From e68c671fc502e1d8251ce02638e93c4978719a2f Mon Sep 17 00:00:00 2001
From: Ian Jauslin <ian@jauslin.org>
Date: Wed, 24 Nov 2021 22:49:42 -0500
Subject: [PATCH] Enforce recurrence depth, with error message

---
 painter.py | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/painter.py b/painter.py
index 4950aab..a532b73 100644
--- a/painter.py
+++ b/painter.py
@@ -146,7 +146,7 @@ class Painter(Widget):
             # only move on left click
             if touch.button=="left" and self.modifiers==[] and self.undermouse!=None:
                 # attempted move determined by the relative position to the relative position of click within self.undermouse
-                delta=self.adjust_move(Point(touch.x/Square_element.size,touch.y/Square_element.size)-(self.offset+self.undermouse.squares[0].pos))
+                delta=self.adjust_move(Point(touch.x/Square_element.size,touch.y/Square_element.size)-(self.offset+self.undermouse.squares[0].pos),0)
                 for particle in self.selected:
                     particle.move(delta)
 
@@ -196,13 +196,13 @@ class Painter(Widget):
 
     # try to move all selected particles by delta, adjust if needed to avoid overlap with unselected particles
     # we only track whether these elements collide with unselected particles, not with each other
-    def adjust_move(self,delta):
+    def adjust_move(self,delta,recursion_depth):
         # actual_delta is the smallest (componentwise) of all the computed delta's
         actual_delta=Point(math.inf,math.inf)
         for particle in self.selected:
             for element in particle.squares:
                 # compute adjustment move due to unselected obstacles
-                adjusted_delta=self.adjust_move_element(delta,element)
+                adjusted_delta=self.adjust_move_element(delta,element,0)
                 # only keep the smallest delta's (in absolute value)
                 if abs(adjusted_delta.x)<abs(actual_delta.x):
                     actual_delta.x=adjusted_delta.x
@@ -213,11 +213,16 @@ class Painter(Widget):
             return actual_delta
         else:
             # cannot move particles at all, try again
-            return self.adjust_move(actual_delta)
+            # give up if tried too many times
+            if recursion_depth>100:
+                print("warning: recursion depth exceeded when adjusting move by delta=(",delta.x,",",delta.y,")",file=sys.stderr)
+                return Point(0,0)
+            else:
+                return self.adjust_move(actual_delta,recursion_depth+1)
 
 
     # trying to move a single element by delta, adjust if needed to avoid overlap with unselected particles
-    def adjust_move_element(self,delta,element):
+    def adjust_move_element(self,delta,element,recursion_depth):
         # whether newpos is acceptable
         accept_newpos=True
         for other in self.unselected:
@@ -237,7 +242,12 @@ class Painter(Widget):
             return delta
         else:
             # cannot move particle at all, try again
-            return self.adjust_move_element(newdelta,element)
+            # give up if tried too many times
+            if recursion_depth>100:
+                print("warning: recursion depth exceeded when adjusting move of element at (",element.pos.x,",",element.pos.y,") by delta=(",delta.x,",",delta.y,")",file=sys.stderr)
+                return Point(0,0)
+            else:
+                return self.adjust_move_element(newdelta,element,recursion_depth+1)
 
 
     # TODO adapt