diff --git a/lib/Slic3r/GUI/3DScene.pm b/lib/Slic3r/GUI/3DScene.pm
index fecfc014f..f63a82146 100644
--- a/lib/Slic3r/GUI/3DScene.pm
+++ b/lib/Slic3r/GUI/3DScene.pm
@@ -304,7 +304,7 @@ sub mouse_event {
         $self->_dragged(undef);
     } elsif ($e->Moving) {
         $self->_mouse_pos($pos);
-        $self->Refresh;
+        $self->Refresh if $self->enable_picking;
     } else {
         $e->Skip();
     }
@@ -976,6 +976,9 @@ sub Render {
     glFlush();
  
     $self->SwapBuffers();
+    
+    # Calling glFinish has a performance penalty, but it seems to fix some OpenGL driver hang-up with extremely large scenes.
+    glFinish();
 }
 
 sub draw_axes {
diff --git a/xs/src/libslic3r/Fill/FillRectilinear.cpp b/xs/src/libslic3r/Fill/FillRectilinear.cpp
index 9af184295..69991db74 100644
--- a/xs/src/libslic3r/Fill/FillRectilinear.cpp
+++ b/xs/src/libslic3r/Fill/FillRectilinear.cpp
@@ -41,7 +41,7 @@ FillRectilinear::_fill_single_direction(ExPolygon expolygon,
         // extend bounding box so that our pattern will be aligned with other layers
         // Transform the reference point to the rotated coordinate system.
         Point p = direction.second.rotated(-direction.first);
-        p.x -= x_shift > 0 ? x_shift : (x_shift + line_spacing);
+        p.x -= x_shift >= 0 ? x_shift : (x_shift + line_spacing);
         bounding_box.min.align_to_grid(
             Point(line_spacing, line_spacing), 
             p
diff --git a/xs/src/libslic3r/libslic3r.h b/xs/src/libslic3r/libslic3r.h
index 561d0b03f..6789d58ff 100644
--- a/xs/src/libslic3r/libslic3r.h
+++ b/xs/src/libslic3r/libslic3r.h
@@ -94,7 +94,7 @@ parallelize(std::queue<T> queue, boost::function<void(T)> func,
     if (threads_count == 0) threads_count = 2;
     boost::mutex queue_mutex;
     boost::thread_group workers;
-    for (int i = 0; i < fminf(threads_count, queue.size()); i++)
+    for (int i = 0; i < std::min(threads_count, (int)queue.size()); i++)
         workers.add_thread(new boost::thread(&_parallelize_do<T>, &queue, &queue_mutex, func));
     workers.join_all();
 }