Add minimal DPI change handler to wxGrid

This handler redoes wxGrid layout and refreshes it to at least avoid
ugly display artifacts when moving wxGrid window between displays with
different DPI.

src/generic/grid.cpp

@@ -2317,6 +2317,7 @@ void wxGridWindow::OnFocus(wxFocusEvent& event)
 
 wxBEGIN_EVENT_TABLE( wxGrid, wxScrolledCanvas )
     EVT_SIZE( wxGrid::OnSize )
+    EVT_DPI_CHANGED( wxGrid::OnDPIChanged )
     EVT_KEY_DOWN( wxGrid::OnKeyDown )
     EVT_KEY_UP( wxGrid::OnKeyUp )
     EVT_CHAR ( wxGrid::OnChar )
@@ -2457,8 +2458,11 @@ void wxGrid::Create()
     m_labelBackgroundColour = m_rowLabelWin->GetBackgroundColour();
     m_labelTextColour = m_rowLabelWin->GetForegroundColour();
 
-    // now that we have the grid window, use its font to compute the default
-    // row height
+    InitPixelFields();
+}
+
+void wxGrid::InitPixelFields()
+{
     m_defaultRowHeight = m_gridWin->GetCharHeight();
 #if defined(__WXMOTIF__) || defined(__WXGTK__) || defined(__WXQT__)  // see also text ctrl sizing in ShowCellEditControl()
     m_defaultRowHeight += 8;
@@ -5346,6 +5350,19 @@ void wxGrid::OnSize(wxSizeEvent& WXUNUSED(event))
     }
 }
 
+void wxGrid::OnDPIChanged(wxDPIChangedEvent& event)
+{
+    InitPixelFields();
+
+    InvalidateBestSize();
+
+    CalcWindowSizes();
+
+    Refresh();
+
+    event.Skip();
+}
+
 void wxGrid::OnKeyDown( wxKeyEvent& event )
 {
     if ( m_inOnKeyDown )