/* gcc -o line_aa line_aa_freeze.c -Wall `pkg-config --cflags --libs x11 gl glu`
 */

#include <X11/Xlib.h>
#include <GL/gl.h>
#include <GL/glx.h>
#include <GL/glu.h>
#include <string.h>

Display *display;
Window window;
GLXContext context;
int width, height;

static int attrListDbl[] =
{
    GLX_RGBA,
    GLX_DOUBLEBUFFER,
    GLX_RED_SIZE, 8,
    GLX_GREEN_SIZE, 8,
    GLX_BLUE_SIZE, 8,
    GLX_ALPHA_SIZE, 8,
    GLX_DEPTH_SIZE, 16,
    None
};

void initGL(int, int);

void createWindow(int width, int height)
{
    display = XOpenDisplay(0);
    int screen = DefaultScreen(display);
    Window root = RootWindow(display, screen);

    XVisualInfo *vi = glXChooseVisual(display, screen, attrListDbl);
    XSetWindowAttributes winAttr;
    memset(&winAttr, 0, sizeof(XSetWindowAttributes));
    winAttr.colormap = XCreateColormap (display, root, vi->visual, AllocNone);
    winAttr.event_mask = ExposureMask | KeyPressMask | ButtonPressMask |
                         StructureNotifyMask;
    window = XCreateWindow(display, root, 0, 0, width, height, 0, vi->depth,
                           InputOutput, vi->visual,
                           CWBorderPixel | CWColormap | CWEventMask, &winAttr);

    XMapRaised(display, window);

    context = glXCreateContext(display, vi, 0, GL_TRUE);
    glXMakeCurrent(display, window, context);

    initGL(width, height);
}

void destroyWindow()
{
    if (context) {
        glXMakeCurrent(display, None, NULL);
        glXDestroyContext(display, context);
        context = NULL;
    }
    XCloseDisplay(display);
}

void resizeGL(int _width, int _height)
{
    width = _width;
    height = _height;

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f, (GLfloat)width / (GLfloat)height, 0.1f, 100.0f);

    glViewport(0, 0, width, height);
}

void initGL(int width, int height)
{
    glEnable(GL_LINE_SMOOTH);
    glShadeModel(GL_SMOOTH);
    glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
    glLineWidth(1.5);
    glEnable(GL_BLEND);
    glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glPolygonMode(GL_FRONT, GL_LINE);

    resizeGL(width, height);
}

void renderGL(int width, int height)
{
    static float angle = 0.0;

    glViewport(0, 0, width, height);

    glClearColor(1, 1, 1, 1);
    glClear(GL_COLOR_BUFFER_BIT);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glTranslatef(0.0f, 0.0f, -4.0);
    glRotatef(15.0,  0, 0, 1);
    glRotatef(angle, 0, 1, 0);

    glBegin(GL_TRIANGLES);
        glColor4f(1.0f,0.0f,0.0f,1.0);
        glVertex3f(-0.1f, -1.0f, 0.0f);

        glColor4f(0.0f,1.0f,0.0f,1.0);
        glVertex3f( 1.0f, -1.0f, 0.0f);

        glColor4f(0.0f,0.0f,1.0f,1.0);
        glVertex3f( 0.0f, 1.0f, 0.0f);
    glEnd();

    glXSwapBuffers(display, window);

    angle += 1.0;
}

int main(int argc, char ** argv)
{
    XEvent event;
    int done = 0;

    createWindow(640, 480);

    while (!done) {
        while (XPending(display) > 0) {
            XNextEvent(display, &event);
            switch (event.type) {
                case ConfigureNotify:
                    resizeGL(event.xconfigure.width, event.xconfigure.height);
                    break;
                case KeyPress:
                    if (XLookupKeysym(&event.xkey, 0) == XK_Escape)
                        done = 1;
                    break;
                default:
                    break;
            }
        }
        renderGL(width, height);
    }

    destroyWindow();

    return 0;
}