Function SK_Win32_IsGUIThread

src/window.cpp:8818–8875

#include <winnt.h>

BOOL
SK_Win32_IsGUIThread ( DWORD    dwTid,
                       SK_TLS **ppTLS )
{
  UNREFERENCED_PARAMETER (ppTLS);

  static volatile LONG64 last_result [3] = { 0x0, 0x0, 0x0 };
                  LONG64 test_result0 =
                    ReadAcquire64 (&last_result [0]),
                         test_result1 =
                    ReadAcquire64 (&last_result [1]),
                         test_result2 =
                    ReadAcquire64 (&last_result [2]);

  static volatile LONG write_idx = 0;

  if (     (DWORD)(test_result0 & 0x00000000FFFFFFFFULL) == dwTid)
    return (       test_result0 >> 32) > 0 ? TRUE : FALSE;
  else if ((DWORD)(test_result1 & 0x00000000FFFFFFFFULL) == dwTid)
    return (       test_result1 >> 32) > 0 ? TRUE : FALSE;
  else if ((DWORD)(test_result2 & 0x00000000FFFFFFFFULL) == dwTid)
    return (       test_result2 >> 32) > 0 ? TRUE : FALSE;

  DWORD dwTidOfMe =
    SK_GetCurrentThreadId ();

  BOOL
    bGUI = FALSE;

  if (dwTidOfMe == dwTid)
  {
    bGUI =
      IsGUIThread (FALSE);
  }

  else
  {
    GUITHREADINFO
      gti        = {                    };
      gti.cbSize = sizeof (GUITHREADINFO);

    bGUI =
      SK_GetGUIThreadInfo (dwTid, &gti);
  }

  auto idx =
    InterlockedIncrement (&write_idx);

  LONG64 test_result = (bGUI ? (1ull << 32) : 0)
    | (LONG64)(dwTid & 0xFFFFFFFFUL);

  InterlockedExchange64 (
    &last_result [idx % 3], test_result
  );

  return
    bGUI;
}