Fixed a potential segfault cause by recursive call of paintEvent

This may happen when painting triggers some action that itself
triggers progress reporter (which paints itself).

The solution consists of blocking process_events during painting.

src/lay/lay/layApplication.cc

@@ -1479,6 +1479,19 @@ GuiApplication::initialize ()
 
 bool
 GuiApplication::notify (QObject *receiver, QEvent *e)
+{
+  if (dynamic_cast<QPaintEvent *> (e)) {
+    //  NOTE: we don't want recursive paint events - the painters are not reentrant.
+    //  Hence we disable process_events_impl (specifically for progress reporters).
+    lay::BusySection busy;
+    return do_notify (receiver, e);
+  } else {
+    return do_notify (receiver, e);
+  }
+}
+
+bool
+GuiApplication::do_notify (QObject *receiver, QEvent *e)
 {
   bool in_notify = (m_in_notify > 0);
 

src/lay/lay/layApplication.h

@@ -480,6 +480,8 @@ private:
   MainWindow *mp_mw;
   gtf::Recorder *mp_recorder;
   int m_in_notify;
+
+  bool do_notify (QObject *receiver, QEvent *e);
 };
 
 /**

src/lay/lay/layProgress.cc

@@ -28,6 +28,7 @@
 #include "layProgress.h"
 #include "layMainWindow.h"
 #include "layProgressWidget.h"
+#include "layApplication.h"
 #include "tlProgress.h"
 #include "tlDeferredExecution.h"
 
@@ -211,11 +212,8 @@ ProgressReporter::update_and_yield ()
 void
 ProgressReporter::process_events ()
 {
-  //  Don't execute deferred methods during progress handling (undesired side effects)
-  tl::NoDeferredMethods silent;
-
-  if (m_pw_visible && lay::MainWindow::instance () && QApplication::instance ()) {
-    QApplication::instance ()->processEvents (QEventLoop::AllEvents);
+  if (m_pw_visible && lay::MainWindow::instance () && lay::ApplicationBase::instance ()) {
+    lay::ApplicationBase::instance ()->process_events (QEventLoop::AllEvents, true /* no deferred methods */);
   }
 }