Is there an existing program, available as a supported Debian package, and that works from within the GNOME desktop, that can show the specific UNIX process that created a specific X window? It's user interface should work in the same manner as the xwininfo
program, by allowing the user to select the specific window in question with the mouse button.
For comparison, on Microsoft Windows, there is a downloadable, free, utility called Process Explorer
that allows you to find the process associated with the window. The user clicks on the "Find Window" icon, then drags the mouse pointer over the window of interest, clicks on the left mouse button, and then the specific process is highlighted in the Process Explorer's main window.
I need to identify the process id at minimum. But, if there exists a tool that provides a GUI front-end that could show additional information akin to Process Explorer, that would be icing on the cake.