From 2ac0e9e086dad67014b6b0b5b2a695b138a02842 Mon Sep 17 00:00:00 2001
From: Konstantin Vorobyev <kvorobyev@gmail.com>
Date: Wed, 20 Jun 2018 16:54:24 +0200
Subject: [PATCH 1/2] Block main event loop with mutex during Suspend() call

---
 application.go | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/application.go b/application.go
index 31821d9..2df2b74 100644
--- a/application.go
+++ b/application.go
@@ -41,8 +41,8 @@ type Application struct {
 	// was drawn.
 	afterDraw func(screen tcell.Screen)
 
-	// If this value is true, the application has entered suspended mode.
-	suspended bool
+	// Used for events loop lock during Suspend()
+	suspendMutex sync.Mutex
 }
 
 // NewApplication creates and returns a new application.
@@ -103,28 +103,20 @@ func (a *Application) Run() error {
 
 	// Start event loop.
 	for {
+		// Do not poll events during suspend mode
+		a.suspendMutex.Lock()
 		a.Lock()
 		screen := a.screen
-		if a.suspended {
-			a.suspended = false // Clear previous suspended flag.
-		}
 		a.Unlock()
 		if screen == nil {
+			a.suspendMutex.Unlock()
 			break
 		}
 
 		// Wait for next event.
 		event := a.screen.PollEvent()
+		a.suspendMutex.Unlock()
 		if event == nil {
-			a.Lock()
-			if a.suspended {
-				// This screen was renewed due to suspended mode.
-				a.suspended = false
-				a.Unlock()
-				continue // Resume.
-			}
-			a.Unlock()
-
 			// The screen was finalized. Exit the loop.
 			break
 		}
@@ -190,14 +182,14 @@ func (a *Application) Stop() {
 func (a *Application) Suspend(f func()) bool {
 	a.Lock()
 
-	if a.suspended || a.screen == nil {
+	if a.screen == nil {
 		// Application is already suspended.
 		a.Unlock()
 		return false
 	}
 
 	// Enter suspended mode.
-	a.suspended = true
+	a.suspendMutex.Lock()
 	a.Unlock()
 	a.Stop()
 
@@ -217,10 +209,12 @@ func (a *Application) Suspend(f func()) bool {
 	var err error
 	a.screen, err = tcell.NewScreen()
 	if err != nil {
+		a.suspendMutex.Unlock()
 		a.Unlock()
 		panic(err)
 	}
 	if err = a.screen.Init(); err != nil {
+		a.suspendMutex.Unlock()
 		a.Unlock()
 		panic(err)
 	}
@@ -228,6 +222,7 @@ func (a *Application) Suspend(f func()) bool {
 	a.Draw()
 
 	// Continue application loop.
+	a.suspendMutex.Unlock()
 	return true
 }
 

From 01a39a486dcc438baa4fb091ab301a20898a02b1 Mon Sep 17 00:00:00 2001
From: Konstantin Vorobyev <kvorobyev@gmail.com>
Date: Wed, 20 Jun 2018 19:32:19 +0200
Subject: [PATCH 2/2] Review feedback

---
 application.go | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/application.go b/application.go
index 2df2b74..d3b5f23 100644
--- a/application.go
+++ b/application.go
@@ -41,7 +41,7 @@ type Application struct {
 	// was drawn.
 	afterDraw func(screen tcell.Screen)
 
-	// Used for events loop lock during Suspend()
+	// Halts the event loop during suspended mode
 	suspendMutex sync.Mutex
 }
 
@@ -183,13 +183,14 @@ func (a *Application) Suspend(f func()) bool {
 	a.Lock()
 
 	if a.screen == nil {
-		// Application is already suspended.
+		// Screen has not yet been initialized
 		a.Unlock()
 		return false
 	}
 
 	// Enter suspended mode.
 	a.suspendMutex.Lock()
+	defer a.suspendMutex.Unlock()
 	a.Unlock()
 	a.Stop()
 
@@ -209,12 +210,10 @@ func (a *Application) Suspend(f func()) bool {
 	var err error
 	a.screen, err = tcell.NewScreen()
 	if err != nil {
-		a.suspendMutex.Unlock()
 		a.Unlock()
 		panic(err)
 	}
 	if err = a.screen.Init(); err != nil {
-		a.suspendMutex.Unlock()
 		a.Unlock()
 		panic(err)
 	}
@@ -222,7 +221,6 @@ func (a *Application) Suspend(f func()) bool {
 	a.Draw()
 
 	// Continue application loop.
-	a.suspendMutex.Unlock()
 	return true
 }