Capturing screenshots on WebOS

ilyai · April 26, 2018, 7:38am

I'm looking for a way to take screenshots either with some utility or programmatically using API. The application I'm using has that functionality (written in Java, AWT library) but it doesn't work since WebOS seem to be using Wayland, and not X11. The following error is logged:

java.awt.AWTError: Can't connect to X11 window server using ':0' as the value of the DISPLAY variable.

I also considered using Xwayland in order to have X11 compatible interface, though couldn't find any related information and if capturing screenshots is possible with it.

Herrie · April 26, 2018, 1:17pm

It seems there's no API available for this in webOS OSE (yet). It used to be in LunaSysMgr from Open webOS as per https://github.com/openwebos/luna-sysmgr/blob/1393f0af5dd8d9f0e9cc79627f4acb226f8c8d45/Src/base/WindowServer.cpp#L646

On legacy webOS 3.0.x you could take screenshots with Home & Power button.

In LuneOS (based on Open webOS) we implemented it in our own UI.

ilyai · April 26, 2018, 1:56pm

Thanks for your response.
And what wayland compositor is used now in webOS OSE? And are there any plans to implement screenshot functionality in it?
As I understand there's no use in installing xwayland as wayland doesn't have screenshot API anyway?

nicolas · April 27, 2018, 12:23am

I don't know whether it is helpful to you or not. but luna-surfacemanager in webOS OSE has a screenshot source.

github.com

webosose/luna-surfacemanager/blob/master/modules/weboscompositor/webosscreenshot.h

// Copyright (c) 2014-2018 LG Electronics, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0

#ifndef WEBOSSCREENSHOT_H
#define WEBOSSCREENSHOT_H

#include <QObject>

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ilyai · June 8, 2018, 4:40pm

I was able to capture screenshot with this command:

luna-send -n 1 -f luna://com.webos.surfacemanager/captureCompositorOutput '{"output":"/home/root/screenshot-temp.jpg","format":"JPG"}'

Though a problem that at the time when screenshot was taken a video was playing on the screen, screenshot is always a black picture. On other content it works.

yuri · April 9, 2020, 3:22pm

Thank you for the luna-send command. It works on WebOSE 1.0 build for raspbery3.

Unfortunately the build for raspbery4, I got in
http://build.webos-ports.org/webosose/
returns "errorText": "com.webos.surfacemanager is not running.".
I'll be very grateful if someone let me now how to get capturescreen?

yuri · April 10, 2020, 9:38am

I got the picture

The reason was If monitor is not connected there will be "errorText": "com.webos.surfacemanager is not running.".

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Capturing screenshots on WebOS

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