Freetype's FT_Load_Glyph may return different glyph metrics (in particular, horiAdvance) depending on load target flags (FT_LOAD_TARGET_MONO, FT_LOAD_TARGET_NORMAL ...). Among the consequences of that are: - the size of, e. g, GetTextExtentPoint() doesn't match the size of actually rendered text; - DrawTextW() with DT_CALCRECT flag returns wrong bounding rectangle.
In the core of that is GetGlyphOutline() returning different values for GGO_METRICS format (used in various glyph metrics query functions) and the actual format used during rendering.
It probably make sense to use effective fonts rendering option for GGO_METRICS so that matches. I did some ad-hoc testing on Windows with currently problematic Tahoma font and quite expectedly GetGlyphOutline(GGO_METRICS) always returns the same metrics as other output format options. While all the options also have the same metrics between each other (which is still not the case with Wine). I guess it is not easily possible to make all the face load options match each other with freetype (nor I am sure that is always the case on Windows for all the possible fonts), but making GGO_METRICS return the metrics matching actual gdi device context setup looks more important.
Fixes Idle Spiral being unable to render typed text in save / load dialogs (which is using Winforms from Unity's Mono).