fix: use PlotItem.sceneBoundingRect() for mouse tracking in gui_common.py

Also fix deferred export_png connection in ff_asym_qt.py and nf_qt.py
to avoid referencing self.image_view before construction.

Author: marinerhemant

gui/gui_common.py

@@ -160,8 +160,9 @@ def _apply_log(self, data):
 
     def _on_mouse_moved(self, evt):
         pos = evt[0]
-        if self.sceneBoundingRect().contains(pos):
-            mouse_point = self.getView().mapSceneToView(pos)
+        vb = self.getView()
+        if vb.sceneBoundingRect().contains(pos):
+            mouse_point = vb.mapSceneToView(pos)
             x, y = mouse_point.x(), mouse_point.y()
             self._vline.setPos(x)
             self._hline.setPos(y)

gui/nf_qt.py

@@ -306,7 +306,7 @@ def _build_toolbar(self):
         tb.addWidget(self.log_check)
 
         export_btn = QtWidgets.QPushButton("Export PNG")
-        export_btn.clicked.connect(self.image_view.export_png)
+        export_btn.clicked.connect(lambda: self.image_view.export_png())
         tb.addWidget(export_btn)
 
         log_btn = QtWidgets.QPushButton("Log Panel")