Partial workaround for stale styling information with GTK3

We can trigger size events when we know the style cache has been updated.
See #16088

include/wx/gtk/window.h

@@ -443,6 +443,8 @@ protected:
 #ifdef __WXGTK3__
     static GdkWindow* GTKFindWindow(GtkWidget* widget);
     static void GTKFindWindow(GtkWidget* widget, wxArrayGdkWindows& windows);
+
+    bool m_needSizeEvent;
 #endif
 
 private:

src/gtk/toplevel.cpp

@@ -1020,9 +1020,7 @@ bool wxTopLevelWindowGTK::Show( bool show )
         // size_allocate signals occur in reverse order (bottom to top).
         // Things work better if the initial wxSizeEvents are sent (from the
         // top down), before the initial size_allocate signals occur.
-        wxSizeEvent event(GetSize(), GetId());
+        SendSizeEvent();
-        event.SetEventObject(this);
-        HandleWindowEvent(event);
 
 #ifdef __WXGTK3__
         GTKSizeRevalidate();
@@ -1031,6 +1029,14 @@ bool wxTopLevelWindowGTK::Show( bool show )
 
     bool change = base_type::Show(show);
 
+#ifdef __WXGTK3__
+    if (m_needSizeEvent)
+    {
+        m_needSizeEvent = false;
+        SendSizeEvent();
+    }
+#endif
+
     if (change && !show)
     {
         // make sure window has a non-default position, so when it is shown
@@ -1325,15 +1331,20 @@ void wxTopLevelWindowGTK::GTKUpdateDecorSize(const DecorSize& decorSize)
         // gtk_widget_show() was deferred, do it now
         m_deferShow = false;
         DoGetClientSize(&m_clientWidth, &m_clientHeight);
-        wxSizeEvent sizeEvent(GetSize(), GetId());
+        SendSizeEvent();
-        sizeEvent.SetEventObject(this);
-        HandleWindowEvent(sizeEvent);
 
 #ifdef __WXGTK3__
         GTKSizeRevalidate();
 #endif
         gtk_widget_show(m_widget);
 
+#ifdef __WXGTK3__
+        if (m_needSizeEvent)
+        {
+            m_needSizeEvent = false;
+            SendSizeEvent();
+        }
+#endif
         wxShowEvent showEvent(GetId(), true);
         showEvent.SetEventObject(this);
         HandleWindowEvent(showEvent);

src/gtk/window.cpp

@@ -2472,6 +2472,7 @@ void wxWindowGTK::Init()
 #ifdef __WXGTK3__
     m_paintContext = NULL;
     m_styleProvider = NULL;
+    m_needSizeEvent = false;
 #endif
 
     m_isScrolling = false;
@@ -3059,8 +3060,15 @@ void wxWindowGTK::DoSetSize( int x, int y, int width, int height, int sizeFlags
         DoMoveWindow(x, y, width, height);
     }
 
-    if ((sizeChange && !m_nativeSizeEvent) || (sizeFlags & wxSIZE_FORCE_EVENT))
+    if (((sizeChange
+#ifdef __WXGTK3__
+                     || m_needSizeEvent
+#endif
+                                       ) && !m_nativeSizeEvent) || (sizeFlags & wxSIZE_FORCE_EVENT))
     {
+#ifdef __WXGTK3__
+        m_needSizeEvent = false;
+#endif
         // update these variables to keep size_allocate handler
         // from sending another size event for this change
         DoGetClientSize(&m_clientWidth, &m_clientHeight);
@@ -4865,6 +4873,15 @@ void wxWindowGTK::GTKSizeRevalidate()
         {
             win->InvalidateBestSize();
             gs_sizeRevalidateList = g_list_delete_link(gs_sizeRevalidateList, p);
+            for (;;)
+            {
+                win = win->m_parent;
+                if (win == NULL || win->m_needSizeEvent)
+                    break;
+                win->m_needSizeEvent = true;
+                if (win->IsTopLevel())
+                    break;
+            }
         }
     }
 }