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Lem's displaying concepts
Lem has some concept for displaying. This document is a result of a survey about them.
Logical concept for physical displaying areas dealt by frontends; like ncurses, electron and so on.
So display has no data representation in source codes, it appears as a word.
(For now) there is one display per one frontend.
Lem doesn't touch displays directly but touch these via method like lem-if:display-width.
Source (for instance): /frontends/ncurses/ncurses.lisp
UI parts like minibuffers or popup windows or normal buffers, in the display(s?). They're defined in each frontend and Lem doesn't touch them directly.
Source (for instance): /frontends/ncurses/ncurses.lisp
Lem's low-level displaying area. Each screens correspond to its view. Each screen has its position and size, and may have modeline.
Source: /lib/core/interface.lisp
Lem's displaying area.
Windows have its screen, buffer and view-point (maybe viewport).
Split area is implemented with windows and window-node structure.
window-node has split type (:hsplit and :vsplit), car and cdr.
Root area is stored in *window-tree* special variable.
*window-tree* may be an window or an window-node, by which Lem manages nest of displaying area.
If it's an window-node it means Lem's displaying area is splitted,
when its child (car or cdr) is an window-node that child area is also splitted, and so forth...
Source: /lib/core/window.lisp
Frames are the concept and the structure that represent whole window configuration in a display. It is introduced by this pull-request https://github.com/cxxxr/lem/pull/500 .
Note the special variable lem::*display-frame-map*.
This mapping correspond from display-thing (for now, it's lem:implementation) to a frame.
It is for multi frame support in the near future.
Source: /lib/core/frame.lisp
The name frame appears some place of /lib/core/window.lisp as arguments of adjust-windows.
This function seems to do a process when frame size is changed, e.g. terminal resizing.
In this case, frame means a display described above.
Virtual frames are introduced by frame-multiplexer (called "fm-mode" at this PR).
Because, in frame-multiplexer, it is needed to store frames and to switch between them.
One virtual frame store multiple frames in it, and modify lem::*display-frame-map* when like frame switching.
Source: /lib/core/frame-multiplexer.lisp