Using xdg-desktop-portal-kde to take screenshots

Damir Porobic damir_porobic at live.com
Tue Sep 29 21:39:00 BST 2020


Hello Jan,

the parent class that I inherited from was QObject based but I was missing the Q_OBJECT macro in the child class. After adding the macro everything worked as expected.

Thank you very much you've been a huge help in getting the base functionality to work. I've been struggling with this for quite some time.

Best regards,
Damir
________________________________
From: kde-devel <kde-devel-bounces at kde.org> on behalf of Jan Grulich <jgrulich at redhat.com>
Sent: Tuesday, September 29, 2020 07:43
To: kde-devel at kde.org <kde-devel at kde.org>
Subject: Re: Using xdg-desktop-portal-kde to take screenshots

Hi,

this all looks good to me. Is your class WaylandImageGrabber QObject based? That's the only thing that comes to my mind.

Regards,
Jan

ne 27. 9. 2020 v 10:03 odesílatel Damir Porobic <damir_porobic at live.com<mailto:damir_porobic at live.com>> napsal:
I have had a look at the dbus monitor and this is what I see after hitting the save button in the dialog:

**************************
signal time=1601192691.549507 sender=:1.17 -> destination=(null destination) serial=55 path=/scheduler; interface=org.kde.baloo.scheduler; member=stateChanged
   int32 3
signal time=1601192691.559384 sender=:1.17 -> destination=(null destination) serial=56 path=/scheduler; interface=org.kde.baloo.scheduler; member=stateChanged
   int32 0
method return time=1601192691.738677 sender=:1.58 -> destination=:1.53 serial=36 reply_serial=141
   uint32 0
   array [
      dict entry(
         string "uri"
         variant             string "file:///home/dporobic/Screenshot_20200927_094451.png"
      )
   ]
signal time=1601192691.739126 sender=:1.53 -> destination=:1.50 serial=143 path=/org/freedesktop/portal/desktop/request/1_50/u3; interface=org.freedesktop.portal.Request; member=Response
   uint32 0
   array [
      dict entry(
         string "uri"
         variant             string "file:///home/dporobic/Screenshot_20200927_094451.png"
      )
   ]
method call time=1601192691.739267 sender=:1.53 -> destination=org.freedesktop.DBus serial=144 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=RemoveMatch
   string "type='signal',sender='org.freedesktop.impl.portal.desktop.kde',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged',path='/org/freedesktop/portal/desktop/request/1_50/u3',arg0='org.freedesktop.impl.portal.Request'"
method return time=1601192691.739275 sender=org.freedesktop.DBus -> destination=:1.53 serial=116 reply_serial=144
method call time=1601192691.739308 sender=:1.53 -> destination=org.freedesktop.DBus serial=145 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=RemoveMatch
   string "type='signal',sender='org.freedesktop.impl.portal.desktop.kde',interface='org.freedesktop.impl.portal.Request',path='/org/freedesktop/portal/desktop/request/1_50/u3'"
method return time=1601192691.739317 sender=org.freedesktop.DBus -> destination=:1.53 serial=117 reply_serial=145
signal time=1601192692.064469 sender=:1.6 -> destination=(null destination) serial=206 path=/; interface=org.kde.KDirNotify; member=FilesAdded
   string "desktop:/"
signal time=1601192692.064637 sender=:1.6 -> destination=(null destination) serial=207 path=/; interface=org.kde.KDirNotify; member=FilesAdded
   string "desktop:/Screenshot_20200927_094451.png"
signal time=1601192692.064789 sender=:1.6 -> destination=(null destination) serial=208 path=/; interface=org.kde.KDirNotify; member=FilesAdded
   string "desktop:/"
method call time=1601192692.071804 sender=:1.60 -> destination=org.freedesktop.DBus serial=15 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=AddMatch
   string "type='signal',sender='org.freedesktop.DBus',interface='org.freedesktop.DBus',member='NameOwnerChanged',arg0='org.kde.kded5'"
method call time=1601192692.071946 sender=:1.60 -> destination=org.freedesktop.DBus serial=16 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=GetNameOwner
   string "org.kde.kded5"
method return time=1601192692.071974 sender=org.freedesktop.DBus -> destination=:1.60 serial=9 reply_serial=16
   string ":1.6"
method call time=1601192692.072129 sender=:1.60 -> destination=org.kde.kded5 serial=17 path=/modules/desktopnotifier; interface=org.kde.DesktopNotifier; member=watchDir
   string "/home/dporobic"
method call time=1601192692.072140 sender=:1.60 -> destination=org.freedesktop.DBus serial=18 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=RemoveMatch
   string "type='signal',sender='org.freedesktop.DBus',interface='org.freedesktop.DBus',member='NameOwnerChanged',arg0='org.kde.kded5'"
method call time=1601192692.082794 sender=:1.60 -> destination=org.freedesktop.DBus serial=19 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=AddMatch
   string "type='signal',sender='org.freedesktop.DBus',interface='org.freedesktop.DBus',member='NameOwnerChanged',arg0='org.kde.kded5'"
method call time=1601192692.082901 sender=:1.60 -> destination=org.freedesktop.DBus serial=20 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=GetNameOwner
   string "org.kde.kded5"
method return time=1601192692.082918 sender=org.freedesktop.DBus -> destination=:1.60 serial=10 reply_serial=20
   string ":1.6"
method call time=1601192692.083083 sender=:1.60 -> destination=org.kde.kded5 serial=21 path=/modules/desktopnotifier; interface=org.kde.DesktopNotifier; member=watchDir
   string "/home/dporobic"
method call time=1601192692.083099 sender=:1.60 -> destination=org.freedesktop.DBus serial=22 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=RemoveMatch
   string "type='signal',sender='org.freedesktop.DBus',interface='org.freedesktop.DBus',member='NameOwnerChanged',arg0='org.kde.kded5'"
signal time=1601192696.749626 sender=:1.17 -> destination=(null destination) serial=57 path=/scheduler; interface=org.kde.baloo.scheduler; member=stateChanged
   int32 4
signal time=1601192696.749779 sender=:1.17 -> destination=(null destination) serial=58 path=/scheduler; interface=org.kde.baloo.scheduler; member=stateChanged
   int32 0

**************************

And this is what my application console output spits out:

**************************
Got reply
The path: /org/freedesktop/portal/desktop/request/1_50/u3
**************************

The call seems to be correct I guess. Any idea?

Regards,
Damir

________________________________
From: Damir Porobic <damir_porobic at live.com<mailto:damir_porobic at live.com>>
Sent: Monday, September 21, 2020 10:31
To: kde-devel at kde.org<mailto:kde-devel at kde.org> <kde-devel at kde.org<mailto:kde-devel at kde.org>>
Subject: Re: Using xdg-desktop-portal-kde to take screenshots

When you run "dbus-monitor --session" and you perform the screenshot, do you see this signal to be called at all?

Thanks Jan, I'll try that.

Unfortunately no, again a limitation of the portal API as the portal is supposed to return an URI. You can however directly use KWin DBus interface to get a screenshot, specifying directly what type of screenshot you want to tak and you get the raw image. This however will make it work only in Plasma and will not work in an application running in sandbox without giving it access to DBus.
My Application already supports native Plasma and Gnome Wayland Screenshots, but that does don't work if the application is packaged as Snap or when non Plasma or Gnome environments are used, so I'm trying to make this generic  Wayland solution work.

Also, I've been playing around with this under Gnome too and they have also a Dialog but with a Share button instead of Save. I believe they are doing it like with the native Wayland solution by saving the image in a temp directory that is deleted on reboot and just providing the path to the image. The user can decide what to do with the image, save it permanently or do nothing and the image is gone. Though there I have the same problem that the gotScreenshotResponse is never called.

Best regards,
Damir

________________________________
From: kde-devel <kde-devel-bounces at kde.org<mailto:kde-devel-bounces at kde.org>> on behalf of Jan Grulich <jgrulich at redhat.com<mailto:jgrulich at redhat.com>>
Sent: Monday, September 21, 2020 08:08
To: kde-devel at kde.org<mailto:kde-devel at kde.org> <kde-devel at kde.org<mailto:kde-devel at kde.org>>
Subject: Re: Using xdg-desktop-portal-kde to take screenshots

Hi,

ne 20. 9. 2020 v 18:37 odesílatel Damir Porobic <damir_porobic at live.com<mailto:damir_porobic at live.com>> napsal:
Hello Jan,

finally I  found some time to upgrade my OS and got a newer Plasma Version but I'm still struggling with the Screenshot Portal.

Here is my implementation, almost identical to yours from the test that you have linked me (pasting here only the relevant methods):I get the dialog which asks me what type of screenshot I want to take I select it, a small image is show in the dialog and I can click on save (which saves the image in my home directory) but the gotScreenshotResponse is never called. Any idea why?

I have no idea. The code looks good and identical to what I have in the example. When you run "dbus-monitor --session" and you perform the screenshot, do you see this signal to be called at all?

Can I tell the dialog where to save those images?

Unfortunately no, I made it very basic, but patches are welcomed, it won't be a hard task to implement it.

Can I tell the dialog right away what type of screenshot I want to take?

Unfortunately no, this is not supported by the portal API.

Can I just share the screenshot with my application without saving it?

Unfortunately no, again a limitation of the portal API as the portal is supposed to return an URI. You can however directly use KWin DBus interface to get a screenshot, specifying directly what type of screenshot you want to tak and you get the raw image. This however will make it work only in Plasma and will not work in an application running in sandbox without giving it access to DBus.

Regards,
Jan

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