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-   -   No refresh using compiz/VNC and X 1.7 (http://www.nvnews.net/vbulletin/showthread.php?t=150346)

rockob 04-25-10 12:03 AM

No refresh using compiz/VNC and X 1.7
 
1 Attachment(s)
If you use VNC to connect to a PC running X server 1.7 (eg I'm running 2:1.7.6-2ubuntu7), compiz and nvidia restricted drivers (including the latest 195.36.24 drivers), the VNC screen stays static (there is no refresh), although the host PC screen refreshes correctly. Running VNC with the -noxdamage argument is a workaround (but this is very slow).

A fuller description is at https://bugs.launchpad.net/bugs/353126:

When using the nvidia-restricted or some ATI drivers and compiz desktop effects the vnc server will not refresh the screen. This is being caused by the xserver not getting "damaged" by the nvidia-restricted drivers. Linked bugs confirm this is not an issue on intel chipsets or nv driver.

Steps to reproduce:
Enable desktop-effects (default) with nvidia-restricted, virtualBox's display or some ATI driver like RV610
Enable remote desktop
Connect with VNC

Results:
You see a screen snapshot of your desktop but if you click a menu item there are no updates to the screen.
Notes:
If you close and restart the vnc session, you get an updated snapshot but still no refreshes.

Workarounds:
Use the -noxdamage argument with vncviewer. This is really inefficient and bandwidth hungry since the whole screen refreshes.
Kill compiz and use a different wm (metacity).

Dragoran 04-25-10 04:32 AM

Re: No refresh using compiz/VNC and X 1.7
 
This is not a driver bug ...

gradinaruvasile 04-25-10 06:23 AM

Re: No refresh using compiz/VNC and X 1.7
 
1. Compiz is buggy.
2.Compiz+vnc is not a good combination.

Just disable compiz on the target machine. I gave up on compiz since i installed Xubuntu 9.10 (and now in Debian) and since then my desktops are way more stable.

Also the nv driver doesnt support compiz at all. And this issue is present on all compiz running machines i ever seen (ati with OSS drivers, nvidia with proprietary).

smani 04-25-10 07:04 AM

Re: No refresh using compiz/VNC and X 1.7
 
Quote:

Originally Posted by gradinaruvasile (Post 2239653)
And this issue is present on all compiz running machines i ever seen (ati with OSS drivers, nvidia with proprietary).

That is not true, with XServer 1.7 as in Fedora 12 and Ubuntu 10.04, it works fine on all open drivers.

gradinaruvasile 04-25-10 08:47 AM

Re: No refresh using compiz/VNC and X 1.7
 
I said i ever seen. I have seen Ubuntu 7.10-9.10.

And compiz is buggy and it is a poor choice of enabling it by default.

smani 04-25-10 11:10 AM

Re: No refresh using compiz/VNC and X 1.7
 
Quote:

Originally Posted by gradinaruvasile (Post 2239677)
And compiz is buggy and it is a poor choice of enabling it by default.

This may indeed be true, but won't calm down most of the people in launchpad experiencing this issue. It would be interesting though to get a statement from a nvidia driver developer whether
1. This issue was not known
2. This issue is known and on the TODO list
3. This issue is known but won't be addressed for some reason

As stated on the launchpad post, the issue does not appear to be with compiz directly since it worked back in 2008. One possibility might be a change at xserver level which was not taken into consideration by the nvidia binary driver (among other) - for this reason an "official" statement would be nice.

gradinaruvasile 04-25-10 02:18 PM

Re: No refresh using compiz/VNC and X 1.7
 
It might work back in 8.04/8.10 for some users (didnt work for me though).
What VNC client did you use? Try out Remmina, it is better than the default vinagre.
May be an xorg/nvidia/compiz issue/regression though. Take in account the fact that compiz too is at newer version.

AaronP 04-26-10 10:35 AM

Re: No refresh using compiz/VNC and X 1.7
 
There were some limitations in the X server that prevented x11vnc from working correctly with Compiz, but I added some code to the X server in the 1.7 timeframe to allow the driver to fix that particular problem. It should be working, but it sounds like something is going wrong with that handshaking. I'll try to take a look soon.

AaronP 04-26-10 08:18 PM

Re: No refresh using compiz/VNC and X 1.7
 
I looked into this today and found that the NVIDIA driver does not correctly generate damage events for a given window when the OpenGL rendering is actually happening to a child window. In this case, x11vnc is listening for damage events on the root, but Compiz is rendering to the Composite Overlay Window, which counts as a child window as far as this code is concerned. I'll try to fix the window hierarchy problem for a future release.

In the meantime, you can work around the problem by using Compiz's --use-root-window option, or by modifying Compiz to call XCreateDamage(dpy, cow, XDamageReportNonEmpty) to trigger damage events on the root window when it renders to the COW.

mobrien 04-28-10 07:21 AM

Re: No refresh using compiz/VNC and X 1.7
 
Wow, this is great information!

It looks like Compiz is run as simply "compiz" (from a binary in /usr/bin/) in Ubuntu (10.04 at least). Does anyone have any idea where Compiz is started/called from, so I can simply change it?

I don't want to just create a shell script redirecting to compiz with this switch, because it may be overwritten by an update. (of course, so could changing a script that starts it on login, I guess)

Also, I would imagine it would be helpful to post here where Compiz is started in other distros, if anyone knows.

Thanks AaronP! This looks like, at least, a great temporary solution!

--mobrien118

Dragoran 04-28-10 10:38 AM

Re: No refresh using compiz/VNC and X 1.7
 
Quote:

Originally Posted by AaronP (Post 2240546)
[...]
In the meantime, you can work around the problem by using Compiz's --use-root-window option

Note that this requires enabling the DisableGLXRootClipping in xorg.conf (device or screen section).


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