I am currently using a remote software to access a computer of mine. The problem is now: I dont want anyone to see what I am doing, so I am trying to write a little tool or script that will blank out the screen.
The software is accessing the picture data using the MIT-SHM extension of X11, so I seek a possiblity to keep X11 rendering the data into the SHM, but simply not forward it to the Monitor (as if the monitor is turned off). Is there any way? As a last resort I would use XVFB, but I would rather not...
P.S.: I am seeking a programmatic attempt. Either via BASH script or C/C++.
x11vnc has options like -clientdpms, -forcedpms.
What they essentially do is - to call dpms commands to blank out display, every time there is a mouse/keyboard action. So, the monitor is unblanked & blanked again. This is not really visible to eyes, because of the hysteresis of the monitor.
NOW, if you have access to that proprietary software's code, you can add a code to blank using dpms commands, after every kbd/mouse event.
Alternately, you can use a dirty hack to keep x11vnc -forcedpms -forever -allow 127.0.0.1 -clip 1x1+0+0 running in the background.
Related
First, a bit of background: I'm running the latest stable build of Crunchbang Linux inside a VirtualBox VM. I'm designing a custom text-based user interface to run on top of bash. This is being done with a combination of C++ and bash scripts.
I need to, at times, completely and totally remove the ability for the user to provide the system with any sort of standard keyboard input. This is because, when I run a part of the system, the user is forced to wait for certain amounts of time.
Unfortunately, the user can still type while this is going on, and whatever they type is put on the screen. This happens when I'm running a C++ program as well as a bash script. The reason this is a problem is that there is text on the screen which the user is to read, and if they can type, it displaces the text. There will be other uses for this later, as well, like making the system seem like it has frozen up.
So, the question - How do I
disable the keyboard, or
prevent anything pressed on the keyboard from showing up on the screen?
Turn off echo mode with stty -echo or the equivalent C code (which would use tcgetattr and tcsetattr). When you are ready to accept input again, turn it back on. You may also wish to discard the input that arrived while you weren't expecting it. That would be done with tcflush but be aware that some users (like me) would consider that an annoyance. Typeahead is a feature, not a bug!
To see how user input to a certain process or tty can be intercepted, the man page and source code of interceptty may be enlightening. (have no experience with it)
However, you can hardly (totally) prevent user input. The user is probably always able to switch to a different virtual terminal (if any) or at least to reboot the system with Alt+Print+B (Magic SysRq_key) if not disabled. It is two different things to ignore input on a given tty and disabling keyboard input altogether.
Is it possible to use GTK without a valid X display?
I want to use GTK with Webkit, but for now I'm only interested in using the DOM functions to experiment, so I have no need to actually display anything. It's very convenient for me to do this over an SSH connection on a server that has no display.
But, without a DISPLAY environment variable, gtk_init() simply fails with the message:
Gtk-WARNING **: cannot open display:
Is there anyway to use GTK without a display?
There is an X server called Xvfb which provides a valid DISPLAY and sends the output to a file instead of to graphics hardware. You can run that on the same machine that's running your gtk client, and gtk will be able to do whatever it wants to do without using any of your network bandwidth. As a bonus, you can read Xvfb's output buffer from the file, allowing you to get a screenshot of what would be on the screen.
While it's not an direct answer to your question, I think what you are looking for is a “headless” web browser. There's one based on WebKit, called PhantomJS. It doesn't require any GUI stack, and you can freely experiment with DOM there.
Gtk+ 3 (well, GDK) has support for multiple backends now, but still requires X11, Wayland, or Broadway (experimental HTML5 backend) to run.
DISPLAY doesn't necessarily need actual hardware; you can run a fake X server such as Xvfb or Xvnc.
I'm glad I read the docs deeper and didn't just believe this answer.
gtk_init_check()
This function does the same work as gtk_init() with only a single change: It does not terminate the program if the windowing system can’t be initialized. Instead it returns FALSE on failure.
I'm writing a program in C++ to implement the keyboard backlight feature from OS X on MacBook Pro's running a Linux distro. So far, it turns the backlight on, on boot and if no keyboard and mouse events are registered for 20 seconds, it will turn it back off, and of course turn it on yet again when an event is registered. Next thing I need the program to do, is to capture keypresses on the keyboard-backlight-up/down keys, but I'm not sure how to approach this.
I am currently using XScreenSaverQueryInfo to get the idle time of keyboard and mouse events, so a method using X11 API would be okay. I have done a lot of googling but havent found a way that I felt sure about going with. The problem I'm seeing with lots of the methods I found, is that they use keycode to identify the key, but I dont think that would be a viable solution since the program should work for any keyboard-layout available.
Any idea of a method and API I should go with? What would work the best?
Regards,
The normal way to do this is with XGrabKey(). It uses keycodes, but you wouldn't hardcode the keycode, you'd get it with XKeysymToKeycode(). To be more correct you'd also want to redo the grab when you get a MappingNotify (XMappingEvent). (Note, MappingNotify, not MapNotify.) If there isn't a keysym for these keys - there probably isn't on old X versions, but hopefully newer X.org versions have one - then you just have to hardwire the keycode. Which won't be very robust or portable but probably works for everyone on Linux with the same hardware model.
Be prepared that key grabs are global, so if you try to XGrabKey() and something else has already grabbed that key, you'll get an X error - by default that exits the program. Another quirk of XGrabKey() is that it grabs the key with a precise modifier set. For example, to handle both with and without NumLock, you need to grab twice. See Global Hotkey with X11/Xlib
In a normal Linux setup (if you wanted to get a feature like this into upstream projects), the desktop environments don't want lots of separate apps fighting over the key grabs and getting errors. So there will be some central coordination points, such as the window manager or a special daemon might do all the keybindings and forward commands to other processes as needed. So you would probably want to look at patching the same upstream code that handles other special keys like this, if you were trying to get your feature integrated into distributions by default.
Another thing to be aware of is the Xkb API, which is a lot more complicated. There is some brain-bending way to grab keys with Xkb but I don't know of any advantage to going that route.
If you haven't done that yet, familiarize yourself with xev. Start it, give it the focus, and press the keys, to see what's happening.
Basically what I am trying to do is write my own pseudo task bar in C++. The program needs to idle until another program is started up, at which point it needs to visually depict that the other program is running. For each other program that is running, the user should be able to click on the visual representation and have Windows switch focus to the selected program.
The big underlying question at this point: is this even a possibility? Or has Windows hidden most/all of its fiddly-bits to make this close to, if not completely, impossible?
[EDIT:] restructured the question
The obvious starting point would be SetWindowsHookEx(WH_SHELL,...); which will get you notifications when top-level windows are created or destroyed (along with some other related events, like a different window being activated, a window's title changing, etc.)
Think ahead to actually bringing the window to the front, as I once researched myself.
SetForegroundWindow() won't work unless issued from the foreground process - neither SwitchToThisWindow() nor the AttachThreadInput() kludge seemed to always work, but maybe I just wasn't doing it right. Anyway as far as I know there no way to make a window foreground as good as Windows does, please enlighten me if say you discover say an undocumented call which actually Works.
It seems possible to me at least in a basic way:
1. Set up a shell hook as described by Jerry
2. figure the executable file from the module handle to access it's icons using shell services
The Vista-like feature of keeping a 'live' miniature of the screen seems much more challenging.
I'm looking to add an element to my wxWidgets GUI that behaves like a terminal emulator. Not in terms of a shell which executes commands, but just the input-output setup of an application running in a terminal.
Basically, the requirements are:
Streaming input/output: When you enter a character, it is added to an input stream, and when something is piped to the terminal, it prints out immediately.
No editing: Once you type in a character, it's permanently there, since it's probably been consumed by the application running in the terminal.
Some sort of scrolling (even if it just shows a few lines or something).
It would be nice if there is something that already does this, but suggestions on how to implement this with already existing controls such as wxTextCtrl would also be welcome.
I know this is a couple weeks late, but hopefully it's still useful. I've got a project called Chameleon that uses a wxWidgets-based VT100 terminal widget, which was itself based off of a project called taTelnet. The Chameleon source is available from my website (download page here). Not sure if it's exactly what you're looking for, but it might give you some ideas. Feel free to let me know if you have any questions about it.
wxWidgets supports redirecting STDOUT to a wxTextCtrl via wxStreamToTextRedirector. As for input, you could override the OnChar event in a wxTextCtrl-derived class to handle this.