qt: defer refreshing tabs until they are visible

very loosely based on Electron-Cash/Electron-Cash@522e7ca59e5d31f10473064f2149b6c6f9049649

electrum/gui/qt/address_list.py

@@ -137,6 +137,8 @@ class AddressList(MyTreeView):
 
     @profiler
     def update(self):
+        if self.maybe_defer_update():
+            return
         current_address = self.current_item_user_role(col=self.Columns.LABEL)
         if self.show_change == AddressTypeFilter.RECEIVING:
             addr_list = self.wallet.get_receiving_addresses()

electrum/gui/qt/contact_list.py

@@ -102,6 +102,8 @@ class ContactList(MyTreeView):
         menu.exec_(self.viewport().mapToGlobal(position))
 
     def update(self):
+        if self.maybe_defer_update():
+            return
         current_key = self.current_item_user_role(col=self.Columns.NAME)
         self.model().clear()
         self.update_headers(self.__class__.headers)

electrum/gui/qt/history_list.py

@@ -264,6 +264,8 @@ class HistoryModel(QAbstractItemModel, Logger):
         self.logger.info(f"refreshing... reason: {reason}")
         assert self.parent.gui_thread == threading.current_thread(), 'must be called from GUI thread'
         assert self.view, 'view not set'
+        if self.view.maybe_defer_update():
+            return
         selected = self.view.selectionModel().currentIndex()
         selected_row = None
         if selected:
@@ -430,6 +432,9 @@ class HistoryList(MyTreeView, AcceptFileDragDrop):
             sm = QHeaderView.Stretch if col == self.stretch_column else QHeaderView.ResizeToContents
             self.header().setSectionResizeMode(col, sm)
 
+    def update(self):
+        self.hm.refresh('HistoryList.update()')
+
     def format_date(self, d):
         return str(datetime.date(d.year, d.month, d.day)) if d else _('None')
 

electrum/gui/qt/invoice_list.py

@@ -94,6 +94,8 @@ class InvoiceList(MyTreeView):
         status_item.setIcon(read_QIcon(pr_icons.get(status)))
 
     def update(self):
+        if self.maybe_defer_update():
+            return
         _list = self.parent.wallet.get_invoices()
         # filter out paid invoices unless we have the log
         lnworker_logs = self.parent.wallet.lnworker.logs if self.parent.wallet.lnworker else {}

electrum/gui/qt/request_list.py

@@ -107,6 +107,8 @@ class RequestList(MyTreeView):
                 status_item.setIcon(read_QIcon(pr_icons.get(status)))
 
     def update(self):
+        if self.maybe_defer_update():
+            return
         self.parent.update_receive_address_styling()
         self.model().clear()
         self.update_headers(self.__class__.headers)

electrum/gui/qt/util.py

@@ -12,7 +12,7 @@ from functools import partial, lru_cache
 from typing import NamedTuple, Callable, Optional, TYPE_CHECKING, Union, List, Dict, Any
 
 from PyQt5.QtGui import (QFont, QColor, QCursor, QPixmap, QStandardItem,
-                         QPalette, QIcon, QFontMetrics)
+                         QPalette, QIcon, QFontMetrics, QShowEvent)
 from PyQt5.QtCore import (Qt, QPersistentModelIndex, QModelIndex, pyqtSignal,
                           QCoreApplication, QItemSelectionModel, QThread,
                           QSortFilterProxyModel, QSize, QLocale)
@@ -513,6 +513,9 @@ class MyTreeView(QTreeView):
         # only look at as many rows as currently visible.
         self.header().setResizeContentsPrecision(0)
 
+        self._pending_update = False
+        self._forced_update = False
+
     def set_editability(self, items):
         for idx, i in enumerate(items):
             i.setEditable(idx in self.editable_columns)
@@ -664,6 +667,20 @@ class MyTreeView(QTreeView):
     def place_text_on_clipboard(self, text: str, *, title: str = None) -> None:
         self.parent.do_copy(text, title=title)
 
+    def showEvent(self, e: 'QShowEvent'):
+        super().showEvent(e)
+        if e.isAccepted() and self._pending_update:
+            self._forced_update = True
+            self.update()
+            self._forced_update = False
+
+    def maybe_defer_update(self) -> bool:
+        """Returns whether we should defer an update/refresh."""
+        defer = not self.isVisible() and not self._forced_update
+        # side-effect: if we decide to defer update, the state will become stale:
+        self._pending_update = defer
+        return defer
+
 
 class ButtonsWidget(QWidget):
 

electrum/gui/qt/utxo_list.py

@@ -71,6 +71,8 @@ class UTXOList(MyTreeView):
         self.update()
 
     def update(self):
+        if self.maybe_defer_update():
+            return
         utxos = self.wallet.get_utxos()
         self._maybe_reset_spend_list(utxos)
         self._utxo_dict = {}