ref: 0a08e1941d43dcba7ded5b4f4492fd2d52b7f84d
dir: /main.c/
#include <assert.h>
#include <limits.h>
#include <locale.h>
#include <ncurses.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
typedef char Term;
typedef uint32_t U32;
typedef int32_t I32;
typedef struct {
Term* buffer;
U32 height;
U32 width;
} Field;
void field_init_zeros(Field* f, U32 height, U32 width) {
size_t num_cells = height * width;
f->buffer = calloc(num_cells, sizeof(Term));
f->height = height;
f->width = width;
}
void field_init_fill(Field* f, U32 height, U32 width, Term fill_char) {
size_t num_cells = height * width;
f->buffer = malloc(num_cells * sizeof(Term));
memset(f->buffer, fill_char, num_cells);
f->height = height;
f->width = width;
}
void field_realloc(Field* f, U32 height, U32 width) {
size_t cells = height * width;
f->buffer = realloc(f->buffer, cells * sizeof(Term));
f->height = height;
f->width = width;
}
void field_deinit(Field* f) {
assert(f->buffer != NULL);
free(f->buffer);
#ifndef NDEBUG
f->buffer = NULL;
#endif
}
void field_copy_subrect(Field* src, Field* dest, U32 src_y, U32 src_x,
U32 dest_y, U32 dest_x, U32 height, U32 width) {
size_t src_height = src->height;
size_t src_width = src->width;
size_t dest_height = dest->height;
size_t dest_width = dest->width;
if (src_height <= src_y || src_width <= src_x || dest_height <= dest_y ||
dest_width <= dest_x)
return;
size_t ny_0 = src_height - src_y;
size_t ny_1 = dest_height - dest_y;
size_t ny = height;
if (ny_0 < ny)
ny = ny_0;
if (ny_1 < ny)
ny = ny_1;
if (ny == 0)
return;
size_t row_copy_0 = src_width - src_x;
size_t row_copy_1 = dest_width - dest_x;
size_t row_copy = width;
if (row_copy_0 < row_copy)
row_copy = row_copy_0;
if (row_copy_1 < row_copy)
row_copy = row_copy_1;
size_t copy_bytes = row_copy * sizeof(Term);
Term* src_p = src->buffer + src_y * src_width + src_x;
Term* dest_p = dest->buffer + dest_y * dest_width + dest_x;
size_t src_stride;
size_t dest_stride;
if (src_y >= dest_y) {
src_stride = src_width;
dest_stride = dest_width;
} else {
src_p += (ny - 1) * src_width;
dest_p += (ny - 1) * dest_width;
src_stride = -src_width;
dest_stride = -dest_width;
}
size_t iy = 0;
for (;;) {
memmove(dest_p, src_p, copy_bytes);
++iy;
if (iy == ny)
break;
src_p += src_stride;
dest_p += dest_stride;
}
}
void field_fill_subrect(Field* f, U32 y, U32 x, U32 height, U32 width,
Term fill_char) {
size_t f_height = f->height;
size_t f_width = f->width;
if (y >= f_height || x >= f_width)
return;
size_t rows_0 = f_height - y;
size_t rows = height;
if (rows_0 < rows)
rows = rows_0;
if (rows == 0)
return;
size_t columns_0 = f_width - x;
size_t columns = width;
if (columns_0 < columns)
columns = columns_0;
size_t fill_bytes = columns * sizeof(Term);
Term* p = f->buffer + y * f_width + x;
size_t iy = 0;
for (;;) {
memset(p, fill_char, fill_bytes);
++iy;
if (iy == rows)
break;
p += f_width;
}
}
void field_debug_draw(Field* f, int term_y, int term_x) {
enum { Line_buffer_count = 4096 };
chtype line_buffer[Line_buffer_count];
size_t f_height = f->height;
size_t f_width = f->width;
Term* f_buffer = f->buffer;
if (f_width > Line_buffer_count)
return;
for (size_t iy = 0; iy < f_height; ++iy) {
Term* row_p = f_buffer + f_width * iy;
for (size_t ix = 0; ix < f_width; ++ix) {
line_buffer[ix] = (chtype)row_p[ix];
}
move(iy + term_y, term_x);
addchnstr(line_buffer, (int)f_width);
}
}
typedef struct {
chtype* buffer;
int size_y;
int size_x;
chtype fill_char;
} view_state;
void init_view_state(view_state* vs) {
vs->buffer = NULL;
vs->size_y = 0;
vs->size_x = 0;
vs->fill_char = '?';
}
void deinit_view_state(view_state* vs) {
// Note that we don't have to check if the buffer was ever actually set to a
// non-null pointer: `free` does this for us.
free(vs->buffer);
}
void update_view_state(view_state* vs, int term_height, int term_width,
chtype fill_char) {
bool same_dimensions = vs->size_y == term_height && vs->size_x == term_width;
bool same_fill_char = vs->fill_char == fill_char;
// If nothing has changed, we don't have any work to do.
if (same_dimensions && same_fill_char)
return;
if (!same_dimensions) {
// Note that this doesn't check for overflow. In theory that's unsafe, but
// really unlikely to happen here.
size_t term_cells = term_height * term_width;
size_t new_mem_size = term_cells * sizeof(chtype);
// 'realloc' is like malloc, but it lets you re-use a buffer instead of
// having to throw away an old one and create a new one. Oftentimes, the
// cost of 'realloc' is cheaper than 'malloc' for the C runtime, and it
// reduces memory fragmentation.
//
// It's called 'realloc', but you can also use it even you're starting out
// with a NULL pointer for your buffer.
vs->buffer = realloc(vs->buffer, new_mem_size);
vs->size_y = term_height;
vs->size_x = term_width;
}
if (!same_fill_char) {
vs->fill_char = fill_char;
}
// (Re-)fill the buffer with the new data.
chtype* buff = vs->buffer;
// For each row, in the buffer, fill it with an alternating pattern of spaces
// and the character the user typed.
for (int iy = 0; iy < term_height; ++iy) {
// Make a pointer to the start of this line in the buffer. We don't
// actually have to do this -- we could replace line[ix] with (buff + iy *
// term_width + ix), but this makes it easier to see what's going on.
chtype* line = buff + iy * term_width;
for (int ix = 0; ix < term_width; ++ix) {
// Note that 'if' here is being used with a numerical value instead a
// boolean. C doesn't actually have real booleans: a 0 value (whatever
// the number type happens to be, int, char, etc.) is considered 'false',
// and anything else is 'true'.
if ((iy + ix) % 2) {
line[ix] = ' ';
} else {
line[ix] = fill_char;
}
}
}
}
void draw_view_state(view_state* vs) {
// Loop over each row in the buffer, and send the entire row to ncurses all
// at once. This is the fastest way to draw to the terminal with ncurses.
for (int i = 0; i < vs->size_y; ++i) {
// Move the cursor directly to the start of the row.
move(i, 0);
// Send the entire line at once. If it's too long, it will be truncated
// instead of wrapping.
//
// We use addchnstr instead of addchstr (notice the 'n') because we know
// exactly how long the line is, and we don't have a null terminator in our
// string. If we tried to use addchstr, it would keep trying to read until
// it got to the end of our buffer, and then past the end of our buffer
// into unknown memory, because we don't have a null terminator in it.
addchnstr(vs->buffer + i * vs->size_x, vs->size_x);
}
}
int main() {
// Enable UTF-8 by explicitly initializing our locale before initializing
// ncurses.
setlocale(LC_ALL, "");
// Initialize ncurses
initscr();
// Allow ncurses to control newline translation. Fine to use with any modern
// terminal, and will let ncurses run faster.
nonl();
// Set interrupt keys (interrupt, break, quit...) to not flush. Helps keep
// ncurses state consistent, at the cost of less responsive terminal
// interrupt. (This will rarely happen.)
intrflush(stdscr, FALSE);
// Receive keyboard input immediately, and receive shift, control, etc. as
// separate events, instead of combined with individual characters.
raw();
// Don't echo keyboard input
noecho();
// Also receive arrow keys, etc.
keypad(stdscr, TRUE);
// Hide the terminal cursor
curs_set(0);
// Don't block on calls like getch() -- have it ERR immediately if the user
// hasn't typed anything. That way we can mix other timers in our code,
// instead of being a slave only to terminal input.
// nodelay(stdscr, TRUE);
Field field;
field_init_fill(&field, 16, 16, '.');
printw("Type any character to fill it in an alternating grid, or\ntype '");
attron(A_BOLD);
printw("q");
attroff(A_BOLD);
printw("' to quit\n");
refresh();
char fill_char = '?';
for (;;) {
int ch = getch();
clear();
if (ch == 'q')
break;
// ncurses gives us ERR if there was no user input. We'll sleep for 0
// seconds, so that we'll yield CPU time to the OS instead of looping as
// fast as possible. This avoids battery drain/excessive CPU usage. There
// are better ways to do this that waste less CPU, but they require doing a
// little more work on each individual platform (Linux, Mac, etc.)
if (ch == ERR) {
sleep(0);
continue;
}
// ncurses gives us the special value KEY_RESIZE if the user didn't
// actually type anything, but the terminal resized. If that happens to us,
// just re-use the fill character from last time.
char new_fill_char;
if (ch < CHAR_MIN || ch > CHAR_MAX || ch == KEY_RESIZE)
new_fill_char = '?';
else
new_fill_char = (char)ch;
int term_height = getmaxy(stdscr);
int term_width = getmaxx(stdscr);
assert(term_height >= 0 && term_width >= 0);
if (new_fill_char != fill_char) {
fill_char = new_fill_char;
}
field_fill_subrect(&field, 1, 1, field.height - 2, field.width - 2,
fill_char);
field_debug_draw(&field, 0, 0);
field_copy_subrect(&field, &field, 0, 0, 4, 4, 8, 8);
field_copy_subrect(&field, &field, 0, 0, 0, 0, 0, 0);
field_debug_draw(&field, field.height + 1, 0);
field_copy_subrect(&field, &field, 6, 6, 9, 9, 30, 30);
field_debug_draw(&field, 0, field.width + 1);
refresh();
}
field_deinit(&field);
endwin();
return 0;
}