x11/xvkbd 4.1 OpenBSD

xvkbd is a virtual (graphical) keyboard program for X Window System which provides facility to enter characters onto other clients (softwares) by clicking on a keyboard displayed on the screen. This may be used for systems without a hardware keyboard such as kiosk terminals or handheld devices. This program also has facility to send characters specified as the command line option to another client.

You need to enable the XTEST extension on your X server. When you use macOS xquartz, enable the XTEST extension by "defaults write org.xquartz.x11 enable_test_extentions -boolean true". See Xquartz(1).