So Ive been using surfaces lately. Im trying to figure how to make undos+redos but I cant quite get it.

I draw on the surface in the mouse left button event. I make a new surface each time I realease it, storing the previous surface in an array. I then draw the previous surface onto the new surface, setting the new one to the currently drawn surface. But when going back the drawing never changes. Here my code-

Create-

surs=1

cur_sur=1

sur[cur_sur]=surface_create(room_width,room_height)

surface_set_target(sur[cur_sur])

draw_clear(c_white)

surface_reset_target()

Global left-

surface_set_target(sur[cur_sur])

draw_circle(mouse_x,mouse_y,5,0)

surface_reset_target()

Global left released-

surs+=1

cur_surs=surs

sur[cur_surs]=surface_create(room_width,room_height)

surface_set_target(sur[cur_surs])

draw_surface(sur[cur_surs-1],0,0)

surface_reset_target()

Draw-

draw_surface(sur[cur_sur],0,0)

Down-

cur_sur-=1

<a href='http://64digits.com/users/Kaz/undo.gm6'>File</a>

Anyone care to help?

If you remember I was going on a trip to NJ. But my moms been busy and hasnt been able to look at the train schedule yet. So Im going after the concert(August 7th).