I start up an application like STAR-CCM+, and click "File" menu and then I click the title bar(xpra window manager), but the "File" pop menu doesn't pull back ,and I drag title of xpra, the pop menu position remains unchanged. I click itself of application, the pop menu pulling back immediately. How can I do through xpra like this?
STAR-CCM+ is a proprietary application. Those are often doing something wrong when creating their windows and declaring the relationship between the menu windows and their parent window. (not using an override-redirect window, or not setting the transient-for hint) Sometimes they also fail to grab the keyboard or mouse, which may work on a low latency setup (ie: with a local window manager).
You can try posting the "-d window,focus,mouse,metadata,geometry" client log output, maybe it will show something, probably not. Fixing it without being able to test is likely to be impossible.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1786