RE: [ROOT] ROOT/QtROOT within a multithreaded Qt application QUIC K UPDATE

From: Colley, Tony (Tony.Colley@itt.com)
Date: Tue Jan 08 2002 - 15:49:13 MET


Fellow rooters,

My recent email may have been slightly misleading. Doing a "new TCanvas" is
a thread other than the ROOT event loop thread does not immediately cause a
crash, but it does always ultimately lead to a crash. However, calling
TCanvas::Update, TGraph::GetXaxis, and TGraph::GetYaxis do immediately cause
a crash.

Sorry for any confusion.
Tony Colley

-----Original Message-----
From: Colley, Tony 
Sent: Tuesday, January 08, 2002 09:37
To: 'roottalk@pcroot.cern.ch'
Subject: RE: [ROOT] ROOT/QtROOT within a multithreaded Qt application


Fellow rooters,

I just wanted to provide an update on this issue since one of you may have
to deal with it someday.

To recap quickly, the problem occurred when merging an existing
multithreaded application with ROOT (as a compiled program... I don't know
if the following will work using CINT). In my case, the multithreaded
application used Qt for its GUI.

When one tries to do certain TCanvas operations in a thread different than
the thread which contains the ROOT Event Processing loop (i.e. where the
call to gSystem->DispatchOneEvent is made, in my case this is the main
thread), the program crashes with "***BREAK*** segmentation violation" and
occassionally "<RootX11ErrorHandler>" messages.

[remainder of original message removed for brevity]

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