DRIVEROBJ structure

The DRIVEROBJ structure is used to track a resource, allocated by a driver, that requires use GDI services. A DRIVEROBJ structure allows a display driver to request the GDI service in managing per-process resources. By creating a DRIVEROBJ structure, a display driver can ensure that resources will be released when an application terminates.

Syntax


typedef struct _DRIVEROBJ {
  PVOID       pvObj;
  FREEOBJPROC pFreeProc;
  HDEV        hdev;
  DHPDEV      dhpdev;
} DRIVEROBJ;

Members

pvObj

Pointer to the driver resource that will be tracked by the DRIVEROBJ structure. The resource is associated with the current client process.

pFreeProc

Pointer to a driver-supplied callback function that frees the resource pointed to by pvObj. This callback function has the following prototype:


BOOL (CALLBACK * FREEOBJPROC) (DRIVEROBJ * pDriverObj);

The callback function returns TRUE if it is able to free the resource, and FALSE otherwise.

hdev

GDI handle to the physical device associated with the object.

dhpdev

Pointer to the driver's private instance data; that is, this member identifies the driver's PDEV.

Remarks

A DRIVEROBJ structure allows a display driver to request the GDI service in managing per-process resources. By creating a DRIVEROBJ structure, a display driver can ensure that resources will be released when an application terminates.

Some drivers, in their Escape support, allocate resources on behalf of applications. In such cases, the DRIVEROBJ structure provides a means for the application to notify the driver when it terminates. GDI will call the driver's cleanup function for each DRIVEROBJ structure allocated in an application's context that is not deleted before the application terminates.

This structure provides a locking mechanism for exclusive access to the associated resource.

Requirements

Header

Winddi.h (include Winddi.h)

See also

EngCreateDriverObj
EngDeleteDriverObj
EngLockDriverObj
EngUnlockDriverObj

 

 

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