[haiku-bugs] Re: [Haiku] #7797: [app_server] Alternative implementation of subpixel rendering (patch)
- From: "pulkomandy" <trac@xxxxxxxxxxxx>
- Date: Thu, 20 Nov 2014 11:06:26 -0000
#7797: [app_server] Alternative implementation of subpixel rendering (patch)
----------------------------------+----------------------------
Reporter: diver | Owner: leavengood
Type: bug | Status: in-progress
Priority: normal | Milestone: R1
Component: Servers/app_server | Version: R1/Development
Resolution: | Keywords:
Blocked By: | Blocking:
Has a Patch: 0 | Platform: All
----------------------------------+----------------------------
Comment (by pulkomandy):
Hi,
It's time to review this again...
The page about patents at Freetype homepage has some information:
http://freetype.sourceforge.net/patents.html
So, the patent is only on the subpixel filter is patented:
{{{
using a different colour filter thus circumvents Microsoft's patent
claims.
}}}
We have our own filter already, which works rather well and has the nice
feature of having this slider to allow adjusting the color fringes. Since
it is a custom filter, I don't see any reason to disable it when font
hinting is enabled.
Now on the freetype compilation options. There are two of them.
{{{
/*************************************************************************/
/*
*/
/* Define TT_CONFIG_OPTION_SUBPIXEL_HINTING if you want to compile
*/
/* EXPERIMENTAL subpixel hinting support into the TrueType driver. This
*/
/* replaces the native TrueType hinting mechanism when anything but
*/
/* FT_RENDER_MODE_MONO is requested.
*/
/*
*/
/* Enabling this causes the TrueType driver to ignore instructions under
*/
/* certain conditions. This is done in accordance with the guide here,
*/
/* with some minor differences:
*/
/*
*/
/* http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx
*/
/*
*/
/* By undefining this, you only compile the code necessary to hint
*/
/* TrueType glyphs with native TT hinting.
*/
/*
*/
/* This option requires TT_CONFIG_OPTION_BYTECODE_INTERPRETER to be
*/
/* defined.
*/
/*
*/
/* #define TT_CONFIG_OPTION_SUBPIXEL_HINTING */
}}}
{{{
/*************************************************************************/
/*
*/
/* Uncomment the line below if you want to activate sub-pixel rendering
*/
/* (a.k.a. LCD rendering, or ClearType) in this build of the library.
*/
/*
*/
/* Note that this feature is covered by several Microsoft patents
*/
/* and should not be activated in any default build of the library.
*/
/*
*/
/* This macro has no impact on the FreeType API, only on its
*/
/* _implementation_. For example, using FT_RENDER_MODE_LCD when calling
*/
/* FT_Render_Glyph still generates a bitmap that is 3 times wider than
*/
/* the original size in case this macro isn't defined; however, each
*/
/* triplet of subpixels has R=G=B.
*/
/*
*/
/* This is done to allow FreeType clients to run unmodified, forcing
*/
/* them to display normal gray-level anti-aliased glyphs.
*/
/*
*/
/* #define FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
}}}
We are disabling both of these, but I think we should disable only the
second one. This way, the API for subpixel hinting is available and does
not lead an error, and app_server can enable it. Then we are able to only
replace the freetype package if we want to enable the Microsoft patented
algorithm.
--
Ticket URL: <https://dev.haiku-os.org/ticket/7797#comment:18>
Haiku <https://dev.haiku-os.org>
Haiku - the operating system.
Other related posts:
