What is this SHIFTED ?

[SaltedTamago]

#define SHIFTED 0x8000

.....some long-and-hard-to-understand code.....
//Message processing
if(GetKeyState(VK_SHIFT) & SHIFTED)
{
//dosomething
}


Someone please tell me what is that SHIFTED's role in the if condition ?

Thank you

[ProgrammerC++]

GetKeyState returns an unsigned short (=16 bits)

The high order bit is set to 1 if the key is being pressed, the return value would be 0x8000
... and 0x8000 & 0x8000 = 0x8000 which would make the if statement TRUE

And the function also has the low order bit 1 if the key is toggled 1 or 0. But that value is ignored with this "& SHIFTED" part, so the if statement is only true if the key is pressed, not toggled.

So if the key is toggled but not pressed its 0x0001 & 0x8000 = 0x0000 (FALSE)
If the key is toggled and pressed its 0x8001 & 0x8000 = 0x8000 (TRUE)

See http://msdn.microsoft.com/en-us/libr...8VS.85%29.aspx

Atleast that's how I see it

[2kaud]

In the examples quoted, SHIFTED is defined as 0x8000 and is used with the return value of GetKeyState(). GetKeyState() returns a SHORT (16 bit) so 0x8000 references the high order bit which is set when the key is pressed.

IMO a better name than SHIFTED would be PRESSED. Tests for shift, ctrl etc can then be done something like (not tried)

#define PRESSED 0x8000

if (GetKeyState(VK_SHIFT) & PRESSED) 
//Shift key pressed

if (GetKeyState(VK_CONTROL) & PRESSED)
//Control key pressed
...

See https://msdn.microsoft.com/en-us/lib...=vs.85%29.aspx for more details.

The possible virtual keys that can be tested are

VK_LSHIFT
VK_RSHIFT
VK_LCONTROL
VK_RCONTROL
VK_LMENU
VK_RMENU
VK_SHIFT
VK_CONTROL
VK_MENU

[crazy boy]

Yes, thank you. I read more:

"In all four of the keyboard messages discussed so far, the wParam parameter contains the virtual-key code of the key. The lParam parameter contains some miscellaneous information packed into 32 bits. You typically do not need the information in lParam. One flag that might be useful is bit 30, the "previous key state" flag, which is set to 1 for repeated key-down messages."
https://msdn.microsoft.com/en-us/lib...=vs.85%29.aspx
Good link