Smooth and bound graph viewer zoom

GNodeGUI/src/graph_viewer.cpp

@@ -1,6 +1,8 @@
 /* Copyright (c) 2024 Otto Link. Distributed under the terms of the GNU General
  * Public License. The full license is in the file LICENSE, distributed with
  * this software. */
+#include <algorithm>
+#include <cmath>
 #include <fstream>
 #include <iostream>
 
@@ -1371,13 +1373,25 @@ void GraphViewer::unpin_nodes()
 
 void GraphViewer::wheelEvent(QWheelEvent *event)
 {
-  const float factor = 1.2f;
-  QPointF     mouse_scene_pos = this->mapToScene(event->position().toPoint());
+  constexpr qreal min_zoom = 0.05;
+  constexpr qreal max_zoom = 8.0;
+  constexpr qreal zoom_base = 1.0015;
+
+  const qreal current_zoom = this->transform().m11();
+  const qreal requested_factor = std::pow(zoom_base, event->angleDelta().y());
+  const qreal target_zoom = std::clamp(current_zoom * requested_factor,
+                                       min_zoom,
+                                       max_zoom);
+  const qreal factor = target_zoom / current_zoom;
+
+  if (qFuzzyCompare(factor, 1.0))
+  {
+    event->accept();
+    return;
+  }
 
-  if (event->angleDelta().y() > 0)
-    this->scale(factor, factor);
-  else
-    this->scale(1.f / factor, 1.f / factor);
+  QPointF     mouse_scene_pos = this->mapToScene(event->position().toPoint());
+  this->scale(factor, factor);
 
   // adjust the view to maintain the zoom centered on the mouse position
   QPointF new_mouse_scene_pos = this->mapToScene(event->position().toPoint());