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[base] Improve kerning tracing and documentation. 

* src/base/ftobjs.c (FT_Get_Kerning): Emit tracing message if
scaled-down kerning values differ.
This commit is contained in:
Werner Lemberg 2015-08-25 07:23:01 +02:00
parent 55fed89e3b
commit 78b014031d
3 changed files with 33 additions and 2 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2015-08-25 Werner Lemberg <wl@gnu.org>
[base] Improve kerning tracing and documentation.
* src/base/ftobjs.c (FT_Get_Kerning): Emit tracing message if
scaled-down kerning values differ.
2015-08-18 Werner Lemberg <wl@gnu.org>
[raster] Remove last remnants of `raster5' driver.

5
include/freetype/freetype.h
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@ -3041,6 +3041,11 @@ FT_BEGIN_HEADER
/* FT_KERNING_UNSCALED :: Return the kerning vector in original font */
/* units. */
/* */
/* <Note> */
/* FT_KERNING_DEFAULT returns full pixel values; it also makes */
/* FreeType heuristically scale down kerning distances at small ppem */
/* values so that they don't become too big. */
/* */
typedef enum FT_Kerning_Mode_
{
FT_KERNING_DEFAULT = 0,

23
src/base/ftobjs.c
View File

@ -3073,18 +3073,37 @@
if ( kern_mode != FT_KERNING_UNFITTED )
{
FT_Pos orig_x = akerning->x;
FT_Pos orig_y = akerning->y;
/* we scale down kerning values for small ppem values */
/* to avoid that rounding makes them too big. */
/* `25' has been determined heuristically. */
if ( face->size->metrics.x_ppem < 25 )
akerning->x = FT_MulDiv( akerning->x,
akerning->x = FT_MulDiv( orig_x,
face->size->metrics.x_ppem, 25 );
if ( face->size->metrics.y_ppem < 25 )
akerning->y = FT_MulDiv( akerning->y,
akerning->y = FT_MulDiv( orig_y,
face->size->metrics.y_ppem, 25 );
akerning->x = FT_PIX_ROUND( akerning->x );
akerning->y = FT_PIX_ROUND( akerning->y );
#ifdef FT_DEBUG_LEVEL_TRACE
{
FT_Pos orig_x_rounded = FT_PIX_ROUND( orig_x );
FT_Pos orig_y_rounded = FT_PIX_ROUND( orig_y );
if ( akerning->x != orig_x_rounded ||
akerning->y != orig_y_rounded )
FT_TRACE5(( "FT_Get_Kerning: horizontal kerning"
" (%d, %d) scaled down to (%d, %d) pixels\n",
orig_x_rounded / 64, orig_y_rounded / 64,
akerning->x / 64, akerning->y / 64 ));
}
#endif
}
}
}