Attempt to fix the Mac DPI grid mixing

When moving windows between monitors on Mac that changes the DPI, we
observe incorrect re-sizing of columns and rows.  This attempts to
rectify the situation by avoiding DPI changes for Mac builds.

Fixes https://gitlab.com/kicad/code/kicad/issues/10586

common/widgets/wx_grid.cpp

@@ -40,6 +40,11 @@ WX_GRID::WX_GRID( wxWindow *parent, wxWindowID id, const wxPoint& pos, const wxS
 
     // Make sure the GUI font scales properly on GTK
     SetDefaultCellFont( KIUI::GetControlFont( this ) );
+
+#if wxCHECK_VERSION( 3, 1, 0 )
+    Connect( wxEVT_DPI_CHANGED, wxDPIChangedEventHandler( WX_GRID::onDPIChanged ), nullptr, this );
+#endif
+
 }
 
 
@@ -47,9 +52,25 @@ WX_GRID::~WX_GRID()
 {
     if( m_weOwnTable )
         DestroyTable( GetTable() );
+
+#if wxCHECK_VERSION( 3, 1, 0 )
+    Disconnect( wxEVT_DPI_CHANGED, wxDPIChangedEventHandler( WX_GRID::onDPIChanged ), nullptr, this );
+#endif
+
 }
 
 
+#if wxCHECK_VERSION( 3, 1, 0 )
+void WX_GRID::onDPIChanged(wxDPIChangedEvent& aEvt)
+{
+    /// This terrible hack is a way to avoid the incredibly disruptive resizing of grids that happens on Macs
+    /// when moving a window between monitors of different DPIs.
+#ifndef __WXMAC__
+    aEvt.Skip();
+#endif
+}
+#endif
+
 void WX_GRID::SetColLabelSize( int aHeight )
 {
     if( aHeight == 0 )

include/widgets/wx_grid.h

@@ -24,7 +24,10 @@
 #ifndef KICAD_WX_GRID_H
 #define KICAD_WX_GRID_H
 
+#include <wx/event.h>
 #include <wx/grid.h>
+#include <wx/version.h>
+
 
 class WX_GRID : public wxGrid
 {
@@ -119,6 +122,10 @@ protected:
     void onGridColMove( wxGridEvent& aEvent );
     void onGridCellSelect( wxGridEvent& aEvent );
 
+#if wxCHECK_VERSION( 3, 1, 0 )
+    void onDPIChanged(wxDPIChangedEvent& event);
+#endif
+
     bool m_weOwnTable;
 };