nswbuff is an Emacs library for quick buffer switching based on swbuff.el, incorporating the changes from swbuff-x.el and a few new features not present in either.
nswbuff can be installed through Melpa.
The primary commands are nswbuff-switch-to-previous-buffer and nswbuff-switch-to-next-buffer, which should be bound to keys of your liking, e.g., <C-tab> and <C-S-iso-lefttab> (i.e., Ctrl-TAB and Shift-Ctrl-TAB).
In a default setup, executing nswbuff-switch-to-next-buffer once has the following effect:
This screen shot shows a buffer switch from nswbuff.el to README.md. The bottom of the frame shows the list of buffers. Special buffers (those whose names start with *) are in red. The bold red, underlined buffer will become active when buffer switching ends. The first buffer in the list is the one you're switching from, which is still visible in the main window. Executing nswbuff-switch-to-next-buffer again will highlight the next buffer in the list (*ielm* in the screen shot).
Buffer switching ends automatically after a short delay, or when you press any key (other than the keys bound to nswbuff-switch-to-next-buffer and nswbuff-switch-to-previous-buffer, obviously). By default, during buffer switching, the initial buffer remains visible until buffer switching ends. If you wish to make the intermediate buffers visible during cycling, you can set the option nswbuff-display-intermediate-buffers to t:
This screen shot shows the same buffer switch, from nswbuff.el to README.md, but this time the README.md buffer is shown during switching. Executing nswbuff-switch-to-next-buffer again would show the *eshell* buffer. Note that the screen shot also shows that the face and colours used for displaying the buffer names are fully customisable.
The buffers that nswbuff offers for cycling are essentially the buffers returned by the function buffer-list. There are a few options to customize this list, however. First, you can exclude buffers with nswbuff-exclude-buffer-regexps. Any buffer whose name matches one of the regexps in this list is not switchable. The default setting excludes buffers with a name that begins with a blank character. To exclude all the internal buffers (that is *scratch*, *Message*, etc...) you could use the following regexps '("^ .*" "^\\*.*\\*").
Buffers can also be excluded based on their major mode through the option nswbuff-exclude-mode-regexps. These regexps are matched against the symbol-name of the buffer's major mode.
Buffers that match one of these options but should be included anyway can be matched using the option nswbuff-include-buffer-regexps. Any buffer matching one of the regexps in this list is included, regardless of whether they also match an exclude regexp. Obviously, the same effect can also be obtained by using more specialized exclude regexps, but using an include regexp is usually easier to understand and less error-prone.
Another option for customizing the list of switchable buffers is nswbuff-buffer-list-function. This can be set to a function that returns a list of buffers, making only those buffers switchable instead of all buffers returned by buffer-list. If the function in nswbuff-buffer-list-function returns nil, nswbuff falls back to the buffers returned by buffer-list.
Note that the list of buffers returned by the function in nswbuff-buffer-list-function is still matched against nswbuff-exclude-buffer-regexps, nswbuff-exclude-mode-regexps and nswbuff-include-buffer-regexps, so set (or keep) these to nil if you don't want this.
Lastly, buffers can be excluded through a buffer-local variable nswbuff-exclude. This variable can be set to t in a file-local variable block or in a .dir-locals.el file to exclude specific files from switching that cannot be easily captured in another way. For example, if you want to exclude certain Org files (e.g., the agenda files) from the buffer list without excluding all Org files, you could use this method.
Quite a few aspects of nswbuff can be customized in addition to the ones already mentioned. See the customization group nswbuff for details. One option worth pointing out here is nswbuff-status-window-layout, which controls how the window displaying the list of buffers during switching is laid out. Normally, the buffer shows the list of buffers on a single line, but if the number of buffers grows too large, you can either choose to scroll the buffer list horizontally (so that not all buffers names are visible in the nswbuff status window), or you can decide to adjust the status window's height. The default value is a combination of these two options: if there is only one window in the frame, the status window's height is adjusted, otherwise the buffer list is scrolled.
Alternatively, you can set nswbuff-status-window-layout to minibuffer, in which case the minibuffer will be used to display the buffer list.
nswbuff provides some very simple but nifty integration with the project-management packages project.el (built-in) and projectile. If you set nswbuff-buffer-list-function to nswbuff-project-buffer-list or nswbuff-projectile-buffer-list, only the buffers belonging to the current project are offered for switching. This makes for a very light-weight (but in my opinion effective) alternative to such modes as perspective.el or persp-mode. Switching buffers with nswbuff keeps you in the project, any other buffer-switching method (switch-to-buffer, but also 3rd-party options such as ivy or helm) is not affected and can thus be used to move out of the project.
Packages such as zoom and golden-ratio automatically resize windows to ensure that the active window always has a certain minimum size. There is no point in resizing the buffer switching window, however, so in order to prevent that from happening, you should add the name of the nswbuff status buffer to golden-ratio-exclude-buffer-names or zoom-ignored-buffer-names. This name defaults to " *nswbuff*" (without the double quotes; note the initial space).