w32term.c:FONT_HEIGHT causes screen noise.

[Kevin Yu]

Hi,
     In function x_draw_glyph_string_backgound, the background of the
string will
be redrawn when FONT_HEIGHT(s->font) < s->height - 2 * box_line_width. The
macro FONT_HEIGHT is defined as: ((f)->height). When f->ascent + f->descent
< s->height but f->height >= s->height the background will never be redrawn. As
a result, you will find some display noise on the screen.
     In w32font.c the f->height is calculated from tmHeight +
tmExternalLeading, so
f->ascent + f->descent < f->height if tmExternalLeading != 0. When
those fonts are
used as default font, you will find screen noise in *info* or
*Completions* buffers.
Because the spaces in those buffers use f->height as their height, and
tmExternalLeading number of pixels of text area will never be cleared.
This leaves
some screen noise in those buffers.



          Best wishes.