Basic skeleton for a C OpenGL program on OSX

What's the bare skeleton to get a triangle drawn on an OpenGL window in C on OSX? I've gone through the tutorials at Nehe and tried to get it working, but the CreateGLWindow seems hopelessly tied to win32.

I want to stick to just opengl and glut, etc. I'll be eventually wrapping this in scheme, but I'd like to have a firmer understanding at the c-level beforehand.

Here's what I have thus far:

#include <OpenGL/gl.h>// Header File For The OpenGL32 Library
#include <OpenGL/glu.h>// Header File For The GLu32 Library
#include <GLUT/glut.h>// Header File For The GLut Library

#define kWindowWidth 400;
#define kWindowHeight 300;

HGLRC hRC=NULL;// Permanent Rendering Context
HDC             hDC=NULL;// Private GDI Device Context
HWND            hWnd=NULL;// Holds Our Window Handle
HINSTANCE       hInstance;// Holds The Instance Of The Application

LRESULTCALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);// Declaration For WndProc

boolkeys[256];// Array Used For The Keyboard Routine
boolactive=TRUE;// Window Active Flag Set To TRUE By Default
boolfullscreen=TRUE;// Fullscreen Flag Set To Fullscreen Mode By Default

GLvoid ReSizeGLScene(GLsizei width, GLsizei height)// Resize And Initialize The GL Window
{
  if (height==0)// Prevent A Divide By Zero By
    {
      height=1;// Making Height Equal One
    }

  glViewport(0, 0, width, height);// Reset The Current Viewport
  glMatrixMode(GL_PROJECTION);// Select The Projection Matrix
  glLoadIdentity();// Reset The Projection Matrix

  // Calculate The Aspect Ratio Of The Window
  gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

  glMatrixMode(GL_MODELVIEW);// Select The Modelview Matrix
  glLoadIdentity();// Reset The Modelview Matrix
}

int InitGL(GLvoid)// All Setup For OpenGL Goes Here
{
  glShadeModel(GL_SMOOTH);// Enables Smooth Shading
  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);// Black Background
  glClearDepth(1.0f);// Depth Buffer Setup
  glEnable(GL_DEPTH_TEST);// Enables Depth Testing
  glDepthFunc(GL_LEQUAL);// The Type Of Depth Test To Do
  glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);// Really Nice Perspective Calculations

  return TRUE;// Initialization Went OK
}

int DrawGLScene(GLvoid)// Here's Where We Do All The Drawing
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear The Screen And The Depth Buffer
  glLoadIdentity();// Reset The Current Modelview Matrix
  return TRUE;// Everything Went OK
}

GLvoid KillGLWindow(GLvoid)// Properly Kill The Window
{
  if (fullscreen)// Are We In Fullscreen Mode?
    {
      ChangeDisplaySettings(NULL,0);// If So Switch Back To The Desktop
      ShowCursor(TRUE);// Show Mouse Pointer
    }

  if (hRC)// Do We Have A Rendering Context?
    {
      if (!wglMakeCurrent(NULL,NULL))// Are We Able To Release The DC And RC Contexts?
        {
          MessageBox(NULL,"Release Of DC And RC Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
        }
      if (!wglDeleteContext(hRC))// Are We Able To Delete The RC?
        {
          MessageBox(NULL,"Release Rendering Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
        }
      hRC=NULL;// Set RC To NULL
    }
  if (hDC && !ReleaseDC(hWnd,hDC))// Are We Able To Release The DC
    {
      MessageBox(NULL,"Release Device Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
      hDC=NULL;// Set DC To NULL
    }

  if (hWnd && !DestroyWindow(hWnd))// Are We Able To Destroy The Window?
    {
      MessageBox(NULL,"Could Not Release hWnd.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
      hWnd=NULL;// Set hWnd To NULL
    }

  if (!UnregisterClass("OpenGL",hInstance))// Are We Able To Unregister Class
    {
      MessageBox(NULL,"Could Not Unregister Class.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
      hInstance=NULL;// Set hInstance To NULL
    }
}

BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)
{
  GLuintPixelFormat;// Holds The Results After Searching For A Match
  WNDCLASSwc;// Windows Class Structure

  DWORDdwExStyle;// Window Extended Style
  DWORDdwStyle;// Window Style

  RECT WindowRect;// Grabs Rectangle Upper Left / Lower Right Values
  WindowRect.left=(long)0;// Set Left Value To 0
  WindowRect.right=(long)width;// Set Right Value To Requested Width
  WindowRect.top=(long)0;// Set Top Value To 0
  WindowRect.bottom=(long)height;// Set Bottom Value To Requested Height

  fullscreen=fullscreenflag;// Set The Global Fullscreen Flag

  hInstance= GetModuleHandle(NULL);// Grab An Instance For Our Window
  wc.style= CS_HREDRAW | CS_VREDRAW | CS_OWNDC;// Redraw On Move, And Own DC For Window
  wc.lpfnWndProc= (WNDPROC) WndProc;// WndProc Handles Messages
  wc.cbClsExtra= 0;// No Extra Window Data
  wc.cbWndExtra= 0;// No Extra Window Data
  wc.hInstance= hInstance;// Set The Instance
  wc.hIcon= LoadIcon(NULL, IDI_WINLOGO);// Load The Default Icon
  wc.hCursor= LoadCursor(NULL, IDC_ARROW);// Load The Arrow Pointer
  wc.hbrBackground= NULL;// No Background Required For GL
  wc.lpszMenuName= NULL;// We Don't Want A Menu
  wc.lpszClassName= "OpenGL";// Set The Class Name

  if (!RegisterClass(&wc))// Attempt To Register The Window Class
    {
      MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Exit And Return FALSE
    }

  if (fullscreen)// Attempt Fullscreen Mode?
    {
      DEVMODE dmScreenSettings;// Device Mode
      memset(&dmScreenSettings,0,sizeof(dmScreenSettings));// Makes Sure Memory's Cleared
      dmScreenSettings.dmSize=sizeof(dmScreenSettings);// Size Of The Devmode Structure
      dmScreenSettings.dmPelsWidth= width;// Selected Screen Width
      dmScreenSettings.dmPelsHeight= height;// Selected Screen Height
      dmScreenSettings.dmBitsPerPel= bits;// Selected Bits Per Pixel
      dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;

      // Try To Set Selected Mode And Get Results.  NOTE: CDS_FULLSCREEN Gets Rid Of Start Bar.
      if (ChangeDisplaySettings(&dmScreenSettings,CDS_FULLSCREEN)!=DISP_CHANGE_SUCCESSFUL)
        {
          // If The Mode Fails, Offer Two Options.  Quit Or Run In A Window.
          if (MessageBox(NULL,"The Requested Fullscreen Mode Is Not Supported By\nYour Video Card. Use Windowed Mode Instead?","NeHe GL",MB_YESNO|MB_ICONEXCLAMATION)==IDYES)
            {
              fullscreen=FALSE;// Select Windowed Mode (Fullscreen=FALSE)
            }
          else
            {
              // Pop Up A Message Box Letting User Know The Program Is Closing.
              MessageBox(NULL,"Program Will Now Close.","ERROR",MB_OK|MB_ICONSTOP);
              return FALSE;// Exit And Return FALSE
            }
        }
    }

  if (fullscreen)// Are We Still In Fullscreen Mode?
    {
      dwExStyle=WS_EX_APPWINDOW;// Window Extended Style
      dwStyle=WS_POPUP;// Windows Style
      ShowCursor(FALSE);// Hide Mouse Pointer
    }
  else
    {
      dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;// Window Extended Style
      dwStyle=WS_OVERLAPPEDWINDOW;// Windows Style
    }

  AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle);// Adjust Window To True Requested Size

  if (!(hWnd=CreateWindowEx(dwExStyle,// Extended Style For The Window
                            "OpenGL",// Class Name
                            title,// Window Title
                            WS_CLIPSIBLINGS |// Required Window Style
                            WS_CLIPCHILDREN |// Required Window Style
                            dwStyle,// Selected Window Style
                            0, 0,// Window Position
                            WindowRect.right-WindowRect.left,// Calculate Adjusted Window Width
                            WindowRect.bottom-WindowRect.top,// Calculate Adjusted Window Height
                            NULL,// No Parent Window
                            NULL,// No Menu
            开发者_如何学运维                hInstance,// Instance
                            NULL)))// Don't Pass Anything To WM_CREATE
    {
      KillGLWindow();// Reset The Display
      MessageBox(NULL,"Window Creation Error.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Return FALSE
    }

  staticPIXELFORMATDESCRIPTOR pfd=// pfd Tells Windows How We Want Things To Be
    {
      sizeof(PIXELFORMATDESCRIPTOR),// Size Of This Pixel Format Descriptor
      1,// Version Number
      PFD_DRAW_TO_WINDOW |// Format Must Support Window
      PFD_SUPPORT_OPENGL |// Format Must Support OpenGL
      PFD_DOUBLEBUFFER,// Must Support Double Buffering
      PFD_TYPE_RGBA,// Request An RGBA Format
      bits,// Select Our Color Depth
      0, 0, 0, 0, 0, 0,// Color Bits Ignored
      0,// No Alpha Buffer
      0,// Shift Bit Ignored
      0,// No Accumulation Buffer
      0, 0, 0, 0,// Accumulation Bits Ignored
      16,// 16Bit Z-Buffer (Depth Buffer)
      0,// No Stencil Buffer
      0,// No Auxiliary Buffer
      PFD_MAIN_PLANE,// Main Drawing Layer
      0,// Reserved
      0, 0, 0// Layer Masks Ignored
    };

  if (!(hDC=GetDC(hWnd)))// Did We Get A Device Context?
    {
      KillGLWindow();// Reset The Display
      MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Return FALSE
    }

  if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd)))// Did Windows Find A Matching Pixel Format?
    {
      KillGLWindow();// Reset The Display
      MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Return FALSE
    }

  if(!SetPixelFormat(hDC,PixelFormat,&pfd))// Are We Able To Set The Pixel Format?
    {
      KillGLWindow();// Reset The Display
      MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Return FALSE
    }

  if (!(hRC=wglCreateContext(hDC)))// Are We Able To Get A Rendering Context?
    {
      KillGLWindow();// Reset The Display
      MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Return FALSE
    }

  if(!wglMakeCurrent(hDC,hRC))// Try To Activate The Rendering Context
    {
      KillGLWindow();// Reset The Display
      MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Return FALSE
    }

  ShowWindow(hWnd,SW_SHOW);// Show The Window
  SetForegroundWindow(hWnd);// Slightly Higher Priority
  SetFocus(hWnd);// Sets Keyboard Focus To The Window
  ReSizeGLScene(width, height);// Set Up Our Perspective GL Screen

  if (!InitGL())// Initialize Our Newly Created GL Window
    {
      KillGLWindow();// Reset The Display
      MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      return FALSE;// Return FALSE
    }
  return TRUE;// Success
}

LRESULT CALLBACK WndProc(HWNDhWnd,// Handle For This Window
                         UINTuMsg,// Message For This Window
                         WPARAMwParam,// Additional Message Information
                         LPARAMlParam)// Additional Message Information
{
  switch (uMsg)// Check For Windows Messages
    {
    case WM_ACTIVATE:// Watch For Window Activate Message
      {
        if (!HIWORD(wParam))// Check Minimization State
          {
            active=TRUE;// Program Is Active
          }
        else
          {
            active=FALSE;// Program Is No Longer Active
          }

        return 0;// Return To The Message Loop
      }
    case WM_SYSCOMMAND:// Intercept System Commands
      {
        switch (wParam)// Check System Calls
          {
          case SC_SCREENSAVE:// Screensaver Trying To Start?
          case SC_MONITORPOWER:// Monitor Trying To Enter Powersave?
            return 0;// Prevent From Happening
          }
        break;// Exit
      }
    case WM_CLOSE:// Did We Receive A Close Message?
      {
        PostQuitMessage(0);// Send A Quit Message
        return 0;// Jump Back
      }
    case WM_KEYDOWN:// Is A Key Being Held Down?
      {
        keys[wParam] = TRUE;// If So, Mark It As TRUE
        return 0;// Jump Back
      }
    case WM_KEYUP:// Has A Key Been Released?
      {
        keys[wParam] = FALSE;// If So, Mark It As FALSE
        return 0;// Jump Back
      }
    case WM_SIZE:// Resize The OpenGL Window
      {
        ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));// LoWord=Width, HiWord=Height
        return 0;// Jump Back
      }
    }
  // Pass All Unhandled Messages To DefWindowProc
  return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

GLvoid InitGL(GLvoid);
GLvoid DrawGLScene(GLvoid);
GLvoid ReSizeGLScene(int Width, int Height);

int main(int argc, char** argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize (kWindowWidth, kWindowHeight);
  glutInitWindowPosition (100, 100);
  glutCreateWindow (argv[0]);

  InitGL();

  glutDisplayFunc(DrawGLScene);
  glutReshapeFunc(ReSizeGLScene);

  glutMainLoop();

  return 0;
}

---

As far as I can tell, the NeHe tutorials are specifically for windows and are great for higher level stuff. However, when it comes to the basics, They can become overcomplicated. So here is a simple skeletal program for rendering a triangle using only glut and opengl functionality. If you want to be Apple specific, try using agl.

// The OpenGL libraries, make sure to include the GLUT and OpenGL frameworks
#include <GLUT/glut.h>
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>

// This is just an example using basic glut functionality.
// If you want specific Apple functionality, look up AGL

void init() // Called before main loop to set up the program
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glEnable(GL_DEPTH_TEST);
    glShadeModel(GL_SMOOTH);
}

// Called at the start of the program, after a glutPostRedisplay() and during idle
// to display a frame
void display()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

    glBegin(GL_TRIANGLES);
        glVertex3f(0.0, 0.0, -10.0);
        glVertex3f(1.0, 0.0, -10.0);
        glVertex3f(0.0, 1.0, -10.0);
    glEnd();

    glutSwapBuffers();
}

// Called every time a window is resized to resize the projection matrix
void reshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glFrustum(-0.1, 0.1, -float(h)/(10.0*float(w)), float(h)/(10.0*float(w)), 0.5, 1000.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}


int main(int argc, char **argv)
{
    glutInit(&argc, argv); // Initializes glut

    // Sets up a double buffer with RGBA components and a depth component
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA);

    // Sets the window size to 512*512 square pixels
    glutInitWindowSize(512, 512);

    // Sets the window position to the upper left
    glutInitWindowPosition(0, 0);

    // Creates a window using internal glut functionality
    glutCreateWindow("Hello!");

    // passes reshape and display functions to the OpenGL machine for callback
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutIdleFunc(display);

    init();

    // Starts the program.
    glutMainLoop();
    return 0;
}

---

NeHe has a tutorial for setting up an OpenGL window on Mac OS X with GLUT here. They also provide the code for all of the lessons for various different platforms. If you scroll to the bottom of lesson 2, you can download the lesson code ready to go for a number of platforms. You probably want either the GLUT sample or the Mac OS X/Cocoa sample.

---

Easiest way is to use Objective-C to get everything set up, then use C for drawing. (not the only way, GLUT is also an option.)

Sample code from Apple

---

Here's the "hello.c" example from the OpenGL Red Book converted to R6RS Scheme:

http://gist.github.com/319363

That program runs in Ikarus Scheme and Ypsilon Scheme.

Notice that the 'import' form is referring to some 'agave' libraries. Those are available at:

http://github.com/dharmatech/agave

Agave is a project which provides a bunch of OpenGL demos and libraries for R6RS Scheme.

Ikarus and Ypsilon are both available for OS X.

Ed