C++ code with OpenGL on OSX using CGL/NSOpenGL without XCode? - c++

Question

I want to use CGL or NSOpenGL to create an OpenGL window without using XCode (compile with command line gcc). I am developing something that is cross platform, and I'd like to keep the code divergence to a minimum if I can! My codebase is fully C++ at the moment. Is this at all possible? I am new to OSX and I haven't touched objective C. I looked through the developer docs and grabbed some example files. They are all using xcode. I successfully compiled the source and linked with the right framework, but the whole app bundle, xib, and info.plist thing seems a bit over the top.

Answer 1

This is bare-bones as one can get:
// g++ glInfo.cpp -o glInfo.x -framework OpenGL
#include <OpenGL/OpenGL.h>
#include <OpenGL/gl3.h>
#include <stdio.h>
int main(int argc, char **argv)
{
CGLContextObj ctx;
CGLPixelFormatObj pix;
GLint npix;
CGLPixelFormatAttribute attribs[] = {
(CGLPixelFormatAttribute) 0
};
CGLChoosePixelFormat( attribs, &pix, &npix );
CGLCreateContext( pix, NULL, &ctx );
CGLSetCurrentContext( ctx );
printf("Vendor: %s\n", glGetString(GL_VENDOR) );
printf("Renderer: %s\n", glGetString(GL_RENDERER) );
printf("Version: %s\n", glGetString(GL_VERSION) );
printf("GLSL: %s\n", glGetString(GL_SHADING_LANGUAGE_VERSION));
return 0;
}

Answer 2

Both fltk and SDL should have enough AGL/CGL code. I've built and run cmdline GL apps on OS X with fltk-1.3.0. It uses the AGL sub-system however, which is deprecated. SDL uses CGL and NSOpenGL for its Quartz video layer: ./src/video/quartz
Use the obj-c flags for the compiler, if you need to build a src.m, and let the native g++, llvm-g++, clang++, or whatever, take care of the linking. You might need to add -framework CGL -framework OpenGL as well as ApplicationServices and Cocoa. A lot of the answer depends on what you mean by 'code divergence'.

Answer 3

You can build apps without using Xcode, but if you want users who aren't sys admins to use them, you'll need an app bundle (and hence .plist) and (unless it's a game) a user interface beyond what OpenGL offers. You don't need to create a .xib for your UI. You can do it all programmatically, though using .xibs is far easier for most things. Why don't you want to use the tools designed to help you? I'm not saying they're the best, but they beat using only a command-line interface. (Once you have an Xcode project for your app, though, you can build it from the command-line and even automate building it.)

Answer 4

Well, you can do it "by hand" (I used to do it at NeXTStep times), but it is a pain before it works for the first time.
XCode uses makefiles under the hood. You can find and adopt the makefiles in
/Developer/Makefiles
(pre XCode 4.3)
or for XCode 4.3 in
/Applications/Xcode.app/Contents/Developer/Makefiles
Good luck!

Answer 5

For the build system, I recommend CMake/CPack which will help you to keep it cross-platform and to build app bundles. For NSGL, it's possible using Obj-C++, but I don't have any code at hand.