Check if screen was loaded before trying to unload

Fixes #88

README_API.md

@@ -48,13 +48,18 @@ Go back to a previous Monarch screen. This operation will be added to the queue
 * `callback` (function) - Optional function to call when the previous screen is visible.
 
 
-## monarch.preload(screen_id, [callback])
+## monarch.preload(screen_id, [options], [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. This operation will be added to the queue if Monarch is busy.
 
 **PARAMETERS**
 * `screen_id` (string|hash) - Id of the screen to preload.
+* `options` (table)
 * `callback` (function) - Optional function to call when the screen is preloaded.
 
+The options table can contain the following fields:
+
+* `keep_loaded` (boolean) - If the `keep_loaded` flag is set Monarch will keep the screen preloaded even after a `hide()` or `back()` navigation event that normally would unload the screen.
+
 
 ## monarch.is_preloading(screen_id)
 Check if a Monarch screen is preloading (via monarch.preload() or the Preload screen setting).

monarch/monarch.lua

@@ -298,6 +298,12 @@ function M.unregister(id)
 	log("unregister()", id)
 	local screen = screens[id]
 	screens[id] = nil
+	-- remove screen from stack
+	for i = #stack, 1, -1 do
+		if stack[i].id == id then
+			table.remove(stack, i)
+		end
+	end
 end
 
 local function acquire_input(screen)
@@ -348,8 +354,10 @@ local function unload(screen, force)
 	if screen.proxy then
 		log("unload() proxy", screen.id)
 		if screen.auto_preload and not force then
-			msg.post(screen.proxy, DISABLE)
-			screen.loaded = false
+			if screen.loaded then
+				msg.post(screen.proxy, DISABLE)
+				screen.loaded = false
+			end
 			screen.preloaded = true
 		else
 			screen.wait_for = PROXY_UNLOADED
@@ -650,10 +658,10 @@ local function back_out(screen, next_screen, wait_for_transition, cb)
 		change_context(screen)
 		release_input(screen, next_screen)
 		focus_lost(screen, next_screen)
+		transition(screen, M.TRANSITION.BACK_OUT, { next_screen = next_screen and next_screen.id }, wait_for_transition)
 		if next_screen and screen.popup then
 			reset_timestep(next_screen)
 		end
-		transition(screen, M.TRANSITION.BACK_OUT, { next_screen = next_screen and next_screen.id }, wait_for_transition)
 		screen.visible = false
 		unload(screen)
 		active_transition_count = active_transition_count - 1
@@ -921,9 +929,20 @@ function M.back(data, cb)
 					if data then
 						top.data = data
 					end
-					back_in(top, screen, DO_NOT_WAIT_FOR_TRANSITION, function()
-						back_out(screen, top, WAIT_FOR_TRANSITION, back_cb)
-					end)
+					-- if the screen we are backing out from is a popup and the screen we go
+					-- back to is not a popup we need to let the popup completely hide before 
+					-- we start working on the screen we go back to
+					-- we do this to ensure that we do not reset the times step of the screen
+					-- we go back to until it is no longer obscured by the popup
+					if screen.popup and not top.popup then
+						back_out(screen, top, WAIT_FOR_TRANSITION, function()
+							back_in(top, screen, WAIT_FOR_TRANSITION, back_cb)
+						end)
+					else
+						back_in(top, screen, DO_NOT_WAIT_FOR_TRANSITION, function()
+							back_out(screen, top, WAIT_FOR_TRANSITION, back_cb)
+						end)
+					end
 				else
 					back_out(screen, top, WAIT_FOR_TRANSITION, back_cb)
 				end
@@ -979,12 +998,19 @@ end
 --- Preload a screen. This will load but not enable and show a screen. Useful for "heavier" screens
 -- that you wish to show without any delay.
 -- @param id (string|hash) - Id of the screen to preload
+-- @param options (table)
 -- @param cb (function) - Optional callback to invoke when screen is loaded
-function M.preload(id, cb)
+function M.preload(id, options, cb)
 	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)))
 
+	-- support old function signature (id, cb)
+	if type(options) == "function" and not cb then
+		cb = options
+		options = nil
+	end
+
 	log("preload() queuing action", id)
 	queue_action(function(action_done, action_error)
 		log("preload()", id)
@@ -995,6 +1021,10 @@ function M.preload(id, cb)
 			return
 		end
 
+		-- keep_loaded is an option for monarch.preload()
+		-- use it to get the same behavior as the auto preload checkbox
+		screen.auto_preload = screen.auto_preload or options and options.keep_loaded
+
 		if screen.preloaded or screen.loaded then
 			pcallfn(cb)
 			pcallfn(action_done)

test/test_monarch.lua

@@ -377,7 +377,21 @@ return function()
 			end)
 			assert(not monarch.is_preloading(TRANSITION1))
 		end)
-		
+
+		it("should be able to preload a screen and keep it loaded", function()
+			assert(not monarch.is_preloading(TRANSITION1))
+			monarch.preload(TRANSITION1, { keep_loaded = true })
+			wait_until_done(function(done)
+				monarch.when_preloaded(TRANSITION1, done)
+			end)
+			
+			monarch.show(TRANSITION1)
+			assert(wait_until_visible(TRANSITION1), "Transition1 was never shown")
+			monarch.back()
+			assert(wait_until_hidden(TRANSITION1), "Transition1 was never hidden")
+			assert(monarch.is_preloaded(TRANSITION1))
+		end)
+
 		it("should ignore any preload calls while busy", function()
 			monarch.show(TRANSITION1)
 			-- previously a call to preload() while also showing a screen would