From 03d31b2225981c5f50436a024a562d2f53981aff Mon Sep 17 00:00:00 2001
From: itsmattkc <itsmattkc@gmail.com>
Date: Fri, 22 Jan 2021 19:52:05 +1100
Subject: [PATCH] fixed cursor zooming algorithm

What the hell is this? How did I write this old algorithm? Did it even work?
---
 app/widget/nodeview/nodeview.cpp       | 15 +++++++++++++++
 app/widget/timebased/timebasedview.cpp |  4 ++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/app/widget/nodeview/nodeview.cpp b/app/widget/nodeview/nodeview.cpp
index 87bbb66a0..e531082d6 100644
--- a/app/widget/nodeview/nodeview.cpp
+++ b/app/widget/nodeview/nodeview.cpp
@@ -22,6 +22,7 @@
 
 #include <QInputDialog>
 #include <QMouseEvent>
+#include <QScrollBar>
 
 #include "core.h"
 #include "nodeviewundo.h"
@@ -564,7 +565,21 @@ void NodeView::wheelEvent(QWheelEvent *event)
     double test_scale = scale_ * multiplier;
 
     if (test_scale > 0.1) {
+      QPointF cursor_pos;
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+      cursor_pos = event->position();
+#else
+      cursor_pos = event->posF();
+#endif
+
+      int anchor_x = qRound(double(cursor_pos.x() + horizontalScrollBar()->value()) / scale_ * test_scale - cursor_pos.x());
+      int anchor_y = qRound(double(cursor_pos.y() + verticalScrollBar()->value()) / scale_ * test_scale - cursor_pos.y());
+
       scale(multiplier, multiplier);
+
+      this->horizontalScrollBar()->setValue(anchor_x);
+      this->verticalScrollBar()->setValue(anchor_y);
+
       scale_ = test_scale;
     }
   } else {
diff --git a/app/widget/timebased/timebasedview.cpp b/app/widget/timebased/timebasedview.cpp
index 8b4089b58..8f29cc21f 100644
--- a/app/widget/timebased/timebasedview.cpp
+++ b/app/widget/timebased/timebasedview.cpp
@@ -302,7 +302,7 @@ bool TimeBasedView::HandleZoomFromScroll(QWheelEvent *event)
       if (!only_vertical) {
         double new_x_scale = GetScale() * scale_multiplier;
 
-        int new_x_scroll = qRound(horizontalScrollBar()->value() / GetScale() * new_x_scale + (cursor_pos.x() - cursor_pos.x() / new_x_scale * GetScale()));
+        int new_x_scroll = qRound(double(cursor_pos.x() + horizontalScrollBar()->value()) / GetScale() * new_x_scale - cursor_pos.x());
 
         emit ScaleChanged(new_x_scale);
 
@@ -312,7 +312,7 @@ bool TimeBasedView::HandleZoomFromScroll(QWheelEvent *event)
       if (!only_horizontal) {
         double new_y_scale = GetYScale() * scale_multiplier;
 
-        int new_y_scroll = qRound(verticalScrollBar()->value() / GetYScale() * new_y_scale + (cursor_pos.y() - cursor_pos.y() / new_y_scale * GetYScale()));
+        int new_y_scroll = qRound(double(cursor_pos.y() + verticalScrollBar()->value()) / GetYScale() * new_y_scale - cursor_pos.y());
 
         SetYScale(new_y_scale);