Ctrl-S to toggle sound during play

fixes https://github.com/a2-4am/million-perfect-letters/issues/6

src/glue.sound.a

@@ -3,6 +3,7 @@
 ;
 ; Public functions:
 ; - InitSound
+; - ToggleSoundPref
 ; - ReinitSoundAfterPrefChange
 ; - PlaySoundToCompletion
 ; - PlaySound
@@ -50,6 +51,13 @@ k16251Progression
          !word M_ii
          !word M_V
 
+ToggleSoundPref
+         lda   gSoundPref
+         eor   #$01
+         sta   gSoundPref
+         jsr   SavePrefs
+         ; /!\ execution falls through to ReinitSoundAfterPrefChange
+
 ;------------------------------------------------------------------------------
 ; ReinitSoundAfterPrefChange
 ; reinitialize self-modified code that relies on preference values

src/ui.help.a

@@ -27,14 +27,15 @@ HelpEventLoop
 DrawHelpText
 ; [private]
          bit   TEXTMODE
-         +PRINT_AT sHelpHeader1, 2, 7
-         +PRINT_AT sHelpHeader2, 4, 7
-         +PRINT_AT sAsterisk, 7, 20
-         +PRINT_AT sHelpLeftRight, 10, 0
-         +PRINT_AT sHelpUpDown, 12, 0
-         +PRINT_AT sHelpLetters, 14, 0
-         +PRINT_AT sHelpRestart, 16, 0
-         +PRINT_AT sHelpSkip, 18, 0
-         +PRINT_AT sHelpQuit, 20, 0
+         +PRINT_AT sHelpHeader1, 1, 7
+         +PRINT_AT sHelpHeader2, 3, 7
+         +PRINT_AT sAsterisk, 6, 20
+         +PRINT_AT sHelpLeftRight, 9, 0
+         +PRINT_AT sHelpUpDown, 11, 0
+         +PRINT_AT sHelpLetters, 13, 0
+         +PRINT_AT sHelpRestart, 15, 0
+         +PRINT_AT sHelpSkip, 17, 0
+         +PRINT_AT sHelpSound, 19, 0
+         +PRINT_AT sHelpQuit, 21, 0
          bit   GFXMODE
          rts

src/ui.main.menu.a

@@ -109,11 +109,7 @@ MainMenuEventC
          rts
 
 MainMenuEventS
-         lda   gSoundPref
-         eor   #$01
-         sta   gSoundPref
-         jsr   SavePrefs
-         jsr   ReinitSoundAfterPrefChange
+         jsr   ToggleSoundPref
          ldx   #kStayOnMainMenu      ; Z=1 so caller will stay in main menu event loop
          clc                         ; C=0 so caller will only do a partial screen refresh
          rts

src/ui.play.a

@@ -45,6 +45,7 @@ kPlayKeys                            ; must keep in sync with kPlayKeyHandlersLo
          !byte $1B                   ; Esc
          !byte $12                   ; Ctrl-R
          !byte $0E                   ; Ctrl-N
+         !byte $13                   ; Ctrl-S
          !byte $0D                   ; Return
          !byte $2F                   ; /
          !byte $3F                   ; ?
@@ -58,6 +59,7 @@ kPlayKeyHandlersLo
          !byte <PlayEventEsc
          !byte <PlayEventCtrlR
          !byte <PlayEventCtrlN
+         !byte <PlayEventCtrlS
          !byte <PlayEventReturn
          !byte <PlayEventQuestion
          !byte <PlayEventQuestion
@@ -71,6 +73,7 @@ kPlayKeyHandlersHi
          !byte >PlayEventEsc
          !byte >PlayEventCtrlR
          !byte >PlayEventCtrlN
+         !byte >PlayEventCtrlS
          !byte >PlayEventReturn
          !byte >PlayEventQuestion
          !byte >PlayEventQuestion
@@ -133,6 +136,11 @@ PlayEventCtrlN
          ldx   #kRequestedSkip       ; caller will exit play event loop
          rts
 
+PlayEventCtrlS
+         jsr   ToggleSoundPref
+         ldx   #kKeepPlaying
+         rts
+
 PlayEventReturn
          ldy   gSelectedLogicalColumn
          beq   +

src/ui.strings.a

@@ -147,6 +147,9 @@ sHelpRestart
 sHelpSkip
          !byte 40
          !raw  "CTRL-N.......................NEXT PUZZLE"
+sHelpSound
+         !byte 40
+         !raw  "CTRL-S......................TOGGLE SOUND"
 sHelpQuit
          !byte 40
          !raw  "ESC............................MAIN MENU"