changes not showing in field in ncurses - c++

Question

I have a ncurses program which is a login menu and I use field for username and password.
The problem is that when I type something in the fields, characters register but do not show in terminal. In other word if you execute the code blow and type something, you won't be able to see it in terminal but if you push F2, you could see that the characters were registered.
Here is my code:
test.cpp
#include <curses.h>
#include <form.h>
#include <menu.h>
#include <string>
#include <cstring>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
class WelcomeMenu {
private:
int _row; // number of rows of the terminal
int _col; // number of columns of the terminal
public:
WelcomeMenu();
~WelcomeMenu();
void welcomeBox();
void loginMenu();
void registerMenu();
};
WelcomeMenu::WelcomeMenu(){
initscr();
noecho();
cbreak();
keypad(stdscr, true);
int row, col;
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
this->_row = row; this->_col = col;
loginMenu();
}
WelcomeMenu::~WelcomeMenu(){
refresh();
endwin();
}
/*
* This is useful because ncurses fill fields blanks with spaces.
*/
char* trim_whitespaces(char *str)
{
char *end;
// trim leading space
while(isspace(*str))
str++;
if(*str == 0) // all spaces?
return str;
// trim trailing space
end = str + strnlen(str, 128) - 1;
while(end > str && isspace(*end))
end--;
// write new null terminator
*(end+1) = '\0';
return str;
}
void WelcomeMenu::loginMenu(){
// erase();
FORM *form;
FIELD *fields[5];
WINDOW *win_body, *win_form;
int ch;
win_body = newwin(24, 80, 0, 0);
assert(win_body != NULL);
box(win_body, 0, 0);
win_form = derwin(win_body, 20, 78, 3, 1);
assert(win_form != NULL);
box(win_form, 0, 0);
mvwprintw(win_body, 1, 2, "Press F1 to quit and F2 to print fields content");
fields[0] = new_field(1, 10, 0, 0, 0, 0);
fields[1] = new_field(1, 40, 0, 15, 0, 0);
fields[2] = new_field(1, 10, 2, 0, 0, 0);
fields[3] = new_field(1, 40, 2, 15, 0, 0);
fields[4] = NULL;
assert(fields[0] != NULL && fields[1] != NULL && fields[2] != NULL && fields[3] != NULL);
set_field_buffer(fields[0], 0, "Username: ");
set_field_buffer(fields[1], 0, "username");
set_field_buffer(fields[2], 0, "Password: ");
set_field_buffer(fields[3], 0, "password");
set_field_opts(fields[0], O_VISIBLE | O_PUBLIC | O_AUTOSKIP);
set_field_opts(fields[1], O_VISIBLE | O_PUBLIC | O_EDIT | O_ACTIVE);
set_field_opts(fields[2], O_VISIBLE | O_PUBLIC | O_AUTOSKIP);
set_field_opts(fields[3], O_VISIBLE | O_PUBLIC | O_EDIT | O_ACTIVE);
set_field_back(fields[1], A_UNDERLINE);
set_field_back(fields[3], A_UNDERLINE);
form = new_form(fields);
assert(form != NULL);
set_form_win(form, win_form);
set_form_sub(form, derwin(win_form, 18, 76, 1, 1));
post_form(form);
refresh();
wrefresh(win_body);
wrefresh(win_form);
while ((ch = getch()) != KEY_F(1)){
switch (ch) {
case KEY_F(2):
// Or the current field buffer won't be sync with what is displayed
form_driver(form, REQ_NEXT_FIELD);
form_driver(form, REQ_PREV_FIELD);
move(LINES-3, 2);
for (int i = 0; fields[i]; i++) {
printw("%s", trim_whitespaces(field_buffer(fields[i], 0)));
if (field_opts(fields[i]) & O_ACTIVE)
printw("\"\t");
else
printw(": \"");
}
refresh();
pos_form_cursor(form);
break;
case KEY_DOWN:
form_driver(form, REQ_NEXT_FIELD);
form_driver(form, REQ_END_LINE);
break;
case KEY_UP:
form_driver(form, REQ_PREV_FIELD);
form_driver(form, REQ_END_LINE);
break;
case KEY_LEFT:
form_driver(form, REQ_PREV_CHAR);
break;
case KEY_RIGHT:
form_driver(form, REQ_NEXT_CHAR);
break;
// Delete the char before cursor
case KEY_BACKSPACE:
case 127:
form_driver(form, REQ_DEL_PREV);
break;
// Delete the char under the cursor
case KEY_DC:
form_driver(form, REQ_DEL_CHAR);
break;
default:
form_driver(form, ch);
break;
}
}
wrefresh(win_form);
unpost_form(form);
free_form(form);
free_field(fields[0]);
free_field(fields[1]);
free_field(fields[2]);
free_field(fields[3]);
delwin(win_form);
delwin(win_body);
}
int main(){
WelcomeMenu * myConWin = new WelcomeMenu();
delete myConWin;
return 0;
}
you can compile it like: g++ -lncurses -lform test.cpp
Thank you in advance for your response

Answer 1

The basic problem with the example is that it does not provide for displaying the characters. In ncurses, that would be done using the form_driver function:
form_driver
Once a form has been posted (displayed), you should funnel input events
to it through form_driver. This routine has three major input cases:
o The input is a form navigation request. Navigation request codes
are constants defined in <form.h>, which are distinct from the key-
and character codes returned by wgetch(3x).
o The input is a printable character. Printable characters (which
must be positive, less than 256) are checked according to the pro-
gram's locale settings.
o The input is the KEY_MOUSE special key associated with an mouse
event.
Making your program use form_driver would involve some reorganization of the program, moving that switch-statement into a function which can be called from the form-driver.
The ncurses examples include a few using form_driver. You might want to read through the test-code, seeing how the basic loop
while (!finished) {
switch (form_driver(form, c = form_virtualize(form, w))) {
case E_OK:
MvAddStr(5, 57, field_buffer(secure, 1));
clrtoeol();
refresh();
break;
case E_UNKNOWN_COMMAND:
finished = my_form_driver(form, c);
break;
default:
beep();
break;
}
uses its form_virtualize function to read characters (or form-requests). The printable characters that you are (not) seeing are handled by form_driver which updates the current field on the form. You can manipulate the field-buffer and do other special things as done in form_virtualize, but updating fields in the form is why you would use form_driver.

Answer 2

You need to use echo and noecho to turn echoing on/off. You could bake that part into an input function if you'd like:
#include <memory>
struct input_context {
input_context() {
echo(); // echo typed characters
curs_set(1); // show the cursor
}
~input_context() {
curs_set(0); // hide the cursor
noecho(); // turn off echoing
}
};
std::string get_string(WINDOW* win, size_t len) {
std::unique_ptr<char[]> buf = std::make_unique<char[]>(len);
input_context dummy;
if(wgetnstr(win, buf.get(), len) != ERR) return std::string{buf.get()};
return {};
}
Note 1: You should only use new/delete (and new[]/delete[]) when all other options have been depleted. In your main, you could just replace the dynamic creation of your WelcomeMenu with an automatic variable:
int main(){
WelcomeMenu myConWin;
}
Note 2: Use nullptr, not NULL.
fields[4] = nullptr; // was NULL
Note 3: As stated by #kebs in the comments, you should use the C++ versions of the header files:
#include <cassert> // was assert.h
#include <cstdio> // was stdio.h
#include <cstdlib> // was stdlib.h