lineindex
bufp = &screenbuf[lineindex(curr_y) + curr_x];
colorp = &colorbuf[lineindex(curr_y) + curr_x];
bufp = &screenbuf[lineindex(y) + x];
colorp = &colorbuf[lineindex(y) + x];
p = &screenbuf[lineindex(virt_y) + virt_x];
if (screenbuf[lineindex(y)] != '\0')
len = lineindex(virt_y) + virt_x;
p = &screenbuf[lineindex(virt_y)];