http://msdn.microsoft.com/en-us/library/z7e878zz.aspx (and whatever other platforms map it to).
The function is meant to take into account the specific glyph pattern with respect to a given font. Looks like dolphin's behavior is just broken here, which probably attributes to the debugger tending to look like crap with different fonts selected.
It's nice that the issue is identified here, but if it's fixed, I think it should be done in a different PR.