I am using Eclipse CDT with Qt plugin. Working on Debian without X, running the GUI with Qt's QWS server.
Simply, I am starting a regular cpp thread doing the logical work and then starting a standart QApplication execution. Works fine on the target machine locally. But when I start the program remotely from Eclipse's Remote System Explorer service or start to debug with gdbserver, the keyboard input is not handled correctly, randomly picks up some of the keyboard events ie, it is in a racing condition. However, the mouse input works just fine.
I am aware the question is not clear enough but I couldn't figure how to focus on the problem. I can provide additional feedback on demand.
Thanks in advance.
Generally when you get odd behavior with QT and input handling, you've somehow mucked up QT's finite state processing loop. You're running in a debug environment, which always tends to mess things up just enough to make them more trouble than they're worth. Can you move to trying to test it on a remote X display?
Related
My app is having tearing problems when I scroll fast horizontally. Normally I'd just enable vsync, but I don't know how to do that in Qt. The tearing is occurring on my dev PC which runs Linux with a X-server, but it will also need to work well on the target system which is either Android or Linux+EGLFS.
One google result was from the Qt4 era and said that the tearing will be gone in Qt 5. But apparently it isn't.
Many google results are about env vars for embedded linux systems, such as QT_QPA_EGLFS_FORCEVSYNC, but I'd prefer the solution to work for my dev PC as well.
One google result said that vsync being enabled/disabled depends on the renderloop in use. I don't override the renderloop, so, since I'm on linux, I think I'm using the threaded renderloop.
Here's a bugreport about nvidia binary drivers causing this.
https://bugreports.qt.io/browse/QTBUG-45480
I too am using those drivers, so this may be it - just a driver bug. If so, at least it's unlikely to happen on my target hardware (I still haven't tested there), so that's good.
This one is a pretty strange question of mine so I'll try to explain the best I can.
On a DOS Linux distribution, without having installed any graphical environment, if I start an application which is supposed to have a GUI, will I be able to interact with that window via code?
What I thought is that if KDE/GNOME's role is to graphically represent an existing GUI, I should be able to interact with it but if these graphical environments have an active role in the window creation there is nothing I can do.
You won't be able to run a graphical program without a window manager.
The reason is that the window manager is doing a lot more than just allowing the window to be shown to the user. It comes with libraries and services for constructing windows and components and interacting with them. Without these libraries and services, the program won't be able to start.
The only exception would be if a program contained all the graphical code built into it, and didn't rely on a window manager. Realistically this would only happen for a fairly simple program and in special cases; for instance, Raspbian includes OMXPlayer, which shows full screen video without relying on any window manager.
Quoting (with some adaptation) from https://raspberrypi.stackexchange.com/a/3974 which answers how to start mplayer in X11 without a window manager:
The X server is really usually called X and you can just start it. You can set the DISPLAY number as an argument along with some other things.
You might want to have some sort of session, though, and still go through xinit or such and start X with startx. You can use .xinitrc or such as a script and simply not start a window manager there. You will need a "magic client" as the last command that stays running so X doesn't terminate immediately. In a traditional "failsafe" session, that was an xterm. If you know what to launch and launch once only, it could be that program or any UI/wrapper that does the launching for you. When the last ("magic") client in the init script terminates, X terminates.
If all you want to do is play video, you might see if you can run mplayer with directfb instead and skip using X11 entirely.
I want to make a system which would get input from USB barcode scanner, validate it on remote server and display an answer (text and images).
I would use JavaFX or in-browser JS web application to grab scanner input somehow.
I'm planning to run this application on Raspberry Pi or plain PC.
Is there a way (or a special linux distribution) to ensure that system always loads the same way and starts JavaFX app or opens particular web page in browser?
e.g. no login page, NO update or other popups are shown.
Any other ideas? Thanks
...
Found an interesting solution here, where JavaFX GUI app is started from command line, without X-Server(linux graphical interface) at all.
I have recently done something similar, and it's not too hard. Obviously working on the Pi, you will want to use something like Linux and having limited hardware will mean that you should be minimising what you are running. Due to this, I would recomend that you run a light weight distro. Something like arch (which is what I used) allows you to build only what you want from the ground up without the need to find and compile everything like you do for LFS or Gentoo.
As for booting, the following two wikis will give you the details of starting the Gui without manual login:
https://wiki.archlinux.org/index.php/Automatic_login_to_virtual_console
https://wiki.archlinux.org/index.php/Start_X_at_Login
After that, it is simply a matter of putting the command to launch your program in .xinitrc.
I have an application using ThreadX 5.1 as the kernel.
The Image is flashed on to a hardware running an ARM 9 processor.
I'm trying to build a Simulator for the application that can be run on Windows (say XP, 32-bit).
Is there any way I can make it run on Windows, without modifying the entire source code to start calling win32 system calls?
You can build a Simulator for the application that can be run on Windows with "ThreadX for Win32".
"ThreadX for Win32"'s specification is hear.
http://rtos.com/products/threadx/Win32
Yes you can if you are willing to put in the work.
First observe that each threadx system call has an equivalent posix call except for events.
So your threadx program can run as a single process using posix threads, mutexes, etc.
Events can be handled by an external library (there are a few out there).
If you find this difficult in windows then the simplest thing to do is set up a linux vm. I use an ubuntu vm running on Virtual Box. It is very easy to set up. All you will need is the cdt version of eclipse.
Next you need to stub out all of your low level system calls.
This is also easier than you might think. For example, if you have a SPI driver to read and write to flash, you can replace your flash with a big array which is quite easy to work with at this level.
Having said all this, you may get more mileage if your threadx application is modular. Then you can test each module on it's own and you don't need to mess with threads, etc.
As a first approximation this may give you what you need without going the distance to port the whole thing to run under posix.
I have done this successfully in the past and developed a full set of unit tests for a module that allowed me to develop and test it (on my mac) before going to the target. Development is much faster and reliable this way.
Another option you may want to consider is to find a qemu project that supports your microprocessor. With some work you can develop a complete simulator for your platform and then run the real firmware under the emulator.
Good luck.
I've got a C/C++ app using the GLFW Library on a netbook-like device running Ubuntu 8.10.
As far as I understand the source the GLFW lib, it creates its window using calls to the X-Window library.
We do not use any desktop on the machine but login to a tty and start a X-server in the background. When running the compiled application from a tty* on the target platform during the call to
glfwOpenWindow( ... );
glXQueryExtension( ...);
_glfwChooseVisual( ... );
XGetVisualInfo( ... );
the application halts. It does NOT crash. When switching to the X-Window by hitting Ctrl+Alt+F7 the application continues normally.
What could cause this weird behaviour?
BEGIN_EDIT:
Now I am quite sure the problem is related to the configuration of either Ubuntu or the x-server. When I try to run
glxinfo
in the shell the command also hangs until I switch to the X-window by hitting CTRL+ALT+F7. When I return to my shell after hitting the keys the command has finished.
Could it be that the X-server is put to 'sleep' when in console mode?
END_EDIT;
If the X window server runs in the background, it (obviously) doesn't own the display. Thus it can't reply to requests until its back in the foreground.
That would be my expectation at least. You can't ask a display server to open a window, if that display server is not actually owning the display hardware at the time of the request.
Blocking until it gets control of the hardware back sounds totally sensible to me.
Is a login manager running on the X server? They typically will grab the X server for exclusive use. Try logging in and see if that makes a difference.