BUG: Fix rebuild of Endoscopy flythrough when modifying the input curve

This commit addresses an issue introduced during the integration of the pull request
associated with commit 717fd6f (ENH: Add support for managing orientation keyframes
in Endoscopy).

The logic that was inadvertently removed is now reinstated to prevent unintended modification
events triggered by changes to the input curve. The variable "ignoreInputCurveModified"
is reintroduced to manage and prevent a second modification event.

Additionally, this commit addresses typos in comments.

Co-authored-by: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

Modules/Scripted/Endoscopy/Endoscopy.py

@@ -79,6 +79,7 @@ def __init__(self, parent=None):
         self.timer = qt.QTimer()
         self.timer.setInterval(20)
         self.timer.connect("timeout()", self.flyToNext)
+        self.ignoreInputCurveModified = 0
 
         self.cameraNode = None
         self.inputCurve = None
@@ -341,7 +342,11 @@ def enableOrDisableCreateButton(self):
 
     def onInputCurveModified(self, observer, eventid):
         """If the input curve  was changed we need to repopulate the keyframe UI"""
-        pass
+        if not self.ignoreInputCurveModified:
+            if self.logic:
+                # We are going to have rebuild the EndoscopyLogic later
+                self.logic.cleanup()
+                self.logic = None
 
     def onCreatePathButtonClicked(self):
         """Connected to 'Use this curve'` button.  It allows to:
@@ -351,6 +356,7 @@ def onCreatePathButtonClicked(self):
         - go to start of the path
         """
         inputCurve = self.inputCurveSelector.currentNode()
+        self.ignoreInputCurveModified += 1
 
         if self.logic:
             self.logic.cleanup()
@@ -361,7 +367,7 @@ def onCreatePathButtonClicked(self):
         # Update frame slider range
         self.frameSlider.maximum = max(0, numberOfControlPoints - 2)
 
-        # Create a cursor so that the user can see where the fly through is progressing.
+        # Create a cursor so that the user can see where the flythrough is progressing.
         self.createCursor()
 
         # Hide the cursor, model and inputCurve from the main 3D view
@@ -378,6 +384,8 @@ def onCreatePathButtonClicked(self):
         self.flythroughCollapsibleButton.enabled = enable
         self.advancedCollapsibleButton.enabled = enable
 
+        self.ignoreInputCurveModified -= 1
+
         # Initialize to the start of the path
         self.flyTo(0)
 
@@ -542,9 +550,11 @@ def saveCameraOrientations(self, cameraOrientations):
             # Rather than a length-zero or length-two string representing an empty dictionary, clear the string.
             cameraOrientationsString = None
 
+        self.ignoreInputCurveModified += 1
         self.inputCurve.SetAttribute(
             EndoscopyLogic.NODE_PATH_CAMERA_ORIENTATIONS_ATTRIBUTE_NAME, cameraOrientationsString,
         )
+        self.ignoreInputCurveModified -= 1
         if self.logic:
             self.logic.cameraOrientations = cameraOrientations
 
@@ -561,6 +571,9 @@ def cameraOrientationsIsCorrectType(self, convertedCameraOrientations):
         )
 
     def flyToNext(self):
+        if self.logic is None:
+            # We invalidated self.logic due to an intervening user modification of the input.  We need it now.
+            self.logic = EndoscopyLogic(self.inputCurve)
         currentStep = int(self.frameSlider.value)
         nextStep = currentStep + self.skip + 1
         if nextStep > self.logic.resampledCurve.GetNumberOfControlPoints() - 2:
@@ -570,9 +583,12 @@ def flyToNext(self):
     def flyTo(self, resampledCurvePointIndex):
         """Apply the resampledCurvePointIndex-th step in the path to the global camera"""
 
+        if self.logic is None:
+            # We invalidated self.logic due to an intervening user modification of the input.  We need it now.
+            self.logic = EndoscopyLogic(self.inputCurve)
+
         if (
-            self.logic is None
-            or self.logic.resampledCurve is None
+            self.logic.resampledCurve is None
             or not 0 <= resampledCurvePointIndex < self.logic.resampledCurve.GetNumberOfControlPoints()
         ):
             return
@@ -769,7 +785,7 @@ def setControlPoints(self, inputCurve: slicer.vtkMRMLMarkupsCurveNode) -> bool:
 
         # Find a plane that approximately includes the points of the resampled curve,
         # so that we can use its normal to define the "up" direction. This is somewhat
-        # nonsensical if self.numberOfResampledCurveControlPoints < 3, but proceed anyway.
+        # nonsensical if self.resampledCurve.GetNumberOfControlPoints() < 3, but proceed anyway.
         _, self.planeNormal = EndoscopyLogic.planeFit(points.T)
 
         # Interpolate the user-supplied orientations to compute (and assign) an orientation to every control point of