From 83e4e4ca55aa58e02c0c34e7d6ded7b84a5ba316 Mon Sep 17 00:00:00 2001
From: Charles Kerr <charles@charleskerr.com>
Date: Tue, 23 Jun 2020 12:16:07 -0500
Subject: [PATCH] refactor: faster action sensitivity updates (#1333)

* refactor: faster action sensitivity updates

Currently we walk through every row in the model and pump its TorrentRole data, which can be expensive for long lists. However since we're only interested in the selected rows, let's save some traversal overhead by getting that list directly and walking it instead.
---
 qt/MainWindow.cc | 85 +++++++++++++++++++++---------------------------
 1 file changed, 37 insertions(+), 48 deletions(-)

diff --git a/qt/MainWindow.cc b/qt/MainWindow.cc
index bcbf9d4dd..5cb418362 100644
--- a/qt/MainWindow.cc
+++ b/qt/MainWindow.cc
@@ -8,6 +8,7 @@
 
 #include <array>
 #include <cassert>
+#include <functional>
 #include <utility>
 
 #include <QCheckBox>
@@ -849,64 +850,52 @@ void MainWindow::refreshTorrentViewHeader()
 
 void MainWindow::refreshActionSensitivity()
 {
-    int paused(0);
-    int selected(0);
-    int selected_and_can_announce(0);
-    int selected_and_paused(0);
-    int selected_and_queued(0);
-    int selected_with_metadata(0);
-    QAbstractItemModel const* model(ui_.listView->model());
-    QItemSelectionModel const* selection_model(ui_.listView->selectionModel());
-    bool const has_selection = selection_model->hasSelection();
-    int const row_count(model->rowCount());
+    auto const* model = ui_.listView->model();
+    auto const* selection_model = ui_.listView->selectionModel();
+    auto const row_count = model->rowCount();
 
     // count how many torrents are selected, paused, etc
+    auto selected = int{};
+    auto selected_and_can_announce = int{};
+    auto selected_and_paused = int{};
+    auto selected_and_queued = int{};
+    auto selected_with_metadata = int{};
     auto const now = time(nullptr);
-    for (int row = 0; row < row_count; ++row)
+    for (auto const& row : selection_model->selectedRows())
     {
-        QModelIndex const model_index(model->index(row, 0));
-        auto const& tor = model->data(model_index, TorrentModel::TorrentRole).value<Torrent const*>();
+        auto const& tor = model->data(row, TorrentModel::TorrentRole).value<Torrent const*>();
 
-        if (tor != nullptr)
+        ++selected;
+
+        if (tor->isPaused())
         {
-            bool const is_selected = has_selection && selection_model->isSelected(model_index);
-            bool const is_paused = tor->isPaused();
+            ++selected_and_paused;
+        }
 
-            if (is_paused)
-            {
-                ++paused;
-            }
+        if (tor->isQueued())
+        {
+            ++selected_and_queued;
+        }
 
-            if (is_selected)
-            {
-                ++selected;
+        if (tor->hasMetadata())
+        {
+            ++selected_with_metadata;
+        }
 
-                if (is_paused)
-                {
-                    ++selected_and_paused;
-                }
-
-                if (tor->isQueued())
-                {
-                    ++selected_and_queued;
-                }
-
-                if (tor->hasMetadata())
-                {
-                    ++selected_with_metadata;
-                }
-
-                if (tor->canManualAnnounceAt(now))
-                {
-                    ++selected_and_can_announce;
-                }
-            }
+        if (tor->canManualAnnounceAt(now))
+        {
+            ++selected_and_can_announce;
         }
     }
 
-    bool const have_selection(selected > 0);
-    bool const have_selection_with_metadata = selected_with_metadata > 0;
-    bool const one_selection(selected == 1);
+    auto const& torrents = model_.torrents();
+    auto const is_paused = [](auto const* tor) { return tor->isPaused(); };
+    auto const any_paused = std::any_of(std::begin(torrents), std::end(torrents), is_paused);
+    auto const any_not_paused = std::any_of(std::begin(torrents), std::end(torrents), std::not_fn(is_paused));
+
+    auto const have_selection = selected > 0;
+    auto const have_selection_with_metadata = selected_with_metadata > 0;
+    auto const one_selection = selected == 1;
 
     ui_.action_Verify->setEnabled(have_selection_with_metadata);
     ui_.action_Remove->setEnabled(have_selection);
@@ -919,8 +908,8 @@ void MainWindow::refreshActionSensitivity()
     ui_.action_CopyMagnetToClipboard->setEnabled(one_selection);
 
     ui_.action_SelectAll->setEnabled(selected < row_count);
-    ui_.action_StartAll->setEnabled(paused > 0);
-    ui_.action_PauseAll->setEnabled(paused < row_count);
+    ui_.action_StartAll->setEnabled(any_paused);
+    ui_.action_PauseAll->setEnabled(any_not_paused);
     ui_.action_Start->setEnabled(selected_and_paused > 0);
     ui_.action_StartNow->setEnabled(selected_and_paused + selected_and_queued > 0);
     ui_.action_Pause->setEnabled(selected_and_paused < selected);