DwmDefWindowProc function (dwmapi.h)

Article
08/14/2024

Default window procedure for Desktop Window Manager (DWM) hit testing within the non-client area.

You also need to ensure that DwmDefWindowProc is called for the WM_NCMOUSELEAVE message. If DwmDefWindowProc is not called for the WM_NCMOUSELEAVE message, DWM does not remove the highlighting from the Maximize, Minimize, and Close buttons when the cursor leaves the window.

Syntax

BOOL DwmDefWindowProc(
  [in]  HWND    hWnd,
  [in]  UINT    msg,
  [in]  WPARAM  wParam,
  [in]  LPARAM  lParam,
  [out] LRESULT *plResult
);

Parameters

[in] hWnd

A handle to the window procedure that received the message.

[in] msg

The message.

[in] wParam

Specifies additional message information. The content of this parameter depends on the value of the msg parameter.

[in] lParam

Specifies additional message information. The content of this parameter depends on the value of the msg parameter.

[out] plResult

A pointer to an LRESULT value that, when this method returns successfully,receives the result of the hit test.

Return value

TRUE if DwmDefWindowProc handled the message; otherwise, FALSE.

Remarks

When creating custom frames that include the standard caption buttons, WM_NCHITTEST and other non-client hit test messages should first be passed to the DwmDefWindowProc function. This enables the DWM to provide hit testing for the captions buttons. If DwmDefWindowProc does not handle the non-client hit test messages, further processing of these messages might be necessary.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Target Platform	Windows
Header	dwmapi.h
Library	Dwmapi.lib
DLL	Dwmapi.dll

Share via