Just add to the code you are using, if you use the WASD keys for movement you will have to use other keys(or the mouse) for tilting and panning:

Add to main:

while(1)
{
// Tilting and panning code here

if (key_w) camera.x += 2 * time_step; // Adjust 2 factor for right speed!
if (key_s) camera.x -= 2 * time_step;
if (key_d) camera.y += 2 * time_step;
if (key_a) camera.y -= 2 * time_step;

wait(1);
}