BUG: GetCharacterPlacement Returns Incorrect Kerning Values

MORE INFORMATION

Most TrueType fonts have a kerning table, but you do not have to use it. To find out whether the current font supports kerning pairs, call GetFontLanguageInfo. When you call GetCharacterPlacement with GCP_USEKERNING to kern the string "AVAVAVAVAVAV", the GetCharacterPlacement function correctly kerns the first two character widths only. If you examine the lpDx array filled by the GetCharacterPlacement API, it confirms this. The first two values are different from and slightly smaller than the rest of the values (which are all identical). Only the first two gaps between characters are kerned. The values should all be the same.

It is recommended that you calculate character placement with kerning pairs manually by calling GetKerningPairs.

Steps to Reproduce Behavior

The following code demonstrates the problem. After executing the code, observe the dx[] array. The first two values are different from the rest:

Sample Code

   case WM_PAINT:

   {
   HDC hdc;
   PAINTSTRUCT ps;
   GCP_RESULTS gcp;
   static char szOut[40];
   int dx[13];
   int pos;
   int order[13];
   UINT glyphs;
   HFONT hPrevFont;

   ZeroMemory(&gcp,sizeof(GCP_RESULTS));
   gcp.lStructSize = sizeof(GCP_RESULTS);
   gcp.lpOutString = szOut;
   gcp.lpDx = &dx[0];
   gcp.lpCaretPos = &pos;
   gcp.lpOrder = &order[0];
   gcp.lpGlyphs = (unsigned short *)&glyphs;
   gcp.nGlyphs = 12;

   hdc = BeginPaint(hWnd, &ps);
   hPrevFont = SelectObject(hdc, hFont);
   GetCharacterPlacement(hdc, "AVAVAVAVAVAV", 12, 0,
                            &gcp, GCP_USEKERNING);

   DeleteObject(SelectObject(hdc, hPrevFont));
   EndPaint(hWnd, &ps);
   break;
   }