Make string to v3f parsing consistent, replace core.setting_get_pos() by core.settings:get_pos() (#15438)

Co-authored-by: sfan5 <sfan5@live.de>
Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>

src/util/string.cpp

@@ -1068,14 +1068,41 @@ void safe_print_string(std::ostream &os, std::string_view str)
 	os.setf(flags);
 }
 
-
-v3f str_to_v3f(std::string_view str)
+std::optional<v3f> str_to_v3f(std::string_view str)
 {
-	v3f value;
-	Strfnd f(str);
-	f.next("(");
-	value.X = stof(f.next(","));
-	value.Y = stof(f.next(","));
-	value.Z = stof(f.next(")"));
-	return value;
+    str = trim(str);
+
+    if (str.empty())
+        return std::nullopt;
+
+    // Strip parentheses if they exist
+    if (str.front() == '(' && str.back() == ')') {
+        str.remove_prefix(1);
+        str.remove_suffix(1);
+        str = trim(str);
+    }
+
+    std::istringstream iss((std::string(str)));
+
+    const auto expect_delimiter = [&]() {
+        const auto c = iss.get();
+        return c == ' ' || c == ',';
+    };
+
+    v3f value;
+    if (!(iss >> value.X))
+        return std::nullopt;
+    if (!expect_delimiter())
+        return std::nullopt;
+    if (!(iss >> value.Y))
+        return std::nullopt;
+    if (!expect_delimiter())
+        return std::nullopt;
+    if (!(iss >> value.Z))
+        return std::nullopt;
+
+    if (!iss.eof())
+        return std::nullopt;
+
+    return value;
 }