[ui] better handling of Reconstruction's current sfm node

* reset sfm node on graph change by using 'sfm' property (ensure previous sfm node is correctly disconnected)
* ui: clear viewers when graph changes

meshroom/ui/qml/Viewer/Viewer2D.qml

@@ -11,6 +11,12 @@ FocusScope {
     property url source
     property var metadata
 
+    function clear()
+    {
+        source = ''
+        metadata = {}
+    }
+
     // slots
     Keys.onPressed: {
         if(event.key == Qt.Key_F) {

meshroom/ui/qml/WorkspaceView.qml

@@ -24,13 +24,13 @@ Item {
     implicitWidth: 300
     implicitHeight: 400
 
-    onMeshFileChanged: viewer3D.clear()
-
     signal requestGraphAutoLayout()
 
     // Load a 3D media file in the 3D viewer
     function load3DMedia(filepath)
     {
+        if(!Filepath.exists(Filepath.urlToString(filepath)))
+            return
         switch(Filepath.extension(filepath))
         {
         case ".abc": viewer3D.abcSource = filepath; break;
@@ -41,13 +41,17 @@ Item {
 
     Connections {
         target: reconstruction
-        onSfmReportChanged: loadSfmAbc()
+        onGraphChanged: {
+            viewer3D.clear()
+            viewer2D.clear()
         }
-
+        onSfmReportChanged: {
-    function loadSfmAbc()
+            viewer3D.abcSource = ''
-    {
+            if(!reconstruction.sfm)
+                return
             load3DMedia(Filepath.stringToUrl(reconstruction.sfm.attribute('output').value))
         }
+    }
 
     SystemPalette { id: palette }
 
@@ -126,7 +130,7 @@ Item {
 
             Label {
                 anchors.centerIn: parent
-                text: "Loading Model..."
+                text: "Loading..."
                 visible: viewer3D.loading
                 padding: 6
                 background: Rectangle { color: palette.base; opacity: 0.5 }

meshroom/ui/reconstruction.py

@@ -175,7 +175,7 @@ class Reconstruction(UIGraph):
     def onGraphChanged(self):
         """ React to the change of the internal graph. """
         self._liveSfmManager.reset()
-        self._sfm = None
+        self.sfm = None
         self._endChunk = None
         self.setMeshFile('')
         self.updateCameraInits()
@@ -404,32 +404,37 @@ class Reconstruction(UIGraph):
             self._views, self._poses = self._sfm.nodeDesc.getViewsAndPoses(self._sfm)
         self.sfmReportChanged.emit()
 
-    def _resetSfm(self):
-        """ Reset sfm-related members. """
-        self._sfm = None
-        self.updateViewsAndPoses()
-
     def getSfm(self):
         """ Returns the current SfM node. """
         return self._sfm
 
-    def setSfm(self, node):
+    def _setSfm(self, node=None):
-        """ Set the current SfM node.
+        """ Set current SfM node to 'node' and update views and poses.
-        This node will be used to retrieve sparse reconstruction result like camera poses.
+        Notes: this should not be called directly, use setSfm instead.
+        See Also: setSfm
         """
-        if self._sfm:
-            self._sfm.chunks[0].statusChanged.disconnect(self.updateViewsAndPoses)
-            self._sfm.destroyed.disconnect(self._resetSfm)
-
         self._sfm = node
         # Update views and poses and do so each time
         # the status of the SfM node's only chunk changes
         self.updateViewsAndPoses()
         if self._sfm:
-            self._sfm.destroyed.connect(self._resetSfm)
+            # when destroyed, directly use '_setSfm' to bypass
+            # disconnection step in 'setSfm' (at this point, 'self._sfm' underlying object
+            # has been destroyed and can't be evaluated anymore)
+            self._sfm.destroyed.connect(self._setSfm)
             self._sfm.chunks[0].statusChanged.connect(self.updateViewsAndPoses)
         self.sfmChanged.emit()
 
+    def setSfm(self, node):
+        """ Set the current SfM node.
+        This node will be used to retrieve sparse reconstruction result like camera poses.
+        """
+        # disconnect from previous SfM node if any
+        if self._sfm:
+            self._sfm.chunks[0].statusChanged.disconnect(self.updateViewsAndPoses)
+            self._sfm.destroyed.disconnect(self._setSfm)
+        self._setSfm(node)
+
     @Slot(QObject, result=bool)
     def isInViews(self, viewpoint):
         # keys are strings (faster lookup)