TigerVNC/tigervnc

Dropped connection not detected with ViewOnly

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#922 opened on Dec 20, 2019

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Description

Good day. I encountered bug using vncviewer under centos 7.7.1908. vncviewer version is 1.10.0-4.el7.x86_64

Test case is:

  1. Start script while true do vncviewer -passwd 7.vnc -AlertOnFatalError=0 -ViewOnly *WINDOWS PC ADDRES" sleep 1 done

  2. Connect to windows machine with vncserver

  3. Reboot windows machine

  4. VncViewer will restart and reconnect, you will see windows shutting down screen.

  5. After that vnc will wait forever for mouse or keyboard event, and don`t disconnect from server that closed connection.

gdb backtrace: (gdb) bt #0 0x00007f6eabd3cbd3 in select () from /usr/lib64/libc.so.6 #1 0x00007f6eaea86a56 in fl_wait(double) () from /usr/lib64/libfltk.so.1.3 #2 0x00007f6eaea2786f in Fl::wait(double) () from /usr/lib64/libfltk.so.1.3 #3 0x000000000042f056 in run_mainloop() () #4 0x000000000041fc25 in main ()

I think, main problem is that network events processed only after keyboard or mouse events acquired. Because without -ViewOnly flag, vncviewer works properly.

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Contributor guide

Research direction
Inspect the main event loop in vncviewer to understand why network events are not processed without mouse/keyboard events when ViewOnly is enabled. Look for how events are polled and how the ViewOnly flag affects event handling.
Tech stack
cpp
Domain
desktop
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++GUI event loop concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60