Add scale up and scale down range (paceholder#3)

* set default (0.3, 2)
* 0 means you can scale up/down indefinitely
* the scale size can be specified by `setupScale`

Author: zmoth

examples/calculator/main.cpp

@@ -94,7 +94,9 @@ main(int argc, char* argv[])
   l->addWidget(menuBar);
   auto scene = new DataFlowGraphicsScene(dataFlowGraphModel,
                                          &mainWidget);
-  l->addWidget(new GraphicsView(scene));
+
+  auto view = new GraphicsView(scene);
+  l->addWidget(view);
   l->setContentsMargins(0, 0, 0, 0);
   l->setSpacing(0);
 
@@ -104,6 +106,9 @@ main(int argc, char* argv[])
   QObject::connect(loadAction, &QAction::triggered,
                    scene, &DataFlowGraphicsScene::load);
 
+  QObject::connect(scene, &DataFlowGraphicsScene::sceneLoaded,
+                   view, &GraphicsView::centerScene);
+
   mainWidget.setWindowTitle("Data Flow: simplest calculator");
   mainWidget.resize(800, 600);
   // Center window.

include/QtNodes/internal/DataFlowGraphicsScene.hpp

@@ -41,6 +41,10 @@ public Q_SLOTS:
   void
   load();
 
+Q_SIGNALS:
+  void
+  sceneLoaded();
+
 private:
   DataFlowGraphModel &_graphModel;
 };

include/QtNodes/internal/GraphicsView.hpp

@@ -9,13 +9,24 @@ namespace QtNodes
 
 class BasicGraphicsScene;
 
+
+/**
+ * @brief A central view able to render objects from `BasicGraphicsScene`.
+ */
 class NODE_EDITOR_PUBLIC GraphicsView
   : public QGraphicsView
 {
   Q_OBJECT
 public:
-  GraphicsView(QWidget *parent = Q_NULLPTR);
-  GraphicsView(BasicGraphicsScene *scene, QWidget *parent = Q_NULLPTR);
+  struct ScaleRange
+  {
+    double minimum = 0;
+    double maximum = 0;
+  };
+
+public:
+  GraphicsView(QWidget* parent = Q_NULLPTR);
+  GraphicsView(BasicGraphicsScene* scene, QWidget* parent = Q_NULLPTR);
 
   GraphicsView(const GraphicsView &) = delete;
   GraphicsView
@@ -28,58 +39,76 @@ class NODE_EDITOR_PUBLIC GraphicsView
   deleteSelectionAction() const;
 
   void
-  setScene(BasicGraphicsScene *scene);
+  setScene(BasicGraphicsScene* scene);
 
   void
   centerScene();
 
+  /// @brief max=0/min=0 indicates infinite zoom in/out
+  void
+  setScaleRange(double minimum = 0, double maximum = 0);
+
+  void
+  setScaleRange(ScaleRange range);
+
+  double
+  getScale() const;
+
 public Q_SLOTS:
   void
   scaleUp();
 
   void
   scaleDown();
 
+  void
+  setupScale(double scale);
+
   void
   onDeleteSelectedObjects();
 
   void
   onDuplicateSelectedObjects();
 
+Q_SIGNALS:
+  void
+  scaleChanged(double scale);
+
 protected:
   void
-  contextMenuEvent(QContextMenuEvent *event) override;
+  contextMenuEvent(QContextMenuEvent* event) override;
 
   void
-  wheelEvent(QWheelEvent *event) override;
+  wheelEvent(QWheelEvent* event) override;
 
   void
-  keyPressEvent(QKeyEvent *event) override;
+  keyPressEvent(QKeyEvent* event) override;
 
   void
-  keyReleaseEvent(QKeyEvent *event) override;
+  keyReleaseEvent(QKeyEvent* event) override;
 
   void
-  mousePressEvent(QMouseEvent *event) override;
+  mousePressEvent(QMouseEvent* event) override;
 
   void
-  mouseMoveEvent(QMouseEvent *event) override;
+  mouseMoveEvent(QMouseEvent* event) override;
 
   void
   drawBackground(QPainter* painter, const QRectF & r) override;
 
   void
-  showEvent(QShowEvent *event) override;
+  showEvent(QShowEvent* event) override;
 
 protected:
-  BasicGraphicsScene *
+  BasicGraphicsScene*
   nodeScene();
 
 private:
-  QAction* _clearSelectionAction;
-  QAction* _deleteSelectionAction;
-  QAction* _duplicateSelectionAction;
+  QAction* _clearSelectionAction = nullptr;
+  QAction* _deleteSelectionAction = nullptr;
+  QAction* _duplicateSelectionAction = nullptr;
 
   QPointF _clickPos;
+  ScaleRange _scaleRange;
 };
 }

src/DataFlowGraphicsScene.cpp

@@ -218,6 +218,8 @@ load()
   QByteArray const wholeFile = file.readAll();
 
   _graphModel.load(QJsonDocument::fromJson(wholeFile).object());
+
+  Q_EMIT sceneLoaded();
 }