/* $Revision: 1.8 $ */
/* compile: cc -o glxmotif glxmotif.c -lGLU -lGL -lXm -lXt -lX11 */
#include <stdlib.h>
#include <stdio.h>
#include <Xm/Form.h>
#include <Xm/Frame.h>
#include <Xm/DrawingA.h>
#include <X11/keysym.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glx.h>

static int snglBuf[] = {GLX_RGBA, GLX_DEPTH_SIZE, 16, None};
static int dblBuf[] = {GLX_RGBA, GLX_DEPTH_SIZE, 16, GLX_DOUBLEBUFFER, None};
static String   fallbackResources[] = {
    "*glxarea*width: 300", "*glxarea*height: 300",
    "*frame*x: 20", "*frame*y: 20",
    "*frame*topOffset: 20", "*frame*bottomOffset: 20",
    "*frame*rightOffset: 20", "*frame*leftOffset: 20",
    "*frame*shadowType: SHADOW_IN",
    NULL
};

Display        *dpy;
GLboolean       doubleBuffer = GL_TRUE, viewportUpdateNeeded = GL_TRUE, spinning = GL_FALSE;
XtAppContext    app;
XtWorkProcId    workId = 0;
Widget          toplevel, form, frame, glxarea;

void
updateViewport(Widget w)
{
    Dimension width, height;

    XtVaGetValues(w, XmNwidth, &width, XmNheight, &height, NULL);
    glViewport(0, 0, (GLint) width, (GLint) height);
    viewportUpdateNeeded = GL_FALSE;
}

void
draw(Widget w)
{
    if (viewportUpdateNeeded) updateViewport(w);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glBegin(GL_POLYGON);
    glColor3f(0.0, 0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
    glColor3f(0.7, 0.7, 0.7); glVertex3f(10.0, -10.0, 0.0);
    glColor3f(1.0, 1.0, 1.0); glVertex3f(-10.0, 10.0, 0.0);
    glEnd();
    glBegin(GL_POLYGON);
    glColor3f(1.0, 1.0, 0.0); glVertex3f(0.0, -10.0, -10.0);
    glColor3f(0.0, 1.0, 0.7); glVertex3f(0.0, -10.0, 10.0);
    glColor3f(0.0, 0.0, 1.0); glVertex3f(0.0, 5.0, -10.0);
    glEnd();
    glBegin(GL_POLYGON);
    glColor3f(1.0, 1.0, 0.0); glVertex3f(-10.0, 6.0, 4.0);
    glColor3f(1.0, 0.0, 1.0); glVertex3f(-10.0, 3.0, 4.0);
    glColor3f(0.0, 0.0, 1.0); glVertex3f(4.0, -9.0, -10.0);
    glColor3f(1.0, 0.0, 1.0); glVertex3f(4.0, -6.0, -10.0);
    glEnd();
    if (doubleBuffer) glXSwapBuffers(dpy, XtWindow(w));
    glFlush();
}

void
expose(Widget w, XtPointer clientData, XtPointer callData)
{
    draw(w);
}

void
resize(Widget w, XtPointer clientData, XtPointer callData)
{
    XmDrawingAreaCallbackStruct *cd = (XmDrawingAreaCallbackStruct *) callData;

    /* don't try OpenGL until window is realized! */
    if (XtIsRealized(w)) updateViewport(w);
        else viewportUpdateNeeded = GL_TRUE;
}

Boolean
spin(XtPointer clientData)
{
    glRotatef(2.5, 1.0, 0.0, 0.0);
    draw(glxarea);
    return False; /* leave work proc active */
}

void
input(Widget w, XtPointer clientData, XtPointer callData)
{
    XmDrawingAreaCallbackStruct *cd = (XmDrawingAreaCallbackStruct *) callData;
    char            buffer[1];
    KeySym          keysym;
    int             rc;

    switch (cd->event->type) {
    case KeyRelease:
	/*
	 * It is necessary to convert the keycode to a keysym before it is
	 * possible to check if it is an escape
	 */
	rc = XLookupString((XKeyEvent *) cd->event, buffer, 1, &keysym, NULL);
	switch (keysym) {
	case XK_Up:
	    glRotatef(10.0, 0.0, 0.0, 1.0);
	    if (!spinning) draw(w);
	    break;
	case XK_Down:
	    glRotatef(-10.0, 0.0, 0.0, 1.0);
	    if (!spinning) draw(w);
	    break;
	case XK_Left:
	    glRotatef(-10.0, 0.0, 1.0, 0.0);
	    if (!spinning) draw(w);
	    break;
	case XK_Right:
	    glRotatef(10.0, 0.0, 1.0, 0.0);
	    if (!spinning) draw(w);
	    break;
	case XK_S: case XK_s: /* the S key */
	    if (spinning) {
		XtRemoveWorkProc(workId);
		spinning = GL_FALSE;
	    } else {
		workId = XtAppAddWorkProc(app, spin, NULL);
		spinning = GL_TRUE;
	    }
	    break;
	case XK_Escape:
	    exit(0);
	}
	break;
    }
}

void
map_state_changed(Widget w, XtPointer clientData, XEvent * event, Boolean * cont)
{
    switch (event->type) {
    case MapNotify:
	if (spinning && workId != 0) workId = XtAppAddWorkProc(app, spin, NULL);
	break;
    case UnmapNotify:
	if (spinning) XtRemoveWorkProc(workId);
	break;
    }
}

main(int argc, char *argv[])
{
    XVisualInfo    *vi;
    Colormap        cmap;
    GLXContext      cx;
    int		    saved_argc;
    String	   *saved_argv;

    toplevel = XtAppInitialize(&app, "Glxmotif", NULL, 0, &argc, argv,
                               fallbackResources, NULL, 0);
    dpy = XtDisplay(toplevel);

    /* find an OpenGL-capable RGB visual with depth buffer */
    vi = glXChooseVisual(dpy, DefaultScreen(dpy), dblBuf);
    if (vi == NULL) {
	vi = glXChooseVisual(dpy, DefaultScreen(dpy), snglBuf);
	if (vi == NULL) XtAppError(app, "no RGB visual with depth buffer");
	doubleBuffer = GL_FALSE;
    }
    /* create an OpenGL rendering context */
    cx = glXCreateContext(dpy, vi, /* no display list sharing */ None, /* favor direct */ GL_TRUE);
    if (cx == NULL) XtAppError(app, "could not create rendering context");
    /* create an X colormap since probably not using default visual */
    cmap = XCreateColormap(dpy, RootWindow(dpy, vi->screen), vi->visual, AllocNone);

    XtVaSetValues(toplevel, XtNvisual, vi->visual, XtNdepth, vi->depth,
       XtNcolormap, cmap, NULL);
    XtAddEventHandler(toplevel, StructureNotifyMask, False, map_state_changed, NULL);

    form = XmCreateForm(toplevel, "form", NULL, 0);
    XtManageChild(form);

    frame = XmCreateFrame(form, "frame", NULL, 0);
    XtVaSetValues(frame, XmNbottomAttachment, XmATTACH_FORM,
        XmNtopAttachment, XmATTACH_FORM, XmNleftAttachment, XmATTACH_FORM,
        XmNrightAttachment, XmATTACH_FORM, NULL);
    XtManageChild(frame);

    glxarea = XtCreateManagedWidget("glxarea", xmDrawingAreaWidgetClass, frame, NULL, 0);
    XtAddCallback(glxarea, XmNexposeCallback, expose, NULL);
    XtAddCallback(glxarea, XmNresizeCallback, resize, NULL);
    XtAddCallback(glxarea, XmNinputCallback, input, NULL);

    XtRealizeWidget(toplevel);

    /* Once widget is realized (ie, associated with a created X window), we
     * can bind the OpenGL rendering context to the window.
     */
    glXMakeCurrent(dpy, XtWindow(glxarea), cx);

    /* setup OpenGL state */
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL); 
    glClearDepth(1.0);
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glLoadIdentity();
    gluPerspective(40.0, 1.0, 10.0, 200.0);
    glTranslatef(0.0, 0.0, -50.0); glRotatef(-58.0, 0.0, 1.0, 0.0);

    XtAppMainLoop(app);
}