Drracket prints definitions as blank pages

[chihyang]

This issue is related to racket/drracket#465. On Linux, "File > Print definitions... > [print dialogue opens]" generates empty pages. This is tested with both Racket 8.13 and 8.14 on multiple Linux distro. And it seems the problem has existed for a while. 8.13 and 8.14 are not the only two versions that suffer from it. My tests show that disabling asynchronous operation in the following line fixes this problem. The reason for that is still not clear. But it should be safe for now to just disable asynchronous printing.

gui/gui-lib/mred/private/wx/gtk/printer-dc.rkt

Line 168 in 03b7ffa

(gtk_print_operation_set_allow_async op-gtk #t)

[chihyang]

More info about the test: this issue has been reproduced with Racket 5.3.4 on Ubuntu 16.04. On Ubuntu 22.04, all versions starting from 6.6 can also reproduce it (older Racket failed to run on my machine). Not every print produces a blank file. Sometimes the printed file is incomplete with the last few pages blank; sometimes all pages are blank; sometimes the printed file is normal. All these make it look more like a synchronization problem. Since it can be reproduced on much older versions of Racket, disabling async mode of GTK printing should be a good option.