Add P_CheckMove

Checks if P_TryMove would succeed without actually moving.

(cherry picked from commit 518de0ce104166c3eacd10ebe6ade422307ce671)

src/deh_tables.c

@@ -4506,6 +4506,7 @@ const char *const STATE_LIST[] = { // array length left dynamic for sanity testi
 // because sadly no one remembers this place while searching for full state names.
 const char *const MOBJTYPE_LIST[] = {  // array length left dynamic for sanity testing later.
 	"MT_NULL",
+	"MT_RAY",
 	"MT_UNKNOWN",
 
 	"MT_THOK", // Thok! mobj

src/info.c

@@ -5120,6 +5120,33 @@ mobjinfo_t mobjinfo[NUMMOBJTYPES] =
 		S_NULL          // raisestate
 	},
 
+	{           // MT_RAY
+		-1,             // doomednum
+		S_NULL,         // spawnstate
+		0,              // spawnhealth
+		S_NULL,         // seestate
+		sfx_None,       // seesound
+		0,              // reactiontime
+		sfx_None,       // attacksound
+		S_NULL,         // painstate
+		0,              // painchance
+		sfx_None,       // painsound
+		S_NULL,         // meleestate
+		S_NULL,         // missilestate
+		S_NULL,         // deathstate
+		S_NULL,         // xdeathstate
+		sfx_None,       // deathsound
+		0,              // speed
+		0,              // radius
+		0,              // height
+		0,              // display offset
+		0,              // mass
+		0,              // damage
+		sfx_None,       // activesound
+		MF_NOBLOCKMAP|MF_NOSECTOR|MF_NOCLIP|MF_NOCLIPHEIGHT|MF_NOGRAVITY|MF_SCENERY, // flags
+		S_NULL          // raisestate
+	},
+
 	{           // MT_UNKNOWN
 		-1,             // doomednum
 		S_UNKNOWN,      // spawnstate

src/info.h

@@ -5532,6 +5532,7 @@ extern playersprite_t free_spr2;
 typedef enum mobj_type
 {
 	MT_NULL,
+	MT_RAY, // General purpose mobj
 	MT_UNKNOWN,
 
 	MT_THOK, // Thok! mobj

src/p_local.h

@@ -410,6 +410,7 @@ boolean P_IsLineBlocking(const line_t *ld, const mobj_t *thing);
 boolean P_IsLineTripWire(const line_t *ld);
 boolean P_CheckPosition(mobj_t *thing, fixed_t x, fixed_t y);
 boolean P_CheckCameraPosition(fixed_t x, fixed_t y, camera_t *thiscam);
+boolean P_CheckMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff);
 fixed_t P_BaseStepUp(void);
 fixed_t P_GetThingStepUp(mobj_t *thing);
 boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff);

src/p_map.c

@@ -2489,21 +2489,19 @@ fixed_t P_GetThingStepUp(mobj_t *thing)
 	return maxstep;
 }
 
-//
+static boolean
-// P_TryMove
+increment_move
-// Attempt to move to a new position.
+(		mobj_t * thing,
-//
+		fixed_t x,
-boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
+		fixed_t y,
+		boolean allowdropoff,
+		fixed_t * return_stairjank)
 {
 	fixed_t tryx = thing->x;
 	fixed_t tryy = thing->y;
-	fixed_t oldx = tryx;
-	fixed_t oldy = tryy;
 	fixed_t radius = thing->radius;
 	fixed_t thingtop;
-	fixed_t startingonground = P_IsObjectOnGround(thing);
 	fixed_t stairjank = 0;
-	pslope_t *oldslope = thing->standingslope;
 	floatok = false;
 
 	// reset this to 0 at the start of each trymove call as it's only used here
@@ -2644,7 +2642,45 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 		}
 	} while (tryx != x || tryy != y);
 
+	if (return_stairjank)
+		*return_stairjank = stairjank;
+
+	return true;
+}
+
+//
+// P_CheckMove
+// Check if a P_TryMove would be successful.
+//
+boolean P_CheckMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
+{
+	boolean moveok;
+	mobj_t *hack = P_SpawnMobjFromMobj(thing, 0, 0, 0, MT_RAY);
+
+	hack->radius = thing->radius;
+	hack->height = thing->height;
+
+	moveok = increment_move(hack, x, y, allowdropoff, NULL);
+	P_RemoveMobj(hack);
+
+	return moveok;
+}
+
+//
+// P_TryMove
+// Attempt to move to a new position.
+//
+boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
+{
+	fixed_t oldx = thing->x;
+	fixed_t oldy = thing->y;
+	fixed_t startingonground = P_IsObjectOnGround(thing);
+	fixed_t stairjank = 0;
+	pslope_t *oldslope = thing->standingslope;
+
 	// The move is ok!
+	if (!increment_move(thing, x, y, allowdropoff, &stairjank))
+		return false;
 
 	// If it's a pushable object, check if anything is
 	// standing on top and move it, too.