increase TV frame resize threshold from 2 to 3 frames

this fixes abberant resizing when using the emulation rewind with
moviecarts - the moviecart rewind system is unaffected by this

moviecart resets the frame state on Plumb()

hardware/memory/cartridge/moviecart/moviecart.go

@@ -248,6 +248,13 @@ func (s *state) Snapshot() *state {
 	return &n
 }
 
+// Plumb implements the mapper.CartMapper interface.
+func (s *state) Plumb() {
+	s.state = stateMachineNewField
+	s.paused = false
+	s.fieldAdv = 1
+}
+
 func (s *state) initialise() {
 	if s.shortTitleCard {
 		// shorten title card. we don't want to eliminate it entirely so say
@@ -257,6 +264,7 @@ func (s *state) initialise() {
 		s.totalCycles = 0
 	}
 	copy(s.sram, coreData)
+
 	s.state = stateMachineNewField
 	s.paused = false
 	s.streamChunk = 0
@@ -341,6 +349,7 @@ func (cart *Moviecart) Snapshot() mapper.CartMapper {
 // Plumb implements the mapper.CartMapper interface.
 func (cart *Moviecart) Plumb(env *environment.Environment) {
 	cart.env = env
+	cart.state.Plumb()
 }
 
 // Reset implements the mapper.CartMapper interface.

hardware/television/resizer.go

@@ -189,7 +189,12 @@ func (sr *resizer) examine(tv *Television, sig signal.SignalAttributes) {
 // the resize top/bottom value) at that point
 //
 // the counter will be reset if the screen size changes in the interim.
-const framesUntilResize = 2
+//
+// (27/04/24) increased to 3 to accomodate MovieCart when being rewound using
+// the emulator's rewind system - the Moviecart rewind is unaffected by this
+// value. it's unclear if there are any adverse affects to this increase but I
+// don't believe there will be
+const framesUntilResize = 3
 
 // commit resizing possibility found through examine() function.
 func (sr *resizer) commit(tv *Television) error {