GUI without X?

[littlebigman]

Hello

This is a general newbie question about using a GUI on Linux: If I got it right, all graphical applications in Linux ultimately call the X server to display output on the screen, even on the local host.

Isn't there a performance penalty to go through a local server application to write output instead of just writing to the video card?

Can Linux GUI apps run without an X server?

Thank you.

[hazel]

I don't know if existing apps will, but it is certainly possible to write Xlib- or gtk-based apps that run in the kernel's framebuffer and therefore don't need X. Here's an example.

[GNU-Fan]

A more active project would be DirectFB. It has a couple of ported applications and there is even an official backend for it in GTK.

Isn't there a performance penalty to go through a local server application to write output instead of just writing to the video card?

That's right. Even though the performance loss due to the routing in X is not that big. The reason for X to feel so sluggish has more to do with its limited set of native drawing operations. For example, there is no common set of decorations for windows and borders. You need additional toolkits for that. This "assume nothing"-approach gives much flexibility but makes it harder to accelerate drawing operations smartly.

If I got it right, all graphical applications in Linux ultimately call the X server to display output on the screen, even on the local host.

There are some mechanisms in place that allow bypassing the server. For example DRI for OpenGL.

[littlebigman]

Thanks guys for the infos.

[twoHats]

Trying to determine the efficiency of a particular software architecture is not that easy for an expert, much less someone just wondering ..."Hmmm? could this be more efficient?".

Usually, software is made from a lot of interconnecting modules, and to look at one and say "is this a good idea?" usually won't work without looking at (perhaps many) others. Also one must have some idea of an alternative architecture in mind to be able to make any judgment at all.

In other words, the answer to your question is ...

It's Complicated!

[littlebigman]

Thanks for the input.

[Rubberman]

One of the contributing factors to the perceived performance issues of X-Windows is that it is a very verbose message-based architecture, designed so that applications that run on one system can be displayed easily on another machine across the network. There are other windowing systems that do not support (easily) remote output, and are generally much smaller and faster - more suited to embedded applications. One good example is the QNX Photon windowing system that runs with the QNX Neutrino real-time operating system. It has a lot of the same capabilities as X, but is designed for local rendering in small footprint systems. As a result, it is smaller, faster, and in many situations a lot easier to program with.

[littlebigman]

Thanks. It's just that users of desktop Linux have no need for remote display, so I was wondering if it were possible to bypass X and have the OS write contents directly to the video card instead.

Another issue I've had with all Linux distros, is that, on the exact same hardware, the fonts look blurry, not as sharp as compared to Windows. I don't know if this is due to X or that the open-source fonts don't work the same way.

[theNbomr]

Thanks. It's just that users of desktop Linux have no need for remote display

That assumption is far from correct. There are many installations of Linux whose primary purpose is to support X for running applications on other hosts. It's one of the real strengths of X over local-only display. I personally cannot imagine going back to any local-only displays. Even Windows users adopt this paradigm occasionally; remote-desktop.

There may be efficiencies to be gained by eliminating part of the the X layer, however X itself has some built-in efficiencies for this reason. The Direct Rendering Interface in particular provides for very efficient access to video hardware. There are other accelerating interfaces, as well.

--- rod.

[Rubberman]

Ditto to what Nbomr said. In any case, you can't just write to video memory any longer with today's video hardware unless you want to be stuck in VGA resolution at best (640x480). My phone does better than that... In any case, there IS a standard set of API's that all modern video hardware supports that provides better resolution than VGA. It's called VESA. However, it is sort of a lowest-common-denominator interface that is only used when better drivers are not available for your particular hardware. So, you COULD write your applications to use the VESA API's directly, but you still have to do all of your own font rendering, window management, etc. Trust me as an engineer who has done this at the most fundamental level, you REALLY don't want to!