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I'm making a presentation mode where I want to vertically center some text in the window, which is the only window in the frame. I'm using a custom face so I can control how large the font is.

To horizontally center the text, I can use window-max-chars-per-line with the face argument, so I can get the number of characters put in a line.

But I also want to know how many lines are in the window. There's window-body-height, but that doesn't let me specify a face.

How can I tell how tall a window is in lines of a specific face?

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    Maybe you can use font-info and (window-body-height nil t)? – Tobias Apr 12 '17 at 12:28
  • Hrm, thanks! It looks like I can do something based off window-font-height. I'll look into it more and see if I can make it work. Thanks for the pointer towards looking into the font. – zck Apr 12 '17 at 14:53
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One can get how many pixels tall a face is with window-font-height, and how many pixels tall a window is with window-body-height. From there it's a simple division with truncating.

(defun zck--lines-in-window (face &optional window)
  "Calculate how many lines of text with face FACE can fit in WINDOW."
  (truncate (window-body-height window t)
            (window-font-height window face)))
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  • If you are waiting for better answers add some notice about that to this one otherwise accept this one please to mark the question as done. Have fun, – Tobias Apr 13 '17 at 13:35
  • I can't accept my own answer until 24 hours after I posted it, but I'm planning on doing so unless there's a flaw in this answer. Thanks for the suggestion to look into fonts and window-body-height! – zck Apr 13 '17 at 17:30

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