Comment 21 for bug 1759950

I modified libxrandr to return the actual error code returned from XRRSetCrtcConfig():

--- libxrandr-1.5.1.orig/src/XrrCrtc.c
+++ libxrandr-1.5.1/src/XrrCrtc.c
@@ -155,9 +155,10 @@ XRRSetCrtcConfig (Display *dpy,
     req->mode = mode;
     req->rotation = rotation;
     Data32 (dpy, outputs, noutputs << 2);
+ int ret_code = _XReply (dpy, (xReply *) &rep, 0, xFalse);
+ if (ret_code != 0)
+ rep.status = ret_code;

- if (!_XReply (dpy, (xReply *) &rep, 0, xFalse))
- rep.status = RRSetConfigFailed;
     UnlockDisplay (dpy);
     SyncHandle ();
     return rep.status;

And it shows:

xfce4-settings(displays): Configuring CRTC 79.
xfce4-settings(displays): Applying changes to CRTC 79.
xfce4-settings(displays): Applying CRTC 79 Transform: x=0.000000 y=0.000000, filter=bilinear.

(xfsettingsd:7726): xfsettingsd-WARNING **: 12:44:13.650: XRRSetCrtcConfig()=1, sleeping

(xfsettingsd:7726): xfsettingsd-WARNING **: 12:44:13.655: XRRSetCrtcConfig()=1, sleeping

(xfsettingsd:7726): xfsettingsd-WARNING **: 12:44:13.657: XRRSetCrtcConfig()=1, sleeping

(xfsettingsd:7726): xfsettingsd-WARNING **: 12:44:13.658: XRRSetCrtcConfig()=1, sleeping

(xfsettingsd:7726): xfsettingsd-WARNING **: 12:44:13.660: XRRSetCrtcConfig()=1, sleeping

(xfsettingsd:7726): xfsettingsd-WARNING **: 12:44:13.661: Failed to configure CRTC 79 XRRSetCrtcConfig()=1.
xfce4-settings(displays): Configuring CRTC 80.

(xfsettingsd:7726): xfsettingsd-CRITICAL **: 12:44:13.662: Failed to apply display settings
xfce4-settings(displays): RRScreenChangeNotify event received.