bindings: try to be smarter with Mod+u to choose Pidgin window

We try to handle the case where we have several Pidgin conversation
windows. Not perfect since it is not possible to remove them all.

rc/bindings.lua

@@ -81,10 +81,34 @@ end
 -- Toggle pidgin conversation window
 local toggle_pidgin = toggle_window(
    function ()
-      return awful.client.cycle(function(c)
-			    return awful.rules.match(c, { class = "Pidgin",
-							  role = "conversation" })
-			 end)()
+      local cls = client.get()
+      local focus = client.focus
+      local rule = { class = "Pidgin",
+                     role = "conversation" }
+      -- Score. We want a Pidgin window. Then:
+      --  1. Urgent, visible, not focused
+      --  2. Urgent, not visible, not focused.
+      --  3. Not urgent, not visible, not focused
+      --  4. Focused
+      --  5. Visible, not focused
+      local function score(cl)
+         if not awful.rules.match(cl, rule) then return -10 end
+
+         local urgent = cl.urgent
+         local focused = (focus == cl)
+         local visible = cl:isvisible()
+         if urgent and visible and not focused then return 100 end
+         if urgent and not visible and not focused then return 90 end
+         if not urgent and not visible then return 80 end
+         if focused then return 50 end
+         return 10
+      end
+      table.sort(cls, function(c1, c2)
+                    local s1 = score(c1)
+                    local s2 = score(c2)
+                    return s1 > s2
+                      end)
+      if awful.rules.match(cls[1], rule) then return cls[1] end
    end)
 
 -- Toggle urgent window