[215_7] fix ellipse array bounds issue (#2944)

devel/215_7.md

@@ -0,0 +1,17 @@
+# 215_7 Fix array out of bounds issue in graphics mode (#2944)
+
+## How to test
+1. Insert a graphics block in Mogan (Insert -> Image -> Draw graphic).
+2. Select the ellipse tool in the toolbar and draw an ellipse on the canvas (click twice to set the foci, and a third time to set a point on the boundary).
+3. Switch to the selection tool and try to click directly on the ellipse or select it using a rectangular selection (box select).
+4. Observe and confirm that the client no longer hangs in an infinite loop or crashes as it did before.
+
+## 2026/03/06 Fix out of bounds caused by `get_control_points`
+### What
+Fixed a program crash issue when selecting or box-selecting an ellipse.
+
+### Why
+In the original `ellipse_rep::get_control_points`, the function informed the caller that it had 3 control points (`np=3`, two foci and one boundary point). However, the `abs` array, which represents the parameter range for each point on the curve, was hardcoded to initialize with only two elements (`array<double> (0.0, 1.0)`). This caused an out-of-bounds access on `abs[2]` during the edge-snapping retrieval or distance calculation in the `curve_box_rep::graphical_select` function (which iterates from 0 to `np` seeking `abs[i]` and `abs[(i+1)%np]`), leading to undefined behavior and infinite loops.
+
+### How
+Modified the initialization of `abs` in `ellipse_rep::get_control_points` within `src/Graphics/Types/curve.cpp`. Explicitly expanded the `abs` array to contain 3 elements: `abs << 0.0 << 0.5 << 1.0;`, aligning it with the number of control points returned and preventing out-of-bounds access in exterior loops.

src/Graphics/Types/curve.cpp

@@ -1074,7 +1074,8 @@ ellipse_rep::get_control_points (array<double>& abs, array<point>& pts,
   // range of parameter values. Since we have a closed curve here, we just need
   // to ensure that the starting point has a parameter value of 0 and the ending
   // point has a parameter value of 1.
-  abs = array<double> (0.0, 1.0);
+  abs= array<double> ();
+  abs << 0.0 << 0.5 << 1.0;
   pts = points;
   rcip= cip;
   return N (points);