Techwiki:Win32k/XCLIPOBJ

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Windows XP version of REGION

typedef struct
{
    LONG  scnPntTop;     // top line (inclusive)
    LONG  scnPntBottom;  // bottom line (exclusive)
    LONG  scnPntX[2];    // v-length array of x pairs
} SCAN2;

// REGION Object minimum size of 0x70, 3 cScan
typedef struct
{
    LONG  scnPntCnt;     // 038 count of x coordinates
    SCAN2 scnPnt[3];     // 03C
    LONG  scnPntCntToo;  // 108 same as scnPntCnt;
} SCAN1;

// REGION Object minimum size of 0x4C, 1 cScan
typedef struct
{
    LONG  scnPntCnt;     // 38    count of x coordinates
    LONG  scnPntTop;     // 3c    top line (inclusive)
    LONG  scnPntBottom;  // 40    bottom line (exclusive)
    LONG  scnPntX[2];    // 44 48 v-length array of x pairs
} SCAN;

typedef struct _RGN
{
    BASEOBJECT BaseObject;
    unsigned   sizeObj;
    ULONG      iUniq;      // from Clip object
    DWORD      nRefCount   // inc/dec Ref count if 0 deleteRGNOBJ
    SCAN *     pscnTail;
    unsigned   sizeRgn;
    unsigned   cScans;
    RECTL      rcl;
    SCAN       scnHead[1]; // 038 + 1 = 0x4C
    SCAN1      scnHead[1]; // 038 + 1 = 0x70
} RGN, *PRGN;

sizeRgn reports 2 minimum sizes, 0x4C and 0x70.

Windows XP version of CLIPOBJ or WNDOBJ

typedef struct _CLIPOBJ
{
    ULONG iUniq;
    RECTL rclBounds;
    BYTE iDComplexity;
    BYTE iFComplexity;
    BYTE iMode;
    BYTE fjOptions;
} CLIPOBJ;
typedef struct _WNDOBJ
{
    CLIPOBJ coClient;
    PVOID pvConsumer;
    RECTL rclClient;
    SURFOBJ *psoOwner;
} WNDOBJ, *PWNDOBJ;

EXtended CLip and Window Region Object Multipurpose E/X/CLIPOBJ and E/WNDOBJ structure

typedef struct _XCLIPOBJ
{
    WNDOBJ  exClipWnd;    // 000
    PVOID   pClipRgn;     // 030 
    RECTL   rclClipRgn;   // 034 
    PVOID   pscanClipRgn; // 044 
    DWORD   cScans;       // 048 
    DWORD   Unknown1;     // 04C
    ULONG   ulBSize;      // 050 
    LONG    lscnSize;     // 054 
    ULONG   ulObjSize;    // 058 
    ULONG   iDirection;   // 05C 
    ULONG   ClipType;     // 060 
    DWORD   Unknown2;     // 064 init z
    LONG    lUpDown;      // 068 
    DWORD   Unknown3;     // 06C init z
    BOOL    ShouldDoAll;  // 070 
    DWORD   nComplexity;  // 074 
    PVOID   pUnknown;     // 078 
} XCLIPOBJ, *PXCLIPOBJ; // Size is 0x7C or 124

exClipWnd

pClipRgn

prgnRao or (prgnVis if prgnRao == 0)

rclClipRgn

If ShouldDoAll is TRUE: Copy of clip prgn.rcl
If ShouldDoAll is FALSE: from exClipWnd.co.rclBounds.

pscanClipRgn

Based on iDirection, ulUpDown -1 *Tail up, 1 *Head down

cScans

From clip rgn cScans.

ulBSize

Recomputed buffer size.

lscnSize

Add (+-)size for pointer based on size of SCAN & iDirection.

ulObjSize

Specifies the size, in bytes, of the enum output buffer.

iDirection

One of CD_ANY CD_LEFTDOWN CD_LEFTUP CD_LEFTWARDS CD_RIGHTDOWN

CD_RIGHTUP CD_UPWARDS

ClipType

Always CT_RECTANGLES aka 0

lUpDown

-1 up, 1 down, based on "iDirection" of reading SCAN list.

ShouldDoAll

Specifies whether the entire region should be enumerated.

nComplexity

count/mode based on # of rect in regions SCAN.

pUnknown

pointer to a large DDA based drawing structure. See Note.

Signed lUpDown is not used, but is a notification which direction the scan list is read.

Note:

On a raster-based device, such as a screen display or a printer, the line drawing uses a class of algorithms called DDA (digital differential analyzer) to select the pixels to paint to represent a line. The Bresenham algorithm is a classical incremental DDA algorithm. The Windows NT/2000 graphics engine uses 28.4 fixed-point coordinate space on physical device surfaces. Lines are drawn following the so-called GIQ (Grid Intersection Quantization) diamond convention, in which each pixel is thought of as having a 1-by-1 pixel size diamond shape around it. A pixel is painted if its diamond shape touches a line segment. From section 8.4 of Windows Graphics Programming Win32 GDI and DirectDraw.

See also