lua: add a timer API

player/lua/defaults.lua

@@ -63,6 +63,69 @@ local function script_dispatch(event)
     end
 end
 
+local timers = {}
+
+-- Install a one-shot timer. Once the given amount of seconds has passed from
+-- now, the callback will be called as cb(), and the timer is removed.
+function mp.add_timeout(seconds, cb)
+    local t = mp.add_periodic_timer(seconds, cb)
+    t.oneshot = true
+    return t
+end
+
+-- Install a periodic timer. It works like add_timeout(), but after cb() is
+-- called, the timer is re-added.
+function mp.add_periodic_timer(seconds, cb)
+    local t = {
+        timeout = seconds,
+        cb = cb,
+        oneshot = false,
+        next_deadline = mp.get_timer() + seconds,
+    }
+    timers[t] = t
+    return t
+end
+
+function mp.cancel_timer(t)
+    if t then
+        timers[t] = nil
+    end
+end
+
+-- Return the timer that expires next.
+local function get_next_timer()
+    local best = nil
+    for t, _ in pairs(timers) do
+        if (best == nil) or (t.next_deadline < best.next_deadline) then
+            best = t
+        end
+    end
+    return best
+end
+
+-- Run timers that have met their deadline.
+-- Return: next absolute time a timer expires as number, or nil if no timers
+local function process_timers()
+    while true do
+        local timer = get_next_timer()
+        if not timer then
+            return
+        end
+        local wait = timer.next_deadline - mp.get_timer()
+        if wait > 0 then
+            return wait
+        else
+            if timer.oneshot then
+                timers[timer] = nil
+            end
+            timer.cb()
+            if not timer.oneshot then
+                timer.next_deadline = mp.get_timer() + timer.timeout
+            end
+        end
+    end
+end
+
 -- used by default event loop (mp_event_loop()) to decide when to quit
 mp.keep_running = true
 
@@ -93,21 +156,27 @@ package.loaded["mp"] = mp
 package.loaded["mp.msg"] = mp.msg
 
 _G.mp_event_loop = function()
-    wait = 0
+    local more_events = true
+    mp.suspend()
     while mp.keep_running do
-        -- Drop all locks - important especially if an error happened while
-        -- locked, and the error was handled, but the lock not dropped.
+        local wait = process_timers()
+        if wait == nil then
+            wait = 1e20 -- infinity for all practical purposes
+        end
+        if more_events then
+            wait = 0
+        end
+        -- Resume playloop - important especially if an error happened while
+        -- suspended, and the error was handled, but no resume was done.
         if wait > 0 then
             mp.resume("all")
         end
         local e = mp.wait_event(wait)
-        if e.event == "none" then
-            wait = 1e20
-        else
-            -- Empty the event queue while suspended; otherwise, each
-            -- event will keep us waiting until the core suspends again.
-            mp.suspend()
-            wait = 0
+        -- Empty the event queue while suspended; otherwise, each
+        -- event will keep us waiting until the core suspends again.
+        mp.suspend()
+        more_events = (e.event ~= "none")
+        if more_events then
             local handler = event_handlers[e.event]
             if handler then
                 handler(e)