Java VNC viewer is not able to accept clipboard data from QEMU VNC Server

[yanjiew1]

Describe the bug
It is not possible to copy text in the guest OS and paste the text in the host OS when using the Java VNC viewer of TigerVNC to connect to the QEMU VNC Server. However, the native VNC viewer of TigerVNC works.

The host OS is Fedora 40.
The QEMU version is 8.2.7.
The guest OS is Windows 10 with spice-vdagent installed.
The qemu-vdagent channel is created for the guest to send the clipboard data.

To Reproduce
Steps to reproduce the behavior:

1. Create a VM using virt-manager. Use VNC as display, and configure qemu-vdagent channel for clipboard sharing.
2. Install Windows 10 in the VM.
3. Install spice-vdagent in the VM.
4. Use Java VNC viewer to connect to the guest, and try to copy some text in the guest, and then try to paste the text in the host OS. The text cannot be pasted.

Expected behavior
After copying the text in the guest, the text can be pasted in host OS.

Screenshots
If applicable, add screenshots to help explain your problem.

Client (please complete the following information):

• OS: Fedora KDE Plasma Desktop
• VNC client: TigerVNC Java VNC Viewer
• VNC client version: v1.14.0
• Client downloaded from: https://sourceforge.net/projects/tigervnc/files/stable/1.14.0/VncViewer-1.14.0.jar/download

Server (please complete the following information):

• OS: Fedora KDE Plasma Desktop
• VNC server: QEMU
• VNC server version: 8.2.7
• Server downloaded from: QEMU from Fedora 40's official repository.
• Server was started using: The VM is started by libvirtd, and the server is built in the QEMU.

Additional context
The Java VNC viewer of TurboVNC also does not work, and the error message shown in TurboVNC is "ZlibInStream: inflate failed". I suspects that the problem is in the jzlib library because the native version of TigerVNC viewer works correctly.

[CendioOssman]

Thanks for your report.

Have you also reported the issue to TurboVNC? It would probably be good to link the issues in that case, so we can share any findings.