME This is slightly broken but still good enough for `mask_modkeys`
-local conversion = {
-    Super_L   = "Mod4",
-    Control_L = "Control",
-    Shift_L   = "Shift",
-    Alt_L     = "Mod1",
-    Super_R   = "Mod4",
-    Control_R = "Control",
-    Shift_R   = "Shift",
-    Alt_R     = "Mod1",
-}
+local conversion = nil
 
 --BEGIN one day create a proper API to add and remove keybindings at runtime.
 -- Doing it this way is horrible.
@@ -103,6 +93,27 @@ local conversion = {
 -- This list of keybindings to add in the next event loop cycle.
 local delay_list = {}
 
+-- Read the modifiers name and map their keysyms to the modkeys
+local function generate_conversion_map()
+    if conversion then return conversion end
+
+    local mods = capi.awesome._modifiers
+    assert(mods)
+
+    conversion = {}
+
+    for mod, keysyms in pairs(mods) do
+        for _, keysym in ipairs(keysyms) do
+            assert(keysym.keysym)
+            conversion[keysym.keysym] = mod
+        end
+    end
+
+    return conversion
+end
+
+capi.awesome.connect_signal("xkb::map_changed"  , function() conversion = nil end)
+
 local function add_root_keybindings(self, list)
     assert(
         list, "`add_root_keybindings` needs to be called with a list of keybindings"
@@ -168,9 +179,11 @@ local function grabber(mod, key, event)
 end
 
 local function runner(self, modifiers, key, event)
+    local converted = generate_conversion_map()[key]
+
     -- Stop the keygrabber with the `stop_key`
-    if key == self.stop_key
-        and event == self.stop_event and self.stop_key then
+    if (key == self.stop_key or (converted and converted == self.stop_key))
+      and event == self.stop_event and self.stop_key then
         self:stop(key, modifiers)
         return false
     end
@@ -191,7 +204,7 @@ local function runner(self, modifiers, key, event)
         end
     end
 
-    local is_modifier = conversion[key] ~= nil
+    local is_modifier = converted ~= nil
 
     -- Reset the inactivity timer on each events.
     if self._private.timer and self._private.timer.started then