> We are using freetype-2.8.1. When we try to print the text
> characters, sometimes little top portion of text characters got
> stripped off. Pixel size passed to FT library is 30. No issue is
> seen with freetype-2.5.2.
Please give an example. Which font, which character, which hinting
mode?
> It is seen, ascent value returned from font metrics is not returned
> properly from the ttdriver.c in recent versions of freetype.
Have you seen the following entry in the `CHANGES' file for
version 2.8?
Global size metrics values in the `FT_Size_Metrics' structure can be
different for TrueType fonts. Reason is that in older FreeType
versions the metrics were rounded differently to integer pixels
compared to all other font formats, yielding an inconsistent
behaviour if you used non-native hinting. Starting with this
version, global size metrics for TrueType fonts are handled the same
as other font formats: `ascender' gets rounded up, `descender' gets
rounded down, `height' gets normally rounded, and `max_advance' gets
normally rounded, too.
If you need more precise values of (global) ascender, descender,
height, or `max_advance', please take the corresponding values from
the `FT_Face' structure and scale them manually.
In version 2.9 I updated the documentation for `FT_Size_Metrics' as
follows.
TrueType fonts with native bytecode hinting
-------------------------------------------
All applications that handle TrueType fonts with native hinting
must be aware that TTFs expect different rounding of vertical font
dimensions. The application has to cater for this, especially if
it wants to rely on a TTF's vertical data (for example, to properly
align box characters vertically).
Only the application knows _in_ _advance_ that it is going to use
native hinting for TTFs! FreeType, on the other hand, selects the
hinting mode not at the time of creating an @FT_Size object but
much later, namely while calling @FT_Load_Glyph.
Here is some pseudo code that illustrates a possible solution.
font_format = FT_Get_Font_Format( face );
if ( !strcmp( font_format, "TrueType" ) &&
do_native_bytecode_hinting )
{
ascender = ROUND( FT_MulFix( face->ascender,
size_metrics->y_scale ) );
descender = ROUND( FT_MulFix( face->descender,
size_metrics->y_scale ) );
}
else
{
ascender = size_metrics->ascender;
descender = size_metrics->descender;
}
height = size_metrics->height;
max_advance = size_metrics->max_advance;
Werner
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