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. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1759950 Title: Lid-close suspend: blank screen when switching to user session To manage notifications about this bug go to: https://bugs.launchpad.net/light-locker/+bug/1759950/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs