This is my fourth venture into GtkGL land... All other times have been
smooth sailing, but now I get trouble.
I am trying to make a mod to the gtk-vnc widget which will allow me to
resize the widget. I chose to use gtkglext and OpenGL to do the
resizing. However, there are two incidents of note here... First, for
some strange reason, the on_configure_event is being called before
on_realize. Is there any reason why this would happen? Second, when
I call gtk_widget_get_gl_context() and gtk_widget_get_gl_drawable(),
they both return NULL. I am initializing the GL library in the
application.
When I run gdk_gl_context_new I get the following assertion:
(lt-gvncviewer:2855): GdkGLExt-CRITICAL **: gdk_gl_context_new:
assertion `GDK_IS_GL_DRAWABLE (gldrawable)' failed
even though the widget that I am using is inherited off of a GtkDrawingArea.
When I try to call gdk_gl_drawable_gl_begin I get the following assertion:
(lt-gvncviewer:1750): GdkGLExt-CRITICAL **: gdk_gl_drawable_gl_begin:
assertion `GDK_IS_GL_DRAWABLE (gldrawable)' failed
The code I am using for my realize and configure event handlers is:
static void realize(VncDisplay *obj)
{
printf("Realizing display.\n");
GtkWidget *widget = GTK_WIDGET(obj);
printf("Beginning OGL init.\n");
/* Try double-buffered visual */
GdkGLConfig *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);
}
}
printf("beginning OGL+widget stuff with widget %p.\n", widget);
obj->priv->glcontext = gdk_gl_context_new(widget, NULL, True, GL_RGBA);
obj->priv->gldrawable = gtk_widget_get_gl_drawable (widget);
printf("OGL begin(%p, %p).\n", obj->priv->gldrawable, obj->priv->glcontext);
/*** OpenGL BEGIN ***/
if (!gdk_gl_drawable_gl_begin (obj->priv->gldrawable,
obj->priv->glcontext))
exit(-1);
printf("Starting in on the gl code.\n");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 1, 1, 0, 1, -1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glDisable(GL_DEPTH_TEST);
glActiveTexture(GL_TEXTURE0);
glEnable(GL_TEXTURE_RECTANGLE_ARB);
glGenTextures(1, &obj->priv->frametex);
obj->priv->displist = glGenLists(1);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
printf("tex id is %d\n", obj->priv->frametex);
glActiveTexture(GL_TEXTURE0);
glClearColor(0xff, 0xff, 0x00, 0x00);
OGLerror("glClearColor or earlier");
}
static void on_configure(VncDisplay *obj)
{
printf("On_configure.\n");
GtkWidget *widget = GTK_WIDGET(obj);
int width = widget->allocation.width;
int height = widget->allocation.height;
printf("on configure OGL begin(%p, %p).\n", obj->priv->gldrawable,
obj->priv->glcontext);
if(obj->priv->gldrawable == NULL || obj->priv->glcontext == NULL)
return 0;
if (!gdk_gl_drawable_gl_begin (obj->priv->gldrawable,
obj->priv->glcontext))
return 0;
printf("calling viewport with %dx%d\n", width, height);
glViewport(0, 0, width, height);
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, obj->priv->frametex);
OGLerror("bind");
glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S,
GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T,
GL_CLAMP_TO_EDGE);
OGLerror("tex param");
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGBA, width,
height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
OGLerror("tex image 2d");
glNewList(obj->priv->displist, GL_COMPILE);
{
glBegin(GL_QUADS);
glTexCoord2f(0.0f, height);
glVertex2f(0.0f, 1.0f);
glTexCoord2f(width, height);
glVertex2f(1.0f, 1.0f);
glTexCoord2f(width, 0.0f);
glVertex2f(1.0f, 0.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glEnd();
}
glEndList();
OGLerror("list creation and compilation");
gdk_gl_drawable_gl_end (obj->priv->gldrawable);
}
The error is easy to recreate, all one must do is download the gtk-vnc
package, add the gtk_gl_init function to the examples/gvncviewer.c
file's main() function, add the code above to the src/vncdisplay.c file,
stick the appropriate g_signal_connect calls.
Thank you for any assistance you may give in this matter.
R Stoddard
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