Straight to the point. I've been using visual studio to run a game I've been making. So far while coding in C++ I've been using inputs like VK_BACK or 0x52 for single key inputs. But I currently need to be able to type a word while the game is running to trigger a function. Basically, I'm asking how you would go about making the program recognize an inputted word. Like pressing the keys in a sequence to trigger a function.
Thanks, Jack
You've left a lot up to us to guess:
What are you using to read keyboard input?
I assume you're polling rather than streaming?
I'm also assuming non-blocking input?
With so many unknowns it's difficult to give a useful answer to the question. But here are a handful of options that may be helpful to you:
Require a terminating character for all keyboard input. This is characteristic of blocking input. The input is only read when the terminating character is placed.
Require the holding of a mode key while inputting a string. For example if I press an 'a' the key's command is executed immediately, but if I'm currently holding down the left Ctrl key and I press an 'a', it is treated as being within a string until the Ctrl key is released.
Use delimiters. If the '\'' is pressed it denoted the beginning of a string input consisting of all characters till the next '\'' key is pressed.
Make string entry keys separate from instantaneous input keys. This may be the most convenient solution because it allows instantaneous input in the middle of string input. But it may also be frustrating to the user if the allowable string commands are not clearly defined.
Related
I searched in a lot of different places and didn't find any conclusive answer, so I'm asking here.
I have to make a basic Windows keylogger as a school project.
I managed to set it up, and it works quite well. It logs characters and dead keys.
My problem is handling case-sensitive and country-specific input. I can get the SHIFT key state just fine to convert keys into their upper/lowercase equivalent, but I can't actually know what upper/lowercase equivalent it corresponds to.
Example : I'm using a French AZERTY keyboard. Numbers can be written via SHIFT + &, SHIFT + é, etc.
Here are the results my keylogger displays when trying to log numbers 1 to 5, first via SHIFT + Number and then by using CAPS LOCK.
If I switch to an English QWERTY keyboard, it will probably work fine, displaying the numbers (but then I'll not be able to access other characters like parentheses).
Is there any way to get a list of all possible keys for a given ScanCode/vkCode, depending on the type of keyboard ?
Here's a part of my code for the Callback function, and the translation of keys to strings.
It's the first time I use Windows' C++ API, so I don't really know much about it.
i would like to know if there is a way to read a string continuously on the console and detect the backspace key if the user erase a character. Let me explain a little bit more, for example:
Write a word on the console: "Word" So i got the string. And i can use all the methods from string like access to the characters item[0] = "W" or item.length()
The user press the backspace key and know my string item will have "Wor"
If the user put another letter the string is updated "Worrtw"
I using this for recommend words according what user is typing. I posting this beacause i really don't found anything usefull at the moment for the keywords or something about the string.
It seems that you can go back one character from current line in the console using \b. However, the console doesn't seem to be able to jump one line up.
I want to mark invalid user input red. After typping input, user presses Enter which put's unerasable new line in the console.
My plan was to do the following:
Check the input for validity.
If it's invalid, print input.length()+1 times \b
Turn console color red
Print the input, print \n
But, the \b will not jump back to the line where user input is. So I have plan B:
Remember the length of string that was before user input (query_string)
Check the input for validity.
If it's invalid, go line up (where the input was entered)
Jump to query_string.length() character
Turn console color red
Print the input, print \n
However, I don't know how to do this using the console API.
There are at least two ways you can do this.
One way is, as #chris implied in a comment, is to save the cursor position of where the user started typing. When you find bad input, you set the cursor back to that position and change the text attribute of the characters he entered.
You probably don't want to scroll the window back up one line. If you do, then the window will appear to "jump" when the user makes an error. It's a really jarring user interface experience. But if you want to try, you can call ScrollConsoleScreenBuffer.
Another way to do it would be to change the console mode so that it doesn't automatically echo characters when the user types them. Instead, you read each character individually, append it to your input buffer, and when the user presses Enter you validate. If the input is valid, you issue a newline to move to the next line. Otherwise you back up and highlight the erroneous input. This sounds like a lot more work, but it's not that difficult and it results in a much better UI experience.
I've searched around and I can't seem to find a way to represent arrow keys or the escape key as single char in c++. Is this even possible? I would expect that it would be similar to \t or \n for tab and new line respectively. Whenever I search for escaped characters, there's only ever a list of five or six well known characters.
The short answer is no.
The long answer is that there are a number of control characters in the standard ANSI character set (from decimal 1 to decimal 31, inclusive), among which are the control codes for linefeed, carriage return, end-of-file, and so on. A few are commonly interpreted as arrows and the escape key, but only for compatibility with terminals.
Standard PC keyboards send a 2- or 3-byte control code that represents the key that was pressed, what state it's in, which control/alt/shift key is pressed, and a few other things. You'll want to look up "key codes" to see how to handle them. Handling them differs between operating systems and the base libraries you use, and their meaning differs based on the operating system's configured keyboard layout (which may include characters not found in the ANSI character set).
Not possible; keyboards built for some languages have characters that can't be represented in a char, and anyway, how do you represent control-option-command-shift-F11 in a char?
Keyboards send scancodes, which are either some kind of event in a GUI system or a short string of bytes that represent the key. What codes depends on your system, but on most terminal-like systems, ncurses knows how to deal with them.
char variables usually represent elements in the ASCII table.
http://www.asciitable.com/
there is also man ascii on unix. If you want arrow keys you'll need a more direct way to access keyboard input. the arrow keys get translated into sequences of characters before hitting stdio. If oyu want direct keyboard access consider a GUI library, sdl, direct input to name a few.
There aren't any escape characters for the arrow keys. They are represented as Keycodes, afaik. I suggest using a higher level input library to detect key presses. If you want to do it from scratch, the approach taken might vary with the specific platform you are programming for.
In any case, back in the days of TURBO C, I used -
//Wait for keypress
//store input in ch
//see if the ASCII code matches the code for one of the arrow keys
I am making an currency change program where I would be providing exact change to the input amount, for example a value of 23 would be one 20 dollars and 3 one dollar bills
I want to restrict the user to input the value only till 2 decimal places. For example: the valid inputs are
20, 20.4, 23.44 but an invalid input would be 20.523 or 20.000.
How can I do this is C/C++.
I read about one function that is setprecision but that is not what I want, setprecision allows to display the value till that decimal point, it still doesn't stop the user from entering any value.
Is there any way to do this?
Read the amount from the user as a string, either character by character or the entire line, and then check its format, and then convert it.
It's generally easier to let the user type whatever they want followed by the program rejecting the input if it isn't valid rather than restricting what they can type on a keystroke basis.
For keystroke analysis you would need a state machine with 4 states, which we can call Number, Numberdot, Numberdotone, and Numberdottwo. Your code would have to make the proper transitions for all keystrokes, including the arrow keys to move the cursor to some arbitrary place and the Backspace key. That's a lot of work.
With input validation, all you have to do is check the input using a regular expression, e.g. ^(([0-9]+) | ([0-9]+.[0-9]) | ([0-9]+.[0-9][0-9])$. This assumes that "20." is not valid. Then if it's invalid you tell the user and make them do it again.
I do not believe that there is any way to set the library to do this for you. Because of that you're going to have to do the work yourself.
There are may ways you can do this, but the only true way to handle restricting the input is to control reading it in yourself.
In this case you would loop on keyboard input, for ever keystroke you would have to decided if it can be accepted in the context of the past input, then display it. That is, if there is a decimal point you would only accept to more numbers. This also allows you to limit input to numbers and decimal places as well, not to mention input length.
The down side is you will have to handle all the editing commands. Even bare bones you would need to support delete and enter.
This is rather a task for the GUI you are using, than for core C/C++. Depending on your GUI/Web Toolkit you can give more or less detailed rules how data can or can not be entered.
If you are writing a normal GUI application you can control and modify the entered keys (in C or C++).
In a WEB application you can do similar things using javascript.
The best solution would be when all illegal input is impossible.