Merge branch 'primary-display'

Handle the situation when primary display is not the first one.

See https://github.com/wxWidgets/wxWidgets/pull/1641

include/wx/display.h

@@ -42,12 +42,14 @@ class WXDLLIMPEXP_FWD_CORE wxDisplayImpl;
 class WXDLLIMPEXP_CORE wxDisplay
 {
 public:
+    // default ctor creates the object corresponding to the primary display
+    wxDisplay();
+
     // initialize the object containing all information about the given
     // display
     //
-    // the displays are numbered from 0 to GetCount() - 1, 0 is always the
-    // primary display and the only one which is always supported
-    wxDisplay(unsigned n = 0);
+    // the displays are numbered from 0 to GetCount() - 1
+    explicit wxDisplay(unsigned n);
 
     // create display object corresponding to the display of the given window
     // or the default one if the window display couldn't be found

include/wx/private/display.h

@@ -37,6 +37,9 @@ public:
         return m_impls[n];
     }
 
+    // Return the primary display object, creating it if necessary.
+    wxDisplayImpl* GetPrimaryDisplay();
+
     // get the total number of displays
     virtual unsigned GetCount() = 0;