dont forget state on closing unrelated tab; forget state if more than one background children is created

qutebrowser/mainwindow/tabbedbrowser.py

@@ -464,9 +464,11 @@ class TabbedBrowser(QWidget):
             return False
 
         opened = self._opened_tab()
-        self._opened_tab = None  # Clear state
+        if opened is tab:
+            self._opened_tab = None  # Consume state
+            return True
 
-        return opened is tab
+        return False
 
     def close_tab(self, tab, *, add_undo=True, new_undo=True, transfer=False,
                   allow_firefox_behavior=True):
@@ -700,7 +702,10 @@ class TabbedBrowser(QWidget):
 
         # Track opened tab for tabs.select_on_remove = 'firefox'
         if self.widget.count() > 0:
-            self._opened_tab = weakref.ref(tab)
+            if self._opened_tab is not None and background:
+                self._opened_tab = None
+            else:
+                self._opened_tab = weakref.ref(tab)
 
         if background:
             # Make sure the background tab has the correct initial size.

tests/end2end/features/tabs_firefox.feature

@@ -76,3 +76,34 @@ Feature: Tab selection on remove (firefox behavior)
         When I set tabs.select_on_remove to firefox
         And I run :tab-close --opposite
         Then the error "-o is not supported with 'tabs.select_on_remove' set to 'firefox'!" should be shown
+
+    Scenario: Opening a second background tab forgets the state
+        When I set tabs.select_on_remove to firefox
+        And I open data/numbers/1.txt
+        And I open data/numbers/4.txt in a new tab
+        And I run :tab-focus 1
+        And I open data/numbers/2.txt in a new background tab
+        And I open data/numbers/3.txt in a new background tab
+        And I run :tab-focus 3
+        And I run :tab-close
+        Then the following tabs should be open:
+            """
+            - data/numbers/1.txt
+            - data/numbers/2.txt
+            - data/numbers/4.txt (active)
+            """
+
+    Scenario: Opening a foreground tab creates a state
+        When I set tabs.select_on_remove to firefox
+        And I open data/numbers/1.txt
+        And I open data/numbers/4.txt in a new tab
+        And I run :tab-focus 1
+        And I open data/numbers/2.txt in a new background tab
+        And I open data/numbers/3.txt in a new tab
+        And I run :tab-close
+        Then the following tabs should be open:
+            """
+            - data/numbers/1.txt (active)
+            - data/numbers/4.txt
+            - data/numbers/2.txt
+            """