diff --git a/apps/apps_container.cpp b/apps/apps_container.cpp
index 255c90133..e01d26fc6 100644
--- a/apps/apps_container.cpp
+++ b/apps/apps_container.cpp
@@ -130,7 +130,7 @@ bool AppsContainer::dispatchEvent(Ion::Events::Event event) {
     return true;
   }
   if (!didProcessEvent && alphaLockWantsRedraw) {
-    windowRedraw();
+    window()->redraw();
     return true;
   }
   return didProcessEvent;
diff --git a/apps/graph/cartesian_function_store.cpp b/apps/graph/cartesian_function_store.cpp
index 087fcb3a8..7c74dacea 100644
--- a/apps/graph/cartesian_function_store.cpp
+++ b/apps/graph/cartesian_function_store.cpp
@@ -18,13 +18,13 @@ CartesianFunctionStore::CartesianFunctionStore() :
 }
 
 uint32_t CartesianFunctionStore::storeChecksum() {
-  size_t dataLengthInBytes = k_maxNumberOfFunctions*TextField::maxBufferSize()*sizeof(char);
+  size_t dataLengthInBytes = k_maxNumberOfFunctions*sizeof(uint32_t);
   assert((dataLengthInBytes & 0x3) == 0); // Assert that dataLengthInBytes is a multiple of 4
-  char data[k_maxNumberOfFunctions*TextField::maxBufferSize()] = {};
+  uint32_t checksums[k_maxNumberOfFunctions];
   for (int i = 0; i < k_maxNumberOfFunctions; i++) {
-    strlcpy(data+i*TextField::maxBufferSize(), m_functions[i].text(), TextField::maxBufferSize());
+    checksums[i] = m_functions[i].checksum();
   }
-  return Ion::crc32((uint32_t *)data, dataLengthInBytes>>2);
+  return Ion::crc32((uint32_t *)checksums, dataLengthInBytes>>2);
 }
 
 CartesianFunction * CartesianFunctionStore::functionAtIndex(int i) {
diff --git a/apps/sequence/sequence.cpp b/apps/sequence/sequence.cpp
index a8a7e348e..cb4470ea6 100644
--- a/apps/sequence/sequence.cpp
+++ b/apps/sequence/sequence.cpp
@@ -2,6 +2,7 @@
 #include "local_context.h"
 #include "../../poincare/src/layout/string_layout.h"
 #include "../../poincare/src/layout/baseline_relative_layout.h"
+#include <assert.h>
 #include <string.h>
 
 using namespace Shared;
@@ -81,6 +82,16 @@ Sequence& Sequence::operator=(const Sequence& other) {
   return *this;
 }
 
+uint32_t Sequence::checksum() {
+  size_t dataLengthInBytes = 3*TextField::maxBufferSize()*sizeof(char);
+  assert((dataLengthInBytes & 0x3) == 0); // Assert that dataLengthInBytes is a multiple of 4
+  char data[3*TextField::maxBufferSize()] = {};
+  strlcpy(data, text(), TextField::maxBufferSize());
+  strlcpy(data+TextField::maxBufferSize(), firstInitialConditionText(), TextField::maxBufferSize());
+  strlcpy(data+2*TextField::maxBufferSize(), secondInitialConditionText(), TextField::maxBufferSize());
+  return Ion::crc32((uint32_t *)data, dataLengthInBytes>>2);
+}
+
 const char * Sequence::firstInitialConditionText() {
   return m_firstInitialConditionText;
 }
diff --git a/apps/sequence/sequence.h b/apps/sequence/sequence.h
index 09563df98..e794192b4 100644
--- a/apps/sequence/sequence.h
+++ b/apps/sequence/sequence.h
@@ -18,6 +18,7 @@ public:
   Sequence& operator=(Sequence&& other) = delete;
   Sequence(const Sequence& other) = delete;
   Sequence(Sequence&& other) = delete;
+  uint32_t checksum() override;
   Type type();
   void setType(Type type);
   const char * firstInitialConditionText();
diff --git a/apps/sequence/sequence_store.cpp b/apps/sequence/sequence_store.cpp
index 7a107baf7..991d30762 100644
--- a/apps/sequence/sequence_store.cpp
+++ b/apps/sequence/sequence_store.cpp
@@ -11,15 +11,13 @@ constexpr KDColor SequenceStore::k_defaultColors[k_maxNumberOfSequences];
 constexpr const char * SequenceStore::k_sequenceNames[k_maxNumberOfSequences];
 
 uint32_t SequenceStore::storeChecksum() {
-  size_t dataLengthInBytes = k_maxNumberOfSequences*3*TextField::maxBufferSize()*sizeof(char);
+  size_t dataLengthInBytes = k_maxNumberOfSequences*sizeof(uint32_t);
   assert((dataLengthInBytes & 0x3) == 0); // Assert that dataLengthInBytes is a multiple of 4
-  char data[3*k_maxNumberOfSequences*TextField::maxBufferSize()] = {};
+  uint32_t checksums[k_maxNumberOfSequences];
   for (int i = 0; i < k_maxNumberOfSequences; i++) {
-    strlcpy(data+i*3*TextField::maxBufferSize(), m_sequences[i].text(), TextField::maxBufferSize());
-    strlcpy(data+i*3*TextField::maxBufferSize()+TextField::maxBufferSize(), m_sequences[i].firstInitialConditionText(), TextField::maxBufferSize());
-    strlcpy(data+i*3*TextField::maxBufferSize()+2*TextField::maxBufferSize(), m_sequences[i].secondInitialConditionText(), TextField::maxBufferSize());
+    checksums[i] = m_sequences[i].checksum();
   }
-  return Ion::crc32((uint32_t *)data, dataLengthInBytes>>2);
+  return Ion::crc32((uint32_t *)checksums, dataLengthInBytes>>2);
 }
 
 Sequence * SequenceStore::functionAtIndex(int i) {
diff --git a/apps/shared/function.cpp b/apps/shared/function.cpp
index 354ba28f9..c53c70e88 100644
--- a/apps/shared/function.cpp
+++ b/apps/shared/function.cpp
@@ -1,6 +1,7 @@
 #include "function.h"
 #include <string.h>
 #include <math.h>
+#include <assert.h>
 
 using namespace Poincare;
 
@@ -25,6 +26,14 @@ Function& Function::operator=(const Function& other) {
   return *this;
 }
 
+uint32_t Function::checksum() {
+  size_t dataLengthInBytes = TextField::maxBufferSize()*sizeof(char);
+  assert((dataLengthInBytes & 0x3) == 0); // Assert that dataLengthInBytes is a multiple of 4
+  char data[TextField::maxBufferSize()] = {};
+  strlcpy(data, m_text, TextField::maxBufferSize());
+  return Ion::crc32((uint32_t *)data, dataLengthInBytes>>2);
+}
+
 void Function::setContent(const char * c) {
   strlcpy(m_text, c, sizeof(m_text));
   if (m_layout != nullptr) {
diff --git a/apps/shared/function.h b/apps/shared/function.h
index cdf64bc4c..1483d28a0 100644
--- a/apps/shared/function.h
+++ b/apps/shared/function.h
@@ -15,6 +15,7 @@ public:
   Function& operator=(Function&& other) = delete;
   Function(const Function& other) = delete;
   Function(Function&& other) = delete;
+  virtual uint32_t checksum();
   const char * text() const;
   const char * name() const;
   KDColor color() const { return m_color; }
diff --git a/escher/include/escher/container.h b/escher/include/escher/container.h
index 8412274ff..e1e4f299c 100644
--- a/escher/include/escher/container.h
+++ b/escher/include/escher/container.h
@@ -29,7 +29,6 @@ public:
   virtual void switchTo(App::Snapshot * snapshot);
 protected:
   virtual Window * window() = 0;
-  void windowRedraw() override;
 private:
   void step();
   App * m_activeApp;
diff --git a/escher/include/escher/run_loop.h b/escher/include/escher/run_loop.h
index 81bc7b1fd..83f9396d6 100644
--- a/escher/include/escher/run_loop.h
+++ b/escher/include/escher/run_loop.h
@@ -9,7 +9,6 @@ public:
   RunLoop();
   void run();
 protected:
-  virtual void windowRedraw() = 0;
   virtual bool dispatchEvent(Ion::Events::Event e) = 0;
   virtual int numberOfTimers();
   virtual Timer * timerAtIndex(int i);
diff --git a/escher/src/container.cpp b/escher/src/container.cpp
index 2314eda06..8e8347902 100644
--- a/escher/src/container.cpp
+++ b/escher/src/container.cpp
@@ -20,11 +20,10 @@ void Container::switchTo(App::Snapshot * snapshot) {
   if (m_activeApp) {
     m_activeApp->willBecomeInactive();
     m_activeApp->snapshot()->pack(m_activeApp);
+    m_activeApp = nullptr;
   }
   if (snapshot) {
     m_activeApp = snapshot->unpack(this);
-  } else {
-    m_activeApp = nullptr;
   }
   if (m_activeApp) {
     m_activeApp->didBecomeActive(window());
@@ -36,8 +35,8 @@ App * Container::activeApp() {
 }
 
 bool Container::dispatchEvent(Ion::Events::Event event) {
-  if (m_activeApp->processEvent(event)) {
-    windowRedraw();
+  if (event == Ion::Events::TimerTick || m_activeApp->processEvent(event)) {
+    window()->redraw();
     return true;
   }
   return false;
@@ -49,6 +48,3 @@ void Container::run() {
   RunLoop::run();
 }
 
-void Container::windowRedraw() {
-  window()->redraw();
-}
diff --git a/escher/src/run_loop.cpp b/escher/src/run_loop.cpp
index 2231f34ed..6c14ced8f 100644
--- a/escher/src/run_loop.cpp
+++ b/escher/src/run_loop.cpp
@@ -49,7 +49,7 @@ bool RunLoop::step() {
     for (int i=0; i<numberOfTimers(); i++) {
       Timer * timer = timerAtIndex(i);
       if (timer->tick()) {
-        windowRedraw();
+        dispatchEvent(Ion::Events::TimerTick);
       }
     }
   }
diff --git a/ion/include/ion/events.h b/ion/include/ion/events.h
index f652098bf..effbe1abb 100644
--- a/ion/include/ion/events.h
+++ b/ion/include/ion/events.h
@@ -200,6 +200,7 @@ constexpr Event UpperZ = Event::ShiftAlphaKey(Keyboard::Key::H4);
 
 constexpr Event None = Event::Special(0);
 constexpr Event Termination = Event::Special(1);
+constexpr Event TimerTick = Event::Special(2);
 
 }
 }