Fix airship descent mid-move

Part of EasyRPG#1429. RPG_RT allows you to land the airship
from an event while the player/airship is moving as part of a move
route.

In RPG_RT, this causes graphical glitches as the descent causes
the airship sprite to warp to the tile and change direction before
finishing its walk animation. This set of changes fixes those
graphical glitches in Player while still allowing the same
event behavior to occur.

src/game_vehicle.cpp

@@ -202,22 +202,34 @@ void Game_Vehicle::GetOff() {
 	} else {
 		Main_Data::game_player->UnboardingFinished();
 	}
-	SetDirection(Left);
-	SetSpriteDirection(Left);
+	// Get off airship can be trigger while airship is moving. Don't break the animation
+	// until its finished.
+	if (type != Airship || (!IsMoving() && !IsJumping())) {
+		SetDirection(Left);
+		SetSpriteDirection(Left);
+	}
 }
 
 bool Game_Vehicle::IsInUse() const {
 	return Main_Data::game_player->GetVehicle() == this;
 }
 
 void Game_Vehicle::SyncWithPlayer() {
-	if (!IsInUse() || IsAscending() || IsDescending())
+	if (!IsInUse()) {
 		return;
+	}
 	SetX(Main_Data::game_player->GetX());
 	SetY(Main_Data::game_player->GetY());
 	SetRemainingStep(Main_Data::game_player->GetRemainingStep());
-	SetDirection(Main_Data::game_player->GetDirection());
-	SetSpriteDirection(Main_Data::game_player->GetSpriteDirection());
+	if (!IsAscendingOrDescending()) {
+		SetDirection(Main_Data::game_player->GetDirection());
+		SetSpriteDirection(Main_Data::game_player->GetSpriteDirection());
+	} else {
+		if (!IsMoving() && !IsJumping()) {
+			SetDirection(Left);
+			SetSpriteDirection(Left);
+		}
+	}
 }
 
 int Game_Vehicle::GetAltitude() const {
@@ -267,20 +279,22 @@ void Game_Vehicle::Update() {
 	}
 
 	if (type == Airship) {
-		if (IsAscending()) {
-			data()->remaining_ascent = data()->remaining_ascent - 8;
-			SetAnimFrame(AnimFrame::Frame_middle);
-		} else if (IsDescending()) {
-			SetAnimFrame(AnimFrame::Frame_middle);
-			data()->remaining_descent = data()->remaining_descent - 8;
-			if (!IsDescending()) {
-				if (CanLand()) {
-					Main_Data::game_player->UnboardingFinished();
-					SetFlying(false);
-					Main_Data::game_player->SetFlying(false);
-				} else {
-					// Can't land here, ascend again
-					data()->remaining_ascent = SCREEN_TILE_SIZE;
+		if (!IsMoving() && !IsJumping()) {
+			if (IsAscending()) {
+				data()->remaining_ascent = data()->remaining_ascent - 8;
+				SetAnimFrame(AnimFrame::Frame_middle);
+			} else if (IsDescending()) {
+				SetAnimFrame(AnimFrame::Frame_middle);
+				data()->remaining_descent = data()->remaining_descent - 8;
+				if (!IsDescending()) {
+					if (CanLand()) {
+						Main_Data::game_player->UnboardingFinished();
+						SetFlying(false);
+						Main_Data::game_player->SetFlying(false);
+					} else {
+						// Can't land here, ascend again
+						data()->remaining_ascent = SCREEN_TILE_SIZE;
+					}
 				}
 			}
 		}