task: improve threading

app/task/task.h

@@ -93,6 +93,7 @@ public slots:
   bool Start()
   {
     start_time_ = QDateTime::currentMSecsSinceEpoch();
+    emit Started(start_time_);
 
     bool ret = Run();
 
@@ -150,6 +151,8 @@ protected:
   }
 
 signals:
+  void Started(qint64 start_time);
+
   /**
    * @brief Signal emitted whenever progress is made
    *

app/task/taskmanager.cpp

@@ -29,6 +29,7 @@ TaskManager* TaskManager::instance_ = nullptr;
 
 TaskManager::TaskManager()
 {
+  thread_pool_.setMaxThreadCount(1);
 }
 
 TaskManager::~TaskManager()
@@ -95,9 +96,9 @@ void TaskManager::AddTask(Task* t)
   // Run task concurrently
   watcher->setFuture(
 #if QT_VERSION_MAJOR >= 6
-        QtConcurrent::run(&Task::Start, t)
+        QtConcurrent::run(&thread_pool_, &Task::Start, t)
 #else
-        QtConcurrent::run(t, &Task::Start)
+        QtConcurrent::run(&thread_pool_, t, &Task::Start)
 #endif
         );
 

app/widget/taskview/elapsedcounterwidget.cpp

@@ -22,6 +22,7 @@
 
 #include <QDateTime>
 #include <QHBoxLayout>
+#include <cmath>
 
 #include "common/timecodefunctions.h"
 
@@ -80,7 +81,7 @@ void ElapsedCounterWidget::UpdateTimers()
     double ms_per_progress_unit = elapsed_ms / last_progress_;
     double remaining_progress = 1.0 - last_progress_;
 
-    remaining_ms = qRound64(ms_per_progress_unit * remaining_progress);
+    remaining_ms = std::ceil(ms_per_progress_unit * remaining_progress);
   } else {
     elapsed_ms = 0;
     remaining_ms = 0;

app/widget/taskview/elapsedcounterwidget.h

@@ -37,8 +37,9 @@ public:
 
   void SetProgress(double d);
 
-  void Start();
+public slots:
   void Start(qint64 start_time);
+  void Start();
 
 public slots:
   void Stop();

app/widget/taskview/taskviewitem.cpp

@@ -72,9 +72,9 @@ TaskViewItem::TaskViewItem(Task* task, QWidget *parent) :
 
   // Set up elapsed timer
   status_stack_->setCurrentWidget(elapsed_timer_lbl_);
-  elapsed_timer_lbl_->Start(task_->GetStartTime());
 
   // Connect to the task
+  connect(task_, &Task::Started, elapsed_timer_lbl_, qOverload<qint64>(&ElapsedCounterWidget::Start));
   connect(task_, &Task::ProgressChanged, this, &TaskViewItem::UpdateProgress);
   connect(cancel_btn_, &QPushButton::clicked, this, [this] { emit TaskCancelled(task_); });
 }