how can I set exactly pixel?

[xiaoliang.sheng]

Hello, developers：

       I am currently working on a Thai text synthesis project which used 
freetype. My code is as follows( I’m using the font:“angsa.ttf” ):
           if (FT_Set_Pixel_Sizes(face, charWidth, charDotSize) !=0)
    {
        return (ERROR);
    }


    ascender = FT_MulFix(face->ascender, face->size->metrics.y_scale);
    descender = FT_MulFix(face->descender, face->size->metrics.y_scale);

    fontHeight =  (UI_16)ceil( (DOUBLE)(ascender - descender) / 64 );



I have some questions. Assume that I need render one character to byte array 
with fixed size, in correct position. Character size must be exactly size that 
fits in output bitmap, no clipping allowed.

I specified character width=height=100. But when I calculate the font height, 
it’s 117.



How should I set height to get exactly 100px output, not 117, for any normal 
font? If it isn't possible, then is there any way to calculate output character 
height exactly in pixels before FT_Render_Glyph.


Best Regards!