[Xcb] xcb_create_colormap, how to use?

[Thomas Fischer]

Thanks, I actually managed to fix it, kinda by luck!

The code that didn't work was:

fb_configs = glXGetFBConfigs(display, default_screen, &num_fb_configs);
if(!fb_configs || num_fb_configs == 0)
{
    fprintf(stderr, "glXGetFBConfigs failed\n");
    return -1;
}
/* Select first framebuffer config and query visualID */
GLXFBConfig fb_config = fb_configs[0];
glXGetFBConfigAttrib(display, fb_config, GLX_VISUAL_ID , &visualID);

It was choosing a display that didn't have GLX_X_RENDERABLE set.

Using glXChooseFBConfig I was able to get it to work:
int visualID = 0;
static int visual_attribs[] =
{
    GLX_X_RENDERABLE, True,
    GLX_DRAWABLE_TYPE, GLX_WINDOW_BIT,
    GLX_RENDER_TYPE, GLX_RGBA_BIT,
    GLX_X_VISUAL_TYPE, GLX_TRUE_COLOR,
    GLX_RED_SIZE, 8,
    GLX_GREEN_SIZE, 8,
    GLX_BLUE_SIZE, 8,
    GLX_ALPHA_SIZE, 8,
    GLX_DEPTH_SIZE, 24,
    GLX_STENCIL_SIZE, 8,
    GLX_DOUBLEBUFFER, True,
    None
};

int num_fb_configs = 0;
GLXFBConfig *fb_configs = 0;
fb_configs = glXChooseFBConfig(display, default_screen, visual_attribs,
&num_fb_configs);

Is there any way I can update the page on the website with this working
code?


On Wed, Jun 6, 2018 at 11:03 AM, Uli Schlachter <psychon at znc.in> wrote:

> Hi,
>
> On 05.06.2018 02:07, Thomas Fischer wrote:
> > I've been trying to compile the code from
> > https://xcb.freedesktop.org/opengl/
> > tl;dr: The code used Xlib to interact with glx, but uses xcb to handle X
> > events.
> >
> > It seems to not run because of something happening in
> xcb_create_colormap,
> >
> > I changed the code to use create_colormap_checked, and printed out the
> > error structure, this was the response, if it's useful:
> > =============ERROR=============
> > Could not create the colormap
> >         error->response_type: 0
> >         error->error_code: 8
> >         error->sequence: 31
> >         error->resource_id: 0
> >         error->minor_code: 0
> >         error->major_code: 78
> >         error->full_sequence: 31
> > ===============================
>
> Error 8 is XCB_MATCH / BadMatch.
>
> According to [1], CreateColormap produces a Match error if the visual is
> not supported by the screen. That's all that I can say, sorry. I know
> basically nothing about GLX. (Well, you could print out the value of
> visualID and look it up in the output of /usr/bin/xdpyinfo)
>
> Cheers,
> Uli
>
> [1]: https://www.x.org/releases/X11R7.5/doc/x11proto/proto.html
> --
> Homophobia - The fear that another man will treat you the way you treat
> women.
>
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