Re: OpenProcess Identify Handle
From: Tom Esh (tjeshGibberish_at_earthlink.net)
Date: 04/21/04
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Date: Wed, 21 Apr 2004 11:23:14 -0400
See inline.
On Tue, 20 Apr 2004 23:06:02 -0700, "Keith"
<anonymous@discussions.microsoft.com> wrote:
>No confusion about this, I'm getting the correct PID, and I know the difference. The closed remard is when I was trying to find the hwnd from a call to OpenProcess, where all the ample code comes with big warnings about closing the process later.
Then I guess you know that OpenProcess returns a ~process~ handle for
a given PID, and not a hwnd (?) If it helps, here's a snip that finds
any MediaPlayer (ver 8) top-level window handle regardless of its
caption / titlebar text:
Dim hwndMP As Long
hwndMP = FindWindow("WMPlayerApp", vbNullString)
Then to determine if that particular instance belongs to a specific
process PID, you can use GetWindowThreadProcessId:
Dim pidThis As Long
GetWindowThreadProcessId hwndMP, pidThis
If pidThis = PID Then 'it matches
SetWindowPos hwndMP, ...whatever
End If
>Though as a confessed newbie, there's a lot about API that I'm confused about. It's getting the hwnd from this PID value that I'm having trouble with.
There is no Api function to enumerate windows for a given process, so
you have to work through the hwnds and look for a PID match.
GetWindowThreadProcessId is useful here.
Public Declare Function GetWindowThreadProcessId Lib "user32" _
(ByVal hwnd As Long, lpdwProcessId As Any) As Long
>That I'm using the correct PID is confirmed by looking at the Task Manager and Spy++. Generally today I found it to have a value between 600 and 2500. It's the return value from the Shell function I'm using to open the mplayer2 Windows.
>
>The problem is when I use this value either though the OpenProcess or FindWindow method, as per the 2 samples I looked at, the values I get are wrong. ( I assume with OpenProcess I'm getting a new handle that references the base one)
Yes, each call to OpenProcess returns a proc handle unique to the
calling context. However typically you don't need a proc handle unless
you intend to monitor or wait for the process to finish.
>Björn Holmgren posted some code in the ShellExecute thread of 4/13/2004 that I though would do the trick, using FindWindow and then looping though the PIDs - but no such luck - It may be the parent/child problem, but - when I plug the hwnd value from the rpiWinSpy - which uses the same trick as Spy++ of drag drop a marker to identify the window then uses WindowFromPoint to get the hwnd - then I can do the moving and positioning. I was using Shell, not ShellExecuteEx, which also has a function call in Björn's sample, so I'll try that next.
>
>Is is possible to set where a window will open using an API calls? This would also be a solution.
Yes, but only if the app cooperates. You could use CreateProcess to
start the app and specify the startup location in the STARTUPINFO
structure and including the STARTF_USEPOSITION flag. However this will
only work if the app actually uses it and does not for example stash &
restore the last positon. Since using the last position is common,
you're better off finding and moving the window after it starts.
-Tom
MVP - Visual Basic
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