Canvas: Add zoom

Author: janezd

Orange/canvas/canvas/view.py

@@ -4,7 +4,7 @@
 import logging
 
 from AnyQt.QtWidgets import QGraphicsView
-from AnyQt.QtGui import QCursor, QIcon
+from AnyQt.QtGui import QCursor, QIcon, QTransform
 from AnyQt.QtCore import Qt, QRect, QSize, QRectF, QPoint, QTimer
 
 log = logging.getLogger(__name__)
@@ -25,6 +25,8 @@ def __init__(self, *args):
         self.__autoScrollTimer = QTimer(self)
         self.__autoScrollTimer.timeout.connect(self.__autoScrollAdvance)
 
+        self.__scale = 1.0
+
     def setScene(self, scene):
         QGraphicsView.setScene(self, scene)
         self._ensureSceneRect(scene)
@@ -63,6 +65,18 @@ def mouseReleaseEvent(self, event):
 
         return QGraphicsView.mouseReleaseEvent(self, event)
 
+    def wheelEvent(self, event):
+        # use mouse position as anchor while zooming
+        self.setTransformationAnchor(2)
+        if event.modifiers() & Qt.ControlModifier:
+            self.__scale += min(50, event.angleDelta().y()) / 120
+            self.__scale = min(1.5, max(self.__scale, 0.25))
+            transform = QTransform()
+            transform.scale(self.__scale, self.__scale)
+            self.setTransform(transform)
+        else:
+            super().wheelEvent(event)
+
     def __shouldAutoScroll(self, pos):
         if self.__autoScroll:
             margin = self.__autoScrollMargin