IOleInPlaceSiteWindowless::OnDefWindowMessage method (ocidl.h)

Article
02/22/2024

Invokes the default processing for all messages passed to an object.

Syntax

HRESULT OnDefWindowMessage(
  [in]  UINT    msg,
  [in]  WPARAM  wParam,
  [in]  LPARAM  lParam,
  [out] LRESULT *plResult
);

Parameters

[in] msg

The identifier for the window message provided to the container by Windows.

[in] wParam

A parameter for the window message provided to the container by Windows.

[in] lParam

A parameter for the window message provided to the container by Windows.

[out] plResult

A pointer to result code for the window message.

Return value

This method returns S_OK on success. Other possible return values include the following.

Return code	Description
S_FALSE	The container's default processing for the window message was not invoked. See Note to Implementers below.

Remarks

A windowless object can explicitly invoke the default processing for a window message by calling this method. A container dispatches window messages to its windowless objects by calling IOleInPlaceObjectWindowless::OnWindowMessage. The object usually returns S_FALSE to indicate that it did not process the message. Then, the container can perform the default behavior for the message by calling the DefWindowProc function.

Instead, the object can call this method on the container's site object to explicitly invoke the default processing. Then, the object can take action on its own if the container does not handle the message.

Notes to Implementers

The container must pass the following window messages to its default window procedure (the DefWindowProc function) and return S_OK. Note that *plResult should contain the value returned by DefWindowProc.

WM_CHAR
WM_DEADCHAR
WM_IMExxx
WM_KEYDOWN
WM_KEYUP
WM_MOUSEMOVE
WM_SYSCHAR
WM_SYSDEADCHAR
WM_SYSKEYUP
WM_XBUTTONDOWN
WM_XBUTTONUP
WM_XBUTTONDBLCLK

The container can either process the window messages as its own and return S_OK or not do anything and return S_FALSE.

WM_CONTEXTMENU
WM_HELP
WM_SETCURSOR

If the container returns S_FALSE, the object can take action to process the window message on its own.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	ocidl.h