Emacs, smooth scrolling, scroll-margin and eshell - emacs

I like a scroll margin of around 8 or so. This means the buffer will start scrolling when the cursor gets within 8 lines of the top or bottom. However, this scheme does not work well with eshell and ansi-term buffers, isql buffers, or any REPL buffers that one might use with emacs. In any of those buffers, when one does anything, it immediately scrolls the buffer up so that there are 8 lines between the bottom of the buffer and the input line, making it awkward at best, unusable at worst, to use any terminal-like buffer in emacs, depending on the situation.
No buffer seems to recognize the scroll-margin variable unless it is global. So while I can set the variable to different values with hooks in different modes, it affects all of my open buffers.
So lets say I'm editing some code. I decide to do some stuff in a shell. My shell-mode-hooks set the scroll-margin to 0 (so that they may be usable). Then the scroll-margin is set to 0 for all buffers, making it awkward to scroll in my coding buffers. But then if I open a new coding buffer, it will set my scroll-margin back to 8. Then my shell buffers are awkward or unusable because it immediately scrolls up 8 spaces whenever they get focus or display output from a command.
Is there any solution to this problem, other than to keep a scroll-margin of 0, globally, for all buffers?

Converting comment into answer. Use a buffer local variable in hook.

Related

emacs follow-mode use/alternatives

I have recently started using Emacs follow-mode to see more of documents I am working on. Unfortunately, it seems to have some limitations, at least as I am using it. I very often use C-x b RET to toggle between two buffers, but this doesn't work as I would expect with follow-mode. I would expect that if both buffers are set up to use follow-mode, it should switch both windows, but it does not. Also, even if only one buffer is set to use follow-mode, hitting C-x b RET after switching to that buffer should get me back to my original configuration, but instead it switches the active window to some third buffer. Can anyone explain some better follow-mode idioms or else an alternative to follow-mode?

emacs zoom in/out globally

I know that I can zoom in/out using C-x C-+, but this applies only to the current file. Once I open another one, the text goes back to the default value and it's really tiresome to do it over and over. How can I keep the zoom level global for the current emacs session?
I know it's possible to set this in the init file if you know the exact font size, which I don't. Plus, I don't want to keep it that permanent - I usually need this when I'm without an external screen for a couple of hours or connected to a beamer while giving a presentation.
This piece of code modify the zoom in/out functionality to apply the commands to every buffer. That should achieve what you are trying to do.
(defadvice text-scale-increase (around all-buffers (arg) activate)
(dolist (buffer (buffer-list))
(with-current-buffer buffer
ad-do-it)))
All of the answers given here, and more, are available on the
EmacsWiki page dedicated to the question of setting and changing font
size, including changing it incrementally.
The answer from #abo-abo is on the right track, regardless of whether
you think the size he used in the example code was too big, and
regardless of whether the solution does not address incremental
adjustment.
The answer from #juanleon essentially makes text scaling simulate
changing the default character size (#abo-abo's answer).
The point of text scaling is to scale the buffer text (one buffer, no
matter where it is shown), not the frame text (all buffers shown in
the frame). But if you want all buffers to have their text size
changed in a given frame then there is no reason to bother with text
scaling in that case: just change the font size.
You can do either or both (scale the buffer text everywhere or zoom a
frame), and do so incrementally, using the same command, if you use
command zoom-in/out from library
zoom-frm.el.
On the other hand, if you really do want to incrementally change the
text size of all buffers in all frames, then the best approaches are
either (1) #juanleon's suggestion or (2) incrementally zoom the standard face
default.
To do the latter, you can use commands zoom-all-frames-in and
zoom-all-frames-out in library
zoom-frm.el
Just paste this in *scratch* and evaluate (with C-j or C-x C-e):
(set-face-attribute 'default nil :height 150)
There's nothing wrong in putting this in the init file
and commenting it out later, when you don't need it.
Its possible to scale all text (including status-line & line-numbers) using a little mode that handles this exact problem: purcell/default-text-scale. It's available in Melpa.
This scales all text to avoid text scale mismatch such as line-numbers of fill-column indicator being offset incorrectly.
The other answers here either don't work for new buffers or require too much manual intervention.
connected to a beamer while giving a presentation.
There is another package for that!
emacs-presentation-mode
Quoting from the site
Execute M-x presentation-mode to start the presentation.
Adjust scale size by C-x C-+ or C-x C--
See https://www.gnu.org/software/emacs/manual/html_node/emacs/Text-Scale.html
After the presentation, execute M-x presentation-mode again.
And then execute M-x presentation-mode again, the last scale will be reproduced.
If you want to persistize its size as the default size of presentation-mode
after restarting Emacs, set presentation-default-text-scale.
It's also have description of differences from other similar modes/package.

Emacs scrollbars with exact positioning

How can I get scrollbars with exact positioning?
To illustrate what I mean:
C-h C-f (Read the The GNU Emacs FAQ)
Now try to position the buffer content such that the paragraph starting with This is the version ... is on top. With the default scrollbar you need several redraws to do this. Or you left-click for cursor positioning then C-lC-l
Now go back to where you have been before. This is impossible with regular scrollbars.
What I would like to have is to just click in the scrollbar at the height of This is the version ... to position this line on top for step 2. And to go back where I came from, I rightclick (without having moved the mouse, indeed).
In the past, I have always installed Emacs with the Athena widgets-like option to get such scrollbars, see a description of them. But I wonder if there is now a better or more modern way to do this. After all, I'd rather like to use standard distributions.
Maybe, it is not even necessary to change the scrollbars at all but to use rather the left-fringe for it. After all, mouse clicking in the fringe is recognized as <left-fringe>
M-x emacs-version
GNU Emacs 23.3.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.10) of 2012-09-21 on batsu, modified by Debian
Maybe a change of usage habits could help? Some Emacs user recommend disabling the scrollbars completely and navigate Emacs exclusively with the keyboard. (This habit is also beneficial for using Emacs inside a shell.)
Emacs provides a large number of navigation shortcuts. For instance, for jumping up and down large amounts of buffer space, you have:
C-v scroll-up
M-v scroll-down
M-} forward-paragraph
M-{ backward-paragaph
C-x ] forward-page
C-x [ backward-page
However, I would argue that by far the most useful navigation commands are:
C-s isearch-forward
C-r isearch-backward
In Emacs, search is so cheap, it is such an integral part of the work flow that it's often times much faster to get to a different point in the buffer by using a reference word as an anchor for a quick search, rather than leaving the home row to reach for the mouse. Hitting C-s or C-r repeatedly will move the point to consecutive matches. (You can even switch to regular expression search by hitting M-r while searching to make search even more powerful.)
You already mentioned C-l C-l to view the current line at the top of the buffer.
Now, if you want to go back to the previous location, you could use
C-u C-x
which jumps back to the mark. All the above commands for navigation push their start position on a "mark-ring" which means you can not only jump back one position, repeatedly hitting C-u C-x will take you back to many previous positions.
For this task I press C-l once, twice, three times.They will switch between middle-top-bottom.

Emacs: help me understand file/buffer management

I've been using emacs for all of my text editing needs for the past three years now. When I'm in a single file, working on code or whatnot, I'm fairly efficient. With two files, I can "C-x b RET" between them and I do fine. However, whenever I need to be working on more than two files at a time, I tend to get lost.
Here are some of the problems that I'd like to work on:
I forget what some of my buffers are called, but I don't understand why C-x C-b splits my window into two buffers and exits the mini buffer. Sure I can switch buffers and choose a buffer to visit, but this feels unintuitive, and leaves me with two buffers open.
When I visit a directory rather than a file, I have a convenient list of all of the files and directories. I usually want to do one of two things with this: 1) Open a single file and never see this buffer again OR 2) Open a bunch of files and never see this buffer again. I don't really know how to do this, as moving the point to a file and hitting return doesn't do either of these things.
I know that my buffers aren't like tabs, but I have an inclination to want to scroll through them to find what I want. I don't know of any key-bindings for this, but I'd like it to be M-n / M-p or the like. Then again, this may be a horribly inefficient way to switch buffers.
When I open interactive help of any kind (for example in ESS), I have a habit of switching back to the buffer I was working in and using C-x 1 to get back to a single buffer. When I do this, however, the help buffer hangs around in my buffer list, further confusing me. I know I can switch to that buffer, kill it, switch back, and then go back to a single buffer, but this seems wrong.
The way I've dealt with this so far involves using a tiling window manager and a few emacs windows in different work-spaces, rather than actually learn the best way to manage a number of files in emacs. I don't necessarily want to change emacs to better fit my needs (although I am open to that if it fits in with what I'm about to say), instead, I'd like to grok the thought process behind handling files/buffers the way that emacs does, and how I can be more efficient with it.
Any answer that would help me understand the correct way, or a more efficient way to manage my buffers or files would be greatly appreciated.
Bind C-x C-b to ibuffer. This is a better buffer listing facility with many advanced features, and its default behaviour is to replace the current buffer with the buffer listing, and then bury the listing when you select a buffer (leaving you with the newly-selected buffer in place of the original one).
You can simply use C-x b to enter your selection in the mini-buffer, of course; however the tab-completion (which is needed to make this a viable option, IMO) does open a new window temporarily, at which point I think you might as well familiarise yourself with something with more features.
Use a instead of RET when selecting from dired. This kills the dired buffer instead of leaving it behind. C-h m in any buffer will show you the help for its major mode (followed by help for the minor modes), and you can read about all the available dired key bindings there.
http://www.emacswiki.org/cgi-bin/wiki/TabBarMode ? (edit: I prefer Rémi's answer for this one, but TabBarMode would give you the visual tab element if you were particularly keen on that.)
q is bound to a 'quit' function in a great many major modes. Generally it buries the buffer rather than killing it, but I certainly find that fine.
To elaborate a little on #1, ibuffer has lots of nice features, and M-x customize-group ibuffer RET will give you some idea of how you can customise it to your liking.
Furthermore, you can filter the buffer list by many criteria (again, use C-h m to see its help page), and then generate a 'group' definition from the current filters, and save your custom filters and groups for future usage.
For example:
/ f ^/var/www/ RET: filter buffer list to show only filenames starting with /var/www/.
/ s Web filters RET: name and save active filter set to your init file.
/ g Web development RET: create a named group from the active filters.
/ S My groups RET: name and save group definitions to your init file.
/ r Web filters RET: invoke the "Web filters" filters.
/ R My groups RET: invoke the "My groups" groups.
RET on a group name to collapse or expand it.
C-k and C-y to kill and yank groups, to re-arrange them.
C-h m for more information...
This way you can have a single Emacs instance running, and create filters and groups for different types of task, and easily switch between them.
I think you will really enjoy Ido for dealing with multiple buffers who's names you can't exactly remember. When you type C-x b it shows a list of open buffers in most used order. As you type some of the characters in a buffer name the list is filtered. The characters you type don't have to be at the begging of the name or contiguous. Using C-f, C-b or left/right arrow keys cycles through the buffer choices.
Also see Smex for Ido like functionality for M-x
Closing windows is done with C-x 0. Intentionally splitting the window is done with C-x 2 for horizontal, C-x 3 for vertical. I love this feature, since it allows me to have test and production code visible at the same time. C-x o takes me to the other window.
I use C-x right (or C-x C-right) and C-x left (or C-x C-right) to go to the next and previous buffer. I don't mind anymore off the few buffer that lay around in Emacs but you could use k in the buffer list to kill the buffer you don't use anymore.
You can also try Iswitchb mode which provides auto-completion for buffer names when you switch buffers via C-x b.
To activate:
M-x iswitchb-mode
Or add to your .emacs file:
(iswitchb-mode)
It is similar to Ido mode for buffer switching but a bit more lightweight.
Also, if you want a more customizable listing of your buffers then use M-x bs-show as an alternative to C-x C-b. In that buffer type ? to get a list of actions you can perform.
I think the number one most useful extension for flipping through buffers is Anything. It lets you start typing part of a buffer (or file!) name and it will figure out what you want. I've rebound C-x b to anything-for-buffers. It makes life so much better.
As always, there are many ways to help you with this; it depends a bit on personal preference what works best, here are some links with explanations:
ibuffer; which is an updated buffer menu (C-x C-b)
ido, which let's you have more powerful autocompletion to switch through buffers. It's a kind-of 'better iswitchb'.
These two are enough for me; but you may also be interested in the tabbar-mode, which gives you rudimentary tabs (like firefox has them).

Emacs - Multiple columns one buffer

I'm trying to edit some assembly code which tends to be formatted in long but thin listings. I'd like to be able to use some of the acres of horizontal space I have and see more code on-screen at one time. Is there a method for getting Emacs (or indeed another editor) to show me multiple columns all pointing to the same buffer?
C-x 3 (emacs) and :vsplit (vim) are great for multiple separate views into the code, but I'd like it to flow from one column to the other (like text in a newspaper).
See follow-mode.
Excerpt:
Follow mode is a minor mode that makes two windows, both showing the same buffer, scroll as a single tall “virtual window.” To use Follow mode, go to a frame with just one window, split it into two side-by-side windows using C-x 3, and then type M-x follow-mode. From then on, you can edit the buffer in either of the two windows, or scroll either one; the other window follows it.
In Follow mode, if you move point outside the portion visible in one window and into the portion visible in the other window, that selects the other window—again, treating the two as if they were parts of one large window.
I use this function to invoke follow-mode, although it would need customization for a different screen size:
;;; I want a key to open the current buffer all over the screen.
(defun all-over-the-screen ()
(interactive)
(delete-other-windows)
(split-window-horizontally)
(split-window-horizontally)
(balance-windows)
(follow-mode t))
The "Multipager" plugin for Vim can do this with VIM splits for people who want to get this behavior in Vim.
Get it from Dr. Chip's page: http://mysite.verizon.net/astronaut/vim/index.html#MPAGE
Docs: http://mysite.verizon.net/astronaut/vim/doc/mpage.txt.html
Vim can do this using :vsplit - and you can have the same buffer open in multiple "windows" (which are actually sections within a single "window").
Documentation here
A quick look at the emacs wiki doesn't show a mode like you describe. However, it shouldn't be too hard to write one... You just need to split the window with C-x 3 and move the text in the other window down, and whenever you move the text, do the same to the other window...
Problems may occur when you get to the bottom of the buffer, do you want the cursor to immediately go to the other window at the top?
Hmm, maybe its not that easy. But it should still be doable...
this is the default behaviour of emacs when splitting the window (C-x 3 for vertical split)
you get two columns which both have the current buffer open
Use vertical-split with C-x 3. This will split the current buffer into two columns that you can switch between with C-x o.