SWS/S&M: Toggle selected FX bypass for selected tracks

For each selected track, if the effects window is open
then iterate through effects and toggle the enabled state.

Fall back to previous behavior if the effects window for the track
is not opened, i.e. toggle the current fx index for the track.

Fixes #1443

SnM/SnM_FX.cpp

@@ -31,6 +31,7 @@
 #include "SnM_FX.h"
 #include "SnM_Track.h"
 #include "SnM_Util.h"
+#include "cfillion/cfillion.hpp"
 
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -101,14 +102,31 @@ bool SetOrToggleFXBypassSelTracks(const char* _undoMsg, int _mode, int _fxCmdId,
 							}
 						}
 						break;
-					case 2: // toggle
-						if (fxId < fxcnt)
+					case 2: // toggle selected fx
+					{
+						// Get handle to FX window for this track
+						HWND fxChain = CF_GetTrackFXChain(tr);
+						if(fxChain)
 						{
-							if (_undoMsg && !updated)
-								Undo_BeginBlock2(NULL);
-							TrackFX_SetEnabled(tr, fxId, !TrackFX_GetEnabled(tr, fxId));
-							updated = true;
+							int index=-1;
+							// enumerate selected FX
+							while( (index = CF_EnumSelectedFX(fxChain, index)) >= 0)
+							{
+								if (_undoMsg && !updated)
+									Undo_BeginBlock2(NULL);
+								// toggle enabled state
+								TrackFX_SetEnabled(tr, index, !TrackFX_GetEnabled(tr, index));
+								updated = true;
+							}
 						}
+						else if(fxId < fxcnt)
+						{
+							  if (_undoMsg && !updated)
+								  Undo_BeginBlock2(NULL);
+							  TrackFX_SetEnabled(tr, fxId, !TrackFX_GetEnabled(tr, fxId));
+							  updated = true;
+						}
+					}
 						break;
 					case 3: // set
 						if (fxId < fxcnt && _val != TrackFX_GetEnabled(tr, fxId))