More P/Invoke in PowerShell

In my last post, I gave an example of how to use P/Invoke through PowerShell  to implement functionality not immediately available via the .Net framework.  My example was to get the owner of a process, and Abhishek wisely pointed out that  this is easier through WMI.

So here’s another example.  It’s actually the one I had written originally, but it didn’t give me an opportunity to illustrate [Ref] parameters, or [Out] parameters via P/Invoke.

param([int] $opacity)

$WS_EX_LAYERED = 0x80000
$LWA_ALPHA = 0x00000002

## Invoke a Win32 P/Invoke call.
function Invoke-Win32([string] $dllName, [Type] $returnType,
[string] $methodName, [Type[]] $parameterTypes, [Object[]] $parameters)
(… from last post …)

function GetWindowLong($hWnd, $style)
$parameterTypes = [IntPtr], [int]
$parameters = [IntPtr] $hWnd, [int] $style

Invoke-Win32 “user32″ ([Int]) “GetWindowLong” $parameterTypes $parameters

function SetWindowLong($hWnd, $style, $value)
$parameterTypes = [IntPtr], [int], [int]
$parameters = [IntPtr] $hWnd, [int] $style, [int] $value

Invoke-Win32 “user32″ ([Int]) “SetWindowLong” $parameterTypes $parameters

function GetForegroundWindow
Invoke-Win32 “user32″ ([Int]) “GetForegroundWindow”

function SetLayeredWindowAttributes([byte] $opacity)
$window = GetForegroundWindow

$oldStyle = GetWindowLong $window $GWL_EXSTYLE
$result = SetWindowLong $window $GWL_EXSTYLE ($oldStyle -bor $WS_EX_LAYERED)
if($result -gt 0)
$parameterTypes = [IntPtr], [int], [byte], [int]
$parameters = [IntPtr] $window, [int] 0x00FFFFFF, [byte] $opacity, [int] $LWA_ALPHA

[void] (Invoke-Win32 “user32″ ([Int]) “SetLayeredWindowAttributes” $parameterTypes $parameters)

if($opacity -gt 100)
throw “Opacity must be between 0 and 100″

“Switch to the window that you want to adjust. The change will happen in 2 seconds.”
“(Note that console windows are not supported)”

sleep 2
SetLayeredWindowAttributes ($opacity * 255 / 100)

P.S.  I’m off to the Mediterranean until the middle of August.  Can you feed the cats while I’m gone?  :)

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