ULTIMA8: Use 2 bytes of intrinsic stack for UINT8

This fixes #12917.

The usecode "push byte" opcodes (0x0A and 0x5D) always push 16 bits on the
stack, but the ARG_UINT8 macro was only removing 1 byte.  Most of the time this
went unnoticed because the UINT8 was the last argument in most cases (eg, a z
val), or unused.

This led to an inconsistency where sometimes z values were being popped with
ARG_UINT16 and sometimes ARG_UINT8.  The original games do not support z values
beyond 254, so this should always be UINT8.

Additionaly, a while back "push byte" was fixed so it always sign extends, but
this could result in a case where we pop incorrect values.  For example, a high
Z value could get sign-extended on push, and then popped back as a UINT16,
giving a z of 64000ish.

Fix by always moving the SP by 2 bytes, only use the first one.

Correcting this also fixes the strange color ordering I thought was needed for
I_jumpToAllGivenColor in Crusader: No Regret, where actually it should have
been popping the values as 16-bit instead of 8-bit.

engines/ultima/ultima8/graphics/palette_fader_process.cpp

@@ -253,9 +253,9 @@ uint32 PaletteFaderProcess::I_fadeToGivenColor(const uint8 *args,
 	else if (_fader) _fader->terminate();
 
 	// TODO: guessing that color order should be same as other one below?
-	ARG_UINT8(b);
 	ARG_UINT8(r);
 	ARG_UINT8(g);
+	ARG_UINT8(b);
 	ARG_UINT16(nsteps);
 	ARG_UINT16(unk);
 
@@ -326,9 +326,9 @@ uint32 PaletteFaderProcess::I_jumpToAllGivenColor(const uint8 *args,
 	if (_fader && _fader->_priority > 0x7FFF) return 0;
 	else if (_fader) _fader->terminate();
 
-	ARG_UINT8(b);
 	ARG_UINT8(r);
 	ARG_UINT8(g);
+	ARG_UINT8(b);
 
 	// Transform matrix goes 0~2048, scale 0-63 vals from input
 	const int16 r16 = static_cast<int16>(r) * 32;

engines/ultima/ultima8/usecode/intrinsics.h

@@ -34,7 +34,9 @@ typedef uint32(*Intrinsic)(const uint8 *args, unsigned int argsize);
 
 // TODO: range checking on args
 
-#define ARG_UINT8(x)   uint8  x = (*args++);
+// UINT8s are pushed on the stack as words (see push byte opcodes),
+// so we ignore the top byte when popping.
+#define ARG_UINT8(x)   uint8  x = (*args++); args++;
 #define ARG_UINT16(x)  uint16 x = (*args++); x += ((*args++) << 8);
 #define ARG_UINT32(x)  uint32 x = (*args++); x += ((*args++) << 8); \
 	x+= ((*args++) << 16); x += ((*args++) << 24);
@@ -88,7 +90,6 @@ typedef uint32(*Intrinsic)(const uint8 *args, unsigned int argsize);
 	WorldPoint x; \
 	UCMachine::get_instance()->dereferencePointer(ucptr_##x, x._buf, 5);
 
-#define ARG_NULL8()  args+=1;
 #define ARG_NULL16() args+=2;
 #define ARG_NULL32() args+=4;
 

engines/ultima/ultima8/world/actors/actor.cpp

@@ -2545,8 +2545,8 @@ uint32 Actor::I_pathfindToPoint(const uint8 *args, unsigned int /*argsize*/) {
 	ARG_ACTOR_FROM_PTR(actor);
 	ARG_UINT16(x);
 	ARG_UINT16(y);
-	ARG_UINT16(z);
-	ARG_NULL16(); // unknown. Only one instance of this in U8, value is 5.
+	ARG_UINT8(z);
+	ARG_NULL16(); // unknown. Only one instance of this in U8, values are 5,1.
 	if (!actor) return 0;
 
 	if (GAME_IS_CRUSADER) {

engines/ultima/ultima8/world/current_map.cpp

@@ -1352,7 +1352,7 @@ uint32 CurrentMap::I_canExistAt(const uint8 *args, unsigned int argsize) {
 	ARG_UINT16(shape);
 	ARG_UINT16(x);
 	ARG_UINT16(y);
-	ARG_UINT16(z);
+	ARG_UINT8(z);
 	if (argsize > 8) {
 		//!! TODO: figure these out
 		ARG_UINT16(unk1); // is either 1 or 4

engines/ultima/ultima8/world/fireball_process.cpp

@@ -173,7 +173,7 @@ uint32 FireballProcess::I_TonysBalls(const uint8 *args,
 	ARG_NULL16(); // unknown
 	ARG_SINT16(x);
 	ARG_SINT16(y);
-	ARG_UINT16(z);
+	ARG_UINT8(z);
 
 	Item *ball = ItemFactory::createItem(260, 4, 0, Item::FLG_FAST_ONLY,
 	                                     0, 0, 0, true);

engines/ultima/ultima8/world/item.cpp

@@ -3160,7 +3160,7 @@ uint32 Item::I_legalCreateAtCoords(const uint8 *args, unsigned int /*argsize*/)
 	ARG_UINT16(frame);
 	ARG_UINT16(x);
 	ARG_UINT16(y);
-	ARG_UINT16(z);
+	ARG_UINT8(z);
 
 	if (GAME_IS_CRUSADER) {
 		x *= 2;
@@ -3357,7 +3357,7 @@ uint32 Item::I_push(const uint8 *args, unsigned int /*argsize*/) {
 		return 0;
 
 	#if 0
-		perr << "Pushing item to ethereal void: " << item->getShape() << "," << item->getFrame() << Std::endl;
+		perr << "Pushing item to ethereal void: id: " << item->getObjId() << " shp: " << item->getShape() << "," << item->getFrame() << Std::endl;
 	#endif
 
 	item->moveToEtherealVoid();
@@ -3423,7 +3423,7 @@ uint32 Item::I_popToCoords(const uint8 *args, unsigned int /*argsize*/) {
 	ARG_NULL32(); // ARG_ITEM_FROM_PTR(item); // unused
 	ARG_UINT16(x);
 	ARG_UINT16(y);
-	ARG_UINT16(z);
+	ARG_UINT8(z);
 
 	World *w = World::get_instance();
 
@@ -3521,7 +3521,7 @@ uint32 Item::I_move(const uint8 *args, unsigned int /*argsize*/) {
 	ARG_ITEM_FROM_PTR(item);
 	ARG_UINT16(x);
 	ARG_UINT16(y);
-	ARG_UINT16(z);
+	ARG_UINT8(z);
 	if (!item)
 		return 0;
 
@@ -3881,7 +3881,7 @@ uint32 Item::I_explode(const uint8 *args, unsigned int argsize) {
 uint32 Item::I_igniteChaos(const uint8 *args, unsigned int /*argsize*/) {
 	ARG_UINT16(x);
 	ARG_UINT16(y);
-	ARG_NULL8();
+	ARG_UINT8(z); // unused
 
 	assert(GAME_IS_U8);