implemented cancel feedback in project saving

The cancel button now sends a signal to the saving thread to stop.

app/project/projectsavemanager.cpp

@@ -1,7 +1,8 @@
 #include "projectsavemanager.h"
 
 ProjectSaveManager::ProjectSaveManager(Project *project) :
-  project_(project)
+  project_(project),
+  cancelled_(false)
 {
 
 }
@@ -11,6 +12,10 @@ void ProjectSaveManager::Start()
   int prog = 0;
 
   do {
+    if (cancelled_) {
+      break;
+    }
+
     prog += 10;
 
     emit ProgressChanged(prog);
@@ -20,3 +25,8 @@ void ProjectSaveManager::Start()
 
   emit Finished();
 }
+
+void ProjectSaveManager::Cancel()
+{
+  cancelled_ = true;
+}

app/project/projectsavemanager.h

@@ -12,8 +12,22 @@ public:
   ProjectSaveManager(Project* project);
 
 public slots:
+  /**
+   * @brief Start the save process
+   *
+   * It's recommended to invoke this through Qt signals/slots/QueuedConnection after moving this object to a separate
+   * thread.
+   */
   void Start();
 
+  /**
+   * @brief Cancel the current save
+   *
+   * Always connect to this with a DirectConnection. Otherwise, it'll be queued AFTER the save function is already
+   * complete.
+   */
+  void Cancel();
+
 signals:
   void ProgressChanged(int);
 
@@ -22,6 +36,8 @@ signals:
 private:
   Project* project_;
 
+  QAtomicInt cancelled_;
+
 };
 
 #endif // PROJECTSAVEMANAGER_H