get-extent

Calculates the snip's width, height, descent (amount of height which is drawn below the baseline), space (amount of height which is ``filler'' space at the top), and horizontal spaces (amount of width which is ``filler'' space at the left and right).

A drawing context is provided for the purpose of finding font sizes, but no drawing should occur. The get-extent and partial-offset methods must not make any assumptions about the state of the drawing context, except that it is scaled properly. In particular, the font for the snip's style is not automatically set in the drawing context before the method is called. If get-extent or partial-offset changes the drawing context's setting, it must restore them before returning. However, the methods should not need to change the drawing context; only font settings can affect measurement results from a device context, and get-text-extent in dc<%> accepts a font% argument for sizing that overrides that device context's current font.

The snip's left and top locations are provided in editor corrdinates. In a text editor, the y-coordinate is the line's top location; the snip's actual top location is potentially undetermined until its height is known.

This method is called by the snip's administrator; it should not be called directly by others. To get the extent of a snip, use get-snip-location in editor<%> .

The snip's editor is usually internally locked for writing and reflowing when this method is called (see also Locks).

• (send an-editor-snip get-extent dc x y w h descent space lspace rspace) -> void
      dc : dc<%> object
      x : real number
      y : real number
      w = #f : boxed non-negative real number or #f
      h = #f : boxed non-negative real number or #f
      descent = #f : boxed non-negative real number or #f
      space = #f : boxed non-negative real number or #f
      lspace = #f : boxed non-negative real number or #f
      rspace = #f : boxed non-negative real number or #f

  Calls its editor's get-extent method, then adds the editor snip's margins.

  The top space always corresponds to the space of the editor's top line, plus the snip's top margin. Normally, the descent corresponds to the descent of the editor's last line plus the snip's bottom margin. However, if the snip is in align-top-line mode (see set-align-top-line), the descent correponds to the descent of the top line, plus the height rest of the editor's lines, plus the snip's bottom margin.

  If the editor is a text editor, then 1 is normally subtracted from the editor's width as returned by get-extent, because the result looks better for editing. If the snip is in tight-text-fit mode (see set-tight-text-fit) then 2 is subtracted from a text editor's width, eliminating the two pixels that the text editor reserves for the blinking caret. In addition, tight-text-fit mode subtracts an amount equal to the line spacing from the editor's height. By default, tight-text-fit mode is disabled.