core: switch to single-project implementation

This has never worked right, it's caused a number of complexities within the code, and I think there are better ways to do this.

app/core.h

@@ -219,7 +219,6 @@ public:
    * The active Project file, or nullptr if the heuristic couldn't find one.
    */
   Project* GetActiveProject() const;
-  ProjectViewModel* GetActiveProjectModel() const;
   Folder* GetSelectedFolderInActiveProject() const;
 
   /**
@@ -265,23 +264,10 @@ public:
    */
   void OpenProjectFromRecentList(int index);
 
-  enum CloseProjectBehavior {
-    kCloseProjectOnlyOne,
-    kCloseProjectAsk,
-    kCloseProjectSave,
-    kCloseProjectDontSave
-  };
-
   /**
    * @brief Closes a project
    */
-  bool CloseProject(Project* p, bool auto_open_new, CloseProjectBehavior& confirm_behavior);
-  bool CloseProject(Project* p, bool auto_open_new);
-
-  /**
-   * @brief Closes all open projects
-   */
-  bool CloseAllProjects(bool auto_open_new);
+  bool CloseProject(bool auto_open_new, bool ignore_modified = false);
 
   /**
    * @brief Runs a modal cache task on the currently active sequence
@@ -298,11 +284,6 @@ public:
    */
   bool SetLanguage(const QString& locale);
 
-  /**
-   * @brief Saves a specific project
-   */
-  bool SaveProject(Project *p);
-
   /**
    * @brief Show message in main window's status bar
    *
@@ -327,46 +308,16 @@ public slots:
   void OpenProject();
 
   /**
-   * @brief Save the currently active project
-   *
-   * If the project hasn't been saved before, this will be equivalent to calling SaveActiveProjectAs().
+   * @brief Saves the current project
    */
-  bool SaveActiveProject();
+  bool SaveProject();
 
   /**
-   * @brief Save the currently active project with a new filename
+   * @brief Performs a "save as" on the current project
    */
-  bool SaveActiveProjectAs();
+  bool SaveProjectAs();
 
-  /**
-   * @brief Save all currently open projects
-   */
-  bool SaveAllProjects();
-
-  /**
-   * @brief Revert project to last saved state (basically close and open it)
-   */
-  void RevertActiveProject();
-
-  /**
-   * @brief Closes the active project
-   *
-   * If no other projects are open, a new one is created automatically.
-   */
-  bool CloseActiveProject();
-
-  /**
-   * @brief Closes all projects except the active project
-   */
-  bool CloseAllExceptActiveProject();
-
-  /**
-   * @brief Closes all open projects
-   *
-   * Equivalent to `CloseAllProjects(true)`, but useful for the signal/slot system where you may not be able to specify
-   * parameters.
-   */
-  bool CloseAllProjects();
+  void RevertProject();
 
   /**
    * @brief Set the current application-wide tool
@@ -523,11 +474,6 @@ private:
    */
   void SetStartupLocale();
 
-  /**
-   * @brief Performs a "save as" on a specific project
-   */
-  bool SaveProjectAs(Project *p);
-
   /**
    * @brief Adds a filename to the top of the recently opened projects list (or moves it if it already exists)
    */
@@ -552,7 +498,7 @@ private:
   /**
    * @brief Internal function for saving a project to a file
    */
-  void SaveProjectInternal(Project *project, const QString &override_filename = QString());
+  void SaveProjectInternal(const QString &override_filename = QString());
 
   /**
    * @brief Retrieves the currently most active sequence for exporting
@@ -563,7 +509,7 @@ private:
 
   void SaveUnrecoveredList();
 
-  bool RevertProjectInternal(Project *p, bool by_opening_existing);
+  bool RevertProjectInternal(bool by_opening_existing);
 
   void SaveRecentProjectsList();
 
@@ -582,7 +528,7 @@ private:
   /**
    * @brief List of currently open projects
    */
-  QList<Project*> open_projects_;
+  Project *open_project_;
 
   /**
    * @brief Currently active tool