I have created a C# Winform that runs in the systray, has no task bar presence, etc. It registers a bunch of hotkeys so I can do stuff inside the app whether it is the active app or not (using user32.dll RegisterHotKey function)
The application itself runs beautifully, no problems.
However, I am now trying to detect when the user has gone idle. I know this can be accomplished by catching the WM_SYSCOMMAND message and testing for the WParam of SC_SCREENSAVE.
I've actually got this to work, but only if the application is active, and not minimized in the systray.
My question:
"Is there a function (in User32.dll?) to register my application as a listener for SC_SCREENSAVE, kind of like RegisterHotKey (User32.dll) does?"
Thanks,
seeflat
This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.
Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.
If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.
Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.
Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.
Access the answers to your technology questions today.
30-day free trial. Register in 60 seconds.
Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.
Try it out and discover for yourself.
30-day free trial. Register in 60 seconds.
Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.
I've been banging on this for a while now.
Thanks for the input Agarici.
However, simply placing the hook inside a dll won't solve my problem, as the form ultimately ends up being the owner of the thread.
So again, I'm left with a thread-based hook.
Anyone else have any suggestions? I can't find anything concrete on the web. There has to be something; I'm just missing it.
Thanks,
seeflat
to catch WM_SYSCOMMAND/SC_SCREENSAV
try this:
1. make a dll and put a function that has the prototipe of a CBTProc in this dll
from msdn:
"The CBTProc hook procedure is an application-defined or library-defined callback function used with the SetWindowsHookEx function. The system calls this function before activating, creating, destroying, minimizing, maximizing, moving, or sizing a window; before completing a system command; before removing a mouse or keyboard event from the system message queue; before setting the keyboard focus; or before synchronizing with the system message queue. A computer-based training (CBT) application uses this hook procedure to receive useful notifications from the system"
a CBTProc function looks like this:
LRESULT CALLBACK CBTProc( int nCode, WPARAM wParam, LPARAM lParam);
- in this function you have to check nCode. if nCode == HCBT_SYSCOMMAND wParam and lParam have the content they usually have in a WM_SYSCOMMAND message
- do not forget to add a call to CallNextHookEx when you finish the processing
2. in your c# app add dll imports like this
[DllImport("user32.dll")]
public static extern IntPtr SetWindowsHookEx(HookType code,CbtHook.CbtProc func, IntPtr hInstance, int threadID);
[DllImport("user32.dll")]
public static extern int UnhookWindowsHookEx(IntPtr
3. install the hook using SetWindowsHookEx and uninstall it with
it is all in the second link i gave you
there is the code available for download also (having c# and vb.net code)
>>Everything I'm trying isn't working.
maybe if you would give more details i or someone else could help you
i mean: what did you try and what is not working?
A.
Business Accounts
Answer for Membership
by: AgariciPosted on 2004-03-04 at 07:36:55ID: 10514776
you can implement a system message hook and search for WM_SYSCOMMAND/SC_SCREENSAV
unfortunately installing a system wide hook requires the hook procedure to be in a dll
look for Win32 Hooks in msdn library or do a search on google
see:
http://msdn.microsoft.com/
and
http://msdn.microsoft.com/
hth.
A.