Microsoft KB Archive/241358

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PRB: The GetGlyphOutlineW Function Fails on Windows 95 and Windows 98

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Q241358

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The information in this article applies to:


 * Microsoft Windows 95
 * Microsoft Windows 98
 * Microsoft Windows 98 Second Edition

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SYMPTOMS
The GetGlyphOutlineW function fails and the GetGlyphOutlineA function succeeds on Windows 95 and Windows 98.

When the GetGlyphOutlineWfunction fails, the error code returned from the GetLastError function is ERROR_CALL_NOT_IMPLEMENTED.

CAUSE
The GetGlyphOutlineW function, which is a wide-character or Unicode version of the function, is not implemented on Windows 95 and Windows 98 because these operating systems are not Unicode-based.

See the References section of this article for more information on the limited subset of wide-character functions that are implemented in the Windows 95 and Windows 98 operating systems.

RESOLUTION
To obtain glyph outline data from a character given only the Unicode character code, convert the Unicode character into its TrueType glyph index equivalent, and use the GGO_GLYPH_INDEX option for the function.

STATUS
This behavior is by design.

MORE INFORMATION
An application that uses Unicode strings internally may attempt to call the wide character (Unicode) version of the GetGlyphOutline function (GetGlyphOutlineW) to access its features through a Unicode character code. The function call always fails on Windows 95 or Windows 98 and returns GDI_ERROR.

On Windows 95 and Windows 98, only the GetGlyphOutlineA function (or simply GetGlyphOutline, as defined by Wingdi.h in the Platform SDK) is implemented. Calling GetGlyphOutlineW on these platforms returns the error code ERROR_CALL_NOT_IMPLEMENTED from the GetLastError function after the function fails.

This failure is by design because these operating systems are not Unicode-based and cannot normally process Unicode character codes. See the References section of this article for more information on the small subset of wide-character functions that are implemented in Windows 95 and subsequent versions.

Similar to the ExtTextOut function, the GetGlyphOutline function can also use glyph index-based parameters rather than character codes. The workaround is to convert the Unicode character code into a glyph index value, and call GetGlyphOutlineA using the GGO_GLYPH_INDEX option. See the Help documentation for the GetGlyphOutline function for details.

No function exists in the Win32 API for Windows 95 (there is no GetCharacterPlacementW implementation) to convert from Unicode to glyph indices. Using the WideCharToMultiByte function to first convert to eight-bit or ANSI character codes is disadvantaged by filtering the Unicode character codes through the current codepage. Any character codes in a Unicode subrange that are not represented by the conversion codepage are not translated.

To convert Unicode character codes to glyph indices, the Unicode to glyph index character map must be pulled from the TrueType font file by using the GetFontData function. It then must be searched to convert the character code to a font file glyph index.