Show renderer process PID in :buffer completion

doc/changelog.asciidoc

@@ -126,6 +126,8 @@ Changed
   `content.headers.custom`, the custom value is now ignored for XHR
   (`XMLHttpRequest`) requests. Instead, the sent value is now `*/*` or the header
   set from JavaScript, as it would be if `content.headers.custom` wasn't set.
+- The `:buffer` completion now shows the underlying renderer process PID if
+  doing so is supported (QtWebEngine 5.15).
 
 Fixed
 ~~~~~

qutebrowser/browser/browsertab.py

@@ -1172,6 +1172,14 @@ class AbstractTab(QWidget):
         self.data.pinned = pinned
         self.pinned_changed.emit(pinned)
 
+    def renderer_process_pid(self) -> Optional[int]:
+        """Get the PID of the underlying renderer process.
+
+        Returns None if the PID can't be determined or if getting the PID isn't
+        supported.
+        """
+        raise NotImplementedError
+
     def __repr__(self) -> str:
         try:
             qurl = self.url()

qutebrowser/browser/webengine/webenginetab.py

@@ -23,7 +23,7 @@ import math
 import functools
 import re
 import html as html_utils
-from typing import cast, Union
+from typing import cast, Union, Optional
 
 from PyQt5.QtCore import pyqtSignal, pyqtSlot, Qt, QPoint, QPointF, QUrl, QObject
 from PyQt5.QtNetwork import QAuthenticator
@@ -1313,6 +1313,14 @@ class WebEngineTab(browsertab.AbstractTab):
     def title(self):
         return self._widget.title()
 
+    def renderer_process_pid(self) -> Optional[int]:
+        page = self._widget.page()
+        try:
+            return page.renderProcessPid()
+        except AttributeError:
+            # Added in Qt 5.15
+            return None
+
     def icon(self):
         return self._widget.icon()
 

qutebrowser/browser/webkit/webkittab.py

@@ -888,6 +888,9 @@ class WebKitTab(browsertab.AbstractTab):
     def title(self):
         return self._widget.title()
 
+    def renderer_process_pid(self) -> Optional[int]:
+        return None
+
     @pyqtSlot()
     def _on_history_trigger(self):
         url = self.url()

qutebrowser/completion/models/miscmodels.py

@@ -117,7 +117,7 @@ def _buffer(*, win_id_filter=lambda _win_id: True, add_win_id=True):
                                     window=int(win_id))
         tabbed_browser.on_tab_close_requested(int(tab_index) - 1)
 
-    model = completionmodel.CompletionModel(column_widths=(6, 40, 54))
+    model = completionmodel.CompletionModel(column_widths=(6, 40, 46, 8))
 
     tabs_are_windows = config.val.tabs.tabs_are_windows
     # list storing all single-tabbed windows when tabs_are_windows
@@ -131,14 +131,20 @@ def _buffer(*, win_id_filter=lambda _win_id: True, add_win_id=True):
                                     window=win_id)
         if tabbed_browser.is_shutting_down:
             continue
-        tabs: List[Tuple[str, str, str]] = []
+        tabs: List[Tuple[str, str, str, str]] = []
         for idx in range(tabbed_browser.widget.count()):
             tab = tabbed_browser.widget.widget(idx)
             tab_str = ("{}/{}".format(win_id, idx + 1) if add_win_id
                        else str(idx + 1))
-            tabs.append((tab_str,
-                         tab.url().toDisplayString(),
-                         tabbed_browser.widget.page_title(idx)))
+
+            pid = tab.renderer_process_pid()
+
+            tabs.append((
+                tab_str,
+                tab.url().toDisplayString(),
+                tabbed_browser.widget.page_title(idx),
+                "" if pid is None else f"PID {pid}",
+             ))
 
         if tabs_are_windows:
             windows += tabs

tests/helpers/stubs.py

@@ -286,6 +286,9 @@ class FakeWebTab(browsertab.AbstractTab):
     def icon(self):
         return QIcon()
 
+    def renderer_process_pid(self):
+        return None
+
 
 class FakeSignal: