Expose "_cairo_font_options_set_round_glyph_positions()"
For the moment, _cairo_font_options_set_round_glyph_positions() is private and this causes a GREAT deal of problems in libgdiplus. For bitmaps, the default option is "CAIRO_ROUND_GLYPH_POS_ON", which creates discrepancy from original Windows GDI+ implementation of font rendering, which does not round glyph positions.
Use case: Because Windows GDI+ does not round glyph positions (and does sub-pixel position rendering), using it just for font/text measurement (MeasureString) is a very common practice, because it returns the same result as when font is measured in a vector rendering context. If this (rounded in cairo) metering is later used for rendering in a vector format (PDF for example), not using cairo, this causes discrepancy - text is not properly wrapped, positioned, or aligned. Exposing this font options method will make it possible for libgdiplus to behave much closer to Windows implementation in terms of font metering and rendering, with VERY small mogidications (literally a row or two of code) to an extent that the differences and discrepancy will be practically insignificant and invisible in vast majority of cases.
Moreover, given the fact that cairo also does not scale fonts in respect to image surface resolution (making font pixel dimensions larger or smaller depending on image DPI compared to sytem default DPI), makes it impossible to achieve the same effect by changing the surface image DPI to a higher value in order acieve finer-grain glyph position rounding.