Re: State of NS port

[YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>]

>>>>> On Sat, 12 Jan 2013 11:49:09 +0800, Chris Zheng <chrisdcheng@gmail.com> said:

> I suffered this problem too, and it's because of two bug fixes after I dig it awhile. 
> bug#11484: 23.4; Scrolling leaves traces of old text behind

> http://lists.gnu.org/archive/html/bug-gnu-emacs/2012-05/msg00383.html

I could reproduce it with the *Mac port*, so the problem would be that
the reported metrics don't exactly reflect the actual display when LCD
font smoothing is turned on.  I think I will apply the following
workaround in the next release of the Mac port.

				     YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp

=== modified file 'src/macfont.c'
*** src/macfont.c	2013-01-11 07:33:09 +0000
--- src/macfont.c	2013-01-13 07:24:32 +0000
***************
*** 483,488 ****
--- 483,489 ----
        METRICS_SET_VALUE (metrics, descent, status);} while (0)
  
  #define METRICS_NCOLS_PER_ROW	(128)
+ #define LCD_FONT_SMOOTHING_RIGHT_MARGIN	(0.396)
  
  static int
  macfont_glyph_extents (struct font *font, CGGlyph glyph,
***************
*** 579,584 ****
--- 580,587 ----
  				     / (CGFloat) WIDTH_FRAC_SCALE));
  	      break;
  	    }
+ 	  if (bounds.size.width > 0)
+ 	    bounds.size.width += LCD_FONT_SMOOTHING_RIGHT_MARGIN;
  	  bounds = CGRectIntegral (bounds);
  	  METRICS_SET_VALUE (cache, lbearing, CGRectGetMinX (bounds));
  	  METRICS_SET_VALUE (cache, rbearing, CGRectGetMaxX (bounds));