[Linuxwacom-discuss] xsetwacom MapToOutput with Nvidia drivers?

[James P. <ja...@mo...>]

The page at <http://linuxwacom.sourceforge.net/wiki/index.php/Dual_and_Multi-Monitor_Set_Up> states:

"Provided you have the latest git version, you can also use MapToOutput with the NVIDIA binary driver. In this case, the monitor must be specified with "HEAD-0", "HEAD-1", etc. "

Also, the xsetwacom source states in need_xinerama() :

 * A server bug causes the NVIDIA driver to report RandR 1.3 support
 * despite not exposing RandR CRTCs. We need to fall back to Xinerama
 * for this case as well.

and the code has:

        if (!XQueryExtension(dpy, "RANDR", &opcode, &event, &error) ||
            !XRRQueryVersion(dpy, &maj, &min) || (maj * 1000 + min) < 1002 ||
            XQueryExtension(dpy, "NV-CONTROL", &opcode, &event, &error))
        {

However, I'm using the Nvidia driver 384.69 (on CentOS 7.4) and 'xrandr -v' reports:

xrandr program version       1.5.0
Server reports RandR version 1.5

If I remove the above 'NV-CONTROL' check in need_xinerama(), then MapToOutput appears to work fine with the 'monitor names' as given in the xrandr output ...

So, I guess this limitation of the Nvidia driver is no longer valid with more recent drivers versions ?

Also, unless I'm missing something, the comments for need_xinerama() and the code don't agree - the comments state:

"We depend on RandR 1.3 or better in order to work"

but the (above) code checks for versions less than 1.2 ? - shouldn't it be checking for versions less than 1.3 ? i.e. checking '(maj * 1000 + min) < 1003' instead ?

Anyway, I think the following patch will allow Nvidia drivers with RandR 1.4 or better to work (assuming the Nvidia bug is fixed in 1.4 and above?)

--- ./tools/xsetwacom.c.dist    2016-08-08 01:06:24.000000000 +0100
+++ ./tools/xsetwacom.c 2018-03-31 18:25:18.533865665 +0100
@@ -2169,10 +2169,13 @@ static Bool need_xinerama(Display *dpy)
 {
        int opcode, event, error;
        int maj, min;
+       int randrv;
+
+       randrv = XQueryExtension(dpy, "NV-CONTROL", &opcode, &event, &error) ?
+           1004 : 1002;

        if (!XQueryExtension(dpy, "RANDR", &opcode, &event, &error) ||
-           !XRRQueryVersion(dpy, &maj, &min) || (maj * 1000 + min) < 1002 ||
-           XQueryExtension(dpy, "NV-CONTROL", &opcode, &event, &error))
+           !XRRQueryVersion(dpy, &maj, &min) || (maj * 1000 + min) < randrv)
        {
                TRACE("RandR extension not found, too old, or NV-CONTROL "
                        "extension is also present.\n");

Thanks

James Pearson