From f43339ad235e003f9cc0ae47de9fa100a4f73f4b Mon Sep 17 00:00:00 2001
From: wwmayer <wmayer@freecad.org>
Date: Mon, 13 Jan 2025 17:42:40 +0100
Subject: [PATCH] Fix issues in ellipse creation (#18800)

* Sketcher: Handle exceptions in onViewValueChanged

Because the method onViewValueChanged is used as a Qt slot it must handle all possibly raised exceptions as otherwise
they will slip through GUIApplication::notify() that usually results into a crash on some platforms like macOS

* Sketch: Handle undefined values in calculateThroughPointMinorAxisParameters

* The argument of acos() must be in the range [-1, +1], otherwise it returns nan (not a number)
* The value of sin(0) = 0. So, it cannot be used in the denominator of a fraction
---
 src/Mod/Sketcher/Gui/DrawSketchController.h     | 16 ++++++++++++++++
 src/Mod/Sketcher/Gui/DrawSketchHandlerEllipse.h | 15 ++++++++++++---
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/src/Mod/Sketcher/Gui/DrawSketchController.h b/src/Mod/Sketcher/Gui/DrawSketchController.h
index 819e8ebf0e..7f0347953d 100644
--- a/src/Mod/Sketcher/Gui/DrawSketchController.h
+++ b/src/Mod/Sketcher/Gui/DrawSketchController.h
@@ -23,6 +23,7 @@
 #ifndef SKETCHERGUI_DrawSketchController_H
 #define SKETCHERGUI_DrawSketchController_H
 
+#include <Base/Console.h>
 #include <Base/Tools2D.h>
 #include <Gui/EditableDatumLabel.h>
 
@@ -350,6 +351,21 @@ public:
      * It is intended to remote control the DrawSketchDefaultWidgetHandler
      */
     void onViewValueChanged(int onviewparameterindex, double value)
+    {
+        // Since this method is used as a Qt slot we must handle
+        // all exceptions here
+        try {
+            tryViewValueChanged(onviewparameterindex, value);
+        }
+        catch (const Base::Exception& e) {
+            e.ReportException();
+        }
+        catch (const std::exception& e) {
+            Base::Console().Error("C++ exception in onViewValueChanged: %s\n", e.what());
+        }
+    }
+
+    void tryViewValueChanged(int onviewparameterindex, double value)
     {
         int nextindex = onviewparameterindex + 1;
         if (isOnViewParameterOfCurrentMode(nextindex)) {
diff --git a/src/Mod/Sketcher/Gui/DrawSketchHandlerEllipse.h b/src/Mod/Sketcher/Gui/DrawSketchHandlerEllipse.h
index 5c319ba18a..1996013ef9 100644
--- a/src/Mod/Sketcher/Gui/DrawSketchHandlerEllipse.h
+++ b/src/Mod/Sketcher/Gui/DrawSketchHandlerEllipse.h
@@ -325,9 +325,18 @@ private:
         auto lprojx = projx.Length();  // Px = a cos t
         auto lprojy = projy.Length();  // Py = b sin t
 
-        double t = std::acos(lprojx / firstRadius);
-
-        secondRadius = lprojy / std::sin(t);  // b = Py / sin t
+        if (lprojx > firstRadius) {
+            secondRadius = 0.0;
+        }
+        else {
+            double t = std::acos(lprojx / firstRadius);
+            if (t == 0.0) {
+                secondRadius = 0.0;
+            }
+            else {
+                secondRadius = lprojy / std::sin(t);  // b = Py / sin t
+            }
+        }
 
         secondAxis = projy.Normalize() * secondRadius;
     }