I am starting to learn how to use ncurses right now, and I do some calculations based on the number of lines and columns when the program starts.
It would be too much work for me to do dynamic calculation to manage the display, so I would need to find a way to block the resize of the shell during the execution, is this possible ?
There is certainly no portable or general-purpose way of blocking display size changes. Specific terminal emulators might offer this feature, but I don't know of any which do. It is generally possible to create a window of fixed size, but the terminal emulator would have to do that; it is invisible to the console code running inside the terminal.
If you find it difficult to respond to dynamic display size changes, you probably need to restructure your code. Otherwise, you can just ignore the size change, which might result in a confusing experience for your users, or might just result in them seeing either a portion of the output or a lot of blank space, depending on the nature of the resizing. (To get the latter effect, you need to avoid relying on automatic line wrapping and scrolling. On the other hand, automatic wrapping and scrolling are often just what you need to make your application window-size-independent.)
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I'm very new to coding in general so please excuse any stupid things I say.
I am trying to print (in c) a rather long text using printf() but since it can't all fit on the screen it jumps to the end of the text and the beginning is not visible unless you scroll up. Is there an easy way to have it print the long text but stay at the beginning and allow the user to scroll down as they read before they put in the next command?
On Unix (including Linux and Mac), there are command line programs built in called more and less that does exactly what you describe. more is a program that simply waits for the user to press enter or space before showing the next page of output. less is slightly improved in that it allows vi editor keystrokes (such as j and k) to scroll up and down in the output.
more is also available on the Windows command line as well. You might even be able to find a version of less for Windows as well.
c:\users\selbie> your_program.exe | more
$> ./your_program | less
As to how to do this programmatically, that's a bit more difficult as it would involve measuring the console width and implementing your own scroll buffers. There might be open-source libraries that provide this functionality, but the console environment already has a solution for apps that produce long output.
Not really, though you may find a reasonable and simple solution is to print only a certain number of lines (say 30), then prompt the user to press Enter before display more lines.
You can even find out the current size of the terminal. That's platform specific; for Linux it's explained here: How to get terminal window width?
Not in a standard way, no.
Your output stream in C is just a stream of characters -- scrolling is handled by your terminal.
Depending on your terminal, it may be possible to control scrolling by outputting special characters, like ANSI escape codes. The ncurses library provides a portable way to manipulate terminals.
However, if you just want a more convenient way to look through your output (or really any command output), #selbie's answer is the best: use more or less. This will avoid any extra complexity in your program.
In my fascination of the knowledge i learned about jscript (see here and here and here) to press keyboard keys and mouse keys within a batch file. However i want to take this to a more practical application.
There are certain games, such as minecraft, that require constant feedback that a button is being pressed. With the current links i provided, there does not seem to be any way of having the buttons pressed down for an extended period of time as to simulate movement or something within a game.
I get that it would be easier to install software to do this automatically but at the same time it is much more efficient to manipulate what is already installed on ones computers as it saves a significant amount of memory and processing power when compared to getting additional software. I do not care what language or how deep the programming must go, all i ask is that i can easily manipulate it through batch files like i could do with the SendKeys method in jscript.
Dug this out of the grave recently...
http://www.vbforums.com/showthread.php?705791-SendKeys-Hold-Down-a-Key
Here, users are using a VB script to hold a key down. However i do not have the time to verse myself in this yet, nor how to properly manipulate it into a batch script
ARG, its for html pages. JavaScript also follows suite with keydown,keypress,and keyup responses to handle user input, but never actually get the thing to be imitated on the local system. If only the games I want to play (tf2 in this case) could handle an environment in Linux then I could use xdotool. In this case I may just give up and revert to using a program that can do this faster than I can. If that's the case, can anyone give me some pointers? I know of autolt and hotkeys, but can they do what I desire?
I am writing a relatively simple C program in Visual C++, and have two global variables which I would like to know the values of as the program runs. The values don't change once they are assigned, but my programming ability is not enough to be able to quickly construct a text box that displays the values (I'm working in Win32) so am looking for a quick routine that can perhaps export the values to a text file so I can look at them and check they are what they ought to be. Values are 'double'.
I was under the impression that this was the purpose of the debugger, but for me the debugger doesn't run as the 'file not found' is always the case.
Any ideas how I can easily check the value of a global variable (double) in a Win32 app?
Get the debugger working. You should maybe post another question with information about why it won't work - with as much info as possible.
Once you have done that, set a breakpoint, and under Visual C++ (I just tried with 2010), hover over the variable name.
You could also use the watch window to enter expressions and track their values.
If your debugger isn't working try using printf statements wherever the program iterates.
Sometimes this can be a useful way of watching a variable without having to step into it.
If however you wish to run through the program in debug mode set a breakpoint as suggested (in VS2010 you can right click on the line you want to set a breakpoint on).
Then you just need to go to Toolbars -> Debug Toolbar.
I usually like to put #ifdef _DEBUG (or write an appropriate macro or even extra code) to do the printing, and send to the output everything that can help me tracking what the program's doing. Since your variables are never changing, I would do so.
However, flooding the console with lots of values is bad imo, and in such cases I would rely on assertions and the debugger - you should really see why it's not working.
I've done enough Python and Ruby to tell you that debugging a complex program when all you have is a printf, although doable, is extremely frustrating and takes way longer than what it should.
Finally, since you mention your data type is double (please make sure you have a good reason for not using floats instead), in case you add some assertion, remember that == is to be avoided unless you know 100% that == is what you really really want (which is unlikely if your data comes from calculations).
How would I change a pixel on a display, in C?
Assume NOTHING: I am using a linux machine from console to do this. I do not want to use GUI toolkits or frameworks to draw the pixel. I do not want to draw the pixel in a window. I want to draw the pixel directly to the screen.
EDIT: I have a screen. I'm on a laptop running linux from console. I'd prefer a solution not using X as I'd rather learn how X works than how to use X.
If theres more information, ask, but don't assume. I'm not trying to build a GUI, and that was the main purpose of blocking assumptions as I don't want people to assume I'm doing things the long way when in reality I'm just tinkering.
EDIT 2: You may use any X11 related libraries provided that you can explain how they work.
If we really assume nothing, can we even assume that X is running? For that matter, can we even assume that there is a video card? Perhaps Linux is running headless and we're accessing it over a serial console.
If we are allowed to assume a few things, let's assume that Linux has booted with framebuffer support. (It's been a couple years since I worked with Linux framebuffers, I may get some of the details wrong.) There will be a device created, probably /dev/fb or /dev/fb0. Open that file and start writing RGB values at an offset, and the screen will change, pretty much regardless of anything: text console, graphical console, full-fledged desktop envrionment, etc. If you want to see if framebuffer support is working, do dd if=/dev/zero of=/dev/fb on the command line, and the display should go all black.
C doesnt have any graphics capabilities - you'd need to use a third party library for this.
You cannot assume a display in C. There is literally no way to do what you ask.
Edit: Okay, you have a display, but again, there's not a whole lot you can get from there. The point is that there are a TON of competing standards for graphics displays, and while some of them (VGA interfaces, for example) are standardized, a lot of the others (display driver interfaces, for example) are NOT. Much of what X (and other display device drivers, such as Windows or the like) do, is have specific interface code for how to talk to the display drivers; they abstract out the complexity of dealing with the display drivers. The windowing systems, though, have HUGE libraries of complicated and specific code for dealing with the display drivers; the fact that these things are relatively transparent is an indication of just how much work they've put into these things over time.
Very primitive and making a lot of assumptions:
fd = open("/dev/fb0", O_RDWR);
lseek(fd, 640*y+x, SEEK_SET);
write(fd, "\377\377\377\377", 4);
In reality, you would use mmap rather than write, and use the appropriate ioctl to query the screen mode rather than assuming 640xHHH 32bpp. There are also endian issues, etc.
So in real reality, you might use some sort of library code that handles this kind of thing for you.
I suppose you could paint to the terminal program that you are using as your console. All you have to do is figure out which one that is and look it up.
Whoops I assumed a terminal. :P
I think what you are looking for is information on how to write to the frame buffer. The easiest way would be to use SDL and render to the frame buffer, or else use GTK+ with DirectFB, although that goes against your edict on not using toolkits or frameworks.
I'm trying to make a nice looking terminal game, but a lot of the things i'd like to do need a constant screen size. So i need the program to request a certain size every time it is ran. Is this possible, if so how?
The ncurses library has functionality for handling terminal sizes. This has been answered here and here regarding terminal dimensions.
You can only get the existing size, but you can't ask for a specific size. This terminal stuff was invented in a time where these sizes where hardcoded to be the physical size of the screen.