fix kivy#6370

kivy/tests/test_uix_carousel.py

@@ -1,15 +1,60 @@
 import pytest
 
 
-def test_remove_widget():
+@pytest.fixture(
+    scope='session', params=(True, False), ids=lambda v: 'loop=' + str(v))
+def loop(request):
+    return request.param
+
+
+def test_remove_widget(loop):
     from kivy.uix.carousel import Carousel
     from kivy.uix.widget import Widget
 
-    c = Carousel()
-    w = Widget()
-    c.add_widget(w)
+    c = Carousel(loop=loop)
+    assert c.index is None
+    assert c.current_slide is None
+    assert len(c.children) == 0
+    assert len(c.slides) == 0
+
+    N_SLIDES = 4
+    for i in range(N_SLIDES):
+        c.add_widget(Widget())
+    assert c.index == 0
+    assert c.current_slide == c.slides[0]
+    assert len(c.children) == 3 if loop else 2
+    assert len(c.slides) == N_SLIDES
+
+    # test issue #6370
+    c.index = len(c.slides) - 1
+    c.remove_widget(c.slides[0])
+
+    # remove a slide(smaller index than the current_slide's).
+    c.index = 1
+    old_current_slide = c.current_slide
+    c.remove_widget(c.slides[c.index - 1])
+    assert c.index == 0
+    assert c.current_slide is old_current_slide
+    assert len(c.children) == 2
+    assert len(c.slides) == 2
+
+    # remove a slide(bigger index than the current_slide's).
+    old_current_slide = c.current_slide
+    c.remove_widget(c.slides[c.index + 1])
+    assert c.index == 0
+    assert c.current_slide is old_current_slide
     assert len(c.children) == 1
     assert len(c.slides) == 1
-    c.remove_widget(w)
+
+    # remove the current_slide(the last one left).
+    c.remove_widget(c.current_slide)
+    assert c.index is None
+    assert c.current_slide is None
     assert len(c.children) == 0
     assert len(c.slides) == 0
+
+
+if __name__ == "__main__":
+    pytest.main(args=[
+        __file__,
+    ])

kivy/uix/carousel.py

@@ -649,9 +649,12 @@ def remove_widget(self, widget, *args, **kwargs):
         # added in add_widget(). But it will break if RelativeLayout
         # implementation change.
         # if we passed the real widget
-        if widget in self.slides:
+        slides = self.slides
+        if widget in slides:
+            if self.index >= slides.index(widget):
+                self.index = max(0, self.index - 1)
             container = widget.parent
-            self.slides.remove(widget)
+            slides.remove(widget)
             super(Carousel, self).remove_widget(container)
             return container.remove_widget(widget, *args, **kwargs)
         return super(Carousel, self).remove_widget(widget, *args, **kwargs)