screensaver | Start the screensaver | Runtime Evironment library

OK I came up with a little shell script and you can put it in crontab for running this script when ever you want :)

TRY USE

After some fiddling, while we can't intercept keyboard (and shouldn't to reliably detect a quit), it's actually possible to listen to some distributed notifications in the screensaver that tells us when the user gets logged in, and use that to call our code to stop animations/sound, as there's a sizable lag between the moment we are effectively killed and the moment the user gets back to desktop.

I did find some events in this answer here : Monitoring Screensaver Events in OSX and while it's a bit dated those events are still fired and can be intercepted inside the screensaver despite the sandboxing. I did found a few new ones though that may be interesting for other purposes.

Anyway, here's what's working for me :

Swing is event driven, this means that you never directly call painting methods. Basics for a custom painting component:

• extends JComponent
• override paintComponent(Graphics g), this is the point where you can put your rendering code
• override getPreferredSize(), so that the layout managers can do their duty, a suitable value is your image size

In addition I don't understand this line:

How to make a Java Swing app as a child of Windows native HWND / Set up ScreenSaver preview panel

NOTE: The code examples here will not compile and omits the error code checks, but is just to show your the order of Windows API calls needed to dock any Java Swing frame inside Windows native HWND parent - for your own implementation in JNI /JNA or JDK16+ Panama.

Firstly work out parent Windows long hWndParent. For Windows Screensavers this is passed into the "SCR" executable as with "/C" or "/P" (upper/lower) plus parent HWND argument. It may have SPACE or ":" separating the flag and HWND, or as two arguments FLAG + HWND so make sure you parse long hWndParent handle from the number passed in to main(String[] args) as:

Look at the description of range-function, there just one way to pass a variable to it:

You're probably not able to have a positive result using SendInput() or other functions because a ScreenSaver runs in special Desktop, named (guess what) Screen-saver.
You need to get the handle to this Desktop to actively interact with it or its Windows.

You can use the SystemParametersInfo function, passing SPI_GETSCREENSAVERRUNNING to determine whether a ScreenSaver is currently active, then call OpenDesktop() get the handle of the Desktop (using its name), find the ScreenSaver Window (the ScreenSaver is a standard executable) and post a WM_CLOSE message to close it.

Here, I'm using EnumDesktopWindows to find the ScreenSaver.
(The ScreenSaver Window should the be Foreground Window anyway).
In case it fails, we can try to close the Desktop, calling CloseDesktop().

Some more possibly interesting info related to ScreenSaver here:
Handling Screen Savers

If you have a procedure that receives a Command through a serial port or something similar, verify whether this procedure is run in a Thread other than the UI Thread, in case you need to access the UI in this occasion.

Add this code to the procedure: it checks whether a ScreenSaver is active and tries to close it.
It's been tested in both Windows 10 (19H2) and Windows 7 SP1.
.Net Framework 4.8 - VB.Net v.15

NOTE: your app is meant to run as a 64bit process. If you have set Prefer 32-bit in your Project's Build option, you need to deselect it.

► Assuming this procedure is run in the UI Thread. Me.Activate() is not strictly required and can be used from the UI Tread only. Remove it if your code runs on a different Thread.

Here is a modified version of your code that uses Clock.schedule_once() instead of signal:

There was a problem with path because when you open cmd ,the path where screen saver is present(i.e system32) is added in system variables so it executes perfectly but when you execute your python script, the path is set to current directory so it cant find Bubbbles.scr.your code is alright except for the path.the following code works:

The name of the screensaver process will vary by which screensaver is running, but it should always end in .scr.