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https://github.com/eddyem/eddys_snippets.git
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add some ncurses snippets
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336
Ncurses/ncurses_and_readline.c
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336
Ncurses/ncurses_and_readline.c
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/*
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* This file is part of the ncurses project.
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* Copyright 2020 Edward V. Emelianov <edward.emelianoff@gmail.com>.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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// based on https://stackoverflow.com/a/28709979/1965803 ->
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// https://github.com/ulfalizer/readline-and-ncurses
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// Copyright (c) 2015-2019, Ulf Magnusson
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// SPDX-License-Identifier: ISC
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#include <curses.h>
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#include <readline/history.h>
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#include <readline/readline.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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// Keeps track of the terminal mode so we can reset the terminal if needed on errors
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static bool visual_mode = false;
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// insert commands when true; roll upper screen when false
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static bool insert_mode = true;
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static bool should_exit = false;
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static void fail_exit(const char *msg){
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// Make sure endwin() is only called in visual mode. As a note, calling it
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// twice does not seem to be supported and messed with the cursor position.
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if(visual_mode) endwin();
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fprintf(stderr, "%s\n", msg);
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exit(EXIT_FAILURE);
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}
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static WINDOW *msg_win; // Message window
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static WINDOW *sep_win; // Separator line above the command (readline) window
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static WINDOW *cmd_win; // Command (readline) window
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// string list
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typedef struct _Line{
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int Nline;
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char *contents;
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struct _Line *prev, *next;
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} Line;
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// head of list, current item and first line on screen
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Line *head = NULL, *curr = NULL, *firstline = NULL;
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int nr_lines = 0; // total anount of data portions @ input
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static unsigned char input; // Input character for readline
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// Used to signal "no more input" after feeding a character to readline
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static bool input_avail = false;
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// Not bothering with 'input_avail' and just returning 0 here seems to do the
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// right thing too, but this might be safer across readline versions
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static int readline_input_avail(){
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return input_avail;
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}
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static int readline_getc(__attribute__((__unused__)) FILE *dummy){
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input_avail = false;
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return input;
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}
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static void forward_to_readline(char c){
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input = c;
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input_avail = true;
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rl_callback_read_char();
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}
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static void msg_win_redisplay(bool for_resize){
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werase(msg_win);
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Line *l = firstline;
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int nlines = 0; // total amount of lines @ output
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for(; l && (nlines < LINES - 2); l = l->next){
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size_t contlen = strlen(l->contents) + 128;
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char *buf = malloc(contlen);
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// don't add trailing '\n' (or last line will be empty with cursor)
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contlen = snprintf(buf, contlen, "%s", l->contents);
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int nlnext = (contlen - 1) / COLS + 1;
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wmove(msg_win, nlines, 0);
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if(nlines + nlnext < LINES-2){ // can put out the full line
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waddstr(msg_win, buf);
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//wprintw(msg_win, "%d (%d): %s -> %d", l->Nline, firstline->Nline, l->contents, nlnext);
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nlines += nlnext;
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}else{ // put only first part
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int rest = LINES-2 - nlines;
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waddnstr(msg_win, buf, rest *COLS);
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break;
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}
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free(buf);
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}
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curs_set(0);
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if(for_resize) wnoutrefresh(msg_win);
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else wrefresh(msg_win);
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}
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static void got_command(char *line){
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if(!line) // Ctrl-D pressed on empty line
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should_exit = true;
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else{
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if(!*line) return; // zero length
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add_history(line);
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Line *lp = malloc(sizeof(Line));
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lp->contents = line;
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lp->prev = curr;
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lp->next = NULL;
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lp->Nline = nr_lines++;
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if(!curr || !head){
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head = curr = firstline = lp;
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}else
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curr->next = lp;
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curr = lp;
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// roll back to show last input
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if(curr->prev){
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firstline = curr;
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int totalln = (strlen(firstline->contents) - 1)/COLS + 1;
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while(firstline->prev){
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totalln += (strlen(firstline->prev->contents) - 1)/COLS + 1;
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if(totalln > LINES-2) break;
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firstline = firstline->prev;
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}
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}
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msg_win_redisplay(false);
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}
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}
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static void cmd_win_redisplay(bool for_resize){
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int cursor_col = 2 + rl_point; // "> " width is 2
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werase(cmd_win);
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int x = 0, maxw = COLS-2;
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if(cursor_col > maxw){
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x = cursor_col - maxw;
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cursor_col = maxw;
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}
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char abuf[4096];
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snprintf(abuf, 4096, "> %s", rl_line_buffer);
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waddstr(cmd_win, abuf+x);
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wmove(cmd_win, 0, cursor_col);
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curs_set(2);
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if(for_resize) wnoutrefresh(cmd_win);
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else wrefresh(cmd_win);
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}
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static void readline_redisplay(void){
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cmd_win_redisplay(false);
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}
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static void show_mode(bool for_resize){
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wclear(sep_win);
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if(insert_mode) waddstr(sep_win, "INSERT (TAB to switch, ctrl+D to quit)");
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else waddstr(sep_win, "SCROLL (TAB to switch, q to quit)");
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if(for_resize) wnoutrefresh(sep_win);
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else wrefresh(sep_win);
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cmd_win_redisplay(for_resize);
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}
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static void resize(void){
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if(LINES > 2){
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wresize(msg_win, LINES - 2, COLS);
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wresize(sep_win, 1, COLS);
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wresize(cmd_win, 1, COLS);
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mvwin(sep_win, LINES - 2, 0);
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mvwin(cmd_win, LINES - 1, 0);
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}
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msg_win_redisplay(true);
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show_mode(true);
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doupdate();
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}
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static void init_ncurses(void){
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if (!initscr())
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fail_exit("Failed to initialize ncurses");
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visual_mode = true;
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if(has_colors()){
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start_color();
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use_default_colors();
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}
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cbreak();
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noecho();
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nonl();
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intrflush(NULL, FALSE);
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// Do not enable keypad() since we want to pass unadulterated input to readline
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keypad(cmd_win, 0);
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// Explicitly specify a "very visible" cursor to make sure it's at least
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// consistent when we turn the cursor on and off (maybe it would make sense
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// to query it and use the value we get back too). "normal" vs. "very
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// visible" makes no difference in gnome-terminal or xterm. Let this fail
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// for terminals that do not support cursor visibility adjustments.
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curs_set(2);
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if(LINES > 2){
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msg_win = newwin(LINES - 2, COLS, 0, 0);
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sep_win = newwin(1, COLS, LINES - 2, 0);
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cmd_win = newwin(1, COLS, LINES - 1, 0);
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}
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else{
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// Degenerate case. Give the windows the minimum workable size to
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// prevent errors from e.g. wmove().
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msg_win = newwin(1, COLS, 0, 0);
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sep_win = newwin(1, COLS, 0, 0);
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cmd_win = newwin(1, COLS, 0, 0);
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}
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if(!msg_win || !sep_win || !cmd_win)
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fail_exit("Failed to allocate windows");
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// Allow strings longer than the command window and show only the last part if the string doesn't fit
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// scrollok(cmd_win, TRUE);
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if(has_colors()){
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// Use white-on-blue cells for the separator window...
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init_pair(1, COLOR_WHITE, COLOR_BLUE);
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wbkgd(sep_win, COLOR_PAIR(1));
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}
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else
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// ...or the "best highlighting mode of the terminal" if it doesn't
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// support colors
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wbkgd(sep_win, A_STANDOUT);
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show_mode(false);
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mousemask(BUTTON4_PRESSED|BUTTON5_PRESSED, NULL);
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}
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static void deinit_ncurses(void){
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delwin(msg_win);
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delwin(sep_win);
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delwin(cmd_win);
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endwin();
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visual_mode = false;
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}
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static void init_readline(void){
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// Let ncurses do all terminal and signal handling
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rl_catch_signals = 0;
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rl_catch_sigwinch = 0;
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rl_deprep_term_function = NULL;
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rl_prep_term_function = NULL;
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// Prevent readline from setting the LINES and COLUMNS environment
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// variables, which override dynamic size adjustments in ncurses. When
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// using the alternate readline interface (as we do here), LINES and
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// COLUMNS are not updated if the terminal is resized between two calls to
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// rl_callback_read_char() (which is almost always the case).
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rl_change_environment = 0;
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// Handle input by manually feeding characters to readline
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rl_getc_function = readline_getc;
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rl_input_available_hook = readline_input_avail;
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rl_redisplay_function = readline_redisplay;
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rl_callback_handler_install("> ", got_command);
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}
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static void deinit_readline(void){
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rl_callback_handler_remove();
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}
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static void rolldown(){
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if(firstline && firstline->prev){
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firstline = firstline->prev;
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msg_win_redisplay(false);
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}
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}
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static void rollup(){
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if(firstline && firstline->next){
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firstline = firstline->next;
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msg_win_redisplay(false);
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}
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}
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int main(void){
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init_ncurses();
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init_readline();
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MEVENT event;
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do{
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int c = wgetch(cmd_win);
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bool processed = true;
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switch(c){
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case KEY_MOUSE:
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if(getmouse(&event) == OK){
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if(event.bstate & (BUTTON4_PRESSED)) rolldown(); // wheel up
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else if(event.bstate & (BUTTON5_PRESSED)) rollup(); // wheel down
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}
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break;
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case '\t': // tab switch between scroll and edit mode
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keypad(cmd_win, insert_mode); // enable/disable reaction @ special characters
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insert_mode = !insert_mode;
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show_mode(false);
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break;
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case KEY_RESIZE:
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resize();
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break;
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default:
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processed = false;
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}
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if(processed) continue;
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if(insert_mode){
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forward_to_readline(c);
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}else{
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switch(c){
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case KEY_UP: // roll down for one item
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rolldown();
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break;
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case KEY_DOWN: // roll up for one item
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rollup();
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break;
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case KEY_PPAGE: // PageUp: roll down for 10 items
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for(int i = 0; i < 10; ++i){
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if(firstline && firstline->prev) firstline = firstline->prev;
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else break;
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}
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msg_win_redisplay(false);
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break;
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case KEY_NPAGE: // PageUp: roll up for 10 items
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for(int i = 0; i < 10; ++i){
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if(firstline && firstline->next) firstline = firstline->next;
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else break;
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}
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msg_win_redisplay(false);
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break;
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default:
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if(c == 'q' || c == 'Q') should_exit = true; // quit
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}
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}
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}while(!should_exit);
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deinit_ncurses();
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deinit_readline();
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puts("Shut down cleanly");
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return 0;
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}
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