It seems like Virtualgl does not want to work with GtkGLArea

[nicholizer]

I compiled the example from https://gtk.dashgl.com/Brickout/Draw_a_Triangle/ and it runs as expected, but when I tried to run it with vglrun, it displayed window with text:

no available configurations for the given rgba pixel format

and terminal throwed:

niko@niko-Satellite-C655:~/Desktop/Untitled Folder$ vglrun +v ./demo3-app
[VGL] Shared memory segment ID for vglconfig: 163856
[VGL] VirtualGL v2.6.4 64-bit (Build 20200626)
[VGL] NOTICE: Replacing dlopen("libGLX.so.1") with dlopen("libvglfaker.so")
[VGL] Opening connection to 3D X server :0
[VGL] NOTICE: Replacing dlopen("libGL.so.1") with dlopen("libvglfaker.so")
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] WARNING: Could not load function "glXBindSwapBarrierNV"
[VGL] WARNING: Could not load function "glXJoinSwapGroupNV"
[VGL] WARNING: Could not load function "glXQueryFrameCountNV"
[VGL] WARNING: Could not load function "glXQueryMaxSwapGroupsNV"
[VGL] WARNING: Could not load function "glXQuerySwapGroupNV"
[VGL] WARNING: Could not load function "glXResetFrameCountNV"
[VGL] NOTICE: Replacing dlopen("libGL.so.1") with dlopen("libvglfaker.so")
on realize
Unknown error

[nicholizer]

I solved this issue. The problem was with GtkWindow. As is said in cztomczak/cefcapi#9 (comment), GTK+ > 3.15.1 uses an X11 visual optimized for GTK+'s OpenGL stuff. There, authour of that comment suggests to force GTK to use the default X11 visual instead the GTK's blessed one(I made minor changes in his code):

GtkWidget* create_gtk_window() {
    printf("create_gtk_window\n");
    // Create window.
    GtkWidget* window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    ////...
    // GTK+ > 3.15.1 uses an X11 visual optimized for GTK+'s OpenGL stuff
    // since revid dae447728d: https://github.com/GNOME/gtk/commit/dae447728d
    // However, it breaks CEF: https://github.com/cztomczak/cefcapi/issues/9
    // Let's use the default X11 visual instead the GTK's blessed one.
    GdkScreen* screen = gdk_screen_get_default();
    GList* visuals = gdk_screen_list_visuals(screen);
    printf("n visuals: %u\n", g_list_length(visuals));
    GdkX11Screen* x11_screen = GDK_X11_SCREEN(screen);
    g_assert(x11_screen != NULL);
    Visual* default_xvisual = DefaultVisual(GDK_SCREEN_XDISPLAY(x11_screen),
        GDK_SCREEN_XNUMBER(x11_screen));
    GdkVisual* default_visual = NULL;
    int i = 0;
    while (visuals != NULL) {
	GdkVisual* visual = GDK_X11_VISUAL (visuals->data);
        if (default_xvisual->visualid == gdk_x11_visual_get_xvisual(
           GDK_X11_VISUAL (visuals->data))->visualid) {
           printf("Default visual %d\n", i);
           default_visual = visual;
        }
        i++;
        visuals = visuals->next;
    }
    gtk_widget_set_visual(GTK_WIDGET(window), default_visual);
    ////gtk_widget_show_all(window);
    return window;
}

So, now I add this to my GTK-code and use create_gtk_window() instead of gtk_window_new(GTK_WINDOW_TOPLEVEL) and my programs work with vglrun.
Thank you for VirtualGL!

[dcommander]

Glad you were able to work around the issue in your code, but I still need to investigate why it is occurring in VirtualGL, since other applications may also encounter it.

[dcommander]

A description of the problem:

GDK first iterates through all available 2D X server visuals and chooses an appropriate "RGBA visual" (the first depth-32 visual with BGRA color masks) and an appropriate "system visual" (the first visual whose visual ID matches the default visual of the 2D X server.) In the case of TurboVNC, the RGBA visual that GDK picks is 0x68, and the system visual it picks is 0x21. So far so good, but then GDK re-orders the visuals such that depth-32 visuals are given precedence over depth-24 visuals and DirectColor visuals are given precedence over TrueColor visuals. The sorting algorithm that GDK uses moves the 2D X server's default visual (0x21) down in the list so that it is no longer the first depth-24 TrueColor visual. GDK then iterates through the re-ordered list of visuals and tries to pick a visual that matches the OpenGL attributes of the system visual, but since VirtualGL 2.x does not assign OpenGL attributes to 2D X server visuals, GDK matches another visual first. This then becomes the new system visual. GDK then iterates through the list of GLXFBConfigs and attempts to find one for which glXGetVisualFromFBConfig() returns the new system visual. That will never happen with VirtualGL 2.x, because VGL 2.x maps all of the 24-bit GLXFBConfigs to the first matching depth-24 TrueColor 2D X server visual (which will be the same as the initial system visual that GDK picks, not the new system visual that it picks after re-ordering.) Thus, it is the re-ordering of visuals that GDK performs in _gdk_x11_screen_init_visuals() that ultimately foils VirtualGL 2.x.

GDK is, to make a long story short, heavily relying on a 1:1 correspondence between GLXFBConfigs (which are on the 3D X server) and X visuals (which are on the 2D X server), which can't be guaranteed in VirtualGL. VGL 2.x works perfectly well with applications that start with a GLXFBConfig and request a visual to match, or with applications that select a visual using explicit OpenGL attributes (glXChooseVisual().) With the use of the VGL_DEFAULTFBCONFIG environment variable, VGL 2.x can be made to work with applications that iterate through the list of 2D X server visuals searching for one with a specific set of OpenGL attributes. However, VGL 2.x can't be made to work with applications that do the latter as well as expect any arbitrary 2D X server visual to have been mapped to a GLXFBConfig. Thus, the application-level workaround you implemented above (explicitly selecting a GDK visual) is the only workaround for VGL 2.x.

Fortunately, however, VirtualGL 3.0 includes a new feature that automatically assigns OpenGL properties, in round-robin fashion, to all available 2D X server visuals and preemptively chooses a GLXFBConfig for each. It also returns 0 when glXGetConfig(GL_USE_GL) is called for any 2D X server visual that doesn't have a GLXFBConfig attached (i.e. any 2D X server visual whose assigned OpenGL properties didn't match a GLXFBConfig in the 3D X server.) This effectively works around the GtkGLArea issue.

[biochem-fan]

@dcommander

I am using virtualgl_3.0_amd64.deb but has the same issue with GtkGLArea.
I am testing on https://github.com/ebassi/glarea-example.
Inserting the above code to use the default X11 visual solved the issue.

So I guess the problem still persists.

[dcommander]

@biochem-fan Reproduced, but I swear it worked before. :| Now GTK is picking Visual 0x2c2 on my system, and I have no idea why. I know it isn't deliberately trying to break VGL, but you couldn't devise a better way to break VGL than the one that GTK is using. I don't see any purpose to their visual selection scheme. It seems needlessly complicated and fragile.

[dcommander]

Reopening because I think this same problem, or at least a very similar one, occurs with Chrome/ANGLE. (Refer to #229.)

[dcommander]

It appears that GNOME/gtk@ca8d9fb in GTK4 might have fixed this, but I have no way to verify, since the GtkGLArea example only works with GTK3. Still, though it would be good for VGL to work around this for GTK3.

[dcommander]

A proper fix for this has been implemented in 398e941. Please test.