CODEWITHSUNDEEP
emacselisp
jplindstrom
jplindstrom

Reputation: 994

Displaying info panel at top of buffer

I'd like to display a few lines at the top of the buffer, but not as part of the actual buffer text, just for display.

Specifically, I'd like to display a Git timeline (not yet released, sorry), like this automatically when I open a file, so I can easily see any recent activity:

                                    P     DP D           D                      
T=F=S=S=M=T=W=T=F=S=S=M=T=W=T=F=S=S=M==T==W==T==F==S==S==M==T==W==T==F==S==S==M=
        11            18            25                   2                    9

(Single chars are first initials of people with commits on those days. There will be a legend below as well)

It sounds like I want something like the header line, but for the buffer. Is there anything like that?

One idea I had was to use an overlay at the start of the buffer and put my text there, but I'm not at all sure this is "the right thing" or a completely inappropriate / unsuitable use of this.

I tried, and got it working, using an overlay of the char at (point-min), with the text-property of 'before-string and the string literal above (with newlines and a trailing newline). Here's a proof of concept:

(defun test/add-overlay ()
  (interactive)
  (setq test/timeline-overlay (make-overlay (point-min) (+ (point-min) 1)))
  (overlay-put test/timeline-overlay 'timeline-panel t)
  (overlay-put test/timeline-overlay 'before-string
               (propertize "                                    P     DP D           D                      \nT=F=S=S=M=T=W=T=F=S=S=M=T=W=T=F=S=S=M==T==W==T==F==S==S==M==T==W==T==F==S==S==M=\n        11            18            25                   2                    9 
" 'face 'font-lock-comment-face))
)

(defun test/remove-overlay ()
  (interactive)
  (remove-overlays (point-min) (point-max) 'timeline-panel t)
)

This does seem to work quite fine, but I'm not sure if it might conflict with something else.

Is this the way to go, or are the more suitable user interface constructs in Emacs to do what I want?

Upvotes: 2

Views: 259

Answers (2)

Stefan
Stefan

Reputation: 28581

Yes, if you want display-only text placed at a particular location in the buffer, then an overlay with some after-string or before-string is the way to go.

Upvotes: 1

Drew
Drew

Reputation: 30718

If you can reduce it to a single line, then use header-line-format -- it's local in every buffer. Just set the variable for the buffer you want. See the Emacs sources for examples, e.g., ruler-mode.el.

You seem to have dismissed using a header line, saying that you want something "for the buffer". I don't understand why you think header-line-format does not give you what you want (except that it is one line only).

Upvotes: 2

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