On 8/28/22 11:29 holm.h...@gmail.com wrote:

Hi,
Seems like there is a example already under examples/OpenGL3test

I however have problems linking the code under linux:
*** Compile OpenGL3test.cxx...

g++ -I.. -I.. -I/usr/local/include -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/freetype2 -I/usr/include/libpng16 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_THREAD_SAFE -D_REENTRANT -Wall -I. -c OpenGL3test.cxx -o OpenGL3test.o

*** Linking OpenGL3test...

g++ OpenGL3test.o ../lib/libfltk.a -lXrender -lXcursor -lXfixes -lXft -lfontconfig -lXinerama -pthread -lpthread -ldl -lm -lX11 ../lib/libfltk_images.a -ljpeg -lpng -lz ../lib/libfltk.a -lXrender -lXcursor -lXfixes -lXft -lfontconfig -lXinerama -pthread -lpthread -ldl -lm -lX11 -o OpenGL3test

OpenGL3test.o: In function `Fl_Gl_Window::mode(int)':

OpenGL3test.cxx:(.text._ZN12Fl_Gl_Window4modeEi[_ZN12Fl_Gl_Window4modeEi]+0x21): undefined reference to `Fl_Gl_Window::mode(int, int const*)'

OpenGL3test.o: In function `Fl_Gl_Window::pixel_w()':

OpenGL3test.cxx:(.text._ZN12Fl_Gl_Window7pixel_wEv[_ZN12Fl_Gl_Window7pixel_wEv]+0x14): undefined reference to `Fl_Gl_Window::pixels_per_unit()'

OpenGL3test.o: In function `Fl_Gl_Window::pixel_h()':

Any hints ?

Yes, please don't top-post in this group, it's hard to keep the context.
https://en.wikipedia.org/wiki/Posting_style#Top-posting

$ ../fltk-config --use-gl --compile OpenGL3test.cxx

[error messages removed]

Now copy the commandline and add -lGLEW:

$

This worked for me. YMMV.

Note: my build includes Cairo and more, your command may be much shorter.

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