On macOS, force a repaint of CustomPaintWidget upon UpdateRequest

* For some reason the actual paint event never makes it through after converting
  to metal-compatible widgets, but painting in response to UpdateRequest (which
  should become a paint really) works about as well.

qrenderdoc/Widgets/CustomPaintWidget.cpp

@@ -115,3 +115,12 @@ void CustomPaintWidget::paintEvent(QPaintEvent *e)
     }
   }
 }
+
+#if defined(RENDERDOC_PLATFORM_APPLE)
+bool CustomPaintWidget::event(QEvent *e)
+{
+  if(m_Ctx && e->type() == QEvent::UpdateRequest)
+    paintEvent(NULL);
+  return QWidget::event(e);
+}
+#endif

qrenderdoc/Widgets/CustomPaintWidget.h

@@ -72,6 +72,10 @@ private:
 public slots:
 
 protected:
+#if defined(RENDERDOC_PLATFORM_APPLE)
+  bool event(QEvent *event) override;
+#endif
+
   void paintEvent(QPaintEvent *e) override;
   QPaintEngine *paintEngine() const override { return m_Ctx ? NULL : QWidget::paintEngine(); }
   ICaptureContext *m_Ctx;