Add `search.delay` config and implementation which delays search-in-page input until

a specified amount of time since last keystroke to help with search performance on large
documents.

qutebrowser/browser/webengine/webenginetab.py

@@ -150,6 +150,8 @@ class WebEngineSearch(browsertab.AbstractSearch):
         self._pending_searches = 0
         self.match = browsertab.SearchMatch()
         self._old_match = browsertab.SearchMatch()
+        self._debounce_timer = usertypes.Timer(self)
+        self._debounce_timer.setSingleShot(True)
 
     def _store_flags(self, reverse, ignore_case):
         self._flags.case_sensitive = self._is_case_sensitive(ignore_case)
@@ -212,7 +214,7 @@ class WebEngineSearch(browsertab.AbstractSearch):
         log.webview.debug(f"Active search match: {self.match}")
         self.match_changed.emit(self.match)
 
-    def search(self, text, *, ignore_case=usertypes.IgnoreCase.never,
+    def _search(self, text, *, ignore_case=usertypes.IgnoreCase.never,
                reverse=False, result_cb=None):
         # Don't go to next entry on duplicate search
         if self.text == text and self.search_displayed:
@@ -227,6 +229,20 @@ class WebEngineSearch(browsertab.AbstractSearch):
 
         self._find(text, self._flags, result_cb, 'search')
 
+    def search(self, *args, **kwargs):
+        delay = config.val.search.delay
+        if delay:
+            self._debounce_timer.stop()
+
+            self._debounce_timer.timeout.disconnect()
+            self._debounce_timer.timeout.connect(
+                lambda: self._search(*args, **kwargs)
+            )
+
+            self._debounce_timer.start(delay)
+        else:
+            self._search(*args, **kwargs)
+
     def clear(self):
         if self.search_displayed:
             self.cleared.emit()

qutebrowser/config/configdata.yml

@@ -50,6 +50,16 @@ changelog_after_upgrade:
 ignore_case:
   renamed: search.ignore_case
 
+search.delay:
+  type:
+    name: Int
+    minval: 0
+    maxval: maxint
+  default: 400
+  desc: Delay (in milliseconds) between last keystroke when searching and the
+    search being submitted. Larger values produce fewer redundant searches but
+    also delay receiving search results.
+
 search.ignore_case:
   type: IgnoreCase
   default: smart