Issue #207: Zoom to Cursor (Zoom Anchoring)

JakubMelka · Aug 31, 2024 · b97e36c · b97e36c
1 parent 2a93ca5
commit b97e36c
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Showing 4 changed files with 32 additions and 10 deletions.
diff --git a/Pdf4QtLibWidgets/sources/pdfdrawspacecontroller.cpp b/Pdf4QtLibWidgets/sources/pdfdrawspacecontroller.cpp
@@ -1231,21 +1231,41 @@ QPoint PDFDrawWidgetProxy::scrollByPixels(QPoint offset)
     return QPoint(m_horizontalOffset - oldHorizontalOffset, m_verticalOffset - oldVerticalOffset);
 }
 
-void PDFDrawWidgetProxy::zoom(PDFReal zoom)
+void PDFDrawWidgetProxy::zoom(PDFReal zoom, std::optional<QPointF> widgetPosition)
 {
     const PDFReal clampedZoom = qBound(MIN_ZOOM, zoom, MAX_ZOOM);
     if (m_zoom != clampedZoom)
     {
-        const PDFReal oldHorizontalOffsetMM = m_horizontalOffset * m_pixelToDeviceSpaceUnit;
-        const PDFReal oldVerticalOffsetMM = m_verticalOffset * m_pixelToDeviceSpaceUnit;
+        if (widgetPosition.has_value())
+        {
+            QPointF point = widgetPosition.value();
 
-        m_zoom = clampedZoom;
+            const PDFReal posX = (m_horizontalOffset - point.x()) * m_pixelToDeviceSpaceUnit;
+            const PDFReal posY = (m_verticalOffset - point.y()) * m_pixelToDeviceSpaceUnit;
 
-        update();
+            m_zoom = clampedZoom;
+
+            update();
 
-        // Try to restore offsets, so we are in the same place
-        setHorizontalOffset(oldHorizontalOffsetMM * m_deviceSpaceUnitToPixel);
-        setVerticalOffset(oldVerticalOffsetMM * m_deviceSpaceUnitToPixel);
+            const PDFReal hp = posX / m_pixelToDeviceSpaceUnit + point.x();
+            const PDFReal vp = posY / m_pixelToDeviceSpaceUnit + point.y();
+
+            setHorizontalOffset(hp);
+            setVerticalOffset(vp);
+        }
+        else
+        {
+            const PDFReal oldHorizontalOffsetMM = m_horizontalOffset * m_pixelToDeviceSpaceUnit;
+            const PDFReal oldVerticalOffsetMM = m_verticalOffset * m_pixelToDeviceSpaceUnit;
+
+            m_zoom = clampedZoom;
+
+            update();
+
+            // Try to restore offsets, so we are in the same place
+            setHorizontalOffset(oldHorizontalOffsetMM * m_deviceSpaceUnitToPixel);
+            setVerticalOffset(oldVerticalOffsetMM * m_deviceSpaceUnitToPixel);
+        }
     }
 }
 

diff --git a/Pdf4QtLibWidgets/sources/pdfdrawspacecontroller.h b/Pdf4QtLibWidgets/sources/pdfdrawspacecontroller.h
@@ -254,7 +254,8 @@ class PDF4QTLIBWIDGETSSHARED_EXPORT PDFDrawWidgetProxy : public QObject
     /// Sets the zoom. Tries to preserve current offsets (so the current visible
     /// area will be visible after the zoom).
     /// \param zoom New zoom
-    void zoom(PDFReal zoom);
+    /// \param widgetPosition Position of the mouse during zooming
+    void zoom(PDFReal zoom, std::optional<QPointF> widgetPosition = std::nullopt);
 
     enum class ZoomHint
     {

diff --git a/Pdf4QtLibWidgets/sources/pdfdrawwidget.cpp b/Pdf4QtLibWidgets/sources/pdfdrawwidget.cpp
@@ -551,7 +551,7 @@ void PDFDrawWidget::wheelEvent(QWheelEvent* event)
         const PDFReal zoom = m_widget->getDrawWidgetProxy()->getZoom();
         const PDFReal zoomStep = std::pow(PDFDrawWidgetProxy::ZOOM_STEP, static_cast<PDFReal>(angleDeltaY) / static_cast<PDFReal>(QWheelEvent::DefaultDeltasPerStep));
         const PDFReal newZoom = zoom * zoomStep;
-        proxy->zoom(newZoom);
+        proxy->zoom(newZoom, event->position());
     }
     else
     {

diff --git a/RELEASES.txt b/RELEASES.txt
@@ -1,4 +1,5 @@
 CURRENT:
+ - Issue #207: Zoom to Cursor (Zoom Anchoring) 
  - Issue #185: Latest git fails to build in linux
 
 V: 1.4.0.0 4.7.2024