Re: Interface for displaying images

As I've told Steve already, I'm the author of the new Emacs redisplay, you may have heard of. The new Emacs redisplay code supports the inclusion of images in buffer text, among other things. Since it does that in a way that is not compatible with XEmacs, Richard, Steve and I agree that it is a good idea to provide a compatibility layer for displaying images, analogous in scope and intent to `easymenu', to package authors. The following is a proposal of such a common interface, that I call `easyimage'. `easyimage.el' ============== - Function: easy-image-types Return a list of supported image types. Each element of the list is a symbol describing a supported image type. The following symbols are used xbm xpm xface gif jpeg png tiff pbm ghostscript Rationale: One can use `featurep' to test for the availability of an image type in XEmacs. Emacs instead has a list of supported types. I believe the list form could be useful for extensions that would like to present available image type to the user (customization (?)). - Function: easy-image-create TYPE FILE Return an image of type TYPE loaded from file FILE. TYPE is a symbol specifying the image type. FILE is the path of the file to be loaded. If FILE doesn't specify an absolute path after `expand-file-name', it's taken to be relative to `data-directory'. Rationale: I believe that loading images from files is the most common case, and the case both Emacs types support. (Please also see `defimage', below). - Function: easy-image-put IMAGE POS &optional AREA BUFFER Put image IMAGE in front of POS in BUFFER. IMAGE is an image created via `easy-image-create' or `defimage'. POS is a buffer position, an integer or a marker. AREA is a symbol or nil. If it is `left-margin' put the image into the left margin area, if it is `right-margin' put it in the right marginal area. If it is `nil' or omitted, put it in the text area. BUFFER nil or omitted means use the current buffer. - Function: easy-image-remove-images START END &optional BUFFER Remove images between START and END in BUFFER. START and END are buffer positions, and may be either integers or markers. BUFFER nil or omitted means use the current buffer. - Macro: defimage IMAGE SPECS &optional DOC-STRING Declare IMAGE as an image. IMAGE is a symbol; it doesn't have to be quoted. SPECS is a list of image specifications. DOC-STRING is a documentation string. The function chooses the first applicable image specification from SPECS, creates an image for it and assigns it to IMAGE via `setq'. Each specification in SPECS is a list. If it has the form (EMACS ...), where EMACS is the the symbol `emacs' or `xemacs', the specification is applicable only if running under the named Emacs type. The contents of the rest of a specification are unspecified, but both Emacs brands support specifications of the form `(:type TYPE :file FILE)' (see `easy-image-create'). A specification of this form is applicable if image type TYPE is available, and FILE exists.