prevent application crash if active_window fails

not sure if this works

#61

src/run/display/x11.cr

@@ -160,7 +160,10 @@ module Run
  {% if ! flag?(:release) %}
  puts "[debug] x11: root_win = #{@root_win}"
  {% end %}
- @_NET_ACTIVE_WINDOW = @display.intern_atom("_NET_ACTIVE_WINDOW", false)
+ @_NET_ACTIVE_WINDOW = @display.intern_atom("_NET_ACTIVE_WINDOW", true)
+ {% if ! flag?(:release) %}
+ puts "[debug] x11: _NET_ACTIVE_WINDOW = #{@_NET_ACTIVE_WINDOW}"
+ {% end %}
  root_win_attributes = ::X11::SetWindowAttributes.new
  root_win_attributes.event_mask = ::X11::PropertyChangeMask
  # So we get notified of active window change
@@ -182,8 +185,18 @@ module Run
  end
 
  private def active_window
- # TODO: manybe use @x_do.active_window if it's similarly fast?
- win = @display.window_property(@root_win, @_NET_ACTIVE_WINDOW, 0_i64, 1_i64, false, ::X11::C::XA_WINDOW.to_u64)[:prop].unsafe_as(Pointer(UInt64)).value
+ # TODO: manybe use @x_do.active_window if it's similarly fast? (evdev branch)
+ return 0_u64 if @_NET_ACTIVE_WINDOW < 1
+ prop = @display.window_property(@root_win, @_NET_ACTIVE_WINDOW, 0_i64, 1_i64, false, ::X11::C::XA_WINDOW.to_u64)
+ nitems = prop[:nitems]
+ data = prop[:prop].unsafe_as(Pointer(UInt64))
+ if data.null? || nitems.nil? || nitems < 1
+ {% if ! flag?(:release) %}
+ puts "[debug] x11: active window detection: _NET_ACTIVE_WINDOW returned NULL prop data"
+ {% end %}
+ return 0_u64
+ end
+ win = data.value
  {% if ! flag?(:release) %}
  puts "[debug] x11: active window detection: #{win}"
  {% end %}