Linux terminal not displaying anything with ncurses - c++

Question

I'm trying to make a library to simplify the ncurses use to display colors. I'm doing it object-oriented so it'll easy to handle changes in the future. But the problem is that I can't get to work this code.
#include <ncurses.h>
#include <string.h>
#include <string>
#include <unistd.h>
#include <iostream>
using namespace std;
class ColorWindow {
private:
bool canColor;
WINDOW* container;
int height, width, startx, starty;
public:
ColorWindow() {
if(has_colors()) {
canColor=true;
}
this->height = 20;
this->width = 84;
this->starty = (LINES - height) / 2; /* Calculating for a center placement */
this->startx = (COLS - width) / 2;
}
bool writeStringWithColor(int x, int y, const char* message) {
if(!canColor) {
writeString(3, 5, "Sorry, your term can't show colors.");
return false;
}
init_pair(1, COLOR_RED, COLOR_BLACK);
writeString(0, 10, "aaaaaaaaa");
wattron(getContainer(), COLOR_PAIR(1));
writeString(x, y, message);
wattroff(getContainer(), COLOR_PAIR(1));
}
void writeString(int x, int y, const char* message) {
mvwprintw(getContainer(), x, y, message);
}
WINDOW* createNewContainer() {
this->container = newwin(height, width, starty, startx);
wrefresh(this->container); /* Show that box */
return getContainer();
}
WINDOW* getContainer() {
return this->container;
}
void refreshContainer() {
refresh();
wrefresh(this->container); /* Show that box */
}
};
int main() {
ColorWindow cw = ColorWindow();
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on
* everything to me */
keypad(stdscr, TRUE);
start_color();
cw.createNewContainer();
bool success = cw.writeStringWithColor(0, 10, "Hello everyone in color!!");
if(!success)
cw.writeString(0, 10, "Write with color failed :(");
cw.refreshContainer();
sleep(2);
endwin();
return 0;
}
Thanks in Advance.

Answer 1

There are a couple of bugs in your code:
You don't initialize canColor and container, so copying the fields into cw in main has undefined behavior. Fixed by:
ColorWindow() : canColor(false), container(nullptr) {
writeStringWithColor is missing a return statement at the end, also leading to undefined behavior in main. Fixed by:
return true;
at the end of writeStringWithColor.
Your x and y arguments are swapped in the call to mvwprintw in writeString. Fixed by:
mvwprintw(getContainer(), y, x, message);
LINES and COLS are only valid after ncurses is initialized, so your starty and startx values are garbage. Fixed by moving the initialization of cw after the ncurses init code in main:
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on
* everything to me */
keypad(stdscr, TRUE);
start_color();
ColorWindow cw = ColorWindow();
Full program:
#include <ncurses.h>
#include <string.h>
#include <string>
#include <unistd.h>
#include <iostream>
using namespace std;
class ColorWindow {
private:
bool canColor;
WINDOW* container;
int height, width, startx, starty;
public:
ColorWindow() : canColor(false), container(nullptr) {
if(has_colors()) {
canColor=true;
}
this->height = 20;
this->width = 84;
this->starty = (LINES - height) / 2; /* Calculating for a center placement */
this->startx = (COLS - width) / 2;
}
bool writeStringWithColor(int x, int y, const char* message) {
if(!canColor) {
writeString(3, 5, "Sorry, your term can't show colors.");
return false;
}
init_pair(1, COLOR_RED, COLOR_BLACK);
writeString(0, 10, "aaaaaaaaa");
wattron(getContainer(), COLOR_PAIR(1));
writeString(x, y, message);
wattroff(getContainer(), COLOR_PAIR(1));
return true;
}
void writeString(int x, int y, const char* message) {
mvwprintw(getContainer(), y, x, message);
}
WINDOW* createNewContainer() {
this->container = newwin(height, width, starty, startx);
wrefresh(this->container); /* Show that box */
return getContainer();
}
WINDOW* getContainer() {
return this->container;
}
void refreshContainer() {
refresh();
wrefresh(this->container); /* Show that box */
}
};
int main() {
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on
* everything to me */
keypad(stdscr, TRUE);
start_color();
ColorWindow cw = ColorWindow();
cw.createNewContainer();
bool success = cw.writeStringWithColor(0, 10, "Hello everyone in color!!");
if(!success)
cw.writeString(0, 10, "Write with color failed :(");
cw.refreshContainer();
sleep(2);
endwin();
return 0;
}