From b3bb1666fa6a0ec674dc5560c6d936f231904795 Mon Sep 17 00:00:00 2001
From: Antonio Carzaniga <antonio.carzaniga@usi.ch>
Date: Fri, 3 Dec 2021 15:58:36 +0100
Subject: [PATCH] (draw_gravity_vector) saving/restoring cairo context, for
 isolation.

---
 balls.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/balls.c b/balls.c
index 073655e..4a3bb88 100644
--- a/balls.c
+++ b/balls.c
@@ -214,6 +214,7 @@ int gravity_vector_init = 300;
 
 void draw_gravity_vector(cairo_t * cr) {
     if (gravity_vector_countdown != 0) {
+	cairo_save(cr);
 	cairo_new_path(cr);
 	cairo_move_to(cr, width/2, height/2);
 	cairo_line_to(cr, width/2 + g_x, height/2 + g_y);
@@ -224,6 +225,7 @@ void draw_gravity_vector(cairo_t * cr) {
 	cairo_fill(cr);
 	if (gravity_vector_countdown > 0)
 	    --gravity_vector_countdown;
+	cairo_restore(cr);
     }
 }