Here is a MWE

var clients = workspace.clientList();
for (var i = 0; i < clients.length; i++)
{
  if (clients[i] === null) {continue;}
  if (clients[i].resourceName.toString() === 'konsole') // or any other client that you have open
  {
    var pre = clients[i].screen;
    clients[i].screen = 1;
    var post = clients[i].screen;
    print(pre, post, workspace.numScreens); // output: 0 0 2, expected output 0 1 2
  }
}

There seems to be a sendToScreen method ( https://github.com/KDE/kwin/blob/fbfd1ac705212892f417aa5cc9df5fcd9ce9cb52/abstract_client.h#L453 ) however it's not accessible to scripts.

using `workspace.activeScreen = 1` doesn't work either, since it's readonly too and it doesn't seem possible to activate a client either.

Finally, https://api.kde.org doesn't seem to contain any scripting docs for KWin 5+

(In reply to LinG from comment #0)
> The screen property of a client is now readonly? I'm pretty sure it used to
> be read and write, thus allowing me to change the screen on which a client
> resides but now I can't? How do I change the screen on which a client
> resides through the scripting API now?
As far as I know, it has always been read-only.

(In reply to Lo from comment #2)
> There seems to be a sendToScreen method (
> https://github.com/KDE/kwin/blob/fbfd1ac705212892f417aa5cc9df5fcd9ce9cb52/
> abstract_client.h#L453 ) however it's not accessible to scripts.
No, what you need is Workspace::sendClientToScreen(), which is not exposed to scripting API unfortunately.

So how does one move a client from a screen to another?

(In reply to Lo from comment #4)
> So how does one move a client from a screen to another?
See https://phabricator.kde.org/D26988.

You would do `workspace.sendClientToScreen(client, screen);` or something.

It would be great if you could test my patch. ;-)

(In reply to Vlad Zahorodnii from comment #3)
> (In reply to LinG from comment #0)
> > The screen property of a client is now readonly? I'm pretty sure it used to
> > be read and write, thus allowing me to change the screen on which a client
> > resides but now I can't? How do I change the screen on which a client
> > resides through the scripting API now?
> As far as I know, it has always been read-only.

I've always used this screen property of the client the same way as I have been using the desktop property and am still using. So it's interesting to me that you say that this property has never been writable.

Question 1: What would be the reason to not make the screen property writable like the desktop property on a client? I'm fine with using your proposed method as well, but isn't the former more in line with the rest of the API?

(In reply to LinG from comment #7)
> I've always used this screen property of the client the same way as I have
> been using the desktop property and am still using. So it's interesting to
> me that you say that this property has never been writable.
You shouldn't actually use that property, it's deprecated.

> Question 1: What would be the reason to not make the screen property
> writable like the desktop property on a client? I'm fine with using your
> proposed method as well, but isn't the former more in line with the rest of
> the API?
It matches what KWin is doing whenever it needs to send a client to another screen.

Git commit 76297196e898c838ed89d21f44e8a8560cd7391f by Vlad Zahorodnii.
Committed on 29/01/2020 at 15:14.
Pushed by vladz into branch 'Plasma/5.18'.

[scripting] Expose Workspace::sendClientToDesktop()

Summary:
FIXED-IN: 5.18.0

Test Plan: Only compile-time check.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D26988

M  +8    -0    scripting/workspace_wrapper.cpp
M  +5    -0    scripting/workspace_wrapper.h

https://commits.kde.org/kwin/76297196e898c838ed89d21f44e8a8560cd7391f

(In reply to Vlad Zahorodnii from comment #8)
> (In reply to LinG from comment #7)
> > I've always used this screen property of the client the same way as I have
> > been using the desktop property and am still using. So it's interesting to
> > me that you say that this property has never been writable.
> You shouldn't actually use that property, it's deprecated.

Alright, where can I find the most recent documentation about the methods and properties that I should use?

(What method should I use to send clients to different desktops and is there also something available to send clients to different activities?)

> 
> > Question 1: What would be the reason to not make the screen property
> > writable like the desktop property on a client? I'm fine with using your
> > proposed method as well, but isn't the former more in line with the rest of
> > the API?
> It matches what KWin is doing whenever it needs to send a client to another
> screen.

That's fair, keeping the API as close to the internals seems like the best way to me as well.

(In reply to LinG from comment #10)
> Alright, where can I find the most recent documentation about the methods
> and properties that I should use?
Unfortunately, only source code. API dox is not generated for KWin since KDE Plasma 5.

> (What method should I use to send clients to different desktops and is there
> also something available to send clients to different activities?)
So, with the new virtual desktop model, a client can enter and leave more than just one desktop. On X11, a client can be either only on one or on all desktops, though. The relevant AbstractClient property I'm talking about is x11DesktopsIds.

It seems like scripts can modify only legacy `desktop` property. :/

(In reply to Vlad Zahorodnii from comment #11)
> (In reply to LinG from comment #10)
> > Alright, where can I find the most recent documentation about the methods
> > and properties that I should use?
> Unfortunately, only source code. API dox is not generated for KWin since KDE
> Plasma 5.

Alright, could you point out to me where I can find the code that is related to the KWin::client and KWin::toplevel (assuming client still inherits from toplevel as in 4.9). The scripting/workspace_wrapper.h is very readable so I'm fine with working with that but I didn't find a client_wrapper.h or something in this directory