[Xcb] xcb_randr_set_screen_size_checked error

[Andrey Af]

Hi,
Your manual is helped me a lot!
I did it xcb_randr_get_screen_info + xcb_randr_set_screen_config
and everything worked out, Thank you!

2021-09-03 11:56 GMT, Uli Schlachter <psychon at znc.in>:
> Hi,
>
> Am 02.09.21 um 02:57 schrieb Andrey Af:
>> Hi,
>> I'm trying to use this function but I get an error:
>> error code: 8, major: 0x8c, minor: 0x07, sequence: 4
>
> Error 8 is BadMatch / XCB_MATCH. But perhaps even better...
>
> [...]
>>     auto _conn = xcb_connect(":0", nullptr);
> [...]
>
> I changed the above ":0" to nullptr and ran your code under xtrace [1].
>
> The result is lots of output which ends with:
>
> 000:<:0004: 20: RANDR-Request(140,7): SetScreenSize window=0x00000761
> width=1680 height=1050 width[mm]=477 height[mm]=268
> 000:<:0005:  4: Request(43): GetInputFocus
> 000:>:0004:Error 8=Match: major=140, minor=7, bad=0x00000761, seq=0004
> 000:>:0005:32: Reply to GetInputFocus: revert-to=PointerRoot(0x01)
> focus=0x02a00009
> main: error code: 8, major: 0x8c, minor: 0x07, sequence: 4
>
> The "0004" before the error is the sequence number. Your error output
> also says "sequence: 4". With this output, we see that the SetScreenSize
> request has the same sequence number, so this is the one generating the
> error.
>
> Next, I looked at [2] and found for RRSetScreenSize:
>
>         All active monitors must be configured to display a
> 	subset of the specified size, else a Match error results.
>
> My current setup looks like this:
>
> $ xrandr | grep ' connected'
> HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x
> axis y axis) 477mm x 268mm
> DP-2 connected 1280x1024+1920+0 (normal left inverted right x axis y
> axis) 376mm x 301mm
>
> My DP-2 would be outside of the screen size that your program tries to
> set and hence the X11 server refused this request.
>
> Are you sure that SetScreenSize is the request that you actually want to
> send? I would guess that you are more interested in SetCrtcConfig.
> To be sure, I would recommend running something like "xtrace xrandr
> --output FOO --right-of BAR" and investigating the output (where this is
> just an example xrandr invocation and you should replace it with what
> you are actually trying to achieve).
>
> Hope this helps,
> Uli
>
> [1]: https://packages.debian.org/bullseye/xtrace
> [2]:
> https://gitlab.freedesktop.org/xorg/proto/randrproto/-/blob/master/randrproto.txt
> --
> "Do you know that books smell like nutmeg or some spice from a foreign
> land?"
>                                               -- Faber in Fahrenheit 451
>