RegisterTouchWindow function (winuser.h)

Article
10/13/2021

Registers a window as being touch-capable.

Syntax

BOOL RegisterTouchWindow(
  [in] HWND  hwnd,
  [in] ULONG ulFlags
);

Parameters

[in] hwnd

The handle of the window being registered. The function fails with ERROR_ACCESS_DENIED if the calling thread does not own the specified window.

[in] ulFlags

A set of bit flags that specify optional modifications. This field may contain 0 or one of the following values.

Value	Meaning
TWF_FINETOUCH	Specifies that hWnd prefers noncoalesced touch input.
TWF_WANTPALM	Setting this flag disables palm rejection which reduces delays for getting WM_TOUCH messages. This is useful if you want as quick of a response as possible when a user touches your application. By default, palm detection is enabled and some WM_TOUCH messages are prevented from being sent to your application. This is useful if you do not want to receive WM_TOUCH messages that are from palm contact.

Value

Meaning

TWF_FINETOUCH

Specifies that hWnd prefers noncoalesced touch input.

TWF_WANTPALM

Setting this flag disables palm rejection which reduces delays for getting WM_TOUCH messages. This is useful if you want as quick of a response as possible when a user touches your application.

By default, palm detection is enabled and some WM_TOUCH messages are prevented from being sent to your application. This is useful if you do not want to receive WM_TOUCH messages that are from palm contact.

Return value

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, use the GetLastError function.

Remarks

Note RegisterTouchWindow must be called on every window that will be used for touch input. This means that if you have an application that has multiple windows within it, RegisterTouchWindow must be called on every window in that application that uses touch features. Also, an application can call RegisterTouchWindow any number of times for the same window if it desires to change the modifier flags. A window can be marked as no longer requiring touch input using the UnregisterTouchWindow function.

If TWF_WANTPALM is enabled, packets from touch input are not buffered and palm detection is not performed before the packets are sent to your application. Enabling TWF_WANTPALM is most useful if you want minimal latencies when processing WM_TOUCH messages.

Examples


BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   HWND hWnd;

   hInst = hInstance; // Store instance handle in the global variable.

   hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);

   RegisterTouchWindow(hWnd, 0);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

Requirements

Requirement	Value
Minimum supported client	Windows 7 [desktop apps only]
Minimum supported server	Windows Server 2008 R2 [desktop apps only]
Target Platform	Windows
Header	winuser.h (include Windows.h)
Library	User32.lib
DLL	User32.dll

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