moverel() function in C

You will probably find a variety of functions that accomplish different tasks while diving into the field of C programming. One of the functions that are important during graphics programming is moveRel(). In this blog post, we will delve into the moveRel() function's syntax, code, and examples to understand how it works. We will also offer full instructions on how you can become proficient in its use.

Understanding the Syntax:

MoveRel() is common for graphics programming where the current position of the move is shifted to the new location, relative. The syntax of the moveRel() function is as follows:

void moveRel(int dx, int dy);

In this case, dx denotes a change made to the x-axis, while dy refers to a change made on the y-axis. This function uses these two parameters to find out where the new position is from the present one.

Let's look at a concrete example to demonstrate the use of moverel() function. As an example, here is a barebone C program that includes moverel() function and helps us to move the cursor through the console.

#include <stdio.h>
#include <stdlib.h>
 
// Function to clear the screen
void clearScreen() {
    // Use "cls" for Windows and "clear" for Linux/Unix
    #ifdef _WIN32
        system("cls");
    #else
        system("clear");
    #endif
}
 
// Function to move the cursor to a specific position
void gotoxy(int x, int y) {
    printf("\033[%d;%dH", y + 1, x + 1);
}
 
// Function to move the cursor relative to its current position
void moveCursor(int *x, int *y, int dx, int dy) {
    int newX = *x + dx;
    int newY = *y + dy;
 
    // Ensure the cursor stays within the console boundaries (adjust as needed)
    if (newX >= 0 && newX < 80 && newY >= 0 && newY < 24) {
        *x = newX;
        *y = newY;
    }
}
 
int main() {
    // Display initial message
    printf("Use arrow keys to move the cursor. Press 'Q' to quit.\n");
 
    // Initial cursor position
    int x = 0, y = 0;
 
    while (1) {
        // Clear the screen
        clearScreen();
 
        // Display cursor at current position
        gotoxy(x, y);
        printf("*");
 
        // Capture user input
        char ch = getchar();
 
        // Move cursor based on user input
        switch (ch) {
            case 'Q':
            case 'q':
                // Exit the program if 'Q' is pressed
                return 0;
            case 27: // Escape key (for arrow keys)
                // Capture the '[' character that follows the Escape key
                getchar();
                switch (getchar()) {
                    case 'A': // Arrow key 'up'
                        moveCursor(&x, &y, 0, -1);
                        break;
                    case 'B': // Arrow key 'down'
                        moveCursor(&x, &y, 0, 1);
                        break;
                    case 'C': // Arrow key 'right'
                        moveCursor(&x, &y, 1, 0);
                        break;
                    case 'D': // Arrow key 'left'
                        moveCursor(&x, &y, -1, 0);
                        break;
                }
                break;
            default:
                // Do nothing for other keys
                break;
        }
    }
 
    return 0;
}

Output:

Use arrow keys to move the cursor. Press 'Q' to quit.
*

Explanation of code:

Clear Screen Function:

The clearScreen function uses system-dependent commands (cls for Windows, clear for Linux/Unix) to wipe the console screen.

Cursor Positioning Function:

The gotoxy function places the cursor at a given coordinate on the console screen with escape sequences.

Move Cursor Function:

The moveCursor function adjusts the cursor position: it uses delta values (dx and dy) to keep the cursor within bounds of the console.

Main Function:

Shows an opening message explaining to the user how he should operate with this program.
Sets the cursor position (x and y) at the top-left corner of the console.
An infinite loop (while(1)). For continuous user interaction.
Clear screen, display cursor at current position.
Captures user input using getchar().

Handles user input:

If 'Q' or 'q' is pressed, the program closes.
Pressing the Escape key (ASCII 27) makes your program capture the '[' character which follows, and interpret input from arrow keys.
'A' moves the cursor up.
'B' moves the cursor down.
'C' moves the cursor right.
'D' moves the cursor left.
Cursor movement is done by calling the moveCursor function with the current position of cursor and appropriate delta values.

Escape Sequences:

Escape sequences are used to move the console cursor around, and they serve a primitive form of user interface.

Console Clearing:

We clear out the console screen in each iteration to create the effect of a cursor moving without leaving behind trails.

Exiting the Program:

If the 'Q' or 'q' key is pressed by the user, the program shuts down the main loop and finally ends execution.

Conclusion:

Finally, the presented C program illustrates in practice the application of the moverel() function of the <conio.h> library for moving a cursor. The specific response of the program to user input, i.e. the direction indicators, allows control over the mouse pointer in the console online. This interactive methodology can improve the user experience for console-based applications. This code showcases basic ideas, including screen clearing, cursor placement, and input management. Mastering this enables one to develop more exciting and reactive console programs using the C language, which can be used to make interactive software applications with customizable objects.

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