14.24: Ctrl or Meta with a middle drag zooms

src/Rendering/EditorCanvas+Brush.cpp

@@ -114,7 +114,7 @@ void CanvasView::endBrushTipDrag(QPointF point)
 // The circle at the pointer, a stroke's own size.
 void CanvasView::updateBrushCursor()
 {
-    const bool shows = isBrushTool(m_session.tool()) && !m_spaceHeld && !picking() && !m_middlePanPoint;
+    const bool shows = isBrushTool(m_session.tool()) && !m_spaceHeld && !picking() && !m_middlePanPoint && !m_middleZoom;
     const double diameter = m_session.brushStroke() ? m_session.brushStroke()->settings.diameter : m_session.brushSettings().diameter;
     // Clone Stamp marks its source; between strokes, previews a click.
     std::optional<QPointF> sample;

src/Rendering/EditorCanvas+Cursors.cpp

@@ -263,7 +263,9 @@ void CanvasView::updateCursor()
 {
     const NavigationTool tool = m_session.tool();
     // A middle-button pan outranks every drag; another keeps its cursor.
-    if (m_middlePanPoint)
+    if (m_middleZoom)
+        setCursor(zoomCursor(m_middleZoom->out, devicePixelRatio()));
+    else if (m_middlePanPoint)
         setCursor(Qt::ClosedHandCursor);
     else if (m_dragCursor)
         setCursor(*m_dragCursor);

src/Rendering/EditorCanvas+Navigation.cpp

@@ -120,9 +120,12 @@ void CanvasView::mousePressEvent(QMouseEvent *event)
 // Swift's mouseDown with its click count.
 void CanvasView::press(QMouseEvent *event, int clicks)
 {
-    // The middle button pans in any tool, beside the left.
+    // The middle button pans anywhere; Ctrl or Meta zooms.
     if (event->button() == Qt::MiddleButton && m_session.document()) {
-        m_middlePanPoint = event->position();
+        if (event->modifiers() & (Qt::ControlModifier | Qt::MetaModifier))
+            m_middleZoom = MiddleZoom{event->position(), m_session.viewport.zoom()};
+        else
+            m_middlePanPoint = event->position();
         updateBrushCursor();
         updateCursor();
         return;
@@ -226,6 +229,17 @@ void CanvasView::mouseMoveEvent(QMouseEvent *event)
     // Swift's mouseMoved: the readout follows a hover alone.
     if (!event->buttons() && m_session.document())
         m_session.updateCameraRawReadout(m_session.viewport.documentPoint(point, m_session.document()->size()));
+    if (m_middleZoom && event->buttons().testFlag(Qt::MiddleButton)) {
+        // Up zooms in, doubling each 100 points, as Zoom drags.
+        const double factor = std::pow(2, (m_middleZoom->start.y() - point.y()) / 100);
+        m_middleZoom->out = factor < 1;
+        m_session.zoom(m_middleZoom->zoom * factor, m_middleZoom->start);
+        updateCursor();
+        if (!event->buttons().testFlag(Qt::LeftButton))
+            return;
+    } else if (m_middleZoom) {
+        endMiddlePan();
+    }
     if (m_middlePanPoint && event->buttons().testFlag(Qt::MiddleButton)) {
         m_session.viewport.translate(QSizeF(point.x() - m_middlePanPoint->x(), point.y() - m_middlePanPoint->y()));
         m_middlePanPoint = point;
@@ -297,7 +311,7 @@ void CanvasView::mouseMoveEvent(QMouseEvent *event)
 
 void CanvasView::mouseReleaseEvent(QMouseEvent *event)
 {
-    if (event->button() == Qt::MiddleButton && m_middlePanPoint) {
+    if (event->button() == Qt::MiddleButton && (m_middlePanPoint || m_middleZoom)) {
         endMiddlePan();
         return;
     }
@@ -394,6 +408,7 @@ void CanvasView::leaveEvent(QEvent *event)
 void CanvasView::endMiddlePan()
 {
     m_middlePanPoint.reset();
+    m_middleZoom.reset();
     updateCursor();
     updateBrushCursor();
 }

src/Rendering/EditorCanvas.h

@@ -134,6 +134,12 @@ private:
         double zoom;
         bool moved;
     };
+    // Swift's middleZoom: its start, the zoom then, the minus.
+    struct MiddleZoom {
+        QPointF start;
+        double zoom;
+        bool out = false;
+    };
     using Center = std::function<QPointF(QPointF)>;
     // What a press off the handles drags, picked or not.
     struct PressTarget {
@@ -303,6 +309,8 @@ private:
     std::optional<QPointF> m_lastDragPoint;
     // Where a middle-button pan last was, its own drag point.
     std::optional<QPointF> m_middlePanPoint;
+    // A middle drag with Ctrl or Meta: Blender's zoom.
+    std::optional<MiddleZoom> m_middleZoom;
     std::optional<ZoomDrag> m_zoomDrag;
     bool m_shiftHeld = false;
     // Document point where a drag of the outline began.