the top left corner of the character glyph clicked on.
@item @var{width}, @var{height}
-These are the pixel width and height of @var{object} or, if this is
-@code{nil}, those of the character glyph clicked on.
+If the click is on a character, either from buffer text or from
+overlay or display string, these are the pixel width and height of
+that character's glyph; otherwise they are dimensions of @var{object}
+clicked on.
@end table
For clicks on a scroll bar, @var{position} has this form: