Re: [gtk-list] Using Mesa (openGL) with GTK

[Ivo Clarysse <soggie riv be>]

On Thu, 25 Sep 1997, Philip Dawes wrote:

> Has anybody tried to use the mesa library with GTK? Is anybody working
> on a mesa drawing panel type widget?

The following program displays a triangle using Mesa. 
I tried it on a couple of SGI machines with SGI Open/GL - it compiles,
but doesn't run on true-color SGIs.  It does work on true-color SGIs
when compiled with Mesa though.  This is probably related to
Mesa being able to render to more graphics contexts than SGI's
OpenGL implementation.  (the code below is mostly ignorant about
the existance of different graphics contexts - THIS IS A BUG).

It works with the GTK/GDK/GLIB from the gimp-0.99.11 release.
Developed and tested with Mesa 2.1.

/*
 * Displays a triangle with Open/GL | Mesa
 *
 * (DISCLAIMER not quite 100% OK)
 *
 * Author: Ivo Clarysse <soggie@riv.be>
 *
 * In Public Domain
 */

#include <gtk/gtk.h>
#include <gdk/gdk.h>
#include <gdk/gdkx.h>
#include <GL/gl.h>
#include <GL/glx.h>
#include <GL/glu.h>

int redraw_needed=TRUE;

Display *dpy=NULL;
GLXContext glx_context;

GLfloat cam_xspin=0.0;
GLfloat cam_yspin=0.0;
GLfloat cam_zspin=0.0;
GLfloat cam_xpos=0.0;
GLfloat cam_ypos=0.0;
GLfloat cam_zpos=-5.0;

GtkWidget *glarea;

void object_redraw();

/* Define model in displaylist */
void            object_define()
{
  glNewList(1, GL_COMPILE_AND_EXECUTE);
  glClear(GL_COLOR_BUFFER_BIT);

  glBegin(GL_LINE_LOOP);
  glVertex3f(-1, 0, 0);
  glVertex3f( 0, -1, 0);
  glVertex3f( 1, -1, 0);
  glEnd();
  
  glEndList();
}


void object_redraw()
{
static int list_inited=FALSE;

  if (!redraw_needed) return;

  glXMakeCurrent(dpy,GDK_WINDOW_XWINDOW(glarea->window),glx_context);
  glShadeModel(GL_FLAT);
  glClearColor(0.0,0.0,0.0,0.0);
  glColor3f(1.0, 1.0, 1.0);
  glLineWidth(1.0);

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();

  glTranslatef(cam_xpos, cam_ypos, cam_zpos);
  glRotatef(cam_xspin, 1.0, 0.0, 0.0);        /* rotate modelmatrix */
  glRotatef(cam_yspin, 0.0, 1.0, 0..0);        /* rotate modelmatrix */
  glRotatef(cam_zspin, 0.0, 0.0, 1.0);        /* rotate modelmatrix */

  if (list_inited) glCallList(1);
  else { 
    object_define(); 
    list_inited=TRUE; 
  }

  glFlush();
  printf("Before swap\n");
  glXSwapBuffers(dpy,GDK_WINDOW_XWINDOW(glarea->window));
  printf("After swap\n");

  redraw_needed=FALSE;

}


/*
 * Callback function for 'Quit' button
 *
 */
void quit_button(GtkWidget *widget, gpointer *data)
{
  gtk_main_quit();
}

/*
 * Callback for GTK events in glarea 
 *
 */
gint glarea_events(GtkWidget *area, GdkEvent *event)
{
GdkEventConfigure *configevent;

  switch (event->type) {
    case GDK_EXPOSE:
      redraw_needed=TRUE;
      object_redraw();
      break;

    case GDK_CONFIGURE:  /* aka Resize */
      printf("entry: GDK_CONFIGURE\n");
      redraw_needed=TRUE;
      configevent=(GdkEventConfigure *)event;
    
      /* Resize OpenGL context in glarea */
      glMatrixMode(GL_PROJECTION);   
      glLoadIdentity();             
      glFrustum(-1.0, 1.0, -1.0, 1.0, 1.5, 20.0);
      glViewport(0, 0, configevent->width, configevent->height); 
      glMatrixMode(GL_MODELVIEW);       
      printf("exit: GDK_CONFIGURE\n");
      break;

    default:
      break;
    }
  return (FALSE);
}


void gui_init()
{
  gint TimerTag;
  GtkWidget *appwindow, *vbox, *button;
  XVisualInfo *vi;
  int dbuf[] = {GLX_DOUBLEBUFFER,GLX_RED_SIZE,1,GLX_GREEN_SIZE,1,
                GLX_BLUE_SIZE,1,None};

  appwindow=gtk_window_new(GTK_WINDOW_TOPLEVEL);
  gtk_window_set_title(GTK_WINDOW(appwindow), "GL-GTK Test");

  vbox=gtk_vbox_new(FALSE,0);

  /* Upper row */

  glarea = gtk_drawing_area_new();
  gtk_drawing_area_size(GTK_DRAWING_AREA(glarea),300,300);
  gtk_widget_set_events(glarea,GDK_EXPOSURE_MASK);
  gtk_signal_connect(GTK_OBJECT(glarea), "event", (GtkSignalFunc)glarea_events, NULL);
  gtk_box_pack_start(GTK_BOX(vbox), glarea, FALSE, FALSE, 0);
  gtk_widget_show(glarea);


  /* Lower row */

  button=gtk_button_new_with_label("Quit");
  gtk_signal_connect(GTK_OBJECT(button), "clicked", GTK_SIGNAL_FUNC(quit_button), NULL);
  gtk_box_pack_start(GTK_BOX(vbox), button, FALSE, FALSE, 0);
  gtk_widget_show(button);


  /* ** */
  gtk_widget_show(vbox);
  gtk_container_add(GTK_CONTAINER(appwindow),vbox);

  gtk_widget_show(appwindow);

  printf("check\n");

  /* Initialize OpenGL */
  dpy=GDK_WINDOW_XDISPLAY(appwindow->window);
  vi=glXChooseVisual(dpy,DefaultScreen(dpy),dbuf);

  if (vi==NULL) { fprintf(stderr,"ERROR: Could not create visual\n"); exit(-1); }
  if (vi->class != TrueColor) printf("Non-TrueColor visual selected\n"); 
  printf("Selected visual = %d\n",vi->visualid);
  glx_context = glXCreateContext(dpy,vi,None,GL_TRUE);
  if (glx_context==NULL) { fprintf(stderr,"ERROR: Could not create context\n"); exit(-1); }

  /* Initialize OpenGL context for rendering */
  printf("glXMakeCurrent\n"); 
  glXMakeCurrent(dpy,GDK_WINDOW_XWINDOW(glarea->window),glx_context);
  glShadeModel(GL_FLAT);
  glClearColor(0.0,0.0,0.0,0.0);
  glColor3f(1.0, 1.0, 1.0);
  glLineWidth(1.0);

}


/**********************************
 *
 * Main function - delegate :)
 *
 **********************************/
int main(int argc, char *argv[])
{
  gtk_init (&argc, &argv);

printf("gui_init\n");
  gui_init();

printf("main widget loop\n");
  gtk_main();

  return 0;
}


-----------------------------------------------------------------------
 Ivo Clarysse <soggie@riv.be>,                Riverland Research Group
 Research Assistant                        http://www.riv.be/research/
                                                      Excelsiorlaan 42
 http://www.riv.be/~soggie/me/                B-1930 Zaventem, Belgium