Fix crash using "play once" (fix #1337)

src/app/ui/editor/editor.cpp

@@ -260,6 +260,17 @@ void Editor::setStateInternal(const EditorStatePtr& newState)
   else {
     m_state->onBeforePopState(this);
 
+    // Save the current state into "m_deletedStates" just to keep a
+    // reference to it to avoid delete it right now. We'll delete it
+    // in the next Editor::onProcessMessage().
+    //
+    // This is necessary for PlayState because it removes itself
+    // calling Editor::stop() from PlayState::onPlaybackTick(). If we
+    // delete the PlayState inside the "Tick" timer signal, the
+    // program will crash (because we're iterating the
+    // PlayState::m_playTimer slots).
+    m_deletedStates.push(m_state);
+
     m_statesHistory.pop();
     m_state = m_statesHistory.top();
   }
@@ -1209,6 +1220,10 @@ app::Color Editor::getColorByPosition(const gfx::Point& mousePos)
 
 bool Editor::onProcessMessage(Message* msg)
 {
+  // Delete states
+  if (!m_deletedStates.empty())
+    m_deletedStates.clear();
+
   switch (msg->type()) {
 
     case kTimerMessage:
@@ -1717,6 +1732,7 @@ void Editor::showAnimationSpeedMultiplierPopup(Option<bool>& playOnce,
   menu.showPopup(ui::get_mouse_position());
 
   if (isPlaying()) {
+    // Re-play
     stop();
     play(playOnce(),
          playAll());

src/app/ui/editor/editor.h

@@ -268,6 +268,7 @@ namespace app {
 
     // Stack of states. The top element in the stack is the current state (m_state).
     EditorStatesHistory m_statesHistory;
+    EditorStatesHistory m_deletedStates;
 
     // Current editor state (it can be shared between several editors to
     // the same document). This member cannot be NULL.

src/app/ui/editor/editor_states_history.h

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2001-2015  David Capello
+// Copyright (C) 2001-2016  David Capello
 //
 // This program is distributed under the terms of
 // the End-User License Agreement for Aseprite.
@@ -21,6 +21,8 @@ namespace app {
     EditorStatesHistory();
     ~EditorStatesHistory();
 
+    bool empty() const { return m_states.empty(); }
+
     // Gets the current state.
     EditorStatePtr top();