Creating and Destroying DirectDraw Surfaces

Direct Draw surfaces are created in a four-stage process. These stages are:

  1. DdCanCreateSurface. The runtime calls the driver's DdCanCreateSurface to see if the driver allows the creation of a surface of this type, size, and format. The driver can return a failure code that is propagated to the application.

  2. DdCreateSurface. The driver creates the surface, potentially allocating memory for the contents of the surface. Complex surfaces can be created all at once, with one call to DdCreateSurface. Thus, the driver may be required to create many surfaces in one call.

  3. Memory allocation. The DirectDraw runtime allocates memory for any surface that is not allocated by the driver in response to the DdCreateSurface call. This process is covered in more detail in the following sections.

  4. D3dCreateSurfaceEx. This function associates a handle with the surface in question for later use in the DirectXD3dDrawPrimitives2 token stream. The driver also creates its own copy of the surface structure maintained by DirectDraw at this time. For more information about D3dCreateSurfaceEx, see the DirectX Driver Development Kit (DDK) documentation.

Note   A DirectDraw driver must never directly allocate user-mode memory for a surface (for example, by calling the EngAllocUserMem function). Instead, the driver can have the DirectDraw runtime allocate user-mode memory for a surface.

If the driver allocates the memory directly, a subsequent request to change the video mode by a process other than the one that created the surface, could cause an operating system crash or memory leaks. To have the DirectDraw runtime allocate user-mode memory, the driver should return the DDHAL_PLEASEALLOC_USERMEM value from its DdCreateSurface function. For more information, see the Remarks section on the DdCreateSurface reference page.

 

Surfaces are destroyed by a single call to the driver's DdDestroySurface entry point only if the driver allocated or was involved in allocating the memory for the surface during surface creation. If the DirectDraw runtime allocated the memory and the driver was not involved, the runtime does not call DdDestroySurface.

Surfaces persist only as long as the mode in which they are created persists. Where there is a mode change, all the surfaces under the driver's control are destroyed, as far as the driver is concerned. There are also other events that can cause all surfaces to be destroyed in this way. It is not necessary for the driver to determine the cause of a DdDestroySurface call.

 

 

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