Hi, I'm not sure to call this a bug in vncviewer, or a bug in VNC protocol.
Anyhow, this bug apply to realvnc 4.0 to 4.1.1. The bug may demonstrate the flaw in VNC protocol, which don't have any mechanism to ensure the synchronization of the pixel format between client and server. Let's see how to reproduce this bug first, and then see how pixel format is out of sync. (To view this bug in a clear formatted text, visit http://opensource.wikia.com/wiki/Bugs:realvnc4/pixel_format_is_unpredictable_after_refreshing_and_suddenly_changing_pixel_format ) == How to reproduce == Run the following command in some terminal, "terminal1", in this example, terminal1 $ Xvnc :1 -nolisten tcp -auth /dev/null -localhost -SecurityTypes=None -geometry 800x600 -depth 24 & terminal1 $ DISPLAY=:1 xterm -e perl -e '$|=1; for(;;){print"."; select(undef,undef,undef,0.001); }' & Then open another terminal, "terminal2", run vncviewer, terminal2 $ vncviewer :1 -shared -AutoSelect=0 -ViewOnly=1 -FullColor VNC Viewer Free Edition 4.1.1 for X - built Jan 6 2007 00:46:26 Copyright (C) 2002-2005 RealVNC Ltd. See http://www.realvnc.com for information on VNC. Fri Dec 7 20:11:20 2007 CConn: connected to host localhost port 5901 Fri Dec 7 20:11:21 2007 CConnection: Server supports RFB protocol version 3.8 CConnection: Using RFB protocol version 3.8 TXImage: Using default colormap and visual, TrueColor, depth 24. CConn: Using pixel format depth 24 (32bpp) little-endian rgb888 CConn: Using ZRLE encoding Switch back to "terminal1", suspend the Xvnc, terminal1 $ killall -TSTP Xvnc Then switch to vncviewer x11 window, refresh screen, and change colour level, vncviewer x11: press F8 --> select "Refresh screen" vncviewer x11: press F8 --> select "Options..." --> select "Very low (8 colours)" in "Encoding and Colour Level:" --> click "Ok" Switch to "terminal1", resume Xvnc, terminal1 $ killall -CONT Xvnc vncviewer will then fail like this, terminal2 $ vncviewer :1 -shared -AutoSelect=0 -ViewOnly=1 -FullColor <--cut--> ... <--cut--> CConn: Using ZRLE encoding Fri Dec 7 20:11:45 2007 CConn: Using pixel format depth 3 (8bpp) rgb111 vncviewer: ../rfb/zrleDecode.h:196: void rfb::zrleDecode8(const rfb::Rect&, rdr::InStream*, rdr::ZlibInStream*, rdr::U8*, rfb::CMsgHandler*): Assertion `len <= end - ptr' failed. Aborted == Cause == This is because the client and server fail to synchronize the pixel format, which is depicted as follow, server send FramebufferUpdate0 server is suspended client receive FramebufferUpdate0 client send FramebufferUpdateRequest1:incremental=true user request refresh screen client send FramebufferUpdateRequest2:incremental=false user change colour level server is resumed server receive FramebufferUpdateRequest1:incremental=true server send FramebufferUpdate1 client receive FramebufferUpdate1 client change its internal pixel format to new pixel format client send SetPixelFormat client send FramebufferUpdateRequest3:incremental=false (non-incremental since pixel format changed) client is now expecting new pixel format from server server receive FramebufferUpdateRequest2:incremental=false server send FramebufferUpdate2 with old pixel format client receive FramebufferUpdate2 with old pixel format client interprete FramebufferUpdate2 as new pixel format client mis-interprete pixel format, and then fail _______________________________________________ VNC-List mailing list VNC-List@realvnc.com To remove yourself from the list visit: http://www.realvnc.com/mailman/listinfo/vnc-list
