BUG: GetGlyphOutline Returns Corrupt Glyphs with GGO_BITMAP

• Microsoft Win32 Software Development Kit (SDK) for Windows NT, version 4.0, on the following platform: x86

SYMPTOMS

The function GetGlyphOutline() will occasionally return corrupted bitmaps of TrueType glyphs when called with the GGO_BITMAP format. This problem occurs only on Windows NT 4.0. The corrupted bitmaps usually resemble a "Venetian" blind where every other scan line appears to have been inserted from some other source.

WORKAROUND

There is no practical workaround for this bug involving the use of GetGlyphOutline. The problem can be avoided by using TextOut on a memory DC and using the BitBlt function to copy a bitmap similar to the one to be returned by GetGlyphOutline.

Additionally, the problem can be avoided by specifying a rotation matrix in the call to GetGlyphOutline that would result in a rotation of 1 degree or more. This approach, however, suffers from the loss of hinting to the resulting bitmap glyph.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

Steps to Reproduce Problem

The problem can be reproduced by asking for glyph bitmaps for a series of characters over a range of Font heights. A specific case can be reproduced with a font height of -104 device units for the Wingdings font and the character code equivalent of the letter "i" in the ANSI character set.