Awesome WM (v3.5.5) keygrabber alternative - lua

Question

I've never liked the default window switching possibilities in Awesome, so I thought I'd implement Alt-Tab behavior that takes history into account (and does fancy opacity effects).
When Alt-Tab is pressed, the entire history is recorded in a table, and appended to that history are the minimized windows (within the same tag). When this table is generated, I instantiate a keygrabber that captures Tab-press events (to switch to the next client in the table) and Alt-release events (to abort entirely).
A flag keeps track of whether the user is in the process of Alt-tabbing, to prevent the table from being generated over and over again.
The code (it's a lot and you probably don't need to see it, but my experience tells me that when I don't post all the code, people will ask for it eventually):
altTabbing = false
altTabIndex = 1
altTabHistory = {}
clientOpacities = {}
function altTabSetOpacities(restore)
for i,c in pairs(altTabHistory) do
if not restore and i ~= altTabIndex then
c.opacity = 0.5
else
c.opacity = clientOpacities[i]
end
end
end
function myAltTab()
-- First check if the user is already alttabbing, in which case the history
-- should NOT be updated. If the user has just pressed alt-tab, generate a new
-- history-table
if not altTabbing then -- generate history-table
-- Clear Tables
for i in pairs(altTabHistory) do altTabHistory[i] = nil end
for i in pairs(clientOpacities) do clientOpacities[i] = nil end
-- Get focus history for current tag
local s = mouse.screen;
local idx = 0
local c = awful.client.focus.history.get(s, idx)
while c do
table.insert(altTabHistory, c)
table.insert(clientOpacities, c.opacity)
idx = idx + 1
c = awful.client.focus.history.get(s, idx)
end
-- Minimized clients will not appear in the focus history
-- Find them by cycling through all clients, and adding them to the list
-- if not already there.
-- This will preserve the history AND enable you to focus on minimized clients
local t = awful.tag.selected(s)
local all = client.get(s)
for i = 1, #all do
local c = all[i]
local ctags = c:tags();
-- check if the client is on the current tag
local isCurrentTag = false
for j = 1, #ctags do
if t == ctags[j] then
isCurrentTag = true
break
end
end
if isCurrentTag then
-- check if client is already in the history
-- if not, add it
local addToHistory = true
for k = 1, #altTabHistory do
if altTabHistory[k] == c then
addToHistory = false
break
end
end
if addToHistory then
table.insert(altTabHistory, c)
table.insert(clientOpacities, c.opacity)
end
end
end
-- reset current index and flag
altTabIndex = 1
altTabbing = true
-- Now that we have collected all windows, we should run a keygrabber
-- as long as the user is alt-tabbing:
keygrabber.run(
function (mod, key, event)
-- Stop alt-tabbing when the alt-key is released
if key == "Alt_L" and event == "release" then
altTabbing = false
altTabSetOpacities(true)
c = altTabHistory[altTabIndex]
client.focus = c
c:raise()
return false -- stop keygrabber
end
-- Move to next client on each Tab-press
if key == "Tab" and event == "press" then
myAltTab()
return true -- keep going
end
return true -- keep going
end
)
end -- if not altTabbing
-- at this point, the user is alt-tabbing, so we should raise
-- the next client in the history-table
if #altTabHistory < 2 then return end
-- Switch to next client
altTabIndex = altTabIndex + 1
if altTabIndex > #altTabHistory then
altTabIndex = 1 -- wrap around
end
-- focus on current client
local c = altTabHistory[altTabIndex]
c.minimized = false
c:raise()
-- make current client stand out
altTabSetOpacities(false)
end
I realize there's a lot of code, but the main thing is the keygrabber. For still unknown reasons, Awesome sometimes crashes while I'm Alt-Tabbing using this approach. I want to replace the keygrabber by connecting signals to the Alt and Tab keys, and disconnecting them as soon as the user is done. However, I'm not able to do this for some reason.
I instantiate a new key-object like this:
local altkey = awful.key({}, "Alt_L")[1]
I found out by trial and error that awful.key() actually returns a table of which I could query the first element for key, keysym etc, hence the [1]. However, when I try to connect a signal to this object, the LUA interpreter complains and tells me it's a nil object. So my question is: am I doing the right thing here? Is it even possible to replace the keygrabber in the way I intend to?

Answer 1

To use the Alt_L key in Awesome you should refer to "Mod1" in your rc.lua file, to make it mor readable I added the following line to the beginning of my configuration so Alt_L can be used.
Alt_L = "Mod1"