This structure models the metrics of a bitmap strike (i.e., a set of glyphs for a given point size and resolution) in a bitmap font. It is used for the ‘available_sizes’ field of Face.
Windows FNT: The nominal size given in a FNT font is not reliable. Thus when the driver finds it incorrect, it sets ‘size’ to some calculated values and sets ‘x_ppem’ and ‘y_ppem’ to the pixel width and height given in the font, respectively.
TrueType embedded bitmaps: ‘size’, ‘width’, and ‘height’ values are not contained in the bitmap strike itself. They are computed from the global font parameters.
The vertical distance, in pixels, between two consecutive baselines. It is always positive.
The nominal size of the strike in 26.6 fractional points. This field is not very useful.
The average width, in pixels, of all glyphs in the strike.
The horizontal ppem (nominal width) in 26.6 fractional pixels.
The vertical ppem (nominal width) in 26.6 fractional pixels.