Disconnect from BeforeCommandExecution signal onBeforePopState to avoid double backToPreviousState() calls

In some special cases (several key press enqueued?) we can receive a
BeforeCommandExecution signal when we are not part of the Editor state
stack anymore.

Related to 5ba8cecddebb789bf2266a1600ea4c7f56fc34b7

src/app/ui/editor/drawing_state.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2020  Igara Studio S.A.
+// Copyright (C) 2018-2021  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -103,6 +103,12 @@ void DrawingState::notifyToolLoopModifiersChange(Editor* editor)
     m_toolLoopManager->notifyToolLoopModifiersChange();
 }
 
+void DrawingState::onBeforePopState(Editor* editor)
+{
+  m_beforeCmdConn.disconnect();
+  StandbyState::onBeforePopState(editor);
+}
+
 bool DrawingState::onMouseDown(Editor* editor, MouseMessage* msg)
 {
   // Drawing loop

src/app/ui/editor/drawing_state.h

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2019-2020  Igara Studio S.A.
+// Copyright (C) 2019-2021  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -29,6 +29,7 @@ namespace app {
                  tools::ToolLoop* loop,
                  const DrawingType type);
     virtual ~DrawingState();
+    virtual void onBeforePopState(Editor* editor) override;
     virtual bool onMouseDown(Editor* editor, ui::MouseMessage* msg) override;
     virtual bool onMouseUp(Editor* editor, ui::MouseMessage* msg) override;
     virtual bool onMouseMove(Editor* editor, ui::MouseMessage* msg) override;

src/app/ui/editor/moving_cel_state.cpp

@@ -112,13 +112,13 @@ MovingCelState::MovingCelState(Editor* editor,
       else
         m_celStarts.push_back(cel->bounds());
     }
-
-    // Hook BeforeCommandExecution signal so we know if the user wants
-    // to execute other command, so we can drop pixels.
-    m_ctxConn = UIContext::instance()->BeforeCommandExecution.connect(
-                  &MovingCelState::onBeforeCommandExecution, this);
   }
 
+  // Hook BeforeCommandExecution signal so we know if the user wants
+  // to execute other command, so we can drop pixels.
+  m_ctxConn = UIContext::instance()->BeforeCommandExecution.connect(
+    &MovingCelState::onBeforeCommandExecution, this);
+
   m_cursorStart = editor->screenToEditorF(msg->position());
   editor->captureMouse();
 
@@ -130,14 +130,10 @@ MovingCelState::MovingCelState(Editor* editor,
   }
 }
 
-MovingCelState::~MovingCelState()
-{
-  m_ctxConn.disconnect();
-}
-
 void MovingCelState::onBeforePopState(Editor* editor)
 {
   m_ctxConn.disconnect();
+  StandbyState::onBeforePopState(editor);
 }
 
 bool MovingCelState::onMouseUp(Editor* editor, MouseMessage* msg)

src/app/ui/editor/moving_cel_state.h

@@ -44,7 +44,6 @@ namespace app {
                    ui::MouseMessage* msg,
                    const HandleType handle,
                    const MovingCelCollect& collect);
-    ~MovingCelState();
 
     virtual void onBeforePopState(Editor* editor) override;
     virtual bool onMouseUp(Editor* editor, ui::MouseMessage* msg) override;
@@ -74,7 +73,7 @@ namespace app {
     HandleType m_handle;
     Editor* m_editor;
 
-    obs::connection m_ctxConn;
+    obs::scoped_connection m_ctxConn;
   };
 
 } // namespace app

src/app/ui/editor/play_state.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2020  Igara Studio S.A.
+// Copyright (C) 2020-2021  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -109,6 +109,12 @@ EditorState::LeaveAction PlayState::onLeaveState(Editor* editor, EditorState* ne
   return KeepState;
 }
 
+void PlayState::onBeforePopState(Editor* editor)
+{
+  m_ctxConn.disconnect();
+  StateWithWheelBehavior::onBeforePopState(editor);
+}
+
 bool PlayState::onMouseDown(Editor* editor, MouseMessage* msg)
 {
   if (editor->hasCapture())

src/app/ui/editor/play_state.h

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2020  Igara Studio S.A.
+// Copyright (C) 2020-2021  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -32,6 +32,7 @@ namespace app {
 
     void onEnterState(Editor* editor) override;
     LeaveAction onLeaveState(Editor* editor, EditorState* newState) override;
+    void onBeforePopState(Editor* editor) override;
     bool onMouseDown(Editor* editor, ui::MouseMessage* msg) override;
     bool onMouseUp(Editor* editor, ui::MouseMessage* msg) override;
     bool onMouseMove(Editor* editor, ui::MouseMessage* msg) override;

src/observable

@@ -1 +1 @@
-Subproject commit af94c4a2317839ce629eb26ce47b80e810cbdaec
+Subproject commit bddbeed8b94d2639fa945bdf14a90d7afbd58506