Add AbstractScroller.before_jump_requested signal

This allows us to save the ' mark without needing access to the TabbedBrowser
object.

This also changes the places the ' mark is saved slightly:

- :navigate doesn't save it anymore as there is no reason to do so (loading the
  new page will render the mark useless anyways).
- When clearing a search, the ' mark isn't saved.
- :scroll-anchor now saves the ' mark.

qutebrowser/browser/browsertab.py

@@ -522,9 +522,17 @@ class AbstractCaret(QObject):
 
 class AbstractScroller(QObject):
 
-    """Attribute of AbstractTab to manage scroll position."""
+    """Attribute of AbstractTab to manage scroll position.
+
+    Signals:
+        perc_changed: The scroll position changed.
+        before_jump_requested:
+            Emitted by other code when the user requested a jump.
+            Used to set the special ' mark so the user can return.
+    """
 
     perc_changed = pyqtSignal(int, int)
+    before_jump_requested = pyqtSignal()
 
     def __init__(self, tab: 'AbstractTab', parent: QWidget = None):
         super().__init__(parent)

qutebrowser/browser/commands.py

@@ -634,9 +634,6 @@ class CommandDispatcher:
             count: For `increment` and `decrement`, the number to change the
                    URL by. For `up`, the number of levels to go up in the URL.
         """
-        # save the pre-jump position in the special ' mark
-        self.set_mark("'")
-
         cmdutils.check_exclusive((tab, bg, window), 'tbw')
         widget = self._current_widget()
         url = self._current_url()
@@ -1712,7 +1709,6 @@ class CommandDispatcher:
             text: The text to search for.
             reverse: Reverse search direction.
         """
-        self.set_mark("'")
         tab = self._current_widget()
 
         if not text:
@@ -1733,6 +1729,7 @@ class CommandDispatcher:
                                options=options, text=text, prev=False)
         options['result_cb'] = cb
 
+        tab.scroller.before_jump_requested.emit()
         tab.search.search(text, **options)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
@@ -1750,7 +1747,7 @@ class CommandDispatcher:
         if window_text is None:
             raise cmdutils.CommandError("No search done yet.")
 
-        self.set_mark("'")
+        tab.scroller.before_jump_requested.emit()
 
         if window_text is not None and window_text != tab.search.text:
             tab.search.clear()
@@ -1784,7 +1781,7 @@ class CommandDispatcher:
         if window_text is None:
             raise cmdutils.CommandError("No search done yet.")
 
-        self.set_mark("'")
+        tab.scroller.before_jump_requested.emit()
 
         if window_text is not None and window_text != tab.search.text:
             tab.search.clear()

qutebrowser/browser/hints.py

@@ -218,9 +218,7 @@ class HintActions:
 
         if context.target in [Target.normal, Target.current]:
             # Set the pre-jump mark ', so we can jump back here after following
-            tabbed_browser = objreg.get('tabbed-browser', scope='window',
-                                        window=self._win_id)
-            tabbed_browser.set_mark("'")
+            context.tab.scroll.before_jump_requested.emit()
 
         try:
             if context.target == Target.hover:

qutebrowser/components/scrollcommands.py

@@ -94,9 +94,6 @@ def scroll_to_perc(tab: tab.Tab, count: int = None,
         horizontal: Scroll horizontally instead of vertically.
         count: Percentage to scroll.
     """
-    # save the pre-jump position in the special ' mark
-    self.set_mark("'")
-
     if perc is None and count is None:
         perc = 100
     elif count is not None:
@@ -109,6 +106,7 @@ def scroll_to_perc(tab: tab.Tab, count: int = None,
         x = None
         y = perc
 
+    tab.scroller.before_jump_requested.emit()
     tab.scroller.to_perc(x, y)
 
 
@@ -120,4 +118,5 @@ def scroll_to_anchor(tab: tab.Tab, name):
     Args:
         name: The anchor to scroll to.
     """
+    tab.scroller.before_jump_requested.emit()
     tab.scroller.to_anchor(name)

qutebrowser/mainwindow/tabbedbrowser.py

@@ -222,6 +222,7 @@ class TabbedBrowser(QWidget):
             self._filter.create(self.cur_caret_selection_toggled, tab))
         # misc
         tab.scroller.perc_changed.connect(self.on_scroll_pos_changed)
+        tab.scroller.before_jump_requested.connect(lambda: self.set_mark("'"))
         tab.url_changed.connect(
             functools.partial(self.on_url_changed, tab))
         tab.title_changed.connect(
@@ -891,8 +892,7 @@ class TabbedBrowser(QWidget):
             # save the pre-jump position in the special ' mark
             # this has to happen after we read the mark, otherwise jump_mark
             # "'" would just jump to the current position every time
-            self.set_mark("'")
-
+            tab.scroller.before_jump_requested.emit()
             tab.scroller.to_point(point)
         else:
             message.error("Mark {} is not set".format(key))