From ad001563fda4a9061909bd09dcf51238138014d6 Mon Sep 17 00:00:00 2001
From: Nikita Kostovsky <nikita@kostovsky.me>
Date: Fri, 19 Sep 2025 14:28:21 +0200
Subject: initial commit

---
 src/graphicsview.cpp | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 src/graphicsview.cpp

(limited to 'src/graphicsview.cpp')

diff --git a/src/graphicsview.cpp b/src/graphicsview.cpp
new file mode 100644
index 0000000..b81cff4
--- /dev/null
+++ b/src/graphicsview.cpp
@@ -0,0 +1,47 @@
+#include "graphicsview.h"
+
+// qt
+#include <QWheelEvent>
+
+GraphicsView::GraphicsView(QWidget* parent)
+    : QGraphicsView{parent}
+{
+    init();
+}
+
+GraphicsView::GraphicsView(QGraphicsScene* scene, QWidget* parent)
+    : QGraphicsView{scene, parent}
+{
+    init();
+}
+
+void GraphicsView::wheelEvent(QWheelEvent* event)
+{
+    setTransformationAnchor(GraphicsView::AnchorUnderMouse);
+
+    QPoint pixels = event->pixelDelta();
+    QPoint degrees = event->angleDelta();
+    const auto oldScenePos = event->scenePosition();
+    const auto oldMapped = mapToScene(event->position().toPoint());
+
+    if (pixels.isNull() && degrees.isNull())
+        return;
+
+    const double scaleMultiplier{1.1};
+    const auto steps = double(pixels.isNull() ? degrees.y() : pixels.y());
+    auto actualScale = std::abs(steps) * scaleMultiplier /
+                       double(QWheelEvent::DefaultDeltasPerStep);
+
+    if (steps < 0)
+        actualScale = 1 / actualScale;
+
+    scale(actualScale, actualScale);
+
+    event->accept();
+}
+
+void GraphicsView::init()
+{
+    setDragMode(QGraphicsView::ScrollHandDrag);
+    setRenderHint(QPainter::Antialiasing, true);
+}
-- 
cgit v1.2.3-70-g09d2