QAbstractOpenGLFunctions, QOpenGLFunctions_2_0 linker errors

Grisha

Hi, I've recently attempted to switch to 5.1, and use the QAbstractOpenGLFunctions method of getting OpenGL extensions. I'm trying out QOpenGLFunctions_2_0 for now, just to start off, and everything compiles fine. I'm trying to build a 32-bit app in MSVC 2012 on windows 7.

The problem is the linker throws an error for every single QOpenGLFunctions_2_0 function I attempt to use. I've tried including every single debug .lib file I could, and still get the linker error. What .lib should I have/link against to make this work?

Thanks!

ZapB

Hi, hmm this sounds weird. Can you paste the exact output please? Also maybe post the relevant piece of code too.

Thanks

Grisha

Sorry for the late reply, I was not in the office during the weekend.

I recreated this issue by starting a new project using the new QT project interface in VS2012. Here is the error:

test.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: void __thiscall QOpenGLFunctions_2_0::glUniformMatrix4fv(int,int,unsigned char,float const *)" (_imp?glUniformMatrix4fv@QOpenGLFunctions_2_0@@QAEXHHEPBM@Z) referenced in function "public: __thiscall test::test(class QWidget *)" (??0test@@QAE@PAVQWidget@@@Z)

Here is the relevant piece of code (it does nothing, just demonstrates the problem):
#include "test.h"

#undef QT_OPENGL_ES_2
#include <qopenglfunctions_2_0>

test::test(QWidget *parent)
: QMainWindow(parent)
{
ui.setupUi(this);

QOpenGLFunctions_2_0* Func = dynamic_cast<QOpenGLFunctions_2_0*>(QOpenGLContext::currentContext()->versionFunctions());
Func->glUniformMatrix4fv(0, 0, false, NULL);

}

test::~test()
{

}

SGaist

Hi,

Looking at the "QOpenGLFunctions":http://qt-project.org/doc/qt-5.0/qtgui/qopenglfunctions.html documentation, it seems that you are not using QOpenGLFunctions the correct way. There might be the problem

ZapB

All of the QOpenGLFunctions_<MAJOR>_<MINOR>[_PROFILE] classes are part of the QtGui library. Are you sure you are linking to QtGui?

To obtain and initialise the functions object I usually use code like this:

In class declaration:
@
QOpenGLFunctions_2_0* m_funcs;
@

In implementation, typically in some init function:
@
// Assumign you have a current QOpenGLContext
m_funcs = m_context->versionFunctions<QOpenGLFunctions_2_0>()
if (!m_funcs)
qFatal("Could not obtain OpenGL 2.0 functions");
m_funcs->initializeOpenGLFunctions();

// Then use it
m_funcs->glUniformMatrix4fv(...)
@

Grisha

Yes, I double checked just now and I was indeed linking against QtGui. Also to be sure I tried linking against every .lib in the bin directory, and the error persists. My QT context is a downloaded 5.1.0 binary for windows 7, x86, msvc2012.

ZapB

Can you post a small compilable example that I can use to try to reproduce the problem please?

Grisha

Here is a link to a google drive shared rar file with the whole project:
https://docs.google.com/file/d/0B0z5KZUIEVmXbjZvZkc3SkhtTUk/edit?pli=1

In this case, I've set the project file to point to the downloaded binary version of QT (qt-windows-opensource-5.1.0-msvc2012-x86-offline.exe) I installed. I've also been compiling various QT versions, and found that when I compile QT myself, this problem disappears, so I can just use that for now if this is a low priority problem.

ZapB

Ah I think I see the issue. I think you are using a version of Qt compiled against ANGLE which only provides OpenGL ES 2 compatibility rather than full OpenGL.

Please try one of the pre-compiled packages that has "opengl" in the filename.

Grisha

Thanks, that solved my issue.