[Qgis-developer] Which compiler should I use to build example code?

[Henri De Feraudy]

I can use my visual C++ environment to see this:
The message is due to a test 

if (!qApp) {
        qFatal("QWidget: Must construct a QApplication before a QPaintDevice");
        return;
inside a call to the constructor QWidgetPrivate::QWidgetPrivate(int version). If right mouse-click and I ask for the definition of qApp I get a message saying "resolve ambiguity:" and gives me a choice between
src\corelib\kernel\qcoreapplication.h
and
src\gui\kernel\qapplication.h
(am I right to suspect that this ambiguity is not good?)
anyway the call to QWidgetPrivate::QWidgetPrivate(int version) is inside
a call to
QDesktopWidgetPrivate::QDesktopWidgetPrivate()
inside a call to
QDesktopWidget::QDesktopWidget()
inside a call to
QApplication::desktop()
inside a call to
QGraphicsView::sizeHint()
inside a call to
QWidgetPrivate::adjustedSize()
inside a call to
QWidget::adjustSize()
inside a call to
QWidget::setVisible(bool visible)
inside the call of mypMapCanvas->setVisible(true); in the main

Hope this helps
Henri




--- On Mon, 11/2/09, Henri De Feraudy <feraudyh at yahoo.com> wrote:

> From: Henri De Feraudy <feraudyh at yahoo.com>
> Subject: Re: [Qgis-developer] Which compiler should I use to build example code?
> To: qgis-developer at lists.osgeo.org
> Date: Monday, November 2, 2009, 11:24 AM
> The problem does not go away if I
> comment out "#include <QWidget>"
> 
> --- On Mon, 11/2/09, Henri De Feraudy <feraudyh at yahoo.com>
> wrote:
> 
> > From: Henri De Feraudy <feraudyh at yahoo.com>
> > Subject: Re: [Qgis-developer] Which compiler should I
> use to build example code?
> > To: qgis-developer at lists.osgeo.org
> > Date: Monday, November 2, 2009, 11:14 AM
> > Hi
> >   I don’t get any visual debugger going but I do
> get
> > a long trace in a command window.  I wont let that
> stop
> > me. I have not changed the code yet appart from the
> obvious
> > path strings .
> > 
> > The last three lines of the trace are 
> > ..\..\..\..\..\src\core\qgsmaprenderer.cpp(424) :
> > (QgsMapRenderer::render) Rendering completed in
> (seconds):
> > 0.203
> > QApplication::regClass: Registering window class
> failed.
> > (The class exists already)
> > QApplication::qAppName: Please instantiate the
> QApplication
> > object first QWidget: Must construct a QApplication
> before a
> > QPaintDevice
> > 
> > Henri
> > 
> > --- On Sun, 11/1/09, Mailing Lists <lists at linfiniti.com>
> > wrote:
> > 
> > > From: Mailing Lists <lists at linfiniti.com>
> > > Subject: Re: Fw: Re: Fw: Re: [Qgis-developer]
> Which
> > compiler should I use to  build example code?
> > > To: "Henri De Feraudy" <feraudyh at yahoo.com>
> > > Cc: qgis-developer at lists.osgeo.org
> > > Date: Sunday, November 1, 2009, 10:12 PM
> > > Hi
> > > 
> > > On Sun, Nov 1, 2009 at 11:01 PM, Henri De
> Feraudy
> > <feraudyh at yahoo.com>
> > > wrote:
> > > 
> > > 
> > > > So, I wonder if the fact that I am using Qt
> 4.5
> > > (rather than 4.3) explains the problem
> > > >
> > > > program ...\timtut1.exe
> > > > file: global::qglobal.cpp
> > > > line 2030
> > > >
> > > > QWidget: Must construct a Qapplication
> before a
> > QPaint
> > > device.
> > > >
> > > 
> > > Try removing the QWidget include in main. But
> > > probably  you need to
> > > step through with the debugger to see what is
> really
> > going
> > > on.
> > > 
> > > BTW I wanted to apologise for my previous 'dont
> email
> > me
> > > privately
> > > only' message - my cell phone mail client showed
> me as
> > the
> > > only
> > > recipient but looking at my gmail client I see
> you
> > had
> > > indeed sent
> > > your reply to the list.
> > > 
> > > Best
> > > 
> > > Regards
> > > -- 
> > > Tim Sutton - QGIS Project Steering Committee
> Member
> > > (Release  Manager)
> > > ==============================================
> > > Please do not email me off-list with technical
> > > support questions. Using the lists will gain
> > > more exposure for your issues and the knowledge
> > > surrounding your issue will be shared with all.
> > > 
> > > Visit http://linfiniti.com to find out about:
> > >  * QGIS programming and support services
> > >  * Mapserver and PostGIS based hosting plans
> > >  * FOSS Consulting Services
> > > Skype: timlinux
> > > Irc: timlinux on #qgis at freenode.net
> > > ==============================================
> > >
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