output/alsa: use IsCleared() instead of IsDrained() in DrainInternal()

src/lib/alsa/PeriodBuffer.hxx

@@ -78,14 +78,6 @@ public:
 	}
 
 	/**
-	 * Has some data already been consumed at the buffer's head in
-	 * this period?
-	 */
-	bool WasConsumed() const noexcept {
-		return head > 0;
-	}
-
-	/**
 	 * Has all data for the current period been drained?  If not,
 	 * then there is pending data.  This ignores the partial frame
 	 * which may have been postponed by FillWithSilence().

src/output/plugins/AlsaOutputPlugin.cxx

@@ -747,7 +747,9 @@ AlsaOutput::DrainInternal()
 	/* drain ring_buffer */
 	CopyRingToPeriodBuffer();
 
-	if (period_buffer.WasConsumed() && !period_buffer.IsFull())
+	/* drain period_buffer */
+	if (!period_buffer.IsCleared()) {
+		if (!period_buffer.IsFull())
 			/* generate some silence to finish the partial
 			   period */
 			period_buffer.FillWithSilence(silence, out_frame_size);
@@ -765,9 +767,11 @@ AlsaOutput::DrainInternal()
 
 			/* need to call CopyRingToPeriodBuffer() and
 			   WriteFromPeriodBuffer() again in the next
-		   iteration, so don't finish the drain just yet */
+			   iteration, so don't finish the drain just
+			   yet */
 			return false;
 		}
+	}
 
 	if (!written)
 		/* if nothing has ever been written to the PCM, we