awful.key: add a matching function

Signed-off-by: Julien Danjou <julien@danjou.info>

lib/awful/key.lua.in

@@ -36,6 +36,27 @@ local function new(_, mod, ...)
     return ret
 end
 
+--- Compare a key object with modifiers and key.
+-- @param key The key object.
+-- @param pressed_mod The modifiers to compare with.
+-- @param pressed_key The key to compare with.
+function match(key, pressed_mod, pressed_key)
+    -- First, compare key.
+    if pressed_key ~= key.key then return false end
+    -- Then, compare mod
+    local mod = key.modifiers
+    local nbmod = 0
+    for _, m in ipairs(pressed_mod) do
+        if awful.util.table.hasitem(mod, m) then
+            nbmod = nbmod + 1
+        end
+    end
+    if nbmod ~= #pressed_mod then
+        return false
+    end
+    return true
+end
+
 setmetatable(_M, { __call = new })
 
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