C - Print to console a string that can be deleted - c

Question

I'm trying to build a program that prints a "default value" an user can quickly change by deleting parts of it and writing again.
The program would print for example:
enter app name: xcode
The user should be able to replace the "xcode" string (but not the ": " part) and then the program should get the entire input.
Is there a way to do it in plain C with the standard console OSX uses?
Thanks a lot

Answer 1

This will place a prompt and default input on the screen. The arrow keys will move the cursor right and left. Mode may be changed from INS (insert) to OVW
(overwrite) using the Ins key. Enter will terminate input as will too many characters. Valid characters may be restricted by using some combination of LETTERS | NUMBERS | DOT | SPACE | SIGN | PUNCT.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <ctype.h>
#include <sys/select.h>
#include <sys/ioctl.h>
#define ESC 27
#define INSERT 50
#define DELETE 51
#define PGUP 53
#define PGDN 54
#define ARROWRIGHT 67
#define ARROWLEFT 68
#define END 70
#define HOME 72
#define OTHER 79
#define BRACKETLEFT 91
#define TILDE 126
#define BACKSPACE 127
#define LETTERS 1
#define NUMBERS 2
#define DOT 4
#define SPACE 8
#define SIGN 16
#define PUNCT 32
#define SIZE 30
static const int STDIN = 0;
typedef struct Field {
int row;//place input on screen row and col
int col;
int contentsize;//allowed length of input
int inputat;//input at this index
int used;//characters used so far
int valid;//limit input to these characters
int insert;//mode insert/overwrite
int promptrow;//place prompt on screen row and col
int promptcol;
int promptsize;
int lastline;
int lastcol;
int stopon;//stop input with this character
char *content;
char *prompt;
} field;
int kbhit(void)
{
int bytesWaiting;
ioctl(STDIN, FIONREAD, &bytesWaiting);
return bytesWaiting;
}
void prompt ( field *psfield) {
printf ( "\033[%d;%dH", psfield->promptrow, psfield->promptcol);
printf ( "%s", psfield->prompt);
}
int input ( field *psfield) {
int ch = 0;
int to = 0;
printf ( "\033[%d;1H", psfield->lastline);
if ( psfield->insert) {
printf ( "INS");
}
else {
printf ( "OVW");
}
printf ( "\033[%d;%dH", psfield->row, psfield->col);
printf ( "\033[K");//erase to end of line
printf ( "%s", psfield->content);
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
while ( ( ch = getchar ()) != psfield->stopon) {
printf ( "\033[%d;10H", psfield->lastline);
printf ( "\033[K");//erase to end of line
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
if (
( ( psfield->valid & LETTERS && isalpha ( ch)))
|| ( ( psfield->valid & SPACE && ch == ' '))
|| ( ( psfield->valid & DOT && ch == '.'))
|| ( ( psfield->valid & SIGN && ( ch == '+' || ch == '-')))
|| ( ( psfield->valid & NUMBERS && isdigit ( ch)))
|| ( ( psfield->valid & PUNCT && ispunct ( ch)))
) {
if ( psfield->insert && psfield->inputat < psfield->used && psfield->used < psfield->contentsize-3) {
//expand
psfield->used++;
for ( to = psfield->used; to >= psfield->inputat; to--) {
psfield->content[to + 1] = psfield->content[to];
}
printf ( "\033[%d;%dH", psfield->row, psfield->col);
printf ( "\033[K");//erase to end of line
printf ( "%s", psfield->content);
}
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
printf ( "%c", ch);
psfield->content[psfield->inputat] = ch;
psfield->inputat++;
if ( psfield->inputat > psfield->used) {
psfield->used = psfield->inputat;
}
if ( psfield->inputat == psfield->used) {
psfield->content[psfield->inputat] = '\0';
}
if ( psfield->inputat >= psfield->contentsize-1) {
return -1;
}
continue;
}
if ( isprint ( ch)) {
printf ( "\033[%d;10H", psfield->lastline);
printf ( "\033[48;5;124m");//set color white text on red
printf ( "Invalid character");
printf ( "\033[0m");//reset to default colors
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
continue;
}
if ( ch == BACKSPACE) {
if ( psfield->inputat) {
psfield->inputat--;
//contract
for ( to = psfield->inputat; to <= psfield->used; to++) {
psfield->content[to] = psfield->content[to + 1];
}
psfield->used--;
printf ( "\033[%d;%dH", psfield->row, psfield->col);
printf ( "\033[K");//erase to end of line
printf ( "%s", psfield->content);
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
}
}
if ( ch == ESC) {
if ( !kbhit ( )) {
continue;
}
ch = getchar ( );
if ( ch == OTHER) {
ch = getchar ( );
if ( ch == HOME) {
psfield->inputat = 0;
printf ( "\033[%d;%dH", psfield->row, psfield->col);
ch = getchar ( );
}
if ( ch == END) {
psfield->inputat = psfield->used;
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
ch = getchar ( );
}
}
if ( ch == BRACKETLEFT) {
ch = getchar ( );
if ( ch == INSERT) {
ch = getchar ( );
if ( ch == TILDE) {
psfield->insert = !psfield->insert;
printf ( "\033[%d;1H", psfield->lastline);
if ( psfield->insert) {
printf ( "INS");
}
else {
printf ( "OVW");
}
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
}
}
if ( ch == DELETE) {
ch = getchar ( );
if ( ch == TILDE) {
//contract
for ( to = psfield->inputat; to <= psfield->used; to++) {
psfield->content[to] = psfield->content[to + 1];
}
psfield->used--;
printf ( "\033[%d;%dH", psfield->row, psfield->col);
printf ( "\033[K");//erase to end of line
printf ( "%s", psfield->content);
printf ( "\033[%d;%dH", psfield->row, psfield->col + psfield->inputat);
}
}
if ( ch == ARROWRIGHT) {
if ( psfield->inputat < psfield->used) {
printf ( "\033[C");//cursor right
psfield->inputat++;
}
}
if ( ch == ARROWLEFT) {
if ( psfield->inputat) {
printf ( "\033[D");//cursor left
psfield->inputat--;
}
}
}
else {
ungetc ( ch, stdin);
}
}
}
return 0;
}
int main ( ) {
struct termios oldattr, newattr;
struct winsize w;
field sfield = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '\n', NULL, NULL};
//set terminal
tcgetattr( STDIN, &oldattr );
newattr = oldattr;
newattr.c_lflag &= ~( ICANON | ECHO );
tcsetattr( STDIN, TCSANOW, &newattr );
setbuf(stdin, NULL);
//get terminal dimensions
ioctl( 0, TIOCGWINSZ, &w );
sfield.lastline = w.ws_row;
sfield.lastcol = w.ws_col;
printf ( "\033[2J");//clear screen
sfield.row = 5;
sfield.col = 26;
sfield.promptrow = 5;
sfield.promptcol = 1;
sfield.stopon = '\n';//newline will end input
sfield.valid = LETTERS | SPACE | DOT;
sfield.contentsize = 40;//allowed length of input
if ( ( sfield.content = calloc ( sfield.contentsize, 1)) == NULL) {
printf ( "calloc failed\n");
return 1;
}
sfield.prompt = strdup ( "Enter letters or spaces:");
sfield.promptsize = strlen ( sfield.prompt) + 1;
strcpy ( sfield.content, "default");
sfield.used = strlen ( sfield.content);
prompt ( &sfield);
input ( &sfield);
printf ( "\n\ninput was [%s]\n", sfield.content);
printf ( "\n\nbye\n");
free ( sfield.content);
free ( sfield.prompt);
//restore terminal
tcsetattr( STDIN, TCSANOW, &oldattr );
return 0;
}