[ft-devel] rendering differences between OS X and Win32

[Kevin Barabash]

I'm try to write a cross platform application and I'd like there to be
uniform behaviour when it comes to rendering fonts.  Unfortunately I
ran into a bug and just to make sure that there wasn't a problem with
my code I wrote a short test program to highlight the bug.  Here's a
list of the program and the output for both OS X and Win32.

program:

#include <stdio.h>
#include <ft2build.h>
#include FT_FREETYPE_H


int main(void) {

  FT_Library library;
  FT_Init_FreeType(&library);

  FT_Face face;
  FT_New_Face(library, "arial.ttf", 0, &face);

  FT_Set_Char_Size(face, 0, (18 << 6), 72, 72);

  unsigned i;
  for (i = 65; i < 90; i++) {
    FT_Load_Char(face, i, FT_LOAD_RENDER | FT_LOAD_NO_AUTOHINT);
    FT_GlyphSlot glyph = face->glyph;
    printf("rows: %d width: %d\n", glyph->bitmap.rows, glyph->bitmap.width);
  }

  return 0;
}


OS X output:

rows: 13 width: 14
rows: 13 width: 11
rows: 15 width: 13
rows: 13 width: 12
rows: 13 width: 11
rows: 13 width: 10
rows: 15 width: 13
rows: 13 width: 11
rows: 13 width: 3
rows: 14 width: 8
rows: 13 width: 11
rows: 13 width: 9
...


Win32 output:

rows: 13 width: 13
rows: 13 width: 10
rows: 13 width: 11
rows: 13 width: 11
rows: 13 width: 10
rows: 13 width: 9
rows: 13 width: 12
rows: 13 width: 11
rows: 13 width: 2
rows: 13 width: 8
rows: 13 width: 11
rows: 13 width: 8
...

One would think that the output would be identical, but it's not. 
Also, there doesn't seem to be a pattern either.  Sometimes the Win32
output is differs in rows or width or both.  Is there something
obvious that I'm not doing or this a bug that other people have come
across?

Kevin