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IDirectDrawSurface::Lock

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This method obtains a pointer to the surface memory.

HRESULT Lock(
  LPRECT lpDestRect, 
  LPDDSURFACEDESC lpDDSurfaceDesc, 
  DWORD dwFlags, 
  HANDLE hEvent
); 

Parameters

  • lpDestRect
    Address of a RECT structure that identifies the region of surface that is being locked. If NULL, the entire surface will be locked.

  • lpDDSurfaceDesc
    Address of a DDSURFACEDESC structure that will be filled with the relevant details about the surface.

  • dwFlags
    The following table shows the possible flags.

    Flag Description
    DDLOCK_DISCARD Indicates that every location within the locked surface will be overwritten (with a write-only operation).
    DDLOCK_READONLY Indicates that the surface being locked will only be read.
    DDLOCK_WAITNOTBUSY Waits for a previously initiated drawing operation to complete instead of returning immediately with the DDERR_WASSTILLDRAWING return value.

    If a previous drawing operation is in progress at the time of the call, this flag defers returning from the call until the surface is locked or an error occurs.

    DDLOCK_WRITEONLY Indicates that the surface being locked will be write-enabled.
  • hEvent
    This parameter is not used and must be set to NULL.

Return Values

If the method succeeds, the return value is DD_OK.

If the method fails, the return value may be one of the following error values:

DDERR_INVALIDOBJECT
DDERR_INVALIDPARAMS
DDERR_OUTOFMEMORY
DDERR_SURFACEBUSY
DDERR_SURFACELOST
DDERR_WASSTILLDRAWING

Remarks

For more information on using this method, see Accessing Surface Memory Directly.

After retrieving a surface memory pointer, you can access the surface memory until a corresponding IDirectDrawSurface::Unlock method is called. When the surface is unlocked, the pointer to the surface memory is invalid.

In a change from previous versions of DirectDraw, only one rectangle can be locked per surface, either the entire surface or a subset of the surface. If you try to lock a second section of the surface, the method will reurn DDERR_SURFACEBUSY.

Do not call DirectDraw blit functions to blit from a locked region of a surface. If you do, the blit returns either DDERR_SURFACEBUSY or DDERR_LOCKEDSURFACES. Additionally, GDI blit functions will silently fail when used on a locked video memory surface.

Requirements

Pocket PC: Windows Mobile 5.0 and later
Smartphone: Windows Mobile 5.0 and later
OS Versions: Windows CE 5.01 and later
Header: Ddraw.h.
Library: Ddraw.lib.

See Also

IDirectDrawSurface::Unlock | IDirectDrawSurface::GetDC | IDirectDrawSurface::ReleaseDC

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