MyFrameMain: work around MacOS side pane layout quirk on resize

When resizing, the listboxes inside the side pane would be offset to
the upper left, this rather ugly workaround prevents this.

Related to 501c795

Try to revert this once a newer wxWidgets version might have fixed this.

Author: bk138

src/gui/MyFrameMain.cpp

@@ -56,6 +56,7 @@ BEGIN_EVENT_TABLE(MyFrameMain, FrameMain)
   EVT_END_PROCESS (ID_WINDOWSHARE_PROC_END, MyFrameMain::onWindowshareTerminate)
   EVT_FULLSCREEN (MyFrameMain::onFullScreenChanged)
   EVT_SYS_COLOUR_CHANGED(MyFrameMain::onSysColourChanged)
+  EVT_SIZE(MyFrameMain::onSize)
 END_EVENT_TABLE()
 
 
@@ -791,6 +792,29 @@ void MyFrameMain::onSysColourChanged(wxSysColourChangedEvent& event)
 
 
 
+void MyFrameMain::onSize(wxSizeEvent& event)
+{
+#ifdef __WXMAC__
+    // Force proper layout calculation by temporarily adjusting sash positions
+    // This mimics what happens when user manually moves the sash
+    CallAfter([this]() {
+        if (splitwin_main->IsSplit() && splitwin_left->IsSplit()) {
+            // Store current sash position
+            int current_sash = splitwin_left->GetSashPosition();
+
+            // Force layout recalculation by temporarily moving the sash
+            splitwin_left->SetSashPosition(current_sash + 1);
+            splitwin_left->SetSashPosition(current_sash);
+
+            // Ensure proper layout
+            splitwin_left->Layout();
+        }
+    });
+#endif
+    event.Skip(); // Allow the event to propagate
+}
+
+
 void MyFrameMain::onVNCConnGetPasswordNotify(wxCommandEvent &event)
 {
     // get sender

src/gui/MyFrameMain.h

@@ -107,6 +107,7 @@ class MyFrameMain: public FrameMain
   void onSDNotify(wxCommandEvent& event);
   void onFullScreenChanged(wxFullScreenEvent &event);
   void onSysColourChanged(wxSysColourChangedEvent& event);
+  void onSize(wxSizeEvent& event);
 
   bool saveStats(VNCConn* c, int conn_index, const wxArrayString& stats, wxString desc, bool autosave);