Trouble using delegatecall to pass msg.sender to another contract

Question

I'm trying to mint an NFT token in contract B by calling a method on contract A, but I want msg.sender (in contract B) to be the address that calls the function on A, not contract A's address.

I thought this should work, but it doesn't. (it reverts on onlyOwner(), etherscan says: Although one or more Error Occurred [Reverted] Contract Execution Completed)

What am I doing wrong here? If I remove onlyOwner on safeMint, it works. So it's definitely a problem with delegatecall. Any help appreciated. Thanks.

    contract A {
        using Counters for Counters.Counter;
        using SafeMath for uint256;
        Counters.Counter private _tokenIds;
        address public nftContract;

        constructor(address _nftContract) public {
         nftContract = _nftContract;
        }

        function mintItem() public returns (uint256) {
                _tokenIds.increment();
        
                uint256 newItemId = _tokenIds.current();
    
    nftContract.delegatecall(abi.encodeWithSignature("safeMint(address,uint256)",msg.sender,newItemid));
                }
}

contract B is ERC721 {

    address public owner;
    modifier onlyOwner() {
        require(owner == msg.sender, "Ownable: caller is not the owner");
        _;
    }

    constructor(string memory name,string memory ticker,string memory uri) ERC721(name,ticker) public {
      owner = msg.sender;
      _setBaseURI(uri);
    }

    function safeMint(address to, uint256 tokenId) public onlyOwner{
      _mint(to, tokenId);
    }

}

Answer 1

You should not use delegatecall for your use case except if you want to modify contract A storage and not contract B. Generally, do not use delegatecall unless you really know what you are doing.

You should use tx.origin if you want the initial sender of the tx and not the function caller (here contract B).

You can modify your require like that:

modifier onlyOwner() {
     require(owner == msg.sender || owner == tx.origin, "Ownable: caller is not the owner");
     _;
}