init: share timers when possible

We need time to give this a proper test with various usage scenarios;
multiple screens (and thus widget object instances), widgets
suspending and resuming and so on. Most benefits should come from
running on battery power (and if not suspending all widgets but
Battery it self on battery power), with less wake-ups.

Signed-off-by: Adrian C. (anrxc) <anrxc@sysphere.org>

init.lua

@@ -116,18 +116,21 @@ local function regregister(reg)
 
         -- Start the timer
         if reg.timer > 0 then
-            timers[reg.update] = {
-                timer = capi.timer({ timeout = reg.timer })
-            }
-
-            local tm = timers[reg.update].timer
+            local tm = timers[reg.timer] and timers[reg.timer].timer
+            tm = tm or capi.timer({ timeout = reg.timer })
             if tm.connect_signal then
                 tm:connect_signal("timeout", reg.update)
             else
                 tm:add_signal("timeout", reg.update)
             end
+            if not timers[reg.timer] then
+                timers[reg.timer] = { timer = tm, refs = 1 }
+            else
+                timers[reg.timer].refs = timers[reg.timer].refs + 1
+            end
+            if not tm.started then
                 tm:start()
-
+            end
             -- Initial update
             tm:emit_signal("timeout")
         end
@@ -195,11 +198,23 @@ function vicious.unregister(widget, keep, reg)
         end
     end
 
-    -- Stop the timer
-    if timers[reg.update].timer.started then
-        timers[reg.update].timer:stop()
+    if not reg.running then
+        return reg
+    end
+
+    -- Disconnect from timer
+    local tm  = timers[reg.timer]
+    if tm.timer.disconnect_signal then
+        tm.timer:disconnect_signal("timeout", reg.update)
+    else
+        tm.timer:remove_signal("timeout", reg.update)
     end
     reg.running = false
+    -- Stop the timer
+    tm.refs = tm.refs - 1
+    if tm.refs == 0 and tm.timer.started then
+        tm.timer:stop()
+    end
 
     return reg
 end