[ft-devel] Small issues in code comments

[Sylvain Pasche]

Hi,

I've been looking at the lcd filtering code when discussing the 
implementation of lcd filtering inside the Cairo library. I saw a few 
small issues in comments.

In 
http://cvs.savannah.gnu.org/viewvc/freetype/freetype2/src/base/ftlcdfil.c?view=markup

  /* FIR filter used by the default and light filters */
  static void
  _ft_lcd_filter_legacy( FT_Bitmap*      bitmap,
                         FT_Render_Mode  mode,
                         FT_Library      library )

Looks like some leftover cut and paste. That function is used by the 
legacy filter only, and is not a FIR filter according to Keith Packard 
(who implemented it in Xft): "it's an intra-pixel filter, which means 
the three components have different curves; green gets a three-element 
gaussian, while r and b get sloping filters to left and right."

There is also an apparently wrong "/* horizontal in-place FIR filter */" 
comment in the function body.


In 
http://cvs.savannah.gnu.org/viewvc/freetype/freetype2/include/freetype/freetype.h?view=markup:

in the <Enum> FT_Render_Mode
  /* <Note> 
    */
  /*   The LCD-optimized glyph bitmaps produced by FT_Render_Glyph are 
    */
  /*   _not_ _filtered_ to reduce color-fringes.  It is up to the 
caller   */
  /*   to perform this pass. 
    */

This is not always true any more, now that lcd filtering is available. 
The note could mention the availability of the FT_LcdFilter function (if 
support is compiled).


Hope that helps,
Sylvain