Emacs global configuration of tabs

emacsexpandspacestabs

I'm attempting to switch from Vim to Emacs, but I'm tearing my hair out trying to configure it to treat tabs how I wish. I require:

Inserted "tabs" to be expanded into two spaces. Emacs stubbornly sticks to eight, no matter what I do.
Tabs (i.e. real \t characters) to be represented on screen by two spaces.
Pressing TAB should insert a tab at the cursor rather than indent the entire line. Currently, I press TAB anywhere and Emacs destroys all whitespace at the start of the line; this is the most infuriating thing so far.

My current ~/.emacs reads

(setq standard-indent 2)
(setq-default indent-tabs-mode nil)

but I have tried no end of suggested configurations from the web, none of which have done what they said they would. (Does the API constantly change? I'm using GNU Emacs 23.1.1, apparently.)

Best Answer

Emacs has extremely flexible support for handling indentation. Generally the mode that you are in dictates how they work - so if you're working on a C file then the way that pressing tab works will be different than if you're working on a Python file.

So it does depend which mode you're working in, which will limit the answers you get. In most cases I would recommend that you don't fight against it - for me the indentation behaviour is one of the best features of emacs. However, you do need to spend the time to customize it for yourself.

To change the way that tabs are displayed you need to set tab-width to 2. If you're editing Java or C style code then it sounds like you want to turn off all the nice indentation features by these to NIL:

c-tab-always-indent
c-syntactic-indentation
indent-tabs-mode

I suggest you set these through the customization interface. If you use "M-x customize-group RET C" then you can see the various settings for C mode.

If you're editting different types of files then the instructions will be different.

Perhaps emacs is in the wrong mode for your file. You could try doing "M-x fundamental-mode" to see if you prefer the behaviour there.

Short answer:

The key point is to tell emacs to insert whatever you want when indenting, this is done by changing the indent-line-function. It is easier to change it to insert a tab and then change tabs into 4 spaces than change it to insert 4 spaces. The following configuration will solve your problem:

(setq-default indent-tabs-mode nil)
(setq-default tab-width 4)
(setq indent-line-function 'insert-tab)

Explanation:

From Indentation Controlled by Major Mode @ emacs manual:

An important function of each major mode is to customize the key to indent properly for the language being edited.

[...]

The indent-line-function variable is the function to be used by (and various commands, like when calling indent-region) to indent the current line. The command indent-according-to-mode does no more than call this function.

[...]

The default value is indent-relative for many modes.

From indent-relative @ emacs manual:

Indent-relative Space out to under next indent point in previous nonblank line.

[...]

If the previous nonblank line has no indent points beyond the column point starts at, `tab-to-tab-stop' is done instead.

Just change the value of indent-line-function to the insert-tab function and configure tab insertion as 4 spaces.

Eclipse – How to change Eclipse to use spaces instead of tabs

Java Editor

Click Window » Preferences
Expand Java » Code Style
Click Formatter
Click the Edit button
Click the Indentation tab
Under General Settings, set Tab policy to: Spaces only
Click OK ad nauseam to apply the changes.

[Note: If necessary save profile with a new name as the default profile cannot be overwritten.]

Default Text Editor

Before version 3.6:

Window->Preferences->Editors->Text Editors->Insert spaces for tabs

Version 3.6 and later:

Click Window » Preferences
Expand General » Editors
Click Text Editors
Check Insert spaces for tabs
Click OK ad nauseam to apply the changes.

Note that the default text editor is used as the basis for many non-Java editors in Eclipse. It's astonishing that this setting wasn't available until 3.3.

C / C++

Click Window » Preferences
Expand C/C++ » Code Style
Click Formatter
Click the New button to create a new profile, then OK to continue
Click the Indentation tab
Under General Settings, set Tab policy to: Spaces only
Click OK ad nauseam to apply the changes.

HTML

Click Window » Preferences
Expand Web » HTML Files
Click Editor
Under Formatting, select the Indent using spaces radio button
Click OK to apply the changes.

CSS

Follow the same instructions for HTML, but select CSS Files instead of HTML Files.

JSP

By default, JSP files follow the formatting preferences for HTML Files.

XML

XML files spacing is configured in Preferences.

Click Window » Preferences
Expand XML » XML Files
Click Editor
Select Indent using spaces
You can specify the Indentation size if needed: number of spaces to indent.