how to use ncurses and Qt Creator

[JohnLocke]

I usually call my app from Qt Creator using run command (green arrow), set to open in external terminal, so it opens in xterm (ubuntu).

Code below is to set terminal to ncurses, need for educational purposes

If I use standard method to run app from Qt Creator it throws:
Error opening terminal: unknown.

if I open it with terminal using ./AppName it works

Process exited with code: 1

qmake:

# MyNcursesApp.pro

QT -= gui

CONFIG += console c++11
CONFIG -= app_bundle

# Add the following line to ensure proper terminal handling
CONFIG += link_pkgconfig
PKGCONFIG += ncurses

SOURCES += main.cpp

welcome code:

#include <ncurses.h>

int main() {
    initscr();  // Initialize the ncurses library
    printw("Hello, ncurses!");
    refresh();  // Refresh the screen
    getch();    // Wait for a key press
    endwin();   // End the ncurses library

    return 0;
}

kindly advise

[JonB]

@JohnLocke said in how to use ncurses and Qt Creator:

if I open it with terminal using ./AppName it works

That "terminal" may not necessarily be xterm. Have you tried your app in just the same xterm as you are having Creator open for you?

If I use standard method to run app from Qt Creator it throws:

Error opening terminal: unknown

It is not clear whether you mean you get this error when Creator opens terminal for you or a message output by your application/curses library?

[ChrisW67]

@JohnLocke said in how to use ncurses and Qt Creator:

If I use standard method to run app from Qt Creator it throws:
Error opening terminal: unknown.

The default (I assume that's what you mean by "standard") method used by Creator when running applications does not provide a fully fledged terminal to the application.

Ncurses initscr() is documented thus:

The initscr() function determines the terminal type and initialises all implementation data structures. The environment variable specifies the terminal type.

The environment variable is TERM and, since there is not a full terminal emulation, it is likely unset. When you launch your application from Creator in a separate terminal emulator (xterm, konsole whatever) that variable is set.

[JonB]

@JohnLocke
As @ChrisW67 says, if the terminal launched by Creator does not have a environment variable named TERM this could easily be the cause. A quick way to find out would be to have your main() do something like system("env") or system("printenv"). That should show all its inherited environment variables. Look for TERM among them and/or compare against the output from this command running your application in a terminal window where it does work successfully.

I am not quite sure what @ChrisW67 means by "does not provide a fully fledged terminal to the application" or "since there is not a full terminal emulation". So far as I recall Creator has a setting where you can see/change what the command is for the terminal you are launching, and I asked earlier whether that is indeed xterm?

[ChrisW67]

@JonB said in how to use ncurses and Qt Creator:

I am not quite sure what @ChrisW67 means by "does not provide a fully fledged terminal to the application" or "since there is not a full terminal emulation".

Just that, unless you use the Qt Creator "Run in terminal" option the application is run in a stub launcher that may not be a full terminal that NCurse can use. When "Run in terminal" is selected, and the "Use internal terminal" disabled, a separate xterm/konsole is launched to start the program.

I've just tried your printenv suggestion (with the NCurses Hello World above) and neither environment gives me TERM, and neither works. A manually launched konsole gives TERM "xterm-256color" and the test app does work. Go figure.

[JonB]

@ChrisW67 said in how to use ncurses and Qt Creator:

"Use internal terminal"

I'm not sure I knew there was an "internal terminal", I only ever used "Run in terminal" where it runs xterm.

I think you are confirming it is the lack of a TERM variable which causes ncurses to barf.

[ChrisW67]

@JonB said in how to use ncurses and Qt Creator:

I'm not sure I knew there was an "internal terminal"

Nor did I until today.