AGI: Add detection for fan games with broken volume bug #7035

Plenty of fan games set volume to mute, because they thought 15
would be loudest. It's in fact "mute" in AGI. Those games were
made primarily for PC AGI, which did not use the volume setting.
We do, so such games would get muted audio. We try to detect
such games. Hopefully fully fixes bug #7035.
Too many games to try them all out.

1 files changed, 26 insertions, 1 deletions

diff --git a/engines/agi/global.cpp b/engines/agi/global.cpp
index 48e1c224ce..23256f27fb 100644
--- a/engines/agi/global.cpp
+++ b/engines/agi/global.cpp
@@ -87,7 +87,32 @@ byte AgiEngine::getVar(int16 varNr) {
 // 15 - mute
 void AgiEngine::setVolumeViaScripts(byte newVolume) {
 	newVolume = CLIP<byte>(newVolume, 0, 15);
-	newVolume = 15 - newVolume; // turn volume around
+
+	if (_veryFirstInitialCycle) {
+		// WORKAROUND:
+		// The very first cycle is currently running and volume got changed
+		// This is surely the initial value. For plenty of fan games, a default of 15 is set
+		// Which actually means "mute" in AGI, but AGI on PC used PC speaker, which did not use
+		// volume setting. We do. So we detect such a situation and set a flag, so that the
+		// volume will get interpreted "correctly" for those fan games.
+		// Note: not all fan games are broken in that regard!
+		// See bug #7035
+		if (getFeatures() & GF_FANMADE) {
+			// We only check for fan games, Sierra always did it properly of course
+			if (newVolume == 15) {
+				// Volume gets set to mute at the start?
+				// Probably broken fan game detected, set flag
+				debug("Broken volume in fan game detected, enabling workaround");
+				_setVolumeBrokenFangame = true;
+			}
+		}
+	}
+
+	if (!_setVolumeBrokenFangame) {
+		// In AGI 15 is mute, 0 is loudest
+		// Some fan games set this incorrectly as 15 for loudest, 0 for mute
+		newVolume = 15 - newVolume; // turn volume around
+	}
 
 	int scummVMVolume = newVolume * Audio::Mixer::kMaxMixerVolume / 15;
 	bool scummVMMute = false;