Prevent show/back operations while busy

Fixes #22

README.md

@@ -245,6 +245,10 @@ The options table can contain the following fields:
 * ```clear``` (boolean) - If the clear flag is set Monarch will search the stack for the screen that is to be shown. If the screen already exists in the stack and the clear flag is set Monarch will remove all screens between the current top and the screen in question.
 * ```reload``` (boolean) - If the reload flag is set Monarch will reload the collection proxy if it's already loaded (this can happen if the previous screen was a popup).
 
+**RETURN**
+* ```success``` (boolean) - True if the process of showing the screen was started successfully. False if already busy showing/hiding a screen.
+
+
 ### monarch.back([data], [callback])
 Go back to a previous Monarch screen
 
@@ -252,6 +256,9 @@ Go back to a previous Monarch screen
 * ```data``` (table) - Optional data to associate with the screen you are going back to.  Retrieve using ```monarch.data()```.
 * ```callback``` (function) - Optional function to call when the previous screen is visible.
 
+**RETURN**
+* ```success``` (boolean) - True if the process of going back to a previous screen was started successfully. False if already busy showing/hiding a screen.
+
 
 ### monarch.preload(screen_id, [callback])
 Preload a Monarch screen. This will load but not enable the screen. This is useful for content heavy screens that you wish to be able to show without having to wait for it load.

monarch/monarch.lua

@@ -1,9 +1,5 @@
 local M = {}
 
-local screens = {}
-
-local stack = {}
-
 local CONTEXT = hash("monarch_context")
 local PROXY_LOADED = hash("proxy_loaded")
 local PROXY_UNLOADED = hash("proxy_unloaded")
@@ -25,6 +21,15 @@ M.FOCUS = {}
 M.FOCUS.GAINED = hash("monarch_focus_gained")
 M.FOCUS.LOST = hash("monarch_focus_lost")
 
+-- all registered screens
+local screens = {}
+
+-- the current stack of screens
+local stack = {}
+
+-- true while busy showing/hiding something
+local busy = false
+
 
 local function log(...) end
 
@@ -225,6 +230,7 @@ local function show_out(screen, next_screen, cb)
 	log("show_out()", screen.id)
 	local co
 	co = coroutine.create(function()
+		busy = true
 		screen.co = co
 		change_context(screen)
 		release_input(screen)
@@ -238,6 +244,7 @@ local function show_out(screen, next_screen, cb)
 			unload(screen)
 		end
 		screen.co = nil
+		busy = false
 		if cb then cb() end
 	end)
 	coroutine.resume(co)
@@ -247,6 +254,7 @@ local function show_in(screen, previous_screen, reload, cb)
 	log("show_in()", screen.id)
 	local co
 	co = coroutine.create(function()
+		busy = true
 		screen.co = co
 		change_context(screen)
 		if reload and screen.loaded then
@@ -271,6 +279,7 @@ local function show_in(screen, previous_screen, reload, cb)
 		acquire_input(screen)
 		focus_gained(screen, previous_screen)
 		screen.co = nil
+		busy = false
 		if cb then cb() end
 	end)
 	coroutine.resume(co)
@@ -280,6 +289,7 @@ local function back_in(screen, previous_screen, cb)
 	log("back_in()", screen.id)
 	local co
 	co = coroutine.create(function()
+		busy = true
 		screen.co = co
 		change_context(screen)
 		if screen.preloaded then
@@ -297,6 +307,7 @@ local function back_in(screen, previous_screen, cb)
 		acquire_input(screen)
 		focus_gained(screen, previous_screen)
 		screen.co = nil
+		busy = false
 		if cb then cb() end
 	end)
 	coroutine.resume(co)
@@ -306,6 +317,7 @@ local function back_out(screen, next_screen, cb)
 	log("back_out()", screen.id)
 	local co
 	co = coroutine.create(function()
+		busy = true
 		screen.co = co
 		change_context(screen)
 		release_input(screen)
@@ -313,6 +325,7 @@ local function back_out(screen, next_screen, cb)
 		transition(screen, M.TRANSITION.BACK_OUT, { next_screen = next_screen and next_screen.id })
 		unload(screen)
 		screen.co = nil
+		busy = false
 		if cb then cb() end
 	end)
 	coroutine.resume(co)
@@ -346,8 +359,13 @@ end
 --				   This would be the case if doing a show() from a popup on the screen just below the popup.
 -- @param data (*) - Optional data to set on the screen. Can be retrieved by the data() function
 -- @param cb (function) - Optional callback to invoke when screen is shown
+-- @return success True if screen is successfully shown, false if busy performing another operation
 function M.show(id, options, data, cb)
 	assert(id, "You must provide a screen id")
+	if busy then
+		return false
+	end
+	
 	id = tohash(id)
 	assert(screens[id], ("There is no screen registered with id %s"):format(tostring(id)))
 
@@ -392,13 +410,20 @@ function M.show(id, options, data, cb)
 
 	-- show screen
 	show_in(screen, top, options and options.reload, cb)
+
+	return true
 end
 
 
 -- Go back to the previous screen in the stack
 -- @param data (*) - Optional data to set for the previous screen
 -- @param cb (function) - Optional callback to invoke when the previous screen is visible again
+-- @return true if successfully going back, false if busy performing another operation
 function M.back(data, cb)
+	if busy then
+		return false
+	end
+
 	local screen = table.remove(stack)
 	if screen then
 		log("back()", screen.id)
@@ -424,6 +449,7 @@ function M.back(data, cb)
 	elseif cb then
 		cb()
 	end
+	return true
 end
 
 --- Preload a screen. This will load but not enable and show a screen. Useful for "heavier" screens

test/test_monarch.lua

@@ -148,6 +148,23 @@ return function()
 		end)
 
 		
+		it("should prevent further operations while hiding/showing a screen", function()
+			assert(monarch.show(SCREEN1) == true)
+			assert(monarch.show(SCREEN2) == false)
+			assert(wait_until_shown(SCREEN1), "Screen1 was never shown")
+			assert_stack({ SCREEN1 })
+
+			assert(monarch.show(SCREEN2) == true)
+			assert(wait_until_shown(SCREEN2), "Screen1 was never shown")
+			assert_stack({ SCREEN1, SCREEN2 })
+
+			assert(monarch.back() == true)
+			assert(monarch.back() == false)
+			assert(wait_until_shown(SCREEN1), "Screen1 was never shown")
+			assert_stack({ SCREEN1 })
+		end)
+		
+		
 		it("should close any open popups when showing a popup without the Popup On Popup flag", function()
 			monarch.show(SCREEN1)
 			assert(wait_until_shown(SCREEN1), "Screen1 was never shown")