Re: [GtkGLExt] troubles with my first OpenGL app

["Vladimir Bashkardin" <bash deg gubkin ru>]

Hi.

I suggest to move the following code from realize () to expose_event ():
>    glBegin(GL_POLYGON);
>       glVertex2f(-0.5, -0.5);
>       glVertex2f(-0.5, 0.5);
>       glVertex2f(0.5, 0.5);
>       glVertex2f(0.5, -0.5);
>    glEnd();

It should be like this:
static void realize (GtkWidget *widget, gpointer data) {
   GdkGLContext *glcontext = gtk_widget_get_gl_context (widget);
   GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable (widget);

   /*** OpenGL BEGIN ***/
   if (!gdk_gl_drawable_gl_begin (gldrawable, glcontext))
      return;

   /*** Begin code from example-1.1 ***/

   glClearColor (0.0, 0.0, 0.0, 0.0);
   glClear (GL_COLOR_BUFFER_BIT);
   glColor3f (1.0, 1.0, 1.0);
   glOrtho (-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
   glFlush();

   /*** End code from example-1.1 ***/

   glViewport (0, 0, widget->allocation.width, widget->allocation.height);

   gdk_gl_drawable_gl_end (gldrawable);
   /*** OpenGL END ***/
}

static gboolean expose_event (GtkWidget *widget, GdkEventExpose
*event, gpointer data) {
   GdkGLContext *glcontext = gtk_widget_get_gl_context (widget);
   GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable (widget);

   /*** OpenGL BEGIN ***/
   if (!gdk_gl_drawable_gl_begin (gldrawable, glcontext))
      return FALSE;

   glBegin(GL_POLYGON);
      glVertex2f(-0.5, -0.5);
      glVertex2f(-0.5, 0.5);
      glVertex2f(0.5, 0.5);
      glVertex2f(0.5, -0.5);
   glEnd();

   if (gdk_gl_drawable_is_double_buffered (gldrawable))
      gdk_gl_drawable_swap_buffers (gldrawable);
   else
      glFlush ();

   gdk_gl_drawable_gl_end (gldrawable);
   /*** OpenGL END ***/

   return TRUE;
}

Now works OK on my configuration: RedHat Enterprise Linux 4.0,
nVidia QuadroFX 1300, nVidia propietary driver version 87.62

PS. Instead of the "realize" event, I would handle the "configure" event.
Currently, it doesn't react properly to resize/maximize/minimize window
events.

Thu, 03 Aug 2006, 06:49 jesus ruiz wrote:
> Hello
>
> First of all, sorry for my English.
>
> I want to learn developing OpenGL applications, so I try gtkglext. The
> examples are great! :) But I would like to follow the redbook from
> OpenGL to learn it from scratch.
>
> So, I try the example1-1 [1] (A white square into a black screen), but
> i didnt get it working. The code (based on simple.c) mentioned is
> commented and posted below.
>
> Thanks in advance
>
> P.S. If this is off topic, please tell me and sorry.
>
> [1] http://www.rush3d.com/reference/opengl-redbook-1.1/chapter01.html
>
> ---------------- CODE: example1_1.c  --------------------
>
> /*
>  * example1_1.c on redBook (The White square)
>  *
>  * Problem: The app only display a black window
>  *
>  * Using GTK+ through libgtkglext
>  *
>  * Functions:
>  * main() create the widgets and connect the signals to their callback
>  * realize() is called only once on startup
>  * expose_event() is called when the drawingarea should be repainted.
>  */
>
> #include <stdlib.h>
> #include <gtk/gtk.h>
> #include <gtk/gtkgl.h>
>
> #include <GL/gl.h>
> #include <GL/glu.h>
>
> static void realize (GtkWidget *widget, gpointer data) {
>    GdkGLContext *glcontext = gtk_widget_get_gl_context (widget);
>    GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable (widget);
>
>    /*** OpenGL BEGIN ***/
>    if (!gdk_gl_drawable_gl_begin (gldrawable, glcontext))
>       return;
>
>    /*** Begin code from example-1.1 ***/
>
>    glClearColor (0.0, 0.0, 0.0, 0.0);
>    glClear (GL_COLOR_BUFFER_BIT);
>    glColor3f (1.0, 1.0, 1.0);
>    glOrtho (-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
>    glBegin(GL_POLYGON);
>       glVertex2f(-0.5, -0.5);
>       glVertex2f(-0.5, 0.5);
>       glVertex2f(0.5, 0.5);
>       glVertex2f(0.5, -0.5);
>    glEnd();
>    glFlush();
>
>    /*** End code from example-1.1 ***/
>
>    glViewport (0, 0, widget->allocation.width, widget->allocation.height);
>
>    gdk_gl_drawable_gl_end (gldrawable);
>    /*** OpenGL END ***/
> }
>
> static gboolean expose_event (GtkWidget *widget, GdkEventExpose
> *event, gpointer data) {
>    GdkGLContext *glcontext = gtk_widget_get_gl_context (widget);
>    GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable (widget);
>
>    /*** OpenGL BEGIN ***/
>    if (!gdk_gl_drawable_gl_begin (gldrawable, glcontext))
>       return FALSE;
>
>    if (gdk_gl_drawable_is_double_buffered (gldrawable))
>       gdk_gl_drawable_swap_buffers (gldrawable);
>    else
>       glFlush ();
>
>    gdk_gl_drawable_gl_end (gldrawable);
>    /*** OpenGL END ***/
>
>    return TRUE;
> }
>
> int main (int argc, char *argv[]) {
>   GdkGLConfig *glconfig;
>   gint major, minor;
>
>   GtkWidget *window;
>   GtkWidget *vbox;
>   GtkWidget *drawing_area;
>   GtkWidget *button;
>
>   /*
>    * Init GTK.
>    */
>
>   gtk_init (&argc, &argv);
>
>   /*
>    * Init GtkGLExt.
>    */
>
>   gtk_gl_init (&argc, &argv);
>
>   /*
>    * Query OpenGL extension version.
>    */
>
>   gdk_gl_query_version (&major, &minor);
>   g_print ("\nOpenGL extension version - %d.%d\n",
>            major, minor);
>
>   /*
>    * Configure OpenGL-capable visual.
>    */
>
>   /* Try double-buffered visual */
>   glconfig = gdk_gl_config_new_by_mode (GDK_GL_MODE_RGB |
> GDK_GL_MODE_DEPTH | GDK_GL_MODE_DOUBLE);
>   if (glconfig == NULL)
>     {
>       g_print ("*** Cannot find the double-buffered visual.\n");
>       g_print ("*** Trying single-buffered visual.\n");
>
>       /* Try single-buffered visual */
>       glconfig = gdk_gl_config_new_by_mode (GDK_GL_MODE_RGB   |
>                                             GDK_GL_MODE_DEPTH);
>       if (glconfig == NULL)
>         {
>           g_print ("*** No appropriate OpenGL-capable visual found.\n");
>           exit (1);
>         }
>     }
>
>
>   /*
>    * Top-level window.
>    */
>
>   window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
>   gtk_window_set_title (GTK_WINDOW (window), "simple");
>
>   /* Get automatically redrawn if any of their children changed
> allocation. */
>   gtk_container_set_reallocate_redraws (GTK_CONTAINER (window), TRUE);
>
>   g_signal_connect (G_OBJECT (window), "delete_event", G_CALLBACK
> (gtk_main_quit), NULL);
>
>   /*
>    * VBox.
>    */
>
>   vbox = gtk_vbox_new (FALSE, 0);
>   gtk_container_add (GTK_CONTAINER (window), vbox);
>   gtk_widget_show (vbox);
>
>   /*
>    * Drawing area for drawing OpenGL scene.
>    */
>
>   drawing_area = gtk_drawing_area_new ();
>   gtk_widget_set_size_request (drawing_area, 200, 200);
>
>   /* Set OpenGL-capability to the widget. */
>   gtk_widget_set_gl_capability (drawing_area, glconfig, NULL, TRUE,
> GDK_GL_RGBA_TYPE);
>
>   g_signal_connect_after (G_OBJECT (drawing_area), "realize",
> G_CALLBACK (realize), NULL);
>   g_signal_connect (G_OBJECT (drawing_area), "expose_event",
> G_CALLBACK (expose_event), NULL);
>
>   gtk_box_pack_start (GTK_BOX (vbox), drawing_area, TRUE, TRUE, 0);
>   gtk_widget_show (drawing_area);
>
>   /*
>    * Simple quit button.
>    */
>
>   button = gtk_button_new_with_label ("Quit");
>
>   g_signal_connect (G_OBJECT (button), "clicked",
>                     G_CALLBACK (gtk_main_quit), NULL);
>
>   gtk_box_pack_start (GTK_BOX (vbox), button, FALSE, FALSE, 0);
>
>   gtk_widget_show (button);
>
>   /*
>    * Show window.
>    */
>
>   gtk_widget_show (window);
>
>   /*
>    * Main loop.
>    */
>
>   gtk_main ();
>
>   return 0;
> }
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>


-- 
Vladimir Bashkardin
Department of Exploration Geophysics
Gubkin's Russian State University of Oil and Gas