gears.object: Import

This implements objects in lua. Objects provide the signal functions that are
known from the C API ({dis,}connect_signal(), emit_signal(), add_signal()).

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/gears/init.lua.in

@@ -5,6 +5,7 @@
 ---------------------------------------------------------------------------
 
 require("gears.color")
+require("gears.object")
 require("gears.sort")
 
 module("gears")

lib/gears/object.lua.in

@@ -0,0 +1,94 @@
+---------------------------------------------------------------------------
+-- @author Uli Schlachter
+-- @copyright 2010 Uli Schlachter
+-- @release @AWESOME_VERSION@
+---------------------------------------------------------------------------
+
+local setmetatable = setmetatable
+local pairs = pairs
+local type = type
+local error = error
+
+module("gears.object")
+
+-- Verify that obj is indeed a valid object as returned by new()
+local function check(obj)
+    if type(obj) ~= "table" or type(obj._signals) ~= "table" then
+        error("add_signal() called on non-object")
+    end
+end
+
+-- Find a given signal
+-- @param obj The object to search in
+-- @param name The signal to find
+-- @param error_msg Error message for if the signal is not found
+-- @returns The signal table
+local function find_signal(obj, name, error_msg)
+    check(obj)
+    if not obj._signals[name] then
+        error("Trying to " .. error_msg .. " non-existent signal")
+    end
+    return obj._signals[name]
+end
+
+-- Add a signal to an object. All signals must be added before they can be used.
+-- @param obj The object
+-- @param name The name of the new signal.
+function add_signal(obj, name)
+    check(obj)
+    if not obj._signals[name] then
+        obj._signals[name] = {}
+    end
+end
+
+-- Connect to a signal
+-- @param obj The object
+-- @param name The name of the signal
+-- @param func The callback to call when the signal is emitted
+function connect_signal(obj, name, func)
+    local sig = find_signal(obj, name, "connect to")
+    sig[func] = func
+end
+
+-- Disonnect to a signal
+-- @param obj The object
+-- @param name The name of the signal
+-- @param func The callback that should be disconnected
+function disconnect_signal(obj, name, func)
+    local sig = find_signal(obj, name, "disconnect from")
+    sig[func] = nil
+end
+
+-- Emit a signal
+-- @param obj The object
+-- @param name The name of the signal
+-- @param ... Extra arguments for the callback functions. Each connected
+--            function receives the object as first argument and then any extra
+--            arguments that are given to emit_signal()
+function emit_signal(obj, name, ...)
+    local sig = find_signal(obj, name, "emit")
+    for func in pairs(sig) do
+        func(obj, ...)
+    end
+end
+
+-- Returns a new object. You can call :emit_signal(), :disconnect_signal,
+-- :connect_signal() and :add_signal() on the resulting object.
+local function new()
+    local ret = {}
+
+    -- Copy all our global functions to our new object
+    for k, v in pairs(_M) do
+        if type(v) == "function" then
+            ret[k] = v
+        end
+    end
+
+    ret._signals = {}
+
+    return ret
+end
+
+setmetatable(_M, { __call = function (_, ...) return new(...) end })
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=80