Terminology reconciliation: Display manager vs. session manager, Windowing system vs. Window manager

display-managerterminologywindow-managerx11

I am taking the Linux Foundation's Introduction to Linux course. Some of the terminology seems to overlap or contradict, especially when I try to supplement the course material with other sources, such as TLDP and Wikipedia.

Is a "Display Manager" the same thing as a "Session Manager"?

Display manager: Program that initiates a windowing system session by launching the windowing system and usually asking for a username and password.

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Session manager: Starts and maintains the components of the graphical session.

Likewise, is a "Windowing system" the same thing as a "Window manager"?

Windowing system: Software which provides the key elements of the GUI for high-level software to use. Provides applications with a (usually) rectangular, resizeable surface to present its GUI to the user.

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Window manager: Controls the placement and movement of windows, window chrome, and controls.

And just to be sure about X: From what I gather it seems that "X Window System" is a windowing system for bitmap displays, "X11" is the current protocol version for the X Window System, and "X.Org Server" is the reference implementation of the X11 protocol. Is that correct?

Best Answer

Is a "Display Manager" the same thing as a "Session Manager"?

Answer: No they are not the same. The session managermanages your session, and the display manager is responsible for providing you with a login interface.

Likewise, is a "Windowing system" the same thing as a "Window manager"?

Answer: No they are different. The window mangager sits on top of the Window system.

The Window system: Each currently running application is assigned a usually resizeable and usually rectangular shaped surface of the display to present its graphical user interface to the user; these windows may overlap each other, as opposed to a tiling interface where they are not allowed to overlap.

The window manager: When a window manager is running, some kinds of interaction between the X server and its clients are redirected through the window manager. In particular, whenever an attempt to show a new window is made, this request is redirected to the window manager, which decides the initial position of the window

Session Manager source

In the X Window System, an X session manager is a session management program, a program that can save and restore the current state of a set of running applications.

X window manager source

An X window manager is a window manager which runs on top of the X Window System, a windowing system mainly used on Unix-like systems.

Types of window managers

  1. Stacking window managers
  2. Tiling window managers
  3. Compositing window managers
  4. Virtual window managers
  5. Window managers that are extensible

The user can choose between various third-party window managers, which differ from one another in several ways, including:

customizability of appearance and functionality:

  • textual menus used to start programs and/or change options

  • docks and other graphical ways to start programs

  • multiple desktops and virtual desktops (desktops larger than the physical monitor size), and pagers1 to switch between them

  • consumption of memory and other system resources

  • degree of integration with a desktop environment, which provides a more complete interface to the operating system, and provides a range of integrated utilities and applications.

While the main aim of a window manager is to manage the windows, many window managers have additional features such as handling mouse clicks in the root window, presenting panes and other visual elements, handling some keystrokes (e.g., Alt-F4 may close a window), deciding which application to run at start-up, etc.

Display manager source (there is a list of display managers in the source website)

A display manager, or login manager, is typically a graphical user interface that is displayed at the end of the boot process in place of the default shell. There are various implementations of display managers, just as there are various types of window managers and desktop environments. There is usually a certain amount of customization and themeability available with each one.

X display manager source

In the X Window System, an X display manager runs as a program that allows the starting of a session on an X server from the same or another computer.

A display manager presents the user with a login screen which prompts for a username and password. A session starts when the user successfully enters a valid combination of username and password.

The X window system source

Debian manual for x window system

xorg site

The X Window System (X11, X, and sometimes informally X-Windows) is a windowing system for bitmap displays, common on UNIX-like computer operating systems.

X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting with a mouse and keyboard. X does not mandate the user interface — this is handled by individual programs. As such, the visual styling of X-based environments varies greatly; different programs may present radically different interfaces.

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