window--size-to-pixel

window--size-to-pixel is a compiled Lisp function in `window.el'.

(window--size-to-pixel WINDOW SIZE &optional HORIZONTAL PIXELWISE ROUND-MAYBE)

For WINDOW convert SIZE lines to pixels.
SIZE is supposed to specify a height of WINDOW in terms of text
lines. The return value is the number of pixels specifying that
height.

WINDOW must be a valid window. Optional argument HORIZONTAL
non-nil means convert SIZE columns to pixels.

Optional argument PIXELWISE non-nil means SIZE already specifies
pixels but may have to be adjusted to a multiple of the character
size of WINDOW's frame. Optional argument ROUND-MAYBE non-nil
means round to the nearest multiple of the character size of
WINDOW's frame if the option `window-resize-pixelwise' is nil.