awful.mouse: Add a generic mousegrabber

Previously, all layouts had their own mouse grabbing logic. The
new one is based on the client request::geometry feature.

lib/awful/mouse/init.lua

@@ -26,7 +26,9 @@ local capi =
     mousegrabber = mousegrabber,
 }
 
-local mouse = {}
+local mouse = {
+    resize = require("awful.mouse.resize")
+}
 
 mouse.client = {}
 mouse.wibox = {}

lib/awful/mouse/resize.lua

@@ -0,0 +1,193 @@
+---------------------------------------------------------------------------
+--- An extandable mouse resizing handler.
+--
+-- This module offer a resizing and moving mechanism for drawable such as
+-- clients and wiboxes.
+--
+-- @author Emmanuel Lepage Vallee <elv1313@gmail.com>
+-- @copyright 2016 Emmanuel Lepage Vallee
+-- @release @AWESOME_VERSION@
+-- @submodule awful.mouse
+---------------------------------------------------------------------------
+
+local aplace = require("awful.placement")
+local capi = {mousegrabber = mousegrabber}
+
+local module = {}
+
+local mode      = "live"
+local req       = "request::geometry"
+local callbacks = {enter={}, move={}, leave={}}
+
+--- Set the resize mode.
+-- The available modes are:
+--
+-- * **live**: Resize the layout everytime the mouse move
+-- * **after**: Resize the layout only when the mouse is released
+--
+-- Some clients, such as XTerm, may lose information if resized too often.
+--
+-- @tparam string m The mode
+function module.set_mode(m)
+    assert(m == "live" or m == "after")
+    mode = m
+end
+
+--- Add a initialization callback.
+-- This callback will be executed before the mouse grabbing start
+-- @tparam function cb The callback (or nil)
+-- @tparam[default=other] string context The callback context
+function module.add_enter_callback(cb, context)
+    context = context or  "other"
+    callbacks.enter[context] =  callbacks.enter[context] or {}
+    table.insert(callbacks.enter[context], cb)
+end
+
+--- Add a "move" callback.
+-- This callback is executed in "after" mode (see `set_mode`) instead of
+-- applying the operation.
+-- @tparam function cb The callback (or nil)
+-- @tparam[default=other] string context The callback context
+function module.add_move_callback(cb, context)
+    context = context or  "other"
+    callbacks.move[context] = callbacks.move[context]  or {}
+    table.insert(callbacks.move[context], cb)
+end
+
+--- Add a "leave" callback
+-- This callback is executed just before the `mousegrabber` stop
+-- @tparam function cb The callback (or nil)
+-- @tparam[default=other] string context The callback context
+function module.add_leave_callback(cb, context)
+    context = context or  "other"
+    callbacks.leave[context] = callbacks.leave[context]  or {}
+    table.insert(callbacks.leave[context], cb)
+end
+
+-- Resize, the drawable
+--
+-- Valid `args` are:
+--
+-- * *enter_callback*: A function called before the `mousegrabber` start
+-- * *move_callback*: A function called when the mouse move
+-- * *leave_callback*: A function called before the `mousegrabber` is released
+-- * *mode*: The resize mode
+--
+-- @tparam client client A client
+-- @tparam[default=mouse.resize] string context The resizing context
+-- @tparam[opt={}] table args A set of `awful.placement` arguments
+local function handler(_, client, context, args) --luacheck: no unused_args
+    args = args or {}
+    context = context or "mouse.resize"
+
+    local placement = args.placement
+
+    if type(placement) == "string" and aplace[placement] then
+        placement = aplace[placement]
+    end
+
+    -- Extend the table with the default arguments
+    args = setmetatable(
+        {
+            placement = placement or aplace.resize_to_mouse,
+            mode      = args.mode or mode,
+            pretend   = true,
+        },
+        {__index = args or {}}
+    )
+
+    local geo
+
+    for _, cb in ipairs(callbacks.enter[context] or {}) do
+        geo = cb(client, args)
+
+        if geo == false then
+            return false
+        end
+    end
+
+    if args.enter_callback then
+        geo = args.enter_callback(client, args)
+
+        if geo == false then
+            return false
+        end
+    end
+
+    geo = nil
+
+    -- Execute the placement function and use request::geometry
+    capi.mousegrabber.run(function (_mouse)
+        if not client.valid then return end
+
+        -- Resize everytime the mouse move (default behavior)
+        if args.mode == "live" then
+            -- Get the new geometry
+            geo = setmetatable(args.placement(client, args),{__index=args})
+        end
+
+        -- Execute the move callbacks. This can be used to add features such as
+        -- snap or adding fancy graphical effects.
+        for _, cb in ipairs(callbacks.move[context] or {}) do
+            -- If something is returned, assume it is a modified geometry
+            geo = cb(client, geo, args) or geo
+
+            if geo == false then
+                return false
+            end
+        end
+
+        if args.move_callback then
+            geo = args.move_callback(client, geo, args)
+
+            if geo == false then
+                return false
+            end
+        end
+
+        -- In case it was modified
+        setmetatable(geo,{__index=args})
+
+        if args.mode == "live" then
+            -- Ask the resizing handler to resize the client
+            client:emit_signal( req, context, geo)
+        end
+
+        -- Quit when the button is released
+        for _,v in pairs(_mouse.buttons) do
+            if v then return true end
+        end
+
+        -- Only resize after the mouse is released, this avoid losing content
+        -- in resize sensitive apps such as XTerm or allow external modules
+        -- to implement custom resizing
+        if args.mode == "after" then
+            -- Get the new geometry
+            geo = args.placement(client, args)
+
+            -- Ask the resizing handler to resize the client
+            client:emit_signal( req, context, geo)
+        end
+
+        geo = nil
+
+        for _, cb in ipairs(callbacks.leave[context] or {}) do
+            geo = cb(client, geo, args)
+        end
+
+        if args.leave_callback then
+            geo = args.leave_callback(client, geo, args)
+        end
+
+        if not geo then return false end
+
+        -- In case it was modified
+        setmetatable(geo,{__index=args})
+
+        client:emit_signal( req, context, geo)
+
+        return false
+    end, "cross")
+end
+
+return setmetatable(module, {__call=handler})