Add a unit test checking that Move() doesn't change frame size

This used to be broken in wxQt until it was fixed by the previous
commit.

See https://github.com/swig/swig/pull/1613

tests/window/setsize.cpp

@@ -18,10 +18,12 @@
 
 #ifndef WX_PRECOMP
     #include "wx/app.h"
+    #include "wx/frame.h"
     #include "wx/window.h"
 #endif // WX_PRECOMP
 
 #include "wx/scopedptr.h"
+#include "wx/stopwatch.h"
 
 #include "asserthelper.h"
 
@@ -45,6 +47,29 @@ protected:
     virtual wxSize DoGetBestSize() const wxOVERRIDE { return wxSize(50, 250); }
 };
 
+// Class used to check if we received the (first) paint event.
+class WaitForPaint
+{
+public:
+    // Note that we have to use a pointer here, i.e. we can't just store the
+    // flag inside the class itself because it's going to be cloned inside wx
+    // and querying the flag of the original copy is not going to work.
+    explicit WaitForPaint(bool* painted)
+        : m_painted(*painted)
+    {
+        m_painted = false;
+    }
+
+    void operator()(wxPaintEvent& event)
+    {
+        event.Skip();
+        m_painted = true;
+    }
+
+private:
+    bool& m_painted;
+};
+
 } // anonymous namespace
 
 // ----------------------------------------------------------------------------
@@ -84,3 +109,38 @@ TEST_CASE("wxWindow::GetBestSize", "[window][size][best-size]")
     w->SetMaxSize(wxSize(200, 200));
     CHECK( wxSize(100, 200) == w->GetBestSize() );
 }
+
+TEST_CASE("wxWindow::MovePreservesSize", "[window][size][move]")
+{
+    wxScopedPtr<wxWindow>
+        w(new wxFrame(wxTheApp->GetTopWindow(), wxID_ANY, "Test child frame"));
+
+    // Unfortunately showing the window is asynchronous, at least when using
+    // X11, so we have to wait for some time before retrieving its true
+    // geometry. And it's not clear how long should we wait, so we do it until
+    // we get the first paint event -- by then the window really should have
+    // its final size.
+    bool painted;
+    WaitForPaint waitForPaint(&painted);
+    w->Bind(wxEVT_PAINT, waitForPaint);
+
+    w->Show();
+
+    wxStopWatch sw;
+    while ( !painted )
+    {
+        wxYield();
+
+        if ( sw.Time() > 250 )
+        {
+            WARN("Didn't get a paint event until timeout expiration");
+            break;
+        }
+    }
+
+    const wxRect rectOrig = w->GetRect();
+
+    // Check that moving the window doesn't change its size.
+    w->Move(rectOrig.GetPosition() + wxPoint(100, 100));
+    CHECK( w->GetSize() == rectOrig.GetSize() );
+}