Op 4-11-2011 22:44, Richard Heck schreef:
Hey, all,
I've been working on making it possible to cancel an export in the
background. I have it working at least part of the way. The problem is
most obvious with XHTML export of the math manual. When we are doing
that, we will have to generate images for some of the math. This
involves starting an external program and waiting for the result. But
when I call cancel() on the QFutureWatcher we have from QtConcurrent,
this seems to kill the external program, and then the background thread
just sits there and waits for it never to finish.
Somehow, then, I need to interrupt this process. I tried deleting the
PreviewLoader before calling cancel(), but this crashes because the
background processing is still happening, and we think we still need a
loader. Anyone have any ideas?
I'm attaching the work done so far if anyone wants to play with it. The
first two patches change from using QtConcurrent::run to
QtConcurrent::mapped, because run() does not allow cancelling for some
reason. The real action is in the third patch, and then the fourth one
is my failed attempt to work around the problem just described.
Richard
It's not really clear to me what Qt means by cancelling a thread.
Without any knowledge of the code being executed in the thread, I don't
know how Qt can make the thread stop nicely.
My feeling says we should acquire all information about which files we
need to convert. Then we convert them one by one (or make it parallel)
and then after each processed file, we should check whether the thread
has been cancelled by the UI or not. If not, we continue. This would
also allow us to return progress information to the UI.
Vincent
