feat: add MCHD command

CHANGELOG

@@ -1,3 +1,7 @@
+1.6.0-bacon20
+    Fixed MIDI muting
+    Added MIDI chord command (MCHD)
+
 1.6.0-bacon19
     Create column Titles.
         * Every view will have a column title (or header).

docs/wiki/What-is-LittlePiggyTracker.md

@@ -546,6 +546,11 @@ don't forget trying to combine it with complex hop structure !
 - LPOF is absolute
 - you can't trigger a note with the LPOF, it has to be executed after a sample is playing
 - every time you trigger a sample LPOF is set back to the instrument parameters
+
+## MCHD aabb
+
+Plays the notes aa and bb semitones higher than the last played note (modulo 128). Note that the value `00` is ignored. The chords tones will last as long as the root note, i.e. until another note is played on the channel.
+
 ## MDCC aabb
 
 **Sends a MIDI “continuous control” message. aa is the control number and bb is the value. It will be sent on the MIDI channel of the currently running instrument.**

sources/Application/Instruments/CommandList.cpp

@@ -1,35 +1,12 @@
 
 #include "CommandList.h"
 
-static FourCC _all[]= {
-	I_CMD_NONE,
-	I_CMD_ARPG,
-	I_CMD_CRSH,
-	I_CMD_DLAY,
-	I_CMD_FBMX,
-	I_CMD_FBTN,
-	I_CMD_FCUT,
-	I_CMD_FLTR,
-	I_CMD_FRES,
-	I_CMD_GROV,
-	I_CMD_HOP,
-	I_CMD_IRTG,
-	I_CMD_KILL,
-	I_CMD_LEGA,
-	I_CMD_LPOF,
-	I_CMD_MDCC,
-	I_CMD_MDPG,
-	I_CMD_MVEL,
-	I_CMD_PAN_,
-	I_CMD_PFIN,
-	I_CMD_PLOF,
-	I_CMD_PTCH,
-	I_CMD_RTRG,
-	I_CMD_STOP,
-	I_CMD_TABL,
-	I_CMD_TMPO,
-	I_CMD_VOLM
-} ;
+static FourCC _all[] = {
+    I_CMD_NONE, I_CMD_ARPG, I_CMD_CRSH, I_CMD_DLAY, I_CMD_FBMX, I_CMD_FBTN,
+    I_CMD_FCUT, I_CMD_FLTR, I_CMD_FRES, I_CMD_GROV, I_CMD_HOP,  I_CMD_IRTG,
+    I_CMD_KILL, I_CMD_LEGA, I_CMD_LPOF, I_CMD_MCHD, I_CMD_MDCC, I_CMD_MDPG,
+    I_CMD_MVEL, I_CMD_PAN_, I_CMD_PFIN, I_CMD_PLOF, I_CMD_PTCH, I_CMD_RTRG,
+    I_CMD_STOP, I_CMD_TABL, I_CMD_TMPO, I_CMD_VOLM};
 
 int CommandList::GetCount() { return sizeof(_all) / sizeof(FourCC); }
 

sources/Application/Instruments/CommandList.h

@@ -14,6 +14,7 @@
 #define I_CMD_LEGA MAKE_FOURCC('L','E','G','A')
 #define I_CMD_RTRG MAKE_FOURCC('R','T','R','G')
 #define I_CMD_TMPO MAKE_FOURCC('T','M','P','O')
+#define I_CMD_MCHD MAKE_FOURCC('M', 'C', 'H', 'D')
 #define I_CMD_MDCC MAKE_FOURCC('M','D','C','C')
 #define I_CMD_MDPG MAKE_FOURCC('M','D','P','G')
 #define I_CMD_MVEL MAKE_FOURCC('M','V','E','L')

sources/Application/Instruments/I_Instrument.h

@@ -23,8 +23,10 @@ class I_Instrument:public VariableContainer, public Observable {
 
 	  virtual bool Init()=0 ;
 
-	  // Start & stop the instument
-      virtual bool Start(int channel,unsigned char note,bool retrigger=true)=0 ;
+      // Start & stop the instument
+      // flags & 1 indicates retriggers (default)
+      // flags & 2 indicates muting (i.e. no trigger)
+      virtual bool Start(int channel,unsigned char note,int flags=1)=0 ;
       virtual void Stop(int channel)=0 ;
 
 	  // Engine playback  start callback
@@ -33,8 +35,10 @@ class I_Instrument:public VariableContainer, public Observable {
 
       // size refers to the number of samples
       // should always fill interleaved stereo / 16bit
-
-      virtual bool Render(int channel,fixed *buffer,int size,bool updateTick)=0 ;
+
+  // flags & 1 indicates 'updateTick'.
+  // flags & 2 indicated muting (i.e. stop notes)
+      virtual bool Render(int channel,fixed *buffer,int size,int flags)=0 ;
 
       virtual bool IsInitialized()=0 ;