how to get task handle from window handle

Hello,

Me need to get the task handle (and then task name) from window under mouse pointer. How to do it?

I guess I should to use Wimp_SendMessage SWI and send User_Message_Acknowledge and then get task handle from the reply.
But which message code I should to use?

May we some better way exists?

From the PRM: “You can use User_Message_Acknowledge to discover the task handle of a given window/icon by calling Wimp_SendMessage with R0=19, your_ref = 0, and R2/R3 the window/icon handle(s). On exit R2 will contain the task handle of the owner, though no message would actually have been sent.” The message code field can be anything I believe.

Thank you Stuart!