The FXScript Reference

The spacing value is used to set the space between letters. In most design applications this value is known as "Tracking" (not kerning which is variable space between individual letter pairs).

This value changed significantly with FCP 4's new text engine. The text engine in earlier versions of FCP and FCE 1 tended to track text to close together. FCP4 seems to use some of OS X's advanced text rendering capabilities, and the resulting text is much cleaner.

A Spacing value of 1 in FCP 4 is approximately equivalent to a spacing value of 2 in previous versions of FCP.

This function does wacky things with color in effects using the InformationFlag("YUVaware") flag.

The type of color input seems to dictate how that color's component data is handled. RGB colors are treated as RGB, regardless of the active color space or the color's assigned values. An RGB color containing the YUV values {255, 200, 200, 200} should be a bright pink in a YUV context, but DrawString interprets the colors as RGB, internally translates the RGB-valued color to YUV and uses that instead, so those values come out gray.

Sending a YUVcolors is treated as YUV, but the values are shifted in what I think is Quicktime's native YUV specification. The Chroma (UV, CbCr) components need to be shifted by -127 so values center on zero, the Luma (Y) may also need to be shifted by -16. I rarely if ever use YUVcolor variables, preferring the simplicity of storing whatever I want in the generic color data type.