Thoughts about Network Trancparency

Original Article by Martin Gräßlin, published on his Blog

Every time there is an article about Wayland you can see that there a lots of uneducated comments about the “fact” that Wayland does not support network trancparency and because of that it is completely wrong to go for network trancparency. These discussions contain a lot of myths and even FUD and I consider it important to share my thoughts about these concerns as I am belonging to those who actively work to bring the benefits of Wayland to the KDE Plasma Workspaces.


Wayland Could Use Network Transparency


Nothing in the Wayland protocol forbidds network transparency. It is not yet implemented, but it is possible to implement it. Wayland uses a Unix Socket for communication but I think it would be rather trivial to either add network transport to the Wayland protocol or to just forward the buffer in the compositor. Stating that Wayland does not support Network Transparency in general is just wrong. It’s not yet implemented but many things are not yet implemented. Obviously it’s true that the Wayland protocol does not support the X11 Network Transparency as it’s not X11 (and that is a good thing). Obviously even a direct X11 successor (let’s name it X12) would also not support the X11 Network Transparency.


X11 Network Transparency is not Suited for Modern Applications


The idea behind the network transparency is to send drawing commands over the wire (useful idee for the requirements of 30 years ago). Nowadays modern applications do not use X11 any more for rendering. They use technologies like Cairo, Clutter, QPainter (Raster) or OpenGL directly. Without using X11 for rendering you end in streaming pixels over the wire. And there are clearly better technologies to do that than X11. Face it: network transparency is going to break very soon even without Wayland. I want to see the Qt 5 used over the wire.


Modern Applications require DBus


Yes DBus is not network transparent and yes most modern application use it, for things like StatusNotifier (this one has fallback to Xembed) or moving the menus somewhere else. Now without network transparency these things are just shown on the wrong system or not at all. Damn stupid devs not thinking about network transparency… So face it: no modern app can be used without DBus which breaks implicitly also the X11 Network Transparency.


Wayland targets Mobile Devices


Those who attended my presentation at Desktop Summit or who have seen my slides might have already got the message: we don’t want to break the desktop and will therefore only target mobile devices in the beginning. The same is true for MeeGo (they don’t have a desktop) and hopefully also GNOME Shell and Unity. So do you really want to forward your X11 application from your (mouse+keyboard) desktop to your touch tablet/smartphone? Probably not. So why do you care about network transparency not available on mobile? For mobile the target groups are the billions of users out there who do not even know that network transparency existed and not the five geeks who cannot live without it. Face it: you are not in the target group of Wayland on mobile devices if you need network transparency. (You probably wouldn’t use an iPad either).


Desktop will continue to Support X11


We will only switch to Wayland as our primary windowing system if we can continue to support legacy X11 applications, because we don’t want to break the desktop. This means you can still run your legacy X11 windows over network even under Wayland and also X11 applications on the Wayland system can still be forwarded to a remote system. So I hear you already complaining about the Wayland windows not being able to be forwarded. Well if the toolkit (like Qt) supports multiple backends there is no reason why you should not use the X11 backend to forward the window. Apart from that: remember, it would not be working at the time when we switch to Wayland even under X11 (see above).


Network Transparency Does Not Belong Into The Windowing System


Adding Network Transparency in the Windowing System is the wrong layer. The windowing system only receives the pixels and that can never be performant. Network Transparency needs to be added to the layer which does the rendering. That used to work with X11 as X11 also did the rendering, but this is not true any more. We need support for Network Transparency in the toolkit. Just imagine the possibilites: remote applications picking up your local font settings, color themes, icon themes… That’s what needs to be done!


But Distros will remove X11 support in $X Years


As long as there is a demand for legacy support distros will still support it. Especially I don’t think that enterprise distributions will dare to remove it in the next 10 to 20 years. Remember that also Mac OS X still supports legacy X11. And even if the distro removes the support: who stopps you to package X11 yourself and provide it to everyone who needs X11? Btw we are talking here about at least three to five years – others have predicted the death of desktop till then.



I hope this post can help to bring future discussions about Wayland to not keep repeating what has already said and is just wrong.

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