bug#61667: 29.0.60; Failure to redisplay

[Dmitry Gutov]

On 22/02/2023 04:41, Po Lu via Bug reports for GNU Emacs, the Swiss army 
knife of text editors wrote:
> In addition, does this happen on a build without Cairo?  One theory is
> that an event somehow arrives during redisplay and causes
> `x_flush_dirty_back_buffer_on' to be called, and the Cairo code is
> missing a call to `x_mark_frame_dirty' somewhere, which causes the next
> buffer flip to not take effect.

It reproduces without Cairo, yes.

With more or less the same frequency.