Feature/state machine (#673)

* Implement simple state machine example in Lua
* Use defaults for trail widths

data/assets/examples/slidedeck.asset

@@ -1,4 +1,4 @@
-local helper = asset.require('util/slidedeck_helper')
+local helper = asset.require('util/slide_deck_helper')
 local deck = nil
 
 asset.onInitialize(function ()

data/assets/examples/statemachine.asset

@@ -0,0 +1,48 @@
+local stateMachineHelper = asset.require('util/state_machine_helper')
+
+states = {
+    {
+        Title = "Highlight EarthTrail",
+        Play = function ()
+            openspace.setPropertyValue("Scene.EarthTrail.renderable.LineWidth", 10, 1)
+        end,
+        Rewind = function ()
+            openspace.setPropertyValue("Scene.EarthTrail.renderable.LineWidth", 2, 1)
+        end
+    }, 
+    {
+        Title = "Highlight MarsTrail",
+        Play = function ()
+            openspace.setPropertyValue("Scene.EarthTrail.renderable.LineWidth", 2, 1)
+            openspace.setPropertyValue("Scene.MarsTrail.renderable.LineWidth", 10, 1)
+        end,
+        Rewind = function ()
+            openspace.setPropertyValue("Scene.MarsTrail.renderable.LineWidth", 2, 1)
+            openspace.setPropertyValue("Scene.EarthTrail.renderable.LineWidth", 10, 1)
+        end
+    }
+}
+
+local stateMachine
+
+function next() 
+    stateMachine.goToNextState()
+end
+
+function previous()
+    stateMachine.goToPreviousState()
+end
+
+asset.onInitialize(function ()
+    stateMachine = stateMachineHelper.createStateMachine(states)
+    openspace.bindKey('RIGHT', 'next()')
+    openspace.bindKey('LEFT', 'previous()')
+end)
+
+
+asset.onDeinitialize(function ()
+    stateMachine = nil
+    openspace.clearKey('RIGHT')
+    openspace.clearKey('LEFT')
+end)
+

data/assets/util/state_machine_helper.asset

@@ -0,0 +1,59 @@
+
+local goToNextStateFunction = function (machine)
+    if (machine.currentStateIndex >= #machine.states) then
+        machine.currentStateIndex = #machine.states
+        return
+    end
+
+    if (machine.currentStateIndex == 0) then
+        openspace.printInfo("Starting state machine with " ..
+            machine.states[machine.currentStateIndex + 1].Title)
+    elseif (machine.currentStateIndex == #machine.states) then
+        openspace.printInfo("Proceed from " ..
+            machine.states[machine.currentStateIndex].Title
+        )
+    else
+        openspace.printInfo("Proceed from " ..
+            machine.states[machine.currentStateIndex].Title .. " to " ..
+            machine.states[machine.currentStateIndex + 1].Title
+        )
+    end
+
+    machine.currentStateIndex = machine.currentStateIndex + 1
+
+    machine.states[machine.currentStateIndex].Play()
+end
+
+local goToPreviousStateFunction = function (machine)
+    if (machine.currentStateIndex < 1) then
+        machine.currentStateIndex = 0
+        return
+    end
+
+    if (machine.currentStateIndex == 1) then
+        openspace.printInfo("Rewind from " ..
+            machine.states[machine.currentStateIndex].Title
+        )
+    else
+        openspace.printInfo("Rewind from " ..
+            machine.states[machine.currentStateIndex].Title .. " to " ..
+            machine.states[machine.currentStateIndex - 1].Title
+        )
+    end
+
+    machine.states[machine.currentStateIndex].Rewind()
+    machine.currentStateIndex = machine.currentStateIndex - 1
+end
+
+local createStateMachine = function (states)
+    local machine = {
+        states = states,
+        currentStateIndex = 0
+    }
+    machine.goToNextState = function () goToNextStateFunction(machine) end
+    machine.goToPreviousState = function () goToPreviousStateFunction(machine) end
+    return machine
+end
+
+
+asset.export('createStateMachine', createStateMachine)