initial commit

src/core/StateStack.lua

@@ -0,0 +1,45 @@
+-- Game state stack.  The top state updates; all states draw bottom-up
+-- (so a text box can overlay the overworld, a battle replaces it, etc).
+-- States are tables with optional enter/exit/update/draw/isOpaque.
+
+local StateStack = {}
+
+function StateStack:init()
+  self.states = {}
+end
+
+function StateStack:push(state, ...)
+  table.insert(self.states, state)
+  if state.enter then state:enter(...) end
+end
+
+function StateStack:pop()
+  local state = table.remove(self.states)
+  if state and state.exit then state:exit() end
+  return state
+end
+
+function StateStack:top()
+  return self.states[#self.states]
+end
+
+function StateStack:update(dt)
+  local top = self:top()
+  if top and top.update then top:update(dt) end
+end
+
+-- index of the lowest state drawn this frame (highest opaque, else 1)
+function StateStack:visibleBase()
+  for i = #self.states, 1, -1 do
+    if self.states[i].isOpaque then return i end
+  end
+  return 1
+end
+
+function StateStack:draw()
+  for i = self:visibleBase(), #self.states do
+    if self.states[i].draw then self.states[i]:draw() end
+  end
+end
+
+return StateStack