Geoff Chappell, Software Analyst
It was only ever inevitable that the WND structure would need yet more bit flags than the age-old state, style and ExStyle, even after the addition of state2 for version 4.0. The first surprise when more came for version 6.0 is the name. The bit fields are in union with a ULONG named ExStyle2, but none of the bits is an extended window style. Though one does at least affect what’s reported as the window’s extended style, the set is very much more an extension of state and state2 than of style and ExStyle.
Another surprise is that although the new ExStyle2 was appended to the WND, and is thus disjoint from the other sets of bit flags, the 16-bit encoding of window flags as if state, state2, ExStyle and style make a large array of bits extends to the ExStyle2 too. In this encoding of any window flag, the high byte is a byte offset from the state to the bit and the low byte is a bit mask within the byte. Though version 6.0 is not known to use this encoding for the ExStyle2 bits, the use is well established by version 6.1.
| Mask | Window Flag Index | Definition | Versions | Remarks |
|---|---|---|---|---|
| 0x00000001 | 0x9801 |
INT bClipboardListener : 1; |
6.0 and higher | |
| 0x00000002 | 0x9802 |
INT bLayeredInvalidate : 1; |
6.0 and higher | |
| 0x00000004 | 0x9804 |
INT bRedirectedForPrint : 1; |
6.0 and higher | |
| 0x00000008 | 0x9808 |
INT bLinked : 1; |
6.0 and higher | |
| 0x00000010 | 0x9810 | 6.2 and higher | no use yet known | |
| 0x00000010 (6.0 to 6.1); 0x00000020 |
0x9810 (6.0 to 6.1); 0x9820 |
INT bLayeredForDWM : 1; |
6.0 and higher | |
| 0x00000020 (6.0 to 6.1); 0x00000040 |
0x9820 (6.0 to 6.1); 0x9840 |
INT bLayeredLimbo : 1; |
6.0 and higher | |
| 0x00000040 (6.0 to 6.1); 0x00000080 |
0x9840 |
INT bHIGH_DPI_UNAWARE_Unused : 1; |
6.0 and higher |
The bRedirectedForPrint flag provides another good example of efficiency that results from the visibility of the WND in user mode. The USER32 export IsWindowRedirectedForPrint needs no kernel-mode transition: it merely resolves the window handle to a pointer and extracts this bit.
Version 6.2 evidently inserted a bit, shifting others to higher values, but I don’t yet know what for, let alone why.
If bLayeredForDWM is set, then the extended window styles produced by the GWL_EXSTYLE case of the USER32 function GetWindowLong have WS_EX_LAYERED clear.
| Mask | Window Flag Index | Definition | Versions |
|---|---|---|---|
| 0x00000080 (6.1); 0x00000100 |
0x9880 (6.1); 0x9901 |
INT bVerticallyMaximizedLeft : 1; |
6.1 and higher |
| 0x00000100 (6.1); 0x00000200 |
0x9901 (6.1); 0x9902 |
INT bVerticallyMaximizedRight : 1; |
6.1 and higher |
| 0x00000200 (6.1); 0x00000400 |
0x9902 (6.1); 0x9904 |
INT bHasOverlay : 1; |
6.1 and higher |
| 0x00000400 (6.1); 0x00000800 |
0x9904 (6.1); 0x9908 |
INT bConsoleWindow : 1; |
6.1 and higher |
| 0x00000800 (6.1); 0x00001000 |
0x9908 (6.1); 0x9910 |
INT bChildNoActivate : 1; |
6.1 and higher |
Microsoft’s names and definitions for bits that have been defined since Windows 7 may never be known. If only for now, I can contribute no more than placeholders.
| Mask | Window Flag Index | Versions |
|---|---|---|
| 0x00002000 | 0x9920 | 6.2 and higher |
| 0x00004000 | 0x9940 | 6.2 and higher |
| 0x00008000 | 0x9980 | 6.3 and higher |
| 0x00010000 | 0x9A01 | 6.3 and higher |
| 0x00020000 | 0x9A02 | 6.3 and higher |
| 0x00040000 | 0x9A04 | 6.3 and higher |
| 0x00080000 | 0x9A08 | 10.0 and higher |
| 0x00100000 | 0x9A10 | 6.3 and higher |
| 0x00200000 | 0x9A20 | 6.3 and higher |
| 0x00400000 | 0x9A40 | 10.0 and higher |
| 0x00800000 | 0x9A80 | 10.0 and higher |
| 0x01000000 | 0x9B01 | 10.0 and higher |
| 0x02000000 | 0x9B02 | 10.0 and higher |
| 0x04000000 | 0x9B04 | 10.0 and higher |
If the 0x00080000 bit is used in version 6.3, I don’t yet know where.