twm

The twm window manager for the X Windows system provides title bars, shaped windows, several forms of icon management, user-defined macro functions, click-to-type and pointer-driven keyboard focus, and user-specified key and mouse button bindings. This program is usually started by the user’s session manager or startup script. When used from xdm or xinit without a session manager, twm is frequently executed in the foreground as the last client. When run this way, exiting twm causes the session to be terminated (that is, logged out).

By default, application windows are surrounded by a “frame,” with a title bar at the top and a special border around the window. The title bar contains the window’s name, a rectangle that’s lit when the window is receiving keyboard input, and function boxes known as title buttons at the left and right edges of the title bar. Clicking Button1 (usually the leftmost button on the mouse, unless it has been changed with xmodmap) on a title button invokes the function associated with the button. In the default interface, windows are iconified (minimized to an icon) by clicking the left title button, which looks like a dot. Conversely, windows are deiconified, or maximized, by clicking the associated icon or entry in the icon manager.

Windows are resized by clicking the right title button (which resembles a group of nested squares), dragging the pointer over the edge that’s to be moved, and releasing the pointer when the outline of the window is the desired size. Similarly, windows are moved by clicking the title bar, dragging a window outline to the new location, and then releasing when the outline is in the desired position. Just clicking the title bar raises the window without moving it.

When new windows are created, twm honors any size and location information requested by the user. Otherwise, an outline of the window’s default size, its title bar, and lines dividing the window into a three-by-three grid that track the pointer are displayed. Each mouse button performs a different operation:

•  Clicking Button1 positions the window at the current position and gives it the default size.

•  Clicking Button2 (usually the middle mouse button) and dragging the outline gives the window its current position but allows the sides to be resized as described above.

•  Clicking Button3 (usually the right mouse button) gives the window its current position but attempts to make it long enough to touch the bottom of the screen.

fvwm

The fvwm window manager for X11 is a derivative of twm, redesigned to minimize memory consumption, provide a three-dimensional look to window frames, and provide a simple virtual desktop. Memory consumption is estimated at about a half to a third the memory consumption of twm, due primarily to a redesign of twm’s inefficient method of storing mouse bindings (associating commands to mouse buttons). Also, many of the configurable options of twm have been removed.

XFree86 provides a virtual screen whose operation can be confusing when used with the fvwm virtual window manager. With XFree86, windows that appear on the virtual screen actually get drawn into video memory, so the virtual screen size is limited by available video memory.

With fvwm’s virtual desktop, windows that don’t appear on-screen don’t actually get drawn into video RAM. The size of the virtual desktop is limited to 32,000×32,000 pixels. It’s impractical to use a virtual desktop of more than five times the size of the visible screen in each direction.

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NOTE:  Memory usage with the virtual desktop is a function of the number of windows that exist. The size of the desktop makes no difference.

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When becoming familiar with fvwm, it’s recommended that you disable XFree86’s virtual screen by setting the virtual screen size to the physical screen size. When you become familiar with fvwm, you may want to re-enable XFree86’s virtual screen.