Change undo behavior

- Undo while holding a card drops it
- Undo can be redone

board.lua

@@ -96,8 +96,9 @@ function board:undo()
  if (not self.checkpoint) return
  if (not self.watcher:intercept("undo")) sounds:dire() return
  sounds:menu()
+ local current_checkpoint=checkpoint:new(self,self.checkpoint.card)
  self.checkpoint:apply(self)
- self.checkpoint=nil
+ self.checkpoint=current_checkpoint
 end
 
 function board:on_idle()

cursor.lua

@@ -81,15 +81,19 @@ function cursor:toggle_grab()
   self:restore_hover()
   sounds:menu()
  elseif acc==acceptance_state.no_move or acc==acceptance_state.would_not_accept then
-  if (not self.board.watcher:intercept("cancel")) sounds:dire() return
+  self:drop_grab()
-  self.grabbed=nil
-  self:restore_hover()
-  sounds:menu()
  else
   assert(false,"invalid acceptance state")
  end
 end
 
+function cursor:drop_grab()
+ if (not self.board.watcher:intercept("cancel")) sounds:dire() return
+ self.grabbed=nil
+ self:restore_hover()
+ sounds:menu()
+end
+
 function cursor:update()
  if (self.wants_to_restore_hover) self:actually_restore_hover()
 end

state_gameround.lua

@@ -41,7 +41,13 @@ function state_gameround:update()
   if (btnp(2)) self.board.cursor:move_y(-1)
   if (btnp(3)) self.board.cursor:move_y(1)
   if (btnp(4)) self.board.cursor:toggle_grab()
-  if (btnp(5)) self.board:undo()
+  if btnp(5) then 
+   if self.board.cursor:grabbed_card() then
+    self.board.cursor:drop_grab() 
+   else
+    self.board:undo()
+   end
+  end
  end
  if (self.board:is_won()) self.outcome="win" self.done=true main.state_manager:push(state_wonround:new(self.board))
 end