Microsoft KB Archive/147647

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BUG: GetTextExtentPoint Fails in App Based on Windows/Win32s

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Q147647

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The information in this article applies to:


 * Microsoft Windows Software Development Kit (SDK) 3.1
 * Microsoft Win32 Application Programming Interface (API), included with:
 * the operating system: Microsoft Windows NT 3.51
 * Microsoft Windows 4.0
 * Microsoft Windows 95
 * Microsoft Win32s version 1.30c

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SYMPTOMS
GetTextExtentPoint fails when all of the following conditions are present:


 * You have either a 16-bit application running under Windows 3.1 or a 32-bit application running under Win32s.
 * The application uses GetTextExtentPoint.
 * The string buffer parameter has been allocated with GlobalAlloc or has been reallocated with GlobalReAlloc.
 * The string size is an exact multiple of 32 bytes.

Under Win32s, GetLastError returns an error 87 (Invalid Parameter). The debug version of Windows 3.1 displays a Fatal Exit code 0x700A with this error message:

GetTextExtentPoint - Invalid string

CAUSE
As stated earlier, this problem occurs only when the allocated size of the string is an exact multiple of 32 bytes.

This is a bug in Microsoft Windows 3.1 that causes ramifications in a 16-bit application running under Windows 3.1. A 16-bit application running under Windows NT 3.51 will have the same problem, but it will run without any problems under Windows 95.

This bug is not specific to Win32s. However, because Win32s runs under the Windows environment, a 32-bit application running under Windows 3.1 by way of Win32s will also exhibit this problem. However, a 32-bit application running under Windows NT or Windows 95 will not exhibit this problem.

STATUS
Microsoft has confirmed this to be a bug 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
Note that GetTextExtentPoint will succeed if you pass a string constant that has a size that is a multiple of 32. For example, the following will work:

  GetTextExtentPoint(hDC, "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", 32, &size);

Sample Code to Reproduce Problem
Note that error checking is not implemented in the following code.

 HGLOBAL hMem; HDC hDC; SIZE size; int blksize, i; char szMsg[256]; LPSTR lpBuf;

blksize=32; #ifdef WIN32 SetLastError(0); #endif

hDC = GetDC(hWnd); hMem = GlobalAlloc(GHND, blksize); lpBuf = (LPSTR) GlobalLock(hMem); for (i=0; i<blksize; i++) lpBuf[i] = 't';

if (!GetTextExtentPoint(hDC, lpBuf, blksize, &size)) {    #ifdef WIN32 wsprintf(szMsg, "GetTextExtentPoint Error %d\r\n", GetLastError); #else wsprintf(szMsg, "GetTextExtentPoint Error\r\n);    #endif     MessageBox(NULL, szMsg, "Test", MB_OK);  }  GlobalUnlock(hMem);

#ifdef WIN32 SetLastError(0); #endif

hMem = GlobalReAlloc(hMem, 2*blksize, GMEM_ZEROINIT); lpBuf = (LPSTR) GlobalLock(hMem); for (i=0; i<blksize; i++) lpBuf[blksize+i] = 'T';

if (!GetTextExtentPoint(hDC, lpBuf, 2*blksize, &size)) {    #ifdef WIN32 wsprintf(szMsg, "GetTextExtentPoint Error %d\r\n", GetLastError); #else wsprintf(szMsg, "GetTextExtentPoint Error \r\n"); #endif MessageBox(NULL, szMsg, "Test", MB_OK); }

GlobalUnlock(hMem); if (hMem) GlobalFree(hMem);

Additional query words: win32s gdi 1.30c 4.00 3.10 3.51

Keywords : kbGDI kbOSWin32s

Issue type :

Technology : kbAudDeveloper kbSDKSearch kbWin32sSearch kbWin32API kbWinSDKSearch