199 lines
8.9 KiB
Plaintext
199 lines
8.9 KiB
Plaintext
Test programs
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-------------
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Cygwin
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emacs
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vim
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mc (Midnight Commander)
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lynx
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links
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less
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more
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wget
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Capturing the console output
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----------------------------
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Initial idea:
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In the agent, keep track of the remote terminal state for N lines of
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(window+history). Also keep track of the terminal size. Regularly poll for
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changes to the console screen buffer, then use some number of edits to bring
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the remote terminal into sync with the console.
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This idea seems to have trouble when a Unix terminal is resized. When the
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server receives a resize notification, it can have a hard time figuring out
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what the terminal did. Race conditions might also be a problem.
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The behavior of the terminal can be tricky:
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- When the window is expanded by one line, does the terminal add a blank line
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to the bottom or move a line from the history into the top?
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- When the window is shrunk by one line, does the terminal delete the topmost
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or the bottommost line? Can it delete the line with the cursor?
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Some popular behaviors for expanding:
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- [all] If there are no history lines, then add a line at the bottom.
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- [konsole] Always add a line at the bottom.
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- [putty,xterm,rxvt] Pull in a history line from the top.
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- [g-t] I can't tell. It seems to add a blank line, until the program writes
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to stdout or until I click the scroll bar, then the output "snaps" back down,
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pulling lines out of the history. I thought I saw different behavior
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between Ubuntu 10.10 and 11.10, so maybe GNOME 3 changed something. Avoid
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using "bash" to test this behavior because "bash" apparently always writes
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the prompt after terminal resize.
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Some popular behaviors for shrinking:
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- [konsole,putty,xterm,rxvt] If the line at the bottom is blank, then delete
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it. Otherwise, move the topmost line into history.
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- [g-t] If the line at the bottom has not been touched, then delete it.
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Otherwise, move the topmost line into history.
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(TODO: I need to test my theories about the terminal behavior better still.
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It's interesting to see how g-t handles clear differently than every other
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terminal.)
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There is an ANSI escape sequence (DSR) that sends the current cursor location
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to the terminal's input. One idea I had was to use this code to figure out how
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the terminal had handled a resize. I currently think this idea won't work due
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to race conditions.
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Newer idea:
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Keep track of the last N lines that have been sent to the remote terminal.
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Poll for changes to console output. When the output changes, send just the
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changed content to the terminal. In particular:
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- Don't send a cursor position (CUP) code. Instead, if the line that's 3
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steps up from the latest line changes, send a relative cursor up (CUU)
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code. It's OK to send an absolute column number code (CHA).
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- At least in general, don't try to send complete screenshots of the current
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console window.
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The idea is that sending just the changes should have good behavior for streams
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of output, even when those streams modify the output (e.g. an archiver, or
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maybe a downloader/packager/wget). I need to think about whether this works
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for full-screen programs (e.g. emacs, less, lynx, the above list of programs).
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I noticed that console programs don't typically modify the window or buffer
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coordinates. edit.com is an exception.
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I tested the pager in native Python (more?), and I verified that ENTER and SPACE
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both paid no attention to the location of the console window within the screen
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buffer. This makes sense -- why would they care? The Cygwin less, on the other
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hand, does care. If I scroll the window up, then Cygwin less will write to a
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position within the window. I didn't really expect this behavior, but it
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doesn't seem to be a problem.
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Setting up a TestNetServer service
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----------------------------------
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First run the deploy.sh script to copy files into deploy. Make sure
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TestNetServer.exe will run in a bare environment (no MinGW or Qt in the path).
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Install the Windows Server 2003 Resource Kit. It will have two programs in it,
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instsrv and srvany.
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Run:
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InstSrv TestNetServer <path-to-srvany>\srvany.exe
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This creates a service named "TestNetServer" that uses the Microsoft service
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wrapper. To configure the new service to run TestNetServer, set a registry
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value:
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[HKLM\SYSTEM\CurrentControlSet\Services\TestNetServer\Parameters]
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Application=<full-path>\TestNetServer.exe
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Also see http://www.iopus.com/guides/srvany.htm.
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To remove the service, run:
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InstSrv TestNetServer REMOVE
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TODO
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----
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Agent: When resizing the console, consider whether to add lines to the top
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or bottom. I remember thinking the current behavior was wrong for some
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application, but I forgot which one.
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Make the font as small as possible. The console window dimensions are limited by
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the screen size, so making the font small reduces an unnecessary limitation on the
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PseudoConsole size. There's a documented Vista/Win7 API for this
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(SetCurrentConsoleFontEx), and apparently WinXP has an undocumented API
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(SetConsoleFont):
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http://blogs.microsoft.co.il/blogs/pavely/archive/2009/07/23/changing-console-fonts.aspx
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Make the agent work with DOS programs like edit and qbasic.
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- Detect that the terminal program has resized the window/buffer and enter a
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simple just-scrape-and-dont-resize mode. Track the client window size and
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send the intersection of the console and the agent's client.
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- I also need to generate keyboard scan codes.
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- Solve the NTVDM.EXE console shutdown problem, probably by ignoring NTVDM.EXE
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when it appears on the GetConsoleProcessList list.
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Rename the agent? Is the term "proxy" more accurate?
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Optimize the polling. e.g. Use a longer poll interval when the console is idle.
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Do a minimal poll that checks whether the sync marker or window has moved.
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Increase the console buffer size to ~9000 lines. Beware making it so big that
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reading the sync column exhausts the 32KB conhost<->agent heap.
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Reduce the memory overhead of the agent. The agent's m_bufferData array can
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be small (a few hundred lines?) relative to the console buffer size.
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Try to handle console background color better.
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Unix terminal emulators have a user-configurable foreground and background
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color, and for best results, the agent really needs to avoid changing the colors,
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especially the background color. It's undesirable/ugly to SSH into a machine
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and see the command prompt change the colors. It's especially ugly that the
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terminal retains its original colors and only drawn cells get the new colors.
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(e.g. Resizing the window to the right uses the local terminal colors rather
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than the remote colors.) It's especially ugly in gnome-terminal, which draws
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user-configurable black as black, but VT100 black as dark-gray.
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If there were a way to query the terminal emulator's colors, then I could
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match the console's colors to the terminal and everything would just work. As
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far as I know, that's not possible.
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I thought of a kludge that might work. Instead of translating console white
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and black to VT/100 white and black, I would translate them to "reset" and
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"invert". I'd translate other colors normally. This approach should produce
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ideal results for command-line work and tolerable results for full-screen
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programs without configuration. Configuring the agent for black-on-white or
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white-on-black would produce ideal results in all situations.
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This kludge only really applies to the SSH application. For a Win32 Konsole
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application, it should be easy to get the colors right all the time.
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Try using the screen reader API:
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- To eliminate polling.
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- To detect when a line wraps. When a line wraps, it'd be nice not to send a
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CRLF to the terminal emulator so copy-and-paste works better.
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- To detect hard tabs with Cygwin.
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Implement VT100/ANSI escape sequence recognition for input. Decide where this
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functionality belongs. PseudoConsole.dll? Disambiguating ESC from an escape
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sequence might be tricky. For the SSH server, I was thinking that when a small
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SSH payload ended with an ESC character, I could assume the character was really
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an ESC keypress, on the assumption that if it were an escape sequence, the
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payload would probably contain the whole sequence. I'm not sure this works,
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especially if there's a lot of other traffic multiplexed on the SSH socket.
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Support Unicode.
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- Some DOS programs draw using line/box characters. Can these characters be
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translated to the Unicode equivalents?
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Create automated tests.
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Experiment with the Terminator emulator, an emulator that doesn't wrap lines.
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How many columns does it report having? What column does it report the cursor
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in as it's writing past the right end of the window? Will Terminator be a
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problem if I implement line wrapping detection in the agent?
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BUG: After the unix-adapter/pconsole.exe program exits, the blinking cursor is
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replaced with a hidden cursor.
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Fix assert() in the agent. If it fails, the failure message needs to be
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reported somewhere. Pop up a dialog box? Maybe switch the active desktop,
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then show a dialog box?
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