1 files changed, 77 insertions, 0 deletions
diff --git a/src/main/python/utils/graphics.py b/src/main/python/utils/graphics.py
new file mode 100644
index 0000000..0fe0030
--- /dev/null
+++ b/src/main/python/utils/graphics.py
@@ -0,0 +1,77 @@
+from PyQt5.QtCore import Qt
+from PyQt5.QtGui import QPen
+from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QGraphicsProxyWidget, QGraphicsItem
+from PyQt5 import QtWidgets
+
+class customView(QGraphicsView):
+    """
+    Defines custom QGraphicsView with zoom features and drag-drop accept event, overriding wheel event
+    """
+    def __init__(self, scene = None, parent=None):
+        if scene is not None: #overloaded constructor
+            super(customView, self).__init__(scene, parent)
+        else:
+            super(customView, self).__init__(parent)
+        self._zoom = 1
+        self.setDragMode(True) #sets pannable using mouse
+        self.setAcceptDrops(True) #sets ability to accept drops
+    
+    #following four functions are required to be overridden for drag-drop functionality
+    def dragEnterEvent(self, QDragEnterEvent):
+        #defines acceptable drop items
+        if QDragEnterEvent.mimeData().hasText():
+            QDragEnterEvent.acceptProposedAction()
+        
+    def dragMoveEvent(self, QDragMoveEvent):
+        #defines acceptable drop items
+        if QDragMoveEvent.mimeData().hasText():
+            QDragMoveEvent.acceptProposedAction()
+            
+    def dragLeaveEvent(self, QDragLeaveEvent):
+        #accept any drag leave event, avoid unnecessary logging
+        QDragLeaveEvent.accept()
+    
+    def dropEvent(self, QDropEvent):
+        #defines item drop, fetches text, creates corresponding QGraphicItem and adds it to scene
+        if QDropEvent.mimeData().hasText():
+            #QDropEvent.mimeData().text() defines intended drop item, the pos values define position
+            graphic = getattr(QtWidgets, QDropEvent.mimeData().text())(QDropEvent.pos().x()-150, QDropEvent.pos().y()-150, 300, 300)
+            graphic.setPen(QPen(Qt.black, 2))
+            graphic.setFlags(QGraphicsItem.ItemIsSelectable | QGraphicsItem.ItemIsMovable)
+            self.scene().addItem(graphic) 
+            QDropEvent.acceptProposedAction()
+     
+    def wheelEvent(self, QWheelEvent):
+        #overload wheelevent, to zoom if control is pressed, else scroll normally
+        if Qt.ControlModifier: #check if control is pressed
+            if QWheelEvent.source() == Qt.MouseEventNotSynthesized: #check if precision mouse(mac)
+                # angle delta is 1/8th of a degree per scroll unit
+                if self.zoom + QWheelEvent.angleDelta().y()/2880 > 0.1: # hit and trial value (2880)
+                    self.zoom += QWheelEvent.angleDelta().y()/2880
+            else:
+                # precision delta is exactly equal to amount to scroll
+                if self.zoom + QWheelEvent.pixelDelta().y() > 0.1:
+                    self.zoom += QWheelEvent.angleDelta().y()
+            QWheelEvent.accept() # accept event so that scrolling doesnt happen simultaneously
+        else:
+            return super().wheelEvent(self, QWheelEvent) # scroll if ctrl not pressed
+    
+    @property
+    def zoom(self):
+        # property for zoom
+        return self._zoom
+    
+    @zoom.setter
+    def zoom(self, value):
+        # set scale according to zoom value being set
+        temp = self.zoom
+        self._zoom = value
+        self.scale(self.zoom / temp, self.zoom / temp)
+        
+class customScene(QGraphicsScene):
+    """
+    re-implement QGraphicsScene for future functionality 
+    hint: QUndoFramework
+    """
+    pass
+        
+\ No newline at end of file