qt4 programming

Four · 02-09-2007, 09:15 PM

I recently got qt4 on kubuntu and ran into a problem compiling a hello world tutorial

Code:

g++ -c -pipe -g -Wall -W -D_REENTRANT  -DQT_GUI_LIB -DQT_CORE_LIB -I/usr/share/qt4/mkspecs/linux-g++ -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I. -I. -o main.o main.cpp
main.cpp: In function ‘int main(int, char**)’:
main.cpp:12: error: ‘class QApplication’ has no member named ‘setMainWidget’
make: *** [main.o] Error 1

What else do I need? I only downloaded the qt4 packages, I selected the qt4-dev package (or similar) when installing. Obviously other packages came with it like the one for qmake.

Thank you

Four · 02-09-2007, 09:30 PM

I noticed the tutorial is for 3.0 I read the documentation for 4.0 and fixed the problem. It turns out that function is no longer supported and is handled slightly differently see here for details (QApplication section)

Nextly how do I compile an optomized version of QT. At school by default the qmake generates a make file that sets -O2 and other related optimizations. But for me at home I get the qt debuging libraries instead. Which is ok, but I want to be able to change qmake some how to produce optomized code (But not neccessarly by default). How do I do this?

qmake --help provided no helpfull resources on this (or atleast of what I understood)

Edit:
Sorry about this thread. Well anyway (Iam a newb with qt

) I found out how to do it. qmake documentation was not first on google but I found it. To make it put optimizations just do in the project file

CONFIG -= debug
CONFIG += release
and it will do the trick

.

The docs are here (QT 3.1) however usable usable for 4.0. I don't know how much is changed.
Thank you.

matthewg42 · 02-09-2007, 09:57 PM

I think all you need to do it add/remove a line in the yourproject.pro, like this:

Code:

CONFIG += qt debug

If this exists, you get debugging compilation options, else not. You need to re-run qmake after the change.

graemef · 02-09-2007, 11:18 PM

There are a lot of differences between QT 3 and QT 4.So I would suggest that you point your browser at the QT 4 documentation. Or even better, install the QT4 documentation on your computer.

Four · 02-10-2007, 10:15 AM

Thanks.

This is cool

I can't wait to start utilizing OpenGL in QT. Soon I will make things that I can share with all my windows and linux friends

.