Fix best size for windows which are hidden when TLW is shown with GTK3

GTK3's style cache is not updated for hidden windows until after they are shown
See #16088

include/wx/gtk/window.h

@@ -493,6 +493,7 @@ public:
         return m_paintContext;
     }
     void GTKSizeRevalidate();
+    void GTKSendSizeEventIfNeeded();
 #endif
 
     wxDECLARE_DYNAMIC_CLASS(wxWindowGTK);

src/gtk/toplevel.cpp

@@ -1171,11 +1171,7 @@ bool wxTopLevelWindowGTK::Show( bool show )
         GTKUpdateClientSizeIfNecessary();
     }
 
-    if (m_needSizeEvent)
+    GTKSendSizeEventIfNeeded();
-    {
-        m_needSizeEvent = false;
-        SendSizeEvent();
-    }
 #endif
 
     if (change && !show)
@@ -1514,13 +1510,8 @@ void wxTopLevelWindowGTK::GTKUpdateDecorSize(const DecorSize& decorSize)
         gtk_widget_show(m_widget);
 
 #ifdef __WXGTK3__
-        if (m_needSizeEvent)
+        GTKSendSizeEventIfNeeded();
-        {
-            m_needSizeEvent = false;
-            SendSizeEvent();
-        }
 #endif
-
         GTKDoAfterShow();
     }
 #endif // GDK_WINDOWING_X11

src/gtk/window.cpp

@@ -2335,6 +2335,11 @@ static void frame_clock_layout(GdkFrameClock*, wxWindow* win)
 {
     win->GTKSizeRevalidate();
 }
+
+static void frame_clock_layout_after(GdkFrameClock*, wxWindowGTK* win)
+{
+    win->GTKSendSizeEventIfNeeded();
+}
 #endif // GTK_CHECK_VERSION(3,8,0)
 
 } // extern "C"
@@ -2395,6 +2400,7 @@ void wxWindowGTK::GTKHandleRealized()
             !g_signal_handler_find(clock, G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, this))
         {
             g_signal_connect(clock, "layout", G_CALLBACK(frame_clock_layout), this);
+            g_signal_connect_after(clock, "layout", G_CALLBACK(frame_clock_layout_after), this);
         }
     }
 #endif
@@ -5862,20 +5868,30 @@ void wxWindowGTK::GTKSizeRevalidate()
     {
         next = p->next;
         wxWindow* win = static_cast<wxWindow*>(p->data);
-        if (wxGetTopLevelParent(win) == this)
+        wxWindow* w = win;
+        while (w && w->IsShown() && !w->IsTopLevel())
+            w = w->GetParent();
+        if (w == this)
         {
             win->InvalidateBestSize();
             gs_sizeRevalidateList = g_list_delete_link(gs_sizeRevalidateList, p);
-            for (;;)
+            do
             {
                 win = win->m_parent;
-                if (win == NULL || win->m_needSizeEvent)
+                if (win->m_needSizeEvent)
                     break;
                 win->m_needSizeEvent = true;
-                if (win->IsTopLevel())
+            } while (win != this);
-                    break;
         }
     }
+}
+
+void wxWindowGTK::GTKSendSizeEventIfNeeded()
+{
+    if (m_needSizeEvent)
+    {
+        m_needSizeEvent = false;
+        SendSizeEvent();
     }
 }