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Jay Helmericks
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 Posted: Mon Sep 22, 2003 6:35 pm Post subject: Help...Problem updating Form from thread |
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I'm trying to update a form from a thread and it is locking up the GUI. I
have a main form that spawns a thread that accepts TCP/IP connections. For
each incoming connection an new form is created to display the connection
info. The thread calls a syncronize method to update the form. It works if I
display the info on the main form, but when I write to the second form the
GUI freezes. The program still exicutes fine, but I can't click any buttons,
etc... The new form was created with new.
Jay
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Remy Lebeau (TeamB)
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| Posted: Mon Sep 22, 2003 6:47 pm Post subject: Re: Help...Problem updating Form from thread |
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"Jay Helmericks" <jayh (AT) gi (DOT) alaska.edu> wrote
| Quote: | I'm trying to update a form from a thread and it is locking up the GUI.
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Are you using the thread's Synchronize() method? If not, you need to. The
VCL is not thread-safe, you must use Synchronize() when accessing the main
VCL thread, particularly GUI elements.
| Quote: | I have a main form that spawns a thread that accepts TCP/IP connections.
For each incoming connection an new form is created to display the
connection
info. The thread calls a syncronize method to update the form. It works if
I
display the info on the main form, but when I write to the second form the
GUI freezes. The program still exicutes fine, but I can't click any
buttons,
etc... The new form was created with new.
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It sounds like you are creating the new forms from within the context of the
worker thread, not the main VCL thread. If so, then you should not be doing
that. VCL forms should always be used in the context of the main VCL
thread. Without seeing your actual code, I would surmise that the reason
your secondary forms are not responsive is because your worker thread is not
running its own message queue. Windows process messages in the same thread
that created them. If you are indeed creating your secondary forms within
the context of the worker thread, then the thread needs its own message
queue. However, even that is not a guarantee that it will work properly,
again because the VCL is not thread-safe. Your best bet is to just use
Synchronize() to force the form creation to occur in the main VCL thread
instead, and always use Synchronize() when updating any GUI elements,
whether they are in the MainForm or the secondary forms.
Gambit
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