message: Align sidebar's separator with editing area visually
  Tweak placement of the horizontal separator between upper and lower
  sidebar areas to match the editing area's borders perfectly. Fix HiDPI
  width. Use lighter color, from editing area, to match it.
diff: #include <algorithm>
  -#define GRAY_LINES_COLOR wxColour(220,220,220)
  -#define GRAY_LINES_COLOR_DARK wxColour(180,180,180)
  -
  class SidebarSeparator : public wxWindow
  {
  @@ -61,14 +58,14 @@ public:
  SidebarSeparator(wxWindow *parent)
  : wxWindow(parent, wxID_ANY),
  m_sides(ColorScheme::Get(Color::SidebarBackground)),
  - m_center(GRAY_LINES_COLOR_DARK)
  + m_center(ColorScheme::Get(Color::EditingSubtleSeparator))
  {
  Bind(wxEVT_PAINT, &SidebarSeparator::OnPaint, this);
  }
  wxSize DoGetBestSize() const override
  {
  - return wxSize(-1, 1);
  + return wxSize(-1, PX(1));
  }
  bool AcceptsFocus() const override { return false; }
  @@ -78,8 +75,8 @@ private:
  {
  wxPaintDC dc(this);
  auto w = dc.GetSize().x;
  - dc.GradientFillLinear(wxRect(0,0,PX(15),PX(1)), m_sides, m_center);
  - dc.GradientFillLinear(wxRect(PX(15),0,w,PX(1)), m_center, m_sides);
  + dc.GradientFillLinear(wxRect(0,0,PX(20),PX(1)), m_sides, m_center);
  + dc.GradientFillLinear(wxRect(PX(20),0,w,PX(1)), m_center, m_sides);
  }
  wxColour m_sides, m_center;
  @@ -842,11 +839,8 @@ void Sidebar::SetUpperHeight(int size)
  wxWindowUpdateLocker lock(this);
  int pos = GetSize().y - size;
  -#ifdef __WXOSX__
  - pos += 4;
  -#else
  - pos += 6;
  -#endif
  + pos += PX(5);
  +
  m_bottomBlocksSizer->SetMinSize(wxSize(-1, pos));
  Layout();
  }
  