From a2aaa3c71b8f7e1846a490525001342c6a17f437 Mon Sep 17 00:00:00 2001
From: "Felix (xq) Queißner" <git@mq32.de>
Date: Wed, 10 Jun 2020 02:01:44 +0200
Subject: Improves image panning and zoom. Image view is now on a better
 default and usability.

---
 lib/luis-l-gist/interactiveview.cpp | 133 ++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 lib/luis-l-gist/interactiveview.cpp

(limited to 'lib/luis-l-gist/interactiveview.cpp')

diff --git a/lib/luis-l-gist/interactiveview.cpp b/lib/luis-l-gist/interactiveview.cpp
new file mode 100644
index 0000000..2707352
--- /dev/null
+++ b/lib/luis-l-gist/interactiveview.cpp
@@ -0,0 +1,133 @@
+#include "interactiveview.hpp"
+
+#define VIEW_CENTER viewport()->rect().center()
+#define VIEW_WIDTH viewport()->rect().width()
+#define VIEW_HEIGHT viewport()->rect().height()
+
+InteractiveView::InteractiveView(QWidget * parent) :
+    QGraphicsView(parent)
+{
+    setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+
+    setMaxSize();
+    centerOn(0, 0);
+
+    zoomDelta = 0.1;
+    panSpeed = 4;
+    _doMousePanning = false;
+    _doKeyZoom = false;
+    _scale = 1.0;
+
+    panButton = Qt::MiddleButton;
+    zoomKey = Qt::Key_Z;
+}
+
+qreal InteractiveView::getScale() const
+{
+    return _scale;
+}
+
+void InteractiveView::keyPressEvent(QKeyEvent * event)
+{
+    qint32 key = event->key();
+
+    if(key == zoomKey){
+        _doKeyZoom = true;
+    }
+
+    if (_doKeyZoom){
+        if (key == Qt::Key_Up)
+            zoomIn();
+
+        else if (key == Qt::Key_Down)
+            zoomOut();
+    }
+
+    else{
+        QGraphicsView::keyPressEvent(event);
+    }
+}
+
+void InteractiveView::keyReleaseEvent(QKeyEvent * event)
+{
+    if (event->key() == zoomKey){
+        _doKeyZoom = false;
+    }
+
+    QGraphicsView::keyReleaseEvent(event);
+}
+
+void InteractiveView::mouseMoveEvent(QMouseEvent * event)
+{
+    if (_doMousePanning){
+        QPointF mouseDelta = mapToScene(event->pos()) - mapToScene(_lastMousePos);
+        pan(mouseDelta);
+    }
+
+    QGraphicsView::mouseMoveEvent(event);
+    _lastMousePos = event->pos();
+}
+
+void InteractiveView::mousePressEvent(QMouseEvent * event)
+{
+    if (event->button() == panButton){
+        _lastMousePos = event->pos();
+        _doMousePanning = true;
+    }
+
+    QGraphicsView::mousePressEvent(event);
+}
+
+void InteractiveView::mouseReleaseEvent(QMouseEvent * event)
+{
+    if (event->button() == panButton){
+        _doMousePanning = false;
+    }
+
+    QGraphicsView::mouseReleaseEvent(event);
+}
+
+void InteractiveView::wheelEvent(QWheelEvent *event)
+{
+    QPoint scrollAmount = event->angleDelta();
+
+    // Apply zoom.
+    scrollAmount.y() > 0 ? zoomIn() : zoomOut();
+}
+
+void InteractiveView::setMaxSize()
+{
+    setSceneRect(INT_MIN/2, INT_MIN/2, INT_MAX, INT_MAX);
+}
+
+void InteractiveView::zoom(float scaleFactor)
+{
+    scale(scaleFactor, scaleFactor);
+    _scale *= scaleFactor;
+}
+
+void InteractiveView::zoomIn()
+{
+    zoom(1 + zoomDelta);
+}
+
+void InteractiveView::zoomOut()
+{
+    zoom (1 - zoomDelta);
+}
+
+void InteractiveView::pan(QPointF delta)
+{
+    // Scale the pan amount by the current zoom.
+    delta *= _scale;
+    delta *= panSpeed;
+
+    // Have panning be anchored from the mouse.
+    setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
+    QPoint newCenter(VIEW_WIDTH / 2 - delta.x(),  VIEW_HEIGHT / 2 - delta.y());
+    centerOn(mapToScene(newCenter));
+
+    // For zooming to anchor from the view center.
+    setTransformationAnchor(QGraphicsView::AnchorViewCenter);
+}
-- 
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