Win32 API Console Programming in C - c

I am stuck with the problems like, reading text from a specific location (x=10, y=5) on the console window.
Where can I find a detail tutorial on Win32 API Console mode programming in C?

You'd need to use ReadConsoleOutput(). Beware of the ambiguity in a coordinate like (10, 5). It could be relative from the console window upper-left corner. Or from the screen buffer. You'd probably need to make the buffer size the same as the window size to avoid this. SetConsoleScreenBufferSize().
These console functions are not wrapped by the C-runtime. The SDK documentation is quite decent, start here.

On MSDN, see the section on Character Mode Applications.
You can read text from the screen using the ReadConsoleOutputCharacter function.

Related

how print in c without jumping to end of text?

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.

Background c program for keyboard mapping

I have installed a Bramma TTF file in my windows 8 system. Through a windows character map, I was able to find individual character code. Attached below the screenshot of the map. We can see at the right bottom side, the character code for "!" is 0x21. Similarly, I can find all the character code of all other letters.
Now I defined a character mapping for this font with my US based keyboard layout. For example, I mapped physical character 'a' in the keyboard to the character shown in 3rd row and 1st column. [whenever I hit 'a' from the keyboard, the corresponding character has to be displayed]
I would like to write a background C program such that it listens the keyboard hit and as per my previously defined character mapping, my C program should output that mapped character. i.e., when i hit character 'a' from the keyboard it should return the mapped character.
Can any one help me out in solving this problem or else just give me a lead towards the solution.
I'm somewhat familiar with these kind of fonts, they popped up in other questions at SO. The kind of questions from users that tried to deal with the consequences of using such a font. They are rather grave.
The biggest problem is that this font is not Unicode compatible. The actual string that underlies the text that's rendered to the screen is very different, containing characters from the ANSI character set. What goes horribly wrong is when the program that displays these strings saves the data. The data file contains the original strings, a good example is an Excel spreadsheet. This spreadsheet just contains gibberish when it is read by any other program. Especially bad when read by a program on another machine that doesn't have the same font installed. Very, very painful.
You are in fact making this problem worse by even destroying the normal mapping between keyboard to ANSI character. The 1st character in the 3rd row is produced by typing a capital I (eye) on the keyboard.
The message is clear: don't do this. Windows supports Unicode compatible fonts with Indic scripts well, fonts like Sylfaen, Mangal, Latha. All of which are available on my Windows 8 machine, about ten thousand miles away from where they are normally used. It also has Indic keyboard layouts available under the Language applet, I just picked one as an example:
Well, it is your funeral. You don't have to write a C program to translate these keystrokes, you need a custom keyboard layout. It is a DLL. You normally need the DDK to build them, but there is simple tooling available to auto-generate them. It doesn't get any easier than with MKLC, the Microsoft Keyboard Layout Creator. Web page and download link are here.
Probably you should use autohotkey.
With this application, you can listen to a set of keys, & then send a different set of keys.
This can be used as implementation of "autocorrect"
e.g.
:*:btw::By the way `
will autocorrect btw to By the way.
autohotkey supports quite complicated scripts, & many scripts are already available online.
On another note, if you only want english keyboard to print malayalam unicode characters, you may also think of a popular software called baraha
Google's Virtual Keyboard (also works with your physical keyboard)
https://code.google.com/apis/ajax/playground/#virtual_keyboard
http://www.tavultesoft.com/ allows you to create keyboards for MSWindows and the web. Over 1000 keyboards are readily provided. There is a developer and a user version. With the developer version you may create installation programs which install fonts, keyboards, keymaps and documentation.

How do console graphics work? (less, curses, vi...)

Can someone explain to me how less, vi and curses programs manage graphics output? Can they change individual characters on the screen or do they have to literary clear and redraw the screen whenever something changes?
It would be really neat if someone could hack a tiny less clone together, without all the boilerplate code.
There exist special Escape Codes that, when sent to the terminal, instruct the terminal to reposition the cursor without disrupting what's already being displayed.

Program to capture desktop screenshot in pure C

I want to write a simple program to capture complete desktop screenshot in pure C on linux i.e no QT or Xlib
Simple: reimplement Xlib inside your program, or at least the portion of it you need to grab the screen. You should start by reading about the X protocol.
Edit: Maybe you should read the Wikipedia page on the X protocol before the formal specification. What you want is to send a GetImage X request, as documented on page 61 of the PDF linked above.

Display pixel on screen in C

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.

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