Correctly calculate the screen dimensions when the resolution is not …

…dividable by the tile size.

Rename the screen variables in the Parallax code as the same name (var shadowing) is confusing.

Fixes incorrect scrolling of the map in Beloved Rapture

src/game_map.cpp

@@ -104,9 +104,6 @@ void Game_Map::OnContinueFromBattle() {
 static Game_Map::Parallax::Params GetParallaxParams();
 
 void Game_Map::Init() {
-	screen_width = (Player::screen_width / 16) * SCREEN_TILE_SIZE;
-	screen_height = (Player::screen_height / 16) * SCREEN_TILE_SIZE;
-
 	Dispose();
 
 	map_info = {};
@@ -156,8 +153,8 @@ int Game_Map::GetMapSaveCount() {
 void Game_Map::Setup(std::unique_ptr<lcf::rpg::Map> map_in) {
 	Dispose();
 
-	screen_width = (Player::screen_width / 16) * SCREEN_TILE_SIZE;
-	screen_height = (Player::screen_height / 16) * SCREEN_TILE_SIZE;
+	screen_width = (Player::screen_width / 16.0) * SCREEN_TILE_SIZE;
+	screen_height = (Player::screen_height / 16.0) * SCREEN_TILE_SIZE;
 
 	map = std::move(map_in);
 
@@ -637,7 +634,7 @@ void Game_Map::Scroll(int dx, int dy) {
 // that acc changed by.
 static void ClampingAdd(int low, int high, int& acc, int& inc) {
 	int original_acc = acc;
-	acc = std::max(low, std::min(high, acc + inc));
+	acc = std::clamp(acc + inc, low, high);
 	inc = acc - original_acc;
 }
 
@@ -1651,7 +1648,7 @@ void Game_Map::SetPositionX(int x, bool reset_panorama) {
 	if (LoopHorizontal()) {
 		x = Utils::PositiveModulo(x, map_width);
 	} else {
-		x = std::max(0, std::min(map_width - screen_width, x));
+		x = std::clamp(x, 0, map_width - screen_width);
 	}
 	map_info.position_x = x;
 	if (reset_panorama) {
@@ -1673,7 +1670,7 @@ void Game_Map::SetPositionY(int y, bool reset_panorama) {
 	if (LoopVertical()) {
 		y = Utils::PositiveModulo(y, map_height);
 	} else {
-		y = std::max(0, std::min(map_height - screen_height, y));
+		y = std::clamp(y, 0, map_height - screen_height);
 	}
 	map_info.position_y = y;
 	if (reset_panorama) {
@@ -2037,19 +2034,19 @@ void Game_Map::Parallax::ResetPositionX() {
 	parallax_fake_x = false;
 
 	if (!params.scroll_horz && !LoopHorizontal()) {
-		int screen_width = Player::screen_width;
+		int pan_screen_width = Player::screen_width;
 		if (Player::game_config.fake_resolution.Get()) {
-			screen_width = SCREEN_TARGET_WIDTH;
+			pan_screen_width = SCREEN_TARGET_WIDTH;
 		}
 
-		int tiles_per_screen = screen_width / TILE_SIZE;
-		if (screen_width % TILE_SIZE != 0) {
+		int tiles_per_screen = pan_screen_width / TILE_SIZE;
+		if (pan_screen_width % TILE_SIZE != 0) {
 			++tiles_per_screen;
 		}
 
-		if (GetTilesX() > tiles_per_screen && parallax_width > screen_width) {
+		if (GetTilesX() > tiles_per_screen && parallax_width > pan_screen_width) {
 			const int w = (GetTilesX() - tiles_per_screen) * TILE_SIZE;
-			const int ph = 2 * std::min(w, parallax_width - screen_width) * map_info.position_x / w;
+			const int ph = 2 * std::min(w, parallax_width - pan_screen_width) * map_info.position_x / w;
 			if (Player::IsRPG2k()) {
 				SetPositionX(ph);
 			} else {
@@ -2075,19 +2072,19 @@ void Game_Map::Parallax::ResetPositionY() {
 	parallax_fake_y = false;
 
 	if (!params.scroll_vert && !Game_Map::LoopVertical()) {
-		int screen_height = Player::screen_height;
+		int pan_screen_height = Player::screen_height;
 		if (Player::game_config.fake_resolution.Get()) {
-			screen_height = SCREEN_TARGET_HEIGHT;
+			pan_screen_height = SCREEN_TARGET_HEIGHT;
 		}
 
-		int tiles_per_screen = screen_height / TILE_SIZE;
-		if (screen_height % TILE_SIZE != 0) {
+		int tiles_per_screen = pan_screen_height / TILE_SIZE;
+		if (pan_screen_height % TILE_SIZE != 0) {
 			++tiles_per_screen;
 		}
 
-		if (GetTilesY() > tiles_per_screen && parallax_height > screen_height) {
+		if (GetTilesY() > tiles_per_screen && parallax_height > pan_screen_height) {
 			const int h = (GetTilesY() - tiles_per_screen) * TILE_SIZE;
-			const int pv = 2 * std::min(h, parallax_height - screen_height) * map_info.position_y / h;
+			const int pv = 2 * std::min(h, parallax_height - pan_screen_height) * map_info.position_y / h;
 			SetPositionY(pv);
 		} else {
 			panorama.pan_y = 0;