SafeViewer.py

from PySide import QtGui
import FreeCAD as App

# Define the translation
translate = App.Qt.translate


class SafeViewer(QtGui.QWidget):
    """FreeCAD uses a modified version of QuarterWidget, so the import pivy.quarter one will cause segfaults.
    FreeCAD's FreeCADGui.createViewer() puts the viewer widget inside an MDI window, and detaching it without causing segfaults on exit is tricky.
    This class contains some kludges to extract the viewer as a standalone widget and destroy it safely.
    """

    enabled = App.ParamGet("User parameter:BaseApp/Preferences/Mod/SearchBar").GetBool(
        "PreviewEnabled", False
    )
    instances = []

    def __init__(self, parent=None):
        super(SafeViewer, self).__init__()
        SafeViewer.instances.append(self)
        self.init_parent = parent
        self.instance_enabled = False  # Has this specific instance been enabled?
        if SafeViewer.enabled:
            self.displaying_warning = False
            self.enable()
        else:
            import FreeCADGui
            from PySide import QtCore

            self.displaying_warning = True
            self.lbl_warning = QtGui.QTextEdit()
            self.lbl_warning.setReadOnly(True)
            self.lbl_warning.setAlignment(QtCore.Qt.AlignTop)
            self.lbl_warning.setText(
                translate(
                    "SearchBar",
                    "Warning: the 3D preview has some stability issues. It can cause FreeCAD to crash (usually when quitting the application) and could in theory cause data loss, inside and outside of App.",
                )
            )
            self.btn_enable_for_this_session = QtGui.QPushButton(
                translate("SearchBar", "Enable 3D preview for this session")
            )
            self.btn_enable_for_this_session.clicked.connect(
                self.enable_for_this_session
            )
            self.btn_enable_for_future_sessions = QtGui.QPushButton(
                translate("SearchBar", "Enable 3D preview for future sessions")
            )
            self.btn_enable_for_future_sessions.clicked.connect(
                self.enable_for_future_sessions
            )
            self.setLayout(QtGui.QVBoxLayout())
            self.layout().addWidget(self.lbl_warning)
            self.layout().addWidget(self.btn_enable_for_this_session)
            self.layout().addWidget(self.btn_enable_for_future_sessions)

    def enable_for_this_session(self):
        if not SafeViewer.enabled:
            for instance in SafeViewer.instances:
                instance.enable()

    def enable_for_future_sessions(self):
        if not SafeViewer.enabled:
            # Store in prefs
            App.ParamGet("User parameter:BaseApp/Preferences/Mod/SearchBar").SetBool(
                "PreviewEnabled", True
            )
            # Then enable as usual
            self.enable_for_this_session()

    def enable(self):
        if not self.instance_enabled:
            import FreeCADGui

            # TODO: use a mutex wrapping the entire method, if possible
            SafeViewer.enabled = True
            self.instance_enabled = True  # Has this specific instance been enabled?

            if self.displaying_warning:
                self.layout().removeWidget(self.lbl_warning)
                self.layout().removeWidget(self.btn_enable_for_this_session)
                self.layout().removeWidget(self.btn_enable_for_future_sessions)

            self.viewer = FreeCADGui.createViewer()
            self.graphicsView = self.viewer.graphicsView()
            self.oldGraphicsViewParent = self.graphicsView.parent()
            self.oldGraphicsViewParentParent = self.oldGraphicsViewParent.parent()
            self.oldGraphicsViewParentParentParent = (
                self.oldGraphicsViewParentParent.parent()
            )

            # Avoid segfault but still hide the undesired window by moving it to a new hidden MDI area.
            self.hiddenQMDIArea = QtGui.QMdiArea()
            self.hiddenQMDIArea.addSubWindow(self.oldGraphicsViewParentParentParent)

            self.private_widget = self.oldGraphicsViewParent
            self.private_widget.setParent(self.init_parent)

            self.setLayout(QtGui.QVBoxLayout())
            self.layout().addWidget(self.private_widget)
            self.layout().setContentsMargins(0, 0, 0, 0)

            def fin(slf):
                slf.finalizer()

            import weakref

            weakref.finalize(self, fin, self)

            self.destroyed.connect(self.finalizer)

    def finalizer(self):
        # Cleanup in an order that doesn't cause a segfault:
        if SafeViewer.enabled:
            self.private_widget.setParent(self.oldGraphicsViewParentParent)
            self.oldGraphicsViewParentParentParent.close()
            self.oldGraphicsViewParentParentParent = None
            self.oldGraphicsViewParentParent = None
            self.oldGraphicsViewParent = None
            self.graphicsView = None
            self.viewer = None
            # self.parent = None
            self.init_parent = None
            self.hiddenQMDIArea = None

    def showSceneGraph(self, g):
        import FreeCAD as App

        if SafeViewer.enabled:
            self.viewer.getViewer().setSceneGraph(g)
            self.viewer.setCameraOrientation(App.Rotation(1, 1, 0, 0.2))
            self.viewer.fitAll()


"""
# Example use:
from PySide import QtGui
import pivy
from SafeViewer import SafeViewer
sv = SafeViewer()
def mk(v):
  w = QtGui.QMainWindow()
  oldFocus = QtGui.QApplication.focusWidget()
  sv.widget.setParent(w)
  oldFocus.setFocus()
  w.show()
  col = pivy.coin.SoBaseColor()
  col.rgb = (1, 0, 0)
  trans = pivy.coin.SoTranslation()
  trans.translation.setValue([0, 0, 0])
  cub = pivy.coin.SoCube()
  myCustomNode = pivy.coin.SoSeparator()
  myCustomNode.addChild(col)
  myCustomNode.addChild(trans)
  myCustomNode.addChild(cub)
  sv.viewer.getViewer().setSceneGraph(myCustomNode)
  sv.viewer.fitAll()
  return w
ww=mk(sv)
"""