refactor: Replace ApplicationController singleton with dependency injection

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

src/ApplicationController.cpp

@@ -9,12 +9,6 @@
 #include <QDir>
 #include <QFileInfo>
 
-ApplicationController* ApplicationController::instance()
-{
-    static ApplicationController instance;
-    return &instance;
-}
-
 ApplicationController::ApplicationController(QObject *parent)
     : QObject(parent)
 {

src/ApplicationController.h

@@ -12,7 +12,8 @@ class ApplicationController : public QObject
 {
     Q_OBJECT
 public:
-    static ApplicationController* instance();
+    explicit ApplicationController(QObject *parent = nullptr);
+    ~ApplicationController();
 
     void setMainWindow(MainWindow* mainWindow);
     Document* document() const;
@@ -33,8 +34,6 @@ signals:
     void currentFileChanged(const QString& path);
 
 private:
-    explicit ApplicationController(QObject *parent = nullptr);
-    ~ApplicationController();
     ApplicationController(const ApplicationController&) = delete;
     ApplicationController& operator=(const ApplicationController&) = delete;
 

src/MainWindow.cpp

@@ -18,8 +18,9 @@
 #include <QInputDialog>
 #include <QStringList>
 
-MainWindow::MainWindow(QWidget *parent)
+MainWindow::MainWindow(ApplicationController* appController, QWidget *parent)
     : QMainWindow(parent)
+    , m_appController(appController)
 {
     setWindowTitle("OpenCAD");
     resize(1920, 1080);
@@ -117,50 +118,50 @@ MainWindow::MainWindow(QWidget *parent)
     m_viewport = new ViewportWidget;
     setCentralWidget(m_viewport);
 
-    ApplicationController::instance()->setMainWindow(this);
-    Document* document = ApplicationController::instance()->document();
+    m_appController->setMainWindow(this);
+    Document* document = m_appController->document();
 
     m_viewport->setDocument(document);
     connect(document, &Document::featureAdded, m_viewport, QOverload<>::of(&QWidget::update));
     connect(document, &Document::cleared, m_viewport, QOverload<>::of(&QWidget::update));
 
-    connect(ApplicationController::instance(), &ApplicationController::sketchModeStarted, this, &MainWindow::enterSketchMode);
-    connect(ApplicationController::instance(), &ApplicationController::sketchModeEnded, this, &MainWindow::exitSketchMode);
-    connect(ApplicationController::instance(), &ApplicationController::sketchModeStarted, m_viewport, &ViewportWidget::onSketchModeStarted);
-    connect(ApplicationController::instance(), &ApplicationController::sketchModeEnded, m_viewport, &ViewportWidget::onSketchModeEnded);
-    connect(ApplicationController::instance(), &ApplicationController::currentFileChanged, this, &MainWindow::updateWindowTitle);
+    connect(m_appController, &ApplicationController::sketchModeStarted, this, &MainWindow::enterSketchMode);
+    connect(m_appController, &ApplicationController::sketchModeEnded, this, &MainWindow::exitSketchMode);
+    connect(m_appController, &ApplicationController::sketchModeStarted, m_viewport, &ViewportWidget::onSketchModeStarted);
+    connect(m_appController, &ApplicationController::sketchModeEnded, m_viewport, &ViewportWidget::onSketchModeEnded);
+    connect(m_appController, &ApplicationController::currentFileChanged, this, &MainWindow::updateWindowTitle);
 
     updateWindowTitle(QString());
 }
 
 void MainWindow::createSketch()
 {
-    ApplicationController::instance()->beginSketchCreation();
+    m_appController->beginSketchCreation();
 }
 
 void MainWindow::saveSketch()
 {
-    ApplicationController::instance()->endSketch();
+    m_appController->endSketch();
 }
 
 void MainWindow::newFile()
 {
-    ApplicationController::instance()->newDocument();
+    m_appController->newDocument();
 }
 
 void MainWindow::open()
 {
-    ApplicationController::instance()->openDocument();
+    m_appController->openDocument();
 }
 
 bool MainWindow::save()
 {
-    return ApplicationController::instance()->saveDocument();
+    return m_appController->saveDocument();
 }
 
 bool MainWindow::saveAs()
 {
-    return ApplicationController::instance()->saveDocumentAs();
+    return m_appController->saveDocumentAs();
 }
 
 void MainWindow::enterSketchMode()

src/MainWindow.h

@@ -8,13 +8,14 @@ class Document;
 class Feature;
 class QTabWidget;
 class QWidget;
+class ApplicationController;
 
 class MainWindow : public QMainWindow
 {
     Q_OBJECT
 
 public:
-    explicit MainWindow(QWidget *parent = nullptr);
+    explicit MainWindow(ApplicationController* appController, QWidget *parent = nullptr);
 
 private slots:
     void newFile();
@@ -29,6 +30,7 @@ private slots:
     void updateWindowTitle(const QString& filePath);
 
 private:
+    ApplicationController* m_appController;
     ViewportWidget *m_viewport;
 
     QTabWidget *m_tabWidget;

src/main.cpp

@@ -1,11 +1,13 @@
 #include <QApplication>
 #include "MainWindow.h"
+#include "ApplicationController.h"
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
 
-    MainWindow window;
+    ApplicationController appController;
+    MainWindow window(&appController);
     window.show();
 
     return app.exec();