mixer,output: prevent setting volume before outputs are really enabled

Previous versions of MPD would call SetVolume on enabled outputs before they are ready, causing all of MPD to crash. Checking the really_enabled flag prevents this, though it also prevents setting volume before the player starts. Before (with the PipeWire output): [i] ~$ mpc clear volume: 81% repeat: off random: off single: off consume: off [i] ~$ systemctl --user restart mpd.service [i] ~$ mpc volume 100 MPD error: Connection closed by the server [i] ~ 1 $ After: [i] ~$ # mpd is freshly started w/o anything in the queue [i] ~$ mpc volume:100% repeat: off random: off single: off consume: off [i] ~$ mpc volume 80 MPD error: problems setting volume [i] ~ 1 $ mpc volume:100% repeat: off random: off single: off consume: off [i] ~$

mixer,output: prevent setting volume before outputs are really enabled
35dbc1a9 · Arsen Arsenović · Max Kellermann · c7a43551 · 35dbc1a9 · 35dbc1a9
Commit 35dbc1a9 authored Mar 08, 2022 by Arsen Arsenović Committed by Max Kellermann Apr 26, 2022
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MixerAll.cxx src/mixer/MixerAll.cxx +1 -1

Control.hxx src/output/Control.hxx +7 -0

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--- a/src/mixer/MixerAll.cxx
+++ b/src/mixer/MixerAll.cxx
@@ -84,7 +84,7 @@ output_mixer_set_volume(AudioOutputControl &ao, unsigned volume) noexcept

 	/* software mixers are always updated, even if they are
 	   disabled */
-	if (!ao.IsEnabled() && !mixer->IsPlugin(software_mixer_plugin))
+	if (!ao.IsReallyEnabled() && !mixer->IsPlugin(software_mixer_plugin))
 		return false;

 	try {

--- a/src/output/Control.hxx
+++ b/src/output/Control.hxx
@@ -291,6 +291,13 @@ public:
 	/**
 	 * Caller must lock the mutex.
 	 */
+	bool IsReallyEnabled() const noexcept {
+		return really_enabled;
+	}
+
+	/**
+	 * Caller must lock the mutex.
+	 */
 	bool IsEnabled() const noexcept {
 		return enabled;
 	}