Panorama fixes

src/game_map.cpp

@@ -362,7 +362,6 @@ void Game_Map::ScrollRight(int distance) {
 	int x = map_info.position_x;
 	AddScreenX(x, distance);
 	map_info.position_x = x;
-	Parallax::Scroll(distance, 0);
 	// Unused, except compatibility with RPG_RT
 	auto& pan_x = Main_Data::game_data.screen.pan_x;
 	const auto pan_limit_x = 20 * SCREEN_TILE_WIDTH;
@@ -373,7 +372,6 @@ void Game_Map::ScrollDown(int distance) {
 	int y = map_info.position_y;
 	AddScreenY(y, distance);
 	map_info.position_y = y;
-	Parallax::Scroll(0, distance);
 	// Unused, except compatibility with RPG_RT
 	auto& pan_y = Main_Data::game_data.screen.pan_y;
 	const auto pan_limit_y = 10 * SCREEN_TILE_WIDTH;
@@ -1161,7 +1159,6 @@ void Game_Map::SetPositionX(int x) {
 		x = std::max(0, std::min(map_width - SCREEN_WIDTH, x));
 	}
 	map_info.position_x = x;
-	Parallax::ResetPosition();
 }
 
 int Game_Map::GetPositionY() {
@@ -1180,7 +1177,6 @@ void Game_Map::SetPositionY(int y) {
 		y = std::max(0, std::min(map_height - SCREEN_HEIGHT, y));
 	}
 	map_info.position_y = y;
-	Parallax::ResetPosition();
 }
 
 Game_Map::RefreshMode Game_Map::GetNeedRefresh() {
@@ -1516,27 +1512,36 @@ void Game_Map::Parallax::Initialize(int width, int height) {
 	parallax_width = width;
 	parallax_height = height;
 
-	ResetPosition();
+	UpdatePosition(true);
 }
 
-void Game_Map::Parallax::ResetPosition() {
+void Game_Map::Parallax::UpdatePosition(bool init) {
 	Params params = GetParallaxParams();
 
-	if (params.scroll_horz)
-		parallax_x = -map_info.position_x / 2;
-	else if (GetWidth() > 20 && parallax_width > SCREEN_TARGET_WIDTH)
-		parallax_x = -std::min(map_info.position_x,
-			(map_info.position_x / (SCREEN_TILE_WIDTH / TILE_SIZE)) * (parallax_width - SCREEN_TARGET_WIDTH) / (GetWidth() - 20));
-	else
-		parallax_x = 0;
+	// RPG_RT bug:
+	// On loaded save games, RPG_RT will always reset
+	// parallax_x/y to 0 when the map is looping.
+	// We don't emulate this.
 
-	if (params.scroll_vert)
-		parallax_y = -map_info.position_y / 2;
-	else if (GetHeight() > 15 && parallax_height > SCREEN_TARGET_HEIGHT)
-		parallax_y = -std::min(map_info.position_y,
-			(map_info.position_y / (SCREEN_TILE_WIDTH / TILE_SIZE)) * (parallax_height - SCREEN_TARGET_HEIGHT) / (GetHeight() - 15));
-	else
-		parallax_y = 0;
+	if (init || !Game_Map::LoopHorizontal()) {
+		if (params.scroll_horz || LoopHorizontal())
+			parallax_x = -map_info.position_x / 2;
+		else if (GetWidth() > 20 && parallax_width > SCREEN_TARGET_WIDTH)
+			parallax_x = -std::min(map_info.position_x,
+					(map_info.position_x / (SCREEN_TILE_WIDTH / TILE_SIZE)) * (parallax_width - SCREEN_TARGET_WIDTH) / (GetWidth() - 20));
+		else
+			parallax_x = 0;
+	}
+
+	if (init || !Game_Map::LoopVertical()) {
+		if (params.scroll_vert || Game_Map::LoopVertical())
+			parallax_y = -map_info.position_y / 2;
+		else if (GetHeight() > 15 && parallax_height > SCREEN_TARGET_HEIGHT)
+			parallax_y = -std::min(map_info.position_y,
+					(map_info.position_y / (SCREEN_TILE_WIDTH / TILE_SIZE)) * (parallax_height - SCREEN_TARGET_HEIGHT) / (GetHeight() - 15));
+		else
+			parallax_y = 0;
+	}
 }
 
 void Game_Map::Parallax::Update() {
@@ -1545,6 +1550,8 @@ void Game_Map::Parallax::Update() {
 	if (params.name.empty())
 		return;
 
+	UpdatePosition();
+
 	auto scroll_amt = [](int speed) {
 		if (speed > 0) return 1 << (speed - 1);
 		if (speed < 0) return -(1 << (-speed - 1));
@@ -1564,43 +1571,6 @@ void Game_Map::Parallax::Update() {
 	}
 }
 
-/** Return the argument that is closer to zero. */
-static int closer_to_zero(int x, int y) {
-	return (std::abs(x) < std::abs(y)) ? x : y;
-}
-
-void Game_Map::Parallax::Scroll(int distance_right, int distance_down) {
-	Params params = GetParallaxParams();
-
-	// TODO: understand and then doc this function :)
-
-	if (params.scroll_vert) {
-		parallax_y -= distance_down / 2;
-	} else if (
-		!LoopVertical() &&
-		GetHeight() > 15 && parallax_height > SCREEN_TARGET_HEIGHT
-	) {
-		parallax_y -=
-			closer_to_zero(
-				distance_down,
-				distance_down * (parallax_height - SCREEN_TARGET_HEIGHT) / (GetHeight() - 15) / (SCREEN_TILE_WIDTH / TILE_SIZE)
-			);
-	}
-
-	if (params.scroll_horz) {
-		parallax_x -= distance_right / 2;
-	} else if (
-		!LoopHorizontal() &&
-		GetWidth() > 20 && parallax_width > SCREEN_TARGET_WIDTH
-	) {
-		parallax_x -=
-			closer_to_zero(
-				distance_right,
-				distance_right * (parallax_width - SCREEN_TARGET_WIDTH) / (GetWidth() - 20) / (SCREEN_TILE_WIDTH / TILE_SIZE)
-			);
-	}
-}
-
 void Game_Map::Parallax::ChangeBG(const Params& params) {
 	map_info.parallax_name = params.name;
 	map_info.parallax_horz = params.scroll_horz;

src/game_map.h

@@ -652,18 +652,16 @@ namespace Game_Map {
 		/** Call this when you find out the width and height of the BG. */
 		void Initialize(int width, int height);
 
-		/** Reset the x- and y- position of the BG (eg. after a teleport). */
-		void ResetPosition();
+		/**
+		 * Reset the x- and y- position of the BG.
+		 *
+		 * @param init if true will always reset position, even on looping maps
+		 */
+		void UpdatePosition(bool init = false);
 
 		/** Update autoscrolling BG (call every frame). */
 		void Update();
 
-		/**
-		 * Scrolls the BG by the correct amount when the screen scrolls
-		 * by the given distances.
-		 */
-		void Scroll(int distance_right, int distance_down);
-
 		/** Change BG (eg. with a "Change Parallax BG" command). */
 		void ChangeBG(const Params& params);