About glyph matrices

[Xue Fuqiao]

In (info "(elisp) Window Internals"):

  `current_matrix'
  `desired_matrix'
     Glyph matrices describing the current and desired display of this
     window.

I didn't know what is "the current and desired display" of window.  Then I went
to window.h:

    /* Glyph matrices.  */
    struct glyph_matrix *current_matrix;
    struct glyph_matrix *desired_matrix;

But they didn't help.  I didn't find it in the manual, either.  Can
anybody help?  Thanks.

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao