[Xcb] problem about fetching xcb_visualtype_t

[Uli Schlachter]

Hi,

On 11.10.2013 17:28, 快乐迷宫 wrote:
>  Hello, guys!
>  I‘m now trying to use XCB instead of XLib of my program backend. And I'm trying to translate these few lines:
> 
>     XVisualInfo vinfo;
>     XSetWindowAttributes attr;
>     screen = DefaultScreen(display);

The DefaultScreen() isn't saved anywhere with xcb. For implementing this, you
need to pass a non-NULL pointer as the second argument to xcb_connect(). This
integer will then be set to the number of the default screen.

>     XMatchVisualInfo(display, screen, 32, TrueColor, &vinfo);                                       //create a transparent window

An example for doing the above with xcb can be found here (function
draw_argb_visual()):

http://git.naquadah.org/?p=awesome.git;a=blob;f=draw.c;h=1a0e4d8f93ca47723949e1e8763d7edbd4c64e5b;hb=HEAD#l261

>     attr.colormap = XCreateColormap(display, rootwin, vinfo.visual, AllocNone);
>     attr.override_redirect = 1;                                                                                        // ... and without the title-bar
> 
> I found a tutor on this web-page, but while I was trying to get the xcb_visualtype_t structure, function screen_of_display() didn't seem existed. I tried xcb_setup_roots_iterator() instead, and the result was, I got a NULL xcb_visualtype_t *...
> 
> --      screen = xcb_setup_roots_iterator(xcb_get_setup(c)).data;
> =>      screen = screen_of_display (c, screen_nbr);

Are you saying that xcb_setup_roots_iterator(xcb_get_setup(c)).data is NULL? I
don't think that can really happen, this should work fine.

> So is there anyway I can create a transparent, no title-bar window and filling the window with cairo?
> Thanks!

Sure, you seem to be having almost all the ingredients already. I assume you are
porting some working code using Xlib to xcb, right?

Uli
-- 
Bruce Schneier can read and understand Perl programs.