Preload fix (#34)

* Don't try to preload if monarch is busy
* Added test for #32

README.md

@@ -34,7 +34,7 @@ For proxies the recommended setup is to create one game object per screen and pe
 * **Transition Url (url)** - Optional URL to call when the screen is about to be shown/hidden. Use this to trigger a transition (see the section on [transitions](#transitions)).
 * **Focus Url (url)** - Optional URL to call when the screen gains or loses focus (see the section on [screen focus](#screen-focus-gainloss)).
 
-![](docs/setup.png)
+![](docs/setup_proxy.png)
 
 ### Collection factories
 For factories the recommended setup is to create one game object per screen and per game object attach a collection factory component and an instance of the ```screen_factory.script``` provided by Monarch. The ```screen_factory.script``` will take care of the setup of the screen. All you need to do is to make sure that the script properties on the script are correct:
@@ -46,6 +46,8 @@ For factories the recommended setup is to create one game object per screen and
 * **Transition Id (url)** - Optional id of the game object to send a message to when the screen is about to be shown/hidden. Use this to trigger a transition (see the section on [transitions](#transitions)).
 * **Focus Id (url)** - Optional id of the game object to send a message to when the screen gains or loses focus (see the section on [screen focus](#screen-focus-gainloss)).
 
+![](docs/setup_factory.png)
+
 
 ## Navigating between screens
 The navigation in Monarch is based around a stack of screens. When a screen is shown it is pushed to the top of the stack. When going back to a previous screen the topmost screen on the stack is removed. Example:

monarch/monarch.lua

@@ -621,6 +621,11 @@ end
 -- @param id (string|hash) - Id of the screen to preload
 -- @param cb (function) - Optional callback to invoke when screen is loaded
 function M.preload(id, cb)
+	if M.is_busy() then
+		log("preload() monarch is busy, ignoring request")
+		return false
+	end
+
 	assert(id, "You must provide a screen id")
 	id = tohash(id)
 	assert(screens[id], ("There is no screen registered with id %s"):format(tostring(id)))

test/test_monarch.lua

@@ -238,6 +238,14 @@ return function()
 			assert(wait_until_not_busy())
 		end)
 
+		it("should ignore any preload calls while busy", function()
+			monarch.show(TRANSITION1)
+			-- previously a call to preload() while also showing a screen would
+			-- lock up monarch. See issue #32
+			monarch.preload(TRANSITION1)
+			assert(wait_until_shown(TRANSITION1), "Transition1 was never shown")
+		end)
+		
 		it("should be able to notify listeners of navigation events", function()
 			local URL1 = msg.url(screens_instances[hash("/listener1")])
 			local URL2 = msg.url(screens_instances[hash("/listener2")])