32.19 Text Properties

Each character position in a buffer or a string can have a text property list, much like the property list of a symbol (see Property Lists). The properties belong to a particular character at a particular place, such as, the letter `T' at the beginning of this sentence or the first `o' in `foo'—if the same character occurs in two different places, the two occurrences in general have different properties.

Each property has a name and a value. Both of these can be any Lisp object, but the name is normally a symbol. Typically each property name symbol is used for a particular purpose; for instance, the text property face specifies the faces for displaying the character (see Special Properties). The usual way to access the property list is to specify a name and ask what value corresponds to it.

If a character has a category property, we call it the property category of the character. It should be a symbol. The properties of the symbol serve as defaults for the properties of the character.

Copying text between strings and buffers preserves the properties along with the characters; this includes such diverse functions as substring, insert, and buffer-substring.

• Examining Properties: Looking at the properties of one character.
• Changing Properties: Setting the properties of a range of text.
• Property Search: Searching for where a property changes value.
• Special Properties: Particular properties with special meanings.
• Format Properties: Properties for representing formatting of text.
• Sticky Properties: How inserted text gets properties from neighboring text.
• Saving Properties: Saving text properties in files, and reading them back.
• Lazy Properties: Computing text properties in a lazy fashion only when text is examined.
• Clickable Text: Using text properties to make regions of text do something when you click on them.
• Links and Mouse-1: How to make <Mouse-1> follow a link.
• Fields: The field property defines fields within the buffer.
• Not Intervals: Why text properties do not use Lisp-visible text intervals.