The following sections provide details about our window manager and multi-head X-Server setups. This information is intended for anyone in the future changing things such as window manager scripts, multi-head layouts, or observing session window placement rules (all of which are more complicated when there are three monitors per terminal!) There is a separate document on the Web with more user oriented information for local users who just want to customize their desktop colors or window manager menus. The information here is more low-level, and intended for setting up observing sessions. It in the interest of anyone developing user interface software for use at CFHT to at least be aware of these basic layers of the window session.
Multi-Head configurations are being phased out in 2015-2017. Refer to old (2003) versions of this document if you needed information about SLS, Xinerama, and multiple displays.
Although we're eliminating multiple monitors, we're still leaving in place virtual desktops (also known as workspaces, or previously known as a ``Pager'' in FVWM). The concept is pretty commonly understood now so there's no need to go into detail describing how it works here.
These days (2016) we run everything with the open source Xorg X-Server. Previously, we used servers from the XFree86 project, and also a commercial one from Xinside Graphics, but these days Xorg is pretty much the standard. We have no immediate plans or need to look at Wayland or Mir for our applications at this time.
Historically, we've had to support a wide range of graphics hardware but as of 2016 it's pretty much all graphics chips from NVidia (covered by their closed-source driver, though ``nouveau'' is available for use as well if we need to use it) and intel integrated graphics. There might be a few ATI/Radeon floating around but we can usually support those and other odd graphics card through the VESA standard driver. Remember that our applications do not have an particularly high performance needs. We just need to display a lot of pixels. There is no need for the best 3D or even 2D acceleration for any of the observer's needs.
8-bit PseudoColor is definitely a thing of the past by now, but believe it or not we were still hanging on to it 10-15 years ago when the rest of the world had long since moved on because of the way some astronomy-specific image display programs worked. If you don't know what this is, don't worry. It's dead. So are 8-bit Overlays. DirectColor mode may have been interesting to us when computers were slower, but it's also not worth looking at anymore.
All of our new displays and display drivers use a mode where the intensity of red, green, and blue can be set separately for each pixel to a precision of 8-bits for each primary color. Essentially, any pixel can be any color.
Window Session software running on the Session Host has been kept purposely light weight. We do not use Gnome session. In fact, we run no desktop/session manager at all, only a basic window manager. The window manager through the mid 90's used to be one called MWM (Motif Window Manager), but then we transitioned to FVWM 1.24r (because it supported virtual desktops, was more lightweight), later FVWM 2.4 (because it supported the multiple monitors which are now mostly gone) and finally XFCE today. XFCE4 is the window manager that Linus Torvalds (was? is?) using. It's very lightweight and does the job for us.