Mouse click doesn't work under shadow mode

[fweng322]

Describe the bug Xpra starts with shadow mode to shadow existing display (:0). Then connect with browser to show the desktop. The cursor could move but mouse clicking does not work at all.

Under start-desktop mode the mouse click works.

To Reproduce Steps to reproduce the behavior:

1. server command: xpra shadow --use-display=yes :0 --bind-tcp=0.0.0.0:33445
2. client: using browser (Firefox 91, Chrome 101) to connect to http://:33445
3. mouse clicking does not work

System Information (please complete the following information):

• Server OS: Ubuntu 20.04
• Client OS: Debian testing
• Xpra Server Version 4.3.3
• Xpra Client Version HTML5 5.0-r1276-1

Additional context Here is how I tested:

• I installed a ubuntu 20.04 in a virtual machine (VirtualBox), with screen size set to 1600x900.
• Starting xpra with xpra start-desktop --use-display=yes :0 --bind-tcp=0.0.0.0:33445 would not make the screen of this vm blank and I could control the display with browser without problem, no matter clicking, dragging, typing with keyboard, they all were okay.
• Starting xpra with xpra shadow --use-display=yes :0 --bind-tcp=0.0.0.0:33445 I could see the display, but mouse clicking did not work at all. Keyboard could input if I got the focus of a window.

[fweng322]

With debug message I saw that the mouse click event was sent, but not worked.

2022-05-18 08:45:12,768 client   2 mouse pointermove: [object PointerEvent]
2022-05-18 08:45:12,959 client   2 mouse pointerout: [object PointerEvent]
2022-05-18 08:45:13,698 client   2 mouse click: 1 true 471 498
2022-05-18 08:45:13,830 client   2 mouse click: 1 false 471 498
2022-05-18 08:45:14,901 client   2 mouse click: 1 true 471 498
2022-05-18 08:45:15,009 client   2 mouse click: 1 false 471 498
2022-05-18 08:45:29,709 client   2 mouse pointermove: [object PointerEvent]
2022-05-18 08:45:29,726 client   2 mouse pointermove: [object PointerEvent]

[Korynkai]

I am experiencing this issue as well, however I discovered that pounding on my touchpad or, for whatever reason, using my touchscreen seem to work to some extent, albeit this is still erroneous input... Likely some messages aren't being transmitted/received correctly, or are being filtered somehow, I assume?

[totaam]

Testing with:

• Ubuntu 20.04 running in VirtualBox
• default desktop environment
• recent versions of xpra (4.4.1 and 5.0 beta) I am unable to reproduce any problems at all and the -d mouse server log shows the expected xtest_fake_motion and xtest_fake_button calls.

My guess is that your problems can come from one of these:

• using unusual / different environment
• having python3-uinput installed and enabled
• not having a window manager running in the shadow session?

Please provide steps to reproduce this bug and / or the problems shown in the server log.