output/Thread: allow Delay() to return duration::max()

Eliminate the periodic wakeups while paused in some output plugins.

src/output/Interface.hxx

@@ -136,6 +136,10 @@ public:
 	 * instead of doing a sleep inside the plugin, because this
 	 * allows MPD to listen to commands meanwhile.
 	 *
+	 * As a special case, this method is allowed to return
+         * std::chrono::steady_clock::duration::max() which lets MPD
+         * sleep forever until a command is received.
+	 *
 	 * @return the duration to wait
 	 */
 	virtual std::chrono::steady_clock::duration Delay() const noexcept {

src/output/Thread.cxx

@@ -197,7 +197,10 @@ AudioOutputControl::WaitForDelay(std::unique_lock<Mutex> &lock) noexcept
 		if (delay <= std::chrono::steady_clock::duration::zero())
 			return true;
 
-		(void)wake_cond.wait_for(lock, delay);
+		if (delay >= std::chrono::steady_clock::duration::max())
+			wake_cond.wait(lock);
+		else
+			(void)wake_cond.wait_for(lock, delay);
 
 		if (command != Command::NONE)
 			return false;

src/output/plugins/AlsaOutputPlugin.cxx

@@ -883,7 +883,7 @@ std::chrono::steady_clock::duration
 AlsaOutput::Delay() const noexcept
 {
 	if (paused)
-		return std::chrono::hours{1};
+		return std::chrono::steady_clock::duration::max();
 
 	return AudioOutput::Delay();
 }

src/output/plugins/JackOutputPlugin.cxx

@@ -155,7 +155,7 @@ public:
 
 	std::chrono::steady_clock::duration Delay() const noexcept override {
 		return pause && !LockWasShutdown()
-			? std::chrono::seconds(1)
+			? std::chrono::steady_clock::duration::max()
 			: std::chrono::steady_clock::duration::zero();
 	}
 

src/output/plugins/PulseOutputPlugin.cxx

@@ -762,7 +762,7 @@ PulseOutput::Delay() const noexcept
 	if (pa_stream_is_corked(stream) &&
 	    pa_stream_get_state(stream) == PA_STREAM_READY)
 		/* idle while paused */
-		result = std::chrono::seconds(1);
+		result = std::chrono::steady_clock::duration::max();
 
 	return result;
 }

src/output/plugins/wasapi/WasapiOutputPlugin.cxx

@@ -684,7 +684,7 @@ WasapiOutput::Delay() const noexcept
 {
 	if (paused) {
 		// idle while paused
-		return std::chrono::seconds(1);
+		return std::chrono::steady_clock::duration::max();
 	}
 
 	return std::chrono::steady_clock::duration::zero();