Linking OpenGL Lib for MinGW and Visual Studio

stvokr

Hi all,

I am using (or I have to use) MinGW and Visual Studio compiler for the same project (Windows 10, Qt 5.6.1, MinGW 4.9.2, MSVC2015).
I can compile my project on linux, so this is not a problem.
I have to add tje OpenGL Lib to the project on Windows, otherwise it doesn't link. I used to use MSVC with the following setting:

win32:LIBS += opengl32.lib    # for visual studio

Now I want to use MinGW in addition to the MSVC2015. And therefore I have to change this code:

win32:LIBS += libopengl32     # for mingw

But this collides with the MSVC2015, because this isn't working for both linkers at the same time.

win32:LIBS += -Lopengl32      # doesn't work either, for both.

It's kind of funny, because on Linux "LIBS += libopengl32" is not necessary.

Is there any kind of seperation of compilers or kits in the pro file?
Does anyone have an idea?

Kind regards
Oliver

SGaist

Hi,

What do you mean by you have to use both for the same project ? Do you mean get it to compile entirely with each them or trying to build parts of your project with each ?

In any case, you shouldn't need to explicitly add the OpenGL library since Qt uses them already and will link your application accordingly.

stvokr

Hi,

I mean I have to compile the entire project with different compilers, so I have two builds of the project each running with another Qt runtime library.

I use OpenGL in my application like this.
My class:

class GLWidget : public QOpenGLWidget, protected QOpenGLFunctions

My code:

glLineWidth( 1.0f );
glColor3f( color.red() / 255.0, color.green() / 255.0, color.blue() / 255.0 );

glBegin( GL_LINE_STRIP );
for( int j = 0; j < polyline->count(); j++ )
{
    glVertex2f( polyline->at( j ).x(), polyline->at( j ).y() );
}
glEnd();

When I remove "win32:LIBS += opengl32.lib" I get these linker errors (and more). So I think it is necessary on Windows, but it is not on Linux. It would be nice if it would not be necessary for Windows.

plotter.obj : error LNK2019: unresolved external symbol __imp__glBegin@4 referenced in function "public: void __thiscall GLWidget::drawDistanceLine(class QPointF,class QPointF,class QColor,class QColor)" (?    drawDistanceLine@GLWidget@@QAEXVQPointF@@0VQColor@@1@Z)
plotter.obj : error LNK2019: unresolved external symbol __imp__glColor3f@12 referenced in function "public: void __thiscall GLWidget::drawDistanceLine(class QPointF,class QPointF,class QColor,class QColor)" (?drawDistanceLine@GLWidget@@QAEXVQPointF@@0VQColor@@1@Z)

Any explanations?

SGaist

AFAIK, glBegin is part of the fixed pipeline so if you want to use it you need to inherit from another set of QOpenGLFunctions.

stvokr

Thanks,

I inherit from QOpenGLFunctions_3_0 and that works for me.