1.9 The Echo Area

The echo area is the region which occupies the bottom few lines on the screen. It is used for two purposes: displaying brief messages to the user and prompting. [annotate]

When a command needs some information from the user, it requests it by displaying a prompt in the echo area. The following is a typical prompt: Select Buffer: [hemlock-init.lisp /usr/foo/] The general format of a prompt is a one or two word description of the input requested, possibly followed by a default in brackets. The default is a standard response to the prompt that Hemlock uses if you type Return without giving any other input. [annotate]

There are four general kinds of prompts: [annotate]

key-event

The response is a single key-event and no confirming Return is needed. [annotate]

keyword

The response is a selection from one of a limited number of choices. Completion is available using Space and Escape, and you only need to supply enough of the keyword to distinguish it from any other choice. In some cases a keyword prompt accepts unknown input, indicating the prompter should create a new entry. If this is the case, then you must enter the keyword fully specified or completed using Escape; this distinguishes entering an old keyword from making a new keyword which is a prefix of an old one since the system completes partial input automatically. [annotate]

file

The response is the name of a file, which may have to exist. Unlike other prompts, the default has some effect even after the user supplies some input: the system merges the default with the input filename. See page 3.3.2 for a description of filename merging. Escape and Space complete the input for a file parse. [annotate]

string

The response is a string which must satisfy some property, such as being the name of an existing file. [annotate]

These key-events have special meanings when prompting: [annotate]

Return

Confirm the current parse. If no input has been entered, then use the default. If for some reason the input is unacceptable, Hemlock does two things: [annotate]

1. beeps, if the variable Beep on Ambiguity set, and [annotate]
2. moves the point to the end of the first word requiring disambiguation. [annotate]

This allows you to add to the input before confirming the it again. [annotate]

[annotate]

Home, C-_

Print some sort of help message. If the parse is a keyword parse, then print all the possible completions of the current input in a pop-up window. [annotate]

Escape

Attempt to complete the input to a keyword or file parse as far as possible, beeping if the result is ambiguous. When the result is ambiguous, Hemlock moves the point to the first ambiguous field, which may be the end of the completed input. [annotate]

Space

In a keyword parse, attempt to complete the input up to the next space. This is useful for completing the names of Hemlock commands and similar things without beeping a lot, and you can continue entering fields while leaving previous fields ambiguous. For example, you can invoke Forward Word as an extended command by typing M-X f Space w Return. Each time the user enters space, Hemlock attempts to complete the current field and all previous fields. [annotate]

C-i, Tab

In a string or keyword parse, insert the default so that it may be edited. [annotate]

C-p

Retrieve the text of the last string input from a history of echo area inputs. Repeating this moves to successively earlier inputs. [annotate]

C-n

Go the other way in the echo area history. [annotate]

C-q

Quote the next key-event so that it is not interpreted as a command. [annotate]