nxml-mode: Completion
2 Completion
************
Apart from real-time validation, the most important feature that nXML
mode provides for assisting in document creation is "completion".
Completion assists the user in inserting characters at point, based on
knowledge of the schema and on the contents of the buffer before point.
nXML mode adapts the standard GNU Emacs command for completion in a
buffer: ‘completion-at-point’, which is bound to ‘C-M-i’ and ‘M-<TAB>’.
Note that many window systems and window managers use ‘M-<TAB>’
themselves (typically for switching between windows) and do not pass it
to applications. In that case, you should type ‘C-M-i’ or ‘<ESC> <TAB>’
for completion, or bind ‘completion-at-point’ to a key that is
convenient for you. In the following, I will assume that you type
‘C-M-i’.
nXML mode completion works by examining the symbol preceding point.
This is the symbol to be completed. The symbol to be completed may be
the empty. Completion considers what symbols starting with the symbol
to be completed would be valid replacements for the symbol to be
completed, given the schema and the contents of the buffer before point.
These symbols are the possible completions. An example may make this
clearer. Suppose the buffer looks like this (where ★ indicates point):
<html xmlns="http://www.w3.org/1999/xhtml">
<h★
and the schema is XHTML. In this context, the symbol to be completed is
‘h’. The possible completions consist of just ‘head’. Another example,
is
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<★
In this case, the symbol to be completed is empty, and the possible
completions are ‘base’, ‘isindex’, ‘link’, ‘meta’, ‘script’, ‘style’,
‘title’. Another example is:
<html xmlns="★
In this case, the symbol to be completed is empty, and the possible
completions are just ‘http://www.w3.org/1999/xhtml’.
When you type ‘C-M-i’, what happens depends on what the set of
possible completions are.
• If the set of completions is empty, nothing happens.
• If there is one possible completion, then that completion is
inserted, together with any following characters that are required.
For example, in this case:
<html xmlns="http://www.w3.org/1999/xhtml">
<★
‘C-M-i’ will yield
<html xmlns="http://www.w3.org/1999/xhtml">
<head★
• If there is more than one possible completion, but all possible
completions share a common non-empty prefix, then that prefix is
inserted. For example, suppose the buffer is:
<html x★
The symbol to be completed is ‘x’. The possible completions are
‘xmlns’ and ‘xml:lang’. These share a common prefix of ‘xml’.
Thus, ‘C-M-i’ will yield:
<html xml★
Typically, you would do ‘C-M-i’ again, which would have the result
described in the next item.
• If there is more than one possible completion, but the possible
completions do not share a non-empty prefix, then Emacs will prompt
you to input the symbol in the minibuffer, initializing the
minibuffer with the symbol to be completed, and popping up a buffer
showing the possible completions. You can now input the symbol to
be inserted. The symbol you input will be inserted in the buffer
instead of the symbol to be completed. Emacs will then insert any
required characters after the symbol. For example, if it contains:
<html xml★
Emacs will prompt you in the minibuffer with
Attribute: xml★
and the buffer showing possible completions will contain
Possible completions are:
xml:lang xmlns
If you input ‘xmlns’, the result will be:
<html xmlns="★
(If you do ‘C-M-i’ again, the namespace URI will be inserted.
Should that happen automatically?)
Info Catalog
nxml-mode: Introduction
nxml-mode: Top
nxml-mode: Inserting end-tags