glfw/examples/triangle.c

//========================================================================
// This is a small test application for GLFW.
// The program opens a window (640x480), and renders a spinning colored
// triangle (it is controlled with both the GLFW timer and the mouse).
//========================================================================

#include <stdio.h>
#include <stdlib.h>
#include <GL/glfw3.h>


int main( void )
{
    int width, height, x;
    double t;
    GLFWwindow window;

    // Initialise GLFW
    if( !glfwInit() )
    {
        fprintf( stderr, "Failed to initialize GLFW\n" );
        exit( EXIT_FAILURE );
    }

    // Open a window and create its OpenGL context
    window = glfwOpenWindow( 640, 480, GLFW_WINDOWED, "Spinning Triangle", NULL );
    if (!window)
    {
        fprintf( stderr, "Failed to open GLFW window\n" );

        glfwTerminate();
        exit( EXIT_FAILURE );
    }

    // Ensure we can capture the escape key being pressed below
    glfwEnable( window, GLFW_STICKY_KEYS );

    // Enable vertical sync (on cards that support it)
    glfwSwapInterval( 1 );

    do
    {
        t = glfwGetTime();
        glfwGetMousePos( window, &x, NULL );

        // Get window size (may be different than the requested size)
        glfwGetWindowSize( window, &width, &height );

        // Special case: avoid division by zero below
        height = height > 0 ? height : 1;

        glViewport( 0, 0, width, height );

        // Clear color buffer to black
        glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
        glClear( GL_COLOR_BUFFER_BIT );

        // Select and setup the projection matrix
        glMatrixMode( GL_PROJECTION );
        glLoadIdentity();
        gluPerspective( 65.0f, (GLfloat)width/(GLfloat)height, 1.0f, 100.0f );

        // Select and setup the modelview matrix
        glMatrixMode( GL_MODELVIEW );
        glLoadIdentity();
        gluLookAt( 0.0f, 1.0f, 0.0f,    // Eye-position
                   0.0f, 20.0f, 0.0f,   // View-point
                   0.0f, 0.0f, 1.0f );  // Up-vector

        // Draw a rotating colorful triangle
        glTranslatef( 0.0f, 14.0f, 0.0f );
        glRotatef( 0.3f*(GLfloat)x + (GLfloat)t*100.0f, 0.0f, 0.0f, 1.0f );
        glBegin( GL_TRIANGLES );
          glColor3f( 1.0f, 0.0f, 0.0f );
          glVertex3f( -5.0f, 0.0f, -4.0f );
          glColor3f( 0.0f, 1.0f, 0.0f );
          glVertex3f( 5.0f, 0.0f, -4.0f );
          glColor3f( 0.0f, 0.0f, 1.0f );
          glVertex3f( 0.0f, 0.0f, 6.0f );
        glEnd();

        // Swap buffers
        glfwSwapBuffers();
        glfwPollEvents();

    } // Check if the ESC key was pressed or the window was closed
    while( glfwIsWindow(window) &&
           glfwGetKey( window, GLFW_KEY_ESC ) != GLFW_PRESS );

    // Close OpenGL window and terminate GLFW
    glfwTerminate();

    exit( EXIT_SUCCESS );
}