Implement basic multithreading support

A few CPU heavy operations, which are opening an archive and displaying
a selected Activity, have been moved to another thread to avoid having
long-running operations on the main thread.

1 files changed, 34 insertions, 6 deletions

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index ede24f8..363f2b1 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -9,6 +9,7 @@
 #include <QRandomGenerator>
 #include <QClipboard>
 #include <QMimeData>
+#include <QtConcurrent/QtConcurrent>
 
 MainWindow::MainWindow(QWidget *parent)
     : QMainWindow(parent)
@@ -17,6 +18,7 @@ MainWindow::MainWindow(QWidget *parent)
     ui->setupUi(this);
     connect(ui->buttonCopy, &QPushButton::clicked, ui->actionCopy_status, &QAction::trigger);
     connect(ui->buttonRandom, &QPushButton::clicked, ui->actionRandom_status, &QAction::trigger);
+    connect(&archive_thread_watcher, &QFutureWatcher<std::variant<QString, Archive::InitError>>::finished, this, &MainWindow::archive_thread_watcher_done);
 }
 
 MainWindow::~MainWindow()
@@ -60,15 +62,22 @@ void MainWindow::on_actionAbout_triggered(bool checked) {
     QMessageBox::information(this, "title", "text");
 }
 
+std::variant<QString, Archive::InitError> start_listWidget_itemActivated(StatusListItem* status, int text_zone_width, QLocale* locale) {
+    return (QString)status->get_info_html(text_zone_width, locale);
+}
+
 void MainWindow::on_listWidget_itemActivated(QListWidgetItem *item) {
     StatusListItem* status = dynamic_cast<StatusListItem*>(item);
     if (status != nullptr) {
-        // TODO: do this in another thread
-        QString status_info = status->get_info_html(ui->statusInfoText->width(), &locale_context);
-        ui->statusInfoText->setHtml(status_info);
+        const QFuture<std::variant<QString, Archive::InitError>> status_info = QtConcurrent::run(start_listWidget_itemActivated, status, ui->statusInfoText->width(), &locale_context);
+        archive_thread_watcher.setFuture(status_info);
     }
 }
 
+void MainWindow::finish_listWidget_itemActivated(const QString& status_info) {
+    ui->statusInfoText->setHtml(status_info);
+}
+
 void MainWindow::on_actionRandom_status_triggered(bool checked) {
     if (data_archive == nullptr) return; // No archive open, avoids crashing
 
@@ -201,14 +210,19 @@ void MainWindow::open_file(const QString &filename) {
         data_archive = nullptr;
     }
 
-    // TODO: Do this in another thread
+    open_file_filename = filename;
+
     QApplication::setOverrideCursor(Qt::WaitCursor);
     data_archive = new Archive(filename, ArchiveType::MASTODON);
-    auto parse_error = data_archive->init();
 
+    QFuture<std::variant<QString, Archive::InitError>> parse_error = QtConcurrent::run(data_archive, &Archive::init);
+    archive_thread_watcher.setFuture(parse_error);
+}
+
+void MainWindow::finish_open_file(const Archive::InitError& parse_error) {
     switch (parse_error) {
         case Archive::FailedOpeningFile:
-            QMessageBox::warning(this, tr("Archive Parser"), tr("Failed opening file %1").arg(filename)); break;
+            QMessageBox::warning(this, tr("Archive Parser"), tr("Failed opening file %1").arg(open_file_filename)); break;
         case Archive::JsonParseError:
             QMessageBox::warning(this, tr("Archive Parser"), tr("Failed parsing outbox JSON.")); break;
         case Archive::JsonEmpty:
@@ -228,3 +242,17 @@ void MainWindow::open_file(const QString &filename) {
 
     QApplication::restoreOverrideCursor();
 }
+
+void MainWindow::archive_thread_watcher_done() {
+    std::variant<QString, Archive::InitError> result = archive_thread_watcher.result();
+
+    // For MainWindow::on_listWidget_itemActivated
+    if (const QString* status_info = std::get_if<QString>(&result)) {
+        finish_listWidget_itemActivated(*status_info);
+    } else
+    // For MainWindow::open_file
+    if (const Archive::InitError* parse_error = std::get_if<Archive::InitError>(&result)) {
+        finish_open_file(*parse_error);
+    } else
+        qDebug() << "What, the variant is weird";
+}