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37.19.1 Abstract Display Functions

In this subsection, ewoc and node stand for the structures described above (see Abstract Display), while data stands for an arbitrary Lisp object used as a data element.

Function: ewoc-create pretty-printer &optional header footer nosep

This constructs and returns a new ewoc, with no nodes (and thus no data elements). pretty-printer should be a function that takes one argument, a data element of the sort you plan to use in this ewoc, and inserts its textual description at point using insert (and never insert-before-markers, because that would interfere with the Ewoc package’s internal mechanisms).

Normally, a newline is automatically inserted after the header, the footer and every node’s textual description. If nosep is non-nil, no newline is inserted. This may be useful for displaying an entire ewoc on a single line, for example, or for making nodes “invisible” by arranging for pretty-printer to do nothing for those nodes.

An ewoc maintains its text in the buffer that is current when you create it, so switch to the intended buffer before calling ewoc-create.

Function: ewoc-buffer ewoc

This returns the buffer where ewoc maintains its text.

Function: ewoc-get-hf ewoc

This returns a cons cell (header . footer) made from ewoc’s header and footer.

Function: ewoc-set-hf ewoc header footer

This sets the header and footer of ewoc to the strings header and footer, respectively.

Function: ewoc-enter-first ewoc data
Function: ewoc-enter-last ewoc data

These add a new node encapsulating data, putting it, respectively, at the beginning or end of ewoc’s chain of nodes.

Function: ewoc-enter-before ewoc node data
Function: ewoc-enter-after ewoc node data

These add a new node encapsulating data, adding it to ewoc before or after node, respectively.

Function: ewoc-prev ewoc node
Function: ewoc-next ewoc node

These return, respectively, the previous node and the next node of node in ewoc.

Function: ewoc-nth ewoc n

This returns the node in ewoc found at zero-based index n. A negative n means count from the end. ewoc-nth returns nil if n is out of range.

Function: ewoc-data node

This extracts the data encapsulated by node and returns it.

Function: ewoc-set-data node data

This sets the data encapsulated by node to data.

Function: ewoc-locate ewoc &optional pos guess

This determines the node in ewoc which contains point (or pos if specified), and returns that node. If ewoc has no nodes, it returns nil. If pos is before the first node, it returns the first node; if pos is after the last node, it returns the last node. The optional third arg guess should be a node that is likely to be near pos; this doesn’t alter the result, but makes the function run faster.

Function: ewoc-location node

This returns the start position of node.

Function: ewoc-goto-prev ewoc arg
Function: ewoc-goto-next ewoc arg

These move point to the previous or next, respectively, argth node in ewoc. ewoc-goto-prev does not move if it is already at the first node or if ewoc is empty, whereas ewoc-goto-next moves past the last node, returning nil. Excepting this special case, these functions return the node moved to.

Function: ewoc-goto-node ewoc node

This moves point to the start of node in ewoc.

Function: ewoc-refresh ewoc

This function regenerates the text of ewoc. It works by deleting the text between the header and the footer, i.e., all the data elements’ representations, and then calling the pretty-printer function for each node, one by one, in order.

Function: ewoc-invalidate ewoc &rest nodes

This is similar to ewoc-refresh, except that only nodes in ewoc are updated instead of the entire set.

Function: ewoc-delete ewoc &rest nodes

This deletes each node in nodes from ewoc.

Function: ewoc-filter ewoc predicate &rest args

This calls predicate for each data element in ewoc and deletes those nodes for which predicate returns nil. Any args are passed to predicate.

Function: ewoc-collect ewoc predicate &rest args

This calls predicate for each data element in ewoc and returns a list of those elements for which predicate returns non-nil. The elements in the list are ordered as in the buffer. Any args are passed to predicate.

Function: ewoc-map map-function ewoc &rest args

This calls map-function for each data element in ewoc and updates those nodes for which map-function returns non-nil. Any args are passed to map-function.

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