[5/9] gdiplus: Fix empty glyph handling.

[Vincent Povirk]

> Thanks for you comments. The answer is yes, as you guessed.
> Typically, native GetGlyphOutlineW(hdc, ' ', GGO_BITMAP, &gm, 0, NULL, ...)
> returns gm.gmBlackBoxX = 1 instead of 0. Unfortunately, Wine's didn't,
> and existing source codes (winex11, gdiplus, gdi32) expect 0 in this
> case.

I don't think the existing code for finding the mask size would have a
problem with gmBlackBoxX being 0. But it would be best to skip
updating min_x, min_y, max_x, and max_y in this case, since we don't
really need the mask to include the position of an empty glyph.

Does Wine's GGO return a non-zero value currently? That would mean a
regression in gdiplus drawing only empty glyphs when you fix GGO.

> Native GGO returns GDI_ERROR in GetGlyphOutlineW(hdc, ' ', GGO_BITMAP,
> &gm, bufsize, buf, ...) case. Please note that bufsize and buf are
> specified and guess they aren't null.
>
> The second loop is for creating mask bitmaps. We don't need to update
> bitmaps if the character is empty. However, we also need to update the
> bitmap mask after that character. So, I just ignore the error and
> continue at that point.

I think a comment saying just /* empty glyph */ inside the if blocks
for these new cases would make the code much clearer.