I want to receive a notification in my C++ application when a screensaver is about to start. I tried listening to WM_SYSCOMMAND messages with wParam == SC_SCREENSAVE which some people think should do the trick.
That didn't work. Spy++ even showed that my window didn't receive any WM_SYSCOMMAND message. Interesting thing is when I turned off the monitor I did receive the message with wParam == SC_MONITORPOWER. Am I understanding it wrong? Or did I just miss something?
Edit: For testing I used the default windows screensaver (the one with windows logo).
It appears that I will receive the SC_SCREENSAVE message only when my window has focus. The way around this is to set global hook. That would require me to put the callback function in a separate DLL and there is also this scary message about hooks slowing down the system so I decided to drop the idea of responding to screensaver start.
This is a relatively complex task (although it would be nice if it were easy).
Some of these tests you'll find online only work if your window is in focus. If it's running in the background it may not receive such messages.
Other tests rely on a screensaver program running (check the currently set screensaver, and then watch the process list to see if it's active) but don't work if you go into powersave mode, or if your screensaver is a black screen (ie, no program, just monitor off).
I don't believe there's an ideal way to do this. You might want to go back to the beginning and think more carefully about why you need to detect this state, and what you are trying to accomplish. You might need a different solution.
Probably my answer comes too late.
The MSDN handles screensavers under "Legacy".
On a notebook they waste battery and on a PC they are also useless.
It is better to turn the monitor off than letting it show a screensaver.
As you don't explain exactly what you want to do I don't know if you really need the notification BEFORE the saver starts or if it is enough to get notified when it already has just started.
In the latter case it is easy.
Write a thread that periodically checks:
BOOL b_SaverRunning;
SystemParametersInfo(SPI_GETSCREENSAVERRUNNING, 0, &b_SaverRunning, 0);
Related
I'm making an application that hooks itself in to a target application and, when activated by the user, prevents all keyboard and mouse window messages from reaching the target application's window proc. My application does this by translating the incoming input messages, such as WM_MOUSEMOVE, to WM_NULL, so that the window proc is unaware input happened.
The problem is that Windows also automatically sends WM_SETCURSOR and WM_NCHITTEST to the window proc (e.g. when the application calls PeekMessage) when mouse input occurs. These messages aren't posted to the window's message queue, so I can't change them to WM_NULL.
I initially worked around this by subclassing the window proc and simply ignoring WM_SETCURSOR and WM_NCHITTEST there, but subclassing seems to have compatibility issues with some of the applications I'm hooked in to.
My question is: How do I prevent WM_SETCURSOR and WM_NCHITTEST from being generated in the first place OR how do I prevent them from reaching the application's window proc.
Some Ideas to Try
I just finished implementing a global/system wide CallWndRetProc with a WH_CALLWNDPROCRET Windows Hook (like it describes in the past post of the link below).
http://help.lockergnome.com/windows2/Igor-SetCursor-SetWindowsHookEx--ftopict285504.html
Using that in combination with hiding all the system cursors using SetSystemCursor has effectively hidden the cursor for most applications.
If you wanted to continue hacking at this target application, you could try using API Monitor to diagnosis what is going on: http://www.rohitab.com/apimonitor
The guy at rohitab hints at releasing his source code eventually; his site seems to have some of the better forums about Hooking, Subclassing, Injecting, etc.
It sounds like you successfully used SetWindowLongPtr(), but there are a few different ways to get into the address space of the program you are working on...
Have you tried SetCapture()?
Other Links
Here are a few other links that may be useful:
http://support.microsoft.com/kb/31747
http://msdn.microsoft.com/en-us/library/windows/desktop/ms646262(v=vs.85).aspx
http://msdn.microsoft.com/en-us/library/windows/desktop/ms633569%28v=vs.85%29.aspx#winproc_subclassing
http://msdn.microsoft.com/en-us/library/windows/desktop/ms648395(v=vs.85).aspx
Hope that helps. Good luck.
I try to send a WM_LBUTTONDOWN and WM_LBUTTONUP messages to a window( simulating mouse clicks without moving the cursor ).
My program is working very good on many windows, but there are a few that don't work :(
Like Registry Editor, Yahoo Messenger, some Firefox sites, etc...
How can I make to work with those from above ??
NOTE#1: I use Win7
NOTE#2: My code is just calling the api and functions and aply them on the specific window handle. Its working ok but not on all windows :(
It is another aspect of UAC, called UIPI or User Interface Privacy Isolation that could cause this trouble. Designed to prevent a program that run un-elevated from hijacking the capabilities of an elevated one. That certainly explains the trouble with Regedit.exe, clearly UAC would be ineffective if a program could commandeer it to poke stuff into the registry. You'd have to run your program elevated to bypass this restriction.
Another one is that SendMessage() doesn't properly simulate mouse input. The messages you are sending are normally posted to the message queue. You need to use PostMessage() instead. You should also emulate WM_MOUSEMOVE.
The proper way to simulate mouse input is through SendInput(). That one exactly emulates the mouse driver behavior, there's no way for a program to tell the difference. But with the added requirement that you have to make sure that whatever program you are trying to automate runs in the foreground. That's very difficult, SetForegroundWindow() isn't reliable enough. So only consider SendInput() if you actually only want to send mouse messages to the foreground window, whatever it might be.
You can call SwitchToThisWindow instead of SetForegroundWindow, which is much better and it works most of the times, and then either call SendInput or mouse_event, which is much more comfortable, because you're not dealing with structs at all.
i am using the createdesktop api to create a desktop and i would like to take a screenshot or send input mouse/keyboard without dispalying the desktop to the user.any ideeas on how to implement this???
The short answer that I've found is that you can't. You can't take a screenshot of an inactive desktop because there are no paint calls because there are no visible windows to redraw.
You can do a SwitchDesktop() call, screen shot, then SwitchDesktop() back. The user won't notice it, but you likely won't get much in the screen shot because in this short time the windows haven't had time to redraw.
Another thing is, you have to make a new thread to call SetThreadDesktop(). If you use your main thread to do so, it will fail when using a GUI application. SetThreadDesktop() fails when you have a window in the current desktop.
SysInternals has an application to manage multiple desktops (like the linux desktop switch). When your about to pick a desktop to switch to it will show you a thumbnail of the desktop. This thumbnail is not live, it is captured by the last known full redraw when the user is in that desktop. In short, if SysInternals can't do a live screenshot I doubt any of us will.
This is of course based on my own research of this exact feature. If someone has actually gotten it to work I'd love to know so I can't use it too!
Edit: This won't work for invisible desktops, I've looked to my old code, and I see that I needed that for catching screenshot of active desktop (which was not 'WinSta0\Default'), to get handle of active user desktop I've used OpenInputDesktop.
+1 ThievingSix you are right.
Sorry everyone for my misunderstanding.
You need to use SetThreadDesktop (if you are creating desktop by CreateDestkop, then you have handle for it which you pass to SetThreadDesktop). After switching desktop for thread, you can catch screenshot. Good idea would be revert to previous desktop for thread (to not 'break' other/future code).
var
lOldDesktop: HDESK;
begin
lOldDesktop:= GetThreadDesktop(GetCurrentThreadId);
try
if not SetThreadDesktop(ADesktop) then // pass handle to your desktop, or dekstop handle obtained from OpenInputDesktop
{error handle, like RaiseLastOSError or Exit(False)};
// your screenshot/input/mouse code here
finally
if lOldDesktop<> 0 then // GetThreadDesktop can fail (I don't know condition when this GetThreadDesktop(GetCurrentThreadId) could fail)
SetThreadDesktop(lOldDesktop); // revert thread to previous desktop
end;
end;
This code should run in non-main thread, as ThievingSix pointed because SetThreadDesktop can fail in that case. Safe way is spawn thread to make screenshot.
PS. I'm not sure if this will work with "send input mouse/keyboard" (it should), but for screenshot works.
Edit:
More on sessions, window stations, desktops here http://blogs.technet.com/b/askperf/archive/2007/07/24/sessions-desktops-and-windows-stations.aspx
Desktop tool (SysInternals) - http://technet.microsoft.com/en-us/sysinternals/cc817881
I don't really know where to begin. Let's start with the stupid questions:
What language should I use for this? What is suited for the task at hand?
Next, the real ones:
Is there a way to stop the screensaver from starting, short of changing the cursor position? If not, will changing the cursor position even work?
SetThreadExecutionState will prevent the screensaver from coming on or the machine from automatically going to sleep if you pass the ES_CONTINUOUS and ES_DISPLAY_REQUIRED flags.
I wrote an app awhile ago that does exactly what you are asking for. It runs as an icon in the System Tray, not the Taskbar, and uses a global message hook to disable the WM_SYSCOMMAND/SC_SCREENSAVE notification from reaching any applications. If that notification does not reach the DefWindowProc() function, the screen saver will never run.
Your program does not need to be visible in the task bar at all.
You don't even need a program at all, if you can disable the screensaver in the registry.
What you want to do can perhaps be achieved by sending a MOUSE_MOVE event to the desktop window. If you want to use C# (the only language I am current with right now), you can look at this article, but maybe a simple C program using the WinAPI is better suited for this task.
.NET will easily allow you to put an application in the system tray (checkout the NotifyIcon object in System.Windows.Forms.Controls).
I believe you can use the SetCursorPos (http://msdn.microsoft.com/en-us/library/ms648394(VS.85).aspx) API call to prevent the screen saver, just make sure you set them to the current location so you don't actually move the mouse.
One solution that one could suggest is to periodically look for a special 'Screen-saver' desktop, and if it's present then count it as a running screensaver.
But apparently this is not the case for all screensavers as with some the mentioned desktop is always present.
Are there more reliable solutions for this?
See the WINAPI function SystemParametersInfo() with the SPI_GETSCREENSAVERRUNNING parameter. It's the only documented way to detect whether the screen saver is currently running. (You can also find out if a screen saver is even enabled, get and set the timeout value, and start the screen saver using this function.)
I think the key is to identify the screensaver by its window class ("WindowsScreenSaverClass"). I found this page
How do I start, detect and stop screen savers? that has some code examples and explanations.
HOW TO: Determine If Screen Saver Is Running by Using Visual Basic 6.0
I know this is for VB6, but it's bound to be a good place to start.
This is my implementation of screen saver event detection.
Notes:
SPI_GETSCREENSAVERRUNNING detects Windows Event id 4802 and 4803 which weren't accurate in my case, see my problem hence user idle time calculation is added
GetLastInputInfo apparently doesn't work if process is a service.
search processes for a process with .scr in its .MainModule.FileName