Info Catalog elisp: Temporary Displays elisp: Display elisp: Size of Displayed Text

elisp: Overlays

 
 37.9 Overlays
 =============
 
 You can use “overlays” to alter the appearance of a buffer’s text on the
 screen, for the sake of presentation features.  An overlay is an object
 that belongs to a particular buffer, and has a specified beginning and
 end.  It also has properties that you can examine and set; these affect
 the display of the text within the overlay.
 
    The visual effect of an overlay is the same as of the corresponding
 text property (Text Properties).  However, due to a different
 implementation, overlays generally don’t scale well (many operations
 take a time that is proportional to the number of overlays in the
 buffer).  If you need to affect the visual appearance of many portions
 in the buffer, we recommend using text properties.
 
    An overlay uses markers to record its beginning and end; thus,
 editing the text of the buffer adjusts the beginning and end of each
 overlay so that it stays with the text.  When you create the overlay,
 you can specify whether text inserted at the beginning should be inside
 the overlay or outside, and likewise for the end of the overlay.
 

Menu

 
· Managing Overlays   Creating and moving overlays.
· Overlay Properties  How to read and set properties.
                           What properties do to the screen display.
· Finding Overlays    Searching for overlays.
 

Info Catalog elisp: Temporary Displays elisp: Display elisp: Size of Displayed Text