ULONG CLIPOBJ_cEnumStart(
| IN CLIPOBJ *pco, | |
| IN BOOL bAll, | |
| IN ULONG iType, | |
| IN ULONG iDir, | |
| IN ULONG cLimit | |
| ); |
CLIPOBJ_cEnumStart sets parameters for enumerating rectangles in a specified clip region.
Parameters
pco
Points to the CLIPOBJ structure that defines the clip region to be enumerated.
bAll
Specifies whether the entire region should be enumerated. This parameter is TRUE if the whole region should be enumerated. It is FALSE if only the parts relevant to the present drawing operation should be enumerated.
A driver that caches clip regions must enumerate the entire region.
iType
Specifies the data structures that are to be written by CLIPOBJ_bEnum. This parameter currently must be CT_RECTANGLES, indicating that the region is to be enumerated as a list of rectangles.
iDir
Determines the order in which the rectangles are to be enumerated. This order can be essential if a DrvBitBlt operation is executing concurrently on the same surface. If the order is not relevant to the device driver, CD_ANY should be specified for complex regions, allowing GDI to optimize the enumeration. This value can be one of the following:
| Value | Meaning |
| CD_RIGHTDOWN | Left to right, top to bottom. |
| CD_LEFTDOWN | Right to left, top to bottom. |
| CD_RIGHTUP | Left to right, bottom to top. |
| CD_LEFTUP | Right to left, bottom to top. |
| CD_ANY | Any order convenient for GDI. |
cLimit
Specifies the maximum number of rectangles to be enumerated. If this parameter is zero, counting is omitted.
Return Value
The return value is the count of enumerated rectangles. If the count exceeds cLimit, the return value is 0xFFFFFFFF.
Comments
A region can be enumerated whether or not this function is called. By default, the driver only enumerates relevant rectangles, starting at the upper left.
The driver can restart enumeration by calling this function again.
See Also