README - CodePointIM

# Code Point Input Method

The Code Point Input Method is a simple input method that allows Unicode characters to be entered using their code point or code unit values.

The input method accepts three different notations, all using hexadecimal digits from the set [0-9a-fA-F]:

- "\uxxxx": The standard Unicode escape notation of the Java programming language. This notation allows input of code points up to U+FFFE; the illegal code point U+FFFF is not allowed.
- "\Uxxxxxx": An extended Unicode escape notation specific to this input method. This notation allows direct input of any Unicode code Point except the illegal code point U+FFFF. The uppercase "U" indicates that six hexadecimal digits follow. "xxxxxx" must be between 000000 and 10FFFF.
- "\uxxxx\uyyyy": Two consecutive standard Unicode escapes, together representing a code point between U+10000 and U+10FFFF (a supplementary character). "xxxx" must be between D800 and DBFF (that is, a high surrogate value), "yyyy" between DC00 and DFFF (a low surrogate value).

In general, the input method passes characters through unchanged. However, when the user types a "\", the input method enters composition mode. In composition mode, the user types the desired code point using one of the notations above, then types a space character to convert to the corresponding Unicode character and commit. The input method then returns to pass-through mode until another "\" character is entered.

While in composition mode, the user can use the left arrow, right arrow, backspace, and delete keys to edit the sequence. The "\u" or "\U" characters can only be deleted if they are not followed by hexadecimal digits in the composition sequence. Deleting the initial "\u" or "\U" returns the input method to pass-through mode.

Since the initial "\" character starts composition mode, a user must type two "\" characters in order to add a single "\" to the text. When an initial "\" has been entered, but the next character is not "u", "U", or "\", both the "\" and the subsequent character are committed, and the input method returns to pass-through mode. Also, typing a new line, or tab character at any time during composition immediately commits the current composed text.

Input methods are extensions to the Java Runtime Environment; they cannot be run as applications. Before you can use an input method, you have to install it in the JRE, run an application that supports input methods (such as the JFC demos Notepad and Stylepad), and select the input method. You can learn more about these steps from the article "Using Input Methods on the Java Platform" and more about supplementary character support from the article "Supplementary Characters in the Java Platform".

This input method requires JRE 5.0 or higher.