awful.mouse/widget: enable drag'n'dropping clients on tags

Signed-off-by: Gregor Best <farhaven@googlemail.com>
Signed-off-by: Julien Danjou <julien@danjou.info>

lib/awful/mouse.lua.in

@@ -9,6 +9,7 @@ local layout = require("awful.layout")
 local tag = require("awful.tag")
 local hooks = require("awful.hooks")
 local aclient = require("awful.client")
+local widget = require("awful.widget")
 local type = type
 local math = math
 local ipairs = ipairs
@@ -158,6 +159,31 @@ function client.move(c, snap)
                           end, "fleur")
 end
 
+--- Move a client to a tag by drag'n'dropping it over a taglist widget
+-- @param c The client to move
+function client.dragtotag(c)
+    capi.mousegrabber.run(function (mouse)
+                              local button_down = false
+                              for k, v in ipairs(mouse.buttons) do
+                                  if v then
+                                      button_down = true
+                                  end
+                              end
+                              if not button_down then
+                                  local w = widget_under_pointer()
+                                  if w and widget.taglist.gettag(w) then
+                                      local t = widget.taglist.gettag(w)
+                                      if t.screen ~= c.screen then
+                                          aclient.movetoscreen(c, t.screen)
+                                      end
+                                      aclient.movetotag(t, c)
+                                  end
+                                  return false
+                              end
+                              return true
+                          end, "fleur")
+end
+
 --- Get a client corner coordinates.
 -- @param c The client to get corner from, focused one by default.
 -- @param corner The corner to use: auto, top_left, top_right, bottom_left,

lib/awful/widget.lua.in

@@ -33,6 +33,9 @@ taglist.label = {}
 tasklist = {}
 tasklist.label = {}
 
+-- Private structures
+local tagwidgets = otable()
+
 local function taglist_update (screen, w, label, buttons, data)
     local tags = capi.screen[screen]:tags()
     -- Hack: if it has been registered as a widget in a wibox,
@@ -42,11 +45,14 @@ local function taglist_update (screen, w, label, buttons, data)
     -- Add more widgets
     if len < #tags then
         for i = len + 1, #tags do
-            w[i] = capi.widget({ type = "textbox" })
+            local wi = capi.widget({ type = "textbox" })
+            w[i] = wi
+            tagwidgets[wi] = tags[i]
         end
     -- Remove widgets
     elseif len > #tags then
         for i = #tags + 1, len do
+            tagwidgets[w[i]] = nil
             w[i] = nil
         end
     end
@@ -74,6 +80,10 @@ local function taglist_update (screen, w, label, buttons, data)
     end
 end
 
+function taglist.gettag(widget)
+    return tagwidgets[widget]
+end
+
 --- Create a new taglist widget.
 -- @param screen The screen to draw tag list for.
 -- @param label Label function to use.