Eeschema: fix crash when undo called during item edit.

Add EDA_DRAW_FRAME::isBusy() method to test if the current item is being
edited or a block operation is in progress.

Ignore undo and redo commands when editor is busy.

Fixes lp:1718656

https://bugs.launchpad.net/kicad/+bug/1718656

common/draw_frame.cpp

@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2004-2017 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 2008-2015 Wayne Stambaugh <stambaughw@verizon.net>
+ * Copyright (C) 2008 Wayne Stambaugh <stambaughw@gmail.com>
  * Copyright (C) 2004-2017 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
@@ -1370,3 +1370,14 @@ void EDA_DRAW_FRAME::GeneralControlKeyMovement( int aHotKey, wxPoint *aPos,
     }
 }
 
+
+bool EDA_DRAW_FRAME::isBusy() const
+{
+    const BASE_SCREEN* screen = const_cast< BASE_SCREEN* >( GetScreen() );
+
+    if( !screen )
+        return false;
+
+    return ( screen->GetCurItem() && screen->GetCurItem()->GetFlags() )
+           || ( screen->m_BlockLocate.GetState() != STATE_NO_BLOCK );
+}

eeschema/schematic_undo_redo.cpp

@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2004 Jean-Pierre Charras, jaen-pierre.charras@gipsa-lab.inpg.com
- * Copyright (C) 2004-2011 KiCad Developers, see change_log.txt for contributors.
+ * Copyright (C) 2004-2017 KiCad Developers, see change_log.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -338,7 +338,7 @@ void SCH_EDIT_FRAME::PutDataInPreviousState( PICKED_ITEMS_LIST* aList, bool aRed
 
 void SCH_EDIT_FRAME::GetSchematicFromUndoList( wxCommandEvent& event )
 {
-    if( GetScreen()->GetUndoCommandCount() <= 0 )
+    if( GetScreen()->GetUndoCommandCount() <= 0 || isBusy() )
         return;
 
     /* Get the old list */
@@ -361,7 +361,7 @@ void SCH_EDIT_FRAME::GetSchematicFromUndoList( wxCommandEvent& event )
 
 void SCH_EDIT_FRAME::GetSchematicFromRedoList( wxCommandEvent& event )
 {
-    if( GetScreen()->GetRedoCommandCount() == 0 )
+    if( GetScreen()->GetRedoCommandCount() == 0 || isBusy() )
         return;
 
     /* Get the old list */

include/draw_frame.h

@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2009 Jean-Pierre Charras, jaen-pierre.charras@gipsa-lab.inpg.com
- * Copyright (C) 2011-2017 Wayne Stambaugh <stambaughw@gmail.com>
+ * Copyright (C) 2011 Wayne Stambaugh <stambaughw@gmail.com>
  * Copyright (C) 1992-2017 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
@@ -154,11 +154,16 @@ protected:
      * cursor keys (i.e. cursor movement by keyboard) */
     void GeneralControlKeyMovement( int aHotKey, wxPoint *aPos, bool aSnapToGrid );
 
-    /* Function RefreshCrosshair
-     * Move and refresh the crosshair after movement; also call the
-     * mouse capture function, if active.
+    /**
+     * Move and refresh the crosshair after movement and call the mouse capture function.
      */
     void RefreshCrossHair( const wxPoint &aOldPos, const wxPoint &aEvtPos, wxDC* aDC );
+
+    /**
+     * @return true if an item edit or a block operation is in progress.
+     */
+    bool isBusy() const;
+
 public:
     EDA_DRAW_FRAME( KIWAY* aKiway, wxWindow* aParent,
                     FRAME_T aFrameType,