This doesn't answer why the pad was smearing, but it does answer the original intent of the problem, which was how to get some text to be able to move around and scroll off screen without loosing anything.
ok,so after much more reading, testing and googling... apparently the answer has a two parts:
A. Pads don't scroll, only windows scroll.
B. Windows do scroll, but not the way that you think. When a window scrolls, any text that falls off the edge of the window is lost forever ( not what I want ).
It looks like the answer is that you have to buffer the chars yourself because Ncurses doesn't.
So... I came up with this which does work
A,S,D,F keys make the window scroll. Q quits.
Change window_width and window_height vars in main to make the window any size you want.
Ofcourse you can also print whatever text you want.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <errno.h>
#include <ncurses.h>
chtype **initialize_screen_buffer(chtype **input_buffer, int window_width, int window_height)
{
int size=0, i=0, j=0;
//Allocate mem for the base pointer
size=sizeof(chtype*)*window_width;
input_buffer=calloc(size,1);
if( input_buffer==NULL ) { fprintf(stderr, "\ninitialize_screen_buffer:> Failed to allocate %d bytes of memory for input_buffer\n", size); exit(1); }
//Allocate mem for all of the columb pointers
for(i=0; i<window_width; i++)
{
size=sizeof(chtype*)*window_height;
input_buffer[i]=calloc(size,1);
if( input_buffer[i]==NULL ) { fprintf(stderr, "\ninitialize_screen_buffer:> Failed to allocate %d bytes of memory for input_buffer[%d]\n", size, i); exit(1); }
}
return input_buffer;
}
void free_screen_buffer(chtype **input_buffer, int window_width, int window_height)
{
int size=0, i=0, j=0;
//Allocate mem for all of the columb pointers
for(i=0; i < window_width; i++)
{
free(input_buffer[i]);
}
//Allocate mem for the base pointer
free(input_buffer);
}
void copy_window_to_buffer(WINDOW *mywin, chtype **input_buffer, int window_width, int window_height)
{
int x=0, y=0;
//start from the beginning
wmove(mywin, 0, 0 );
//Copy all chars and from the given window into the buffer
for(x=0; x < window_width; x++)
{
for(y=0; y < window_height; y++)
{
input_buffer[x][y]=(chtype)mvwinch(mywin, y, x);
}
}
}
void copy_buffer_to_window(WINDOW *mywin, chtype **input_buffer, int window_width, int window_height, int x_offset, int y_offset)
{
int x=0, y=0;
//start from the beginning
//Copy all chars and from the given window into the buffer
for(x=0; x < window_width; x++)
{
for(y=0; y < window_height; y++)
{
mvwaddch(mywin, y + y_offset, x + x_offset, input_buffer[x][y]);
}
}
}
int main() {
WINDOW *mywin;
int key=0, window_width=15, window_height=15, size=0, i=0, j=0, x_offset=0, y_offset=0;
chtype **screen_buffer;
screen_buffer=initialize_screen_buffer(screen_buffer, window_width, window_height);
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on everything to me */
timeout(0); /* wait for user input */
noecho();
keypad(stdscr, TRUE); /* I need those nifty Function keys */
start_color();
mywin = newwin(window_width, window_height, 0, 0);
waddstr(mywin, "0-0-0-0-0-\n");
waddstr(mywin, "1-1-1-1-1-\n");
waddstr(mywin, "2-2-2-2-2-\n");
waddstr(mywin, "3-3-3-3-3-\n");
waddstr(mywin, "4-4-4-4-4-\n");
waddstr(mywin, "5-5-5-5-5-\n");
waddstr(mywin, "6-6-6-6-6-\n");
waddstr(mywin, "7-7-7-7-7-\n");
waddstr(mywin, "8-8-8-8-8-\n");
waddstr(mywin, "9-9-9-9-9-\n");
wrefresh(mywin);
copy_window_to_buffer(mywin, screen_buffer, window_width, window_height);
key=-1;
while(key!='q')
{
key = wgetch(mywin);
if(key=='w') { y_offset--; }
if(key=='s') { y_offset++; }
if(key=='a') { x_offset--; }
if(key=='d') { x_offset++; }
wclear(mywin);
copy_buffer_to_window(mywin, screen_buffer, window_width, window_height, x_offset, y_offset);
wrefresh(mywin);
}
delwin(mywin);
endwin();
free_screen_buffer(screen_buffer, window_width, window_height);
return 0;
}
This does solve the problem of making a window scroll in all directions with no text loss, but it has a problem. It is static. It's a snapshot of the window that you have in front of your face at that moment. It doesn't allow for adding more lines of text without overwriting old lines.
The next step would be to add some re-allocation so that as text is added, the screen buffer will grow so that it can hold that extra text
