Freetype is very slow at opening large PostScript Asian
fonts. I have a font with 8000 characters in it and Freetype takes upwards of 20
seconds just to return from FT_New_Face() on a PIII 1GHz PC. The time is
compounded by the fact that I have to do this multiple times for different fonts
and variations. I traced the slowness and it comes down to the PS_Table_Add
function. In particular, these lines of code:
while ( new_size
< table->cursor + length )
new_size +=
1024;
error = reallocate_t1_table( table, new_size
);
The
problem is that with large fonts, this reallocation can happen thousands of
times. I tried changing the code to use new_size *= 2 instead of new_size +=
1024 and the FT_NewFace() function now goes about 10 times as fast. It would be
even faster if the reallocation code didn't do all those tests and instead the
caller of PS_Table_Add allocated the required amount up front. I'm not sure what
the best solution is, but I tend to think that new_size += 1024 is not it. Doing
*= 2 and then scaling the allocation back to minimum when done is one way to get
the speed but not use any extra memory.
Until
I hear back from somebody, I'll just change my version of the code to
new_size *= 2 so I can stop getting bug reports that my app has hung.
:)
The
code below is from Freetype 2.12 (the most recent as of this
writing).
/*************************************************************************/
/* */
/* <Function> */
/* PS_Table_Add */
/* */
/* <Description> */
/* Adds an object to a PS_Table, possibly growing its memory block. */
/* */
/* <InOut> */
/* table :: The target table. */
/* */
/* <Input> */
/* idx :: The index of the object in the table. */
/* */
/* object :: The address of the object to copy in memory. */
/* */
/* length :: The length in bytes of the source object. */
/* */
/* <Return> */
/* FreeType error code. 0 means success. An error is returned if a */
/* reallocation fails. */
/* */
FT_LOCAL_DEF( FT_Error )
PS_Table_Add( PS_Table table,
FT_Int idx,
void* object,
FT_Int length )
{
if ( idx < 0 || idx > table->max_elems )
{
FT_ERROR(( "PS_Table_Add: invalid index\n" ));
return PSaux_Err_Invalid_Argument;
} /* grow the base block if needed */
if ( table->cursor + length > table->capacity )
{
FT_Error error;
FT_Offset new_size = table->capacity;
FT_Long in_offset;
in_offset = (FT_Long)((FT_Byte*)object - table->block);
if ( (FT_ULong)in_offset >= table->capacity )
in_offset = -1; while ( new_size < table->cursor + length )
new_size += 1024; error = reallocate_t1_table( table, new_size );
if ( error )
return error; if ( in_offset >= 0 )
object = table->block + in_offset;
} /* add the object to the base block and adjust offset */
table->elements[idx] = table->block + table->cursor;
table->lengths [idx] = length;
FT_MEM_COPY( table->block + table->cursor, object, length ); table->cursor += length;
return PSaux_Err_Ok;
}
. BTW, the French version,
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