I'd like to be able to share a URL (or a QR code thereof) prompting the user's wallet to open to call a function, and pass in some parameters.
There are a couple of EIPs - EIP67 and EIP681 - with detailed proposals for URLs that include data fields, but neither seems to be finalized, and some people are opposed to doing this for fear that users will be tricked into calling functions they do not intend.
However, according to this answer, at least MyEthereumWallet already support data in the URL: Can any information beside the address be encoded into QR code?
How widely do wallets other than MyEthereumWallet currently support data URLs? Relatedly, will wallets that don't support data tell the user that they don't support the URL they've received, or will they just silently ignore the data parameter and prompt the user to send a transaction without it?