How to Specify Virtual Desktop for a Cron Task?

[Bob P]

I'm looking for some help writing a cron task that opens a browser instance and assigns it to appear on a specific virtual desktop in X11.

My window manager is KDE. So far I've been able to deploy the task, but I have had no luck designating the virtual desktop where I 'd like it to appear.

My KDE desktop has multiple virtual desktops that I can select with Pager. I'd like to restrict the specified task to appearing only on the specified virtual desktop. Right now I've got things working to the point that deploying the task works reliably, but the window manager is assigning the task to whichever virtual desktop happens to have focus, or to have recently had focus, rather than putting it on the virtual desktop I'd like it to be assigned to.

I'm using:
KDE Plasma 5.27.11
KDE FRameworks 5.116.0
Qt 5.15.14

Here's an example of a cron entry where I can call Brave Browser to open the Gentoo Forums home page:

[sMueggli]

Why are you using a cronjob for this task? I think XDG autostart is a better aproach to automatically start graphical applications.

Virtual desktops looks like a desktop specific thing. I do not think that cronjob and XDG autostart are aware of this.

[Bob P]

Thanks for responding.

My feeble undestanding of XDG Autostart is that it's used to:
a) autostart applications when the desktop is started, or
b) autostart applications when a drive is mounted

In my case, those events aren't correlated with the time that I want the application to be deployed. So I'm looking at BASH and cron.

I'm thinking there's got to be some way to communicate with the window manager to assign a virtual desktop ... I just haven't found it yet.

Thanks again.

[szatox]

Long long time ago KDE had an option in the config manager to bind an application to a workspace, is it still there?
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[Ralphred]

There are a few ways to do this, but both have implications regarding "interrupting" what you are doing when the job runs:

• Use KDE's "special window settings/rules"
  Easiest way to try this is let the task run, then right click the top left icon and use "special window settings" in the "more" menu.
  The downside of this is with a browser the window title changes with once the page is loaded, so you might find it ignores "window title".
  There are multiple options of when to apply the "desktop" property, but if you end up having to use "Force" and can't get the "window title" to work you'll confine all instances of Brave to the same desktop.
  
• Use xdotool
  There are two ways to use this, the first is simple, use xdotool to read the current active desktop, if it isn't the one brave is to spawn in, change to that (xdotool again), once it's spawned, change back.
  The second way would be to have xdotool find the window after it's spawned, and use set_desktop_for_window to move it where it's supposed to be.

Below is a snippet from my media thingy, it starts the browser, waits for it to connect the amazon video site, then set focus on it so I can send the keystrokes for fullscreen etc.

[Bob P]

[Bob P]

[Ralphred]

[Bob P]

My experience is that when launching an app from the command line KDE/Plasma completely ignores all of your window or application window rules/settings in KDE, as well as your command line specifications, if there is any existing open browser instance. If no browser instance is open, then the window will be deployed honoring the on-screen location and dimensions parameters passed via the command line, but the desktop assignment in the KDE window rule will not be honored under any circumstance and the window gets opened on whatever vdesktop has focus.

OTOH if any browser window is open on any other vdesktop then all of the command line parameters regarding window size and location get ignored: vDesktop number, window location, window dimensions all get ignored. The parameters assigned to the window/application window rules in KDE will also be completely ignored. The location and dimensions for the newly generated browser window get cloned from whatever open browser instance most recently had focus, and the new window is opened on whatever desktop currently has focus.

For example, if I have browser instances on desktop 3 and 5, where the instance on 3 is narrow and 5 is wider, and I'm on desktop 1 in a terminal, then when the cron task executes the browser will be opened on desktop 1 with the dimensions copied from the instance on 3 or 5 depending on which one most recently had focus. All of the window management class rules get completely ignored, even when all of the browser instances have unique window titles and the rules are set to pay strict attention only to title and there are separate rules for each window instance. The bottom line is that the KDE window class thingy doesn't work unless there is only 1 instance of the window class (the one it opens). As soon as a second one exists the rules seem to be completely ignored.

Interestingly, the vdesktop number in the window classes only gets honored if there's a single instance of a window class AND the browser gets launched from within KDE. If the browser is launched via a shell script then the window manager comletely ignores KDE's window rule set to cast that new browser instance to a specific desktop.

I hadn't thought about this when I wrote my previous posts, but I've been using virt-manager within KDE/Plasma to launch virutal machines, with them reliably cast to a specific desktop if and only if they are launched from wthin the window manager. If I invoke them from the command line the window class rules for vdesktop assignment get ignored, just like with the browser instances.

It's hard for me to imagine that I'm the first person who's ever wanted to invoke an application from a command line and cast it to a specific vdesktop. It really amazes me that there isn't a straightforward solution to this problem. that is to say, if one does exist, I've had a hard time finding it.

I have LOTS of auto-opening web pages in my cron task. Having a unique browser for each instance doesn't really simplify the problem for me as I'd need many many different browsers. That and I'm really not a fan of browser-hopping.

[szatox]

You mentioned you want those windows popping on a different workspace, because stealing focus breaks some automation for you. Maybe you could send those windows to a different instance of X? Maybe even start a new instance of X for each of them, so they won't be stepping on each others' toes?
There are ways to run an X-server for a remote user, like xrdp for example (something with SPICE would probably be better for a linux user, but that's not the point). Haven't used them myself, but they surely can run completely detached from any terminals at all, so it should be possible to use them for isolating those cron jobs.

[Ralphred]