fix(canvas): clear snap highlight after every paint

The NEAR_VERTEX highlight set on self.current during snap persisted on
the shape state between events. Any repaint that fired without a
preceding mouseMoveEvent (scroll, zoom, resize, window expose) would
redraw the stale white circle at vertex 0 even though the cursor had
moved far away from the snap range.

Clear self.current's highlight at the end of paintEvent so transient
snap state never survives across paint events. mouseMoveEvent sets it
again on every move, so the live snap indicator still shows correctly.

(cherry picked from commit fcb3a8e)

Author: wkentaro

labelme/widgets/canvas.py

@@ -385,7 +385,6 @@ def mouseMoveEvent(self, a0: QtGui.QMouseEvent) -> None:
                 self._update_status()
                 return
 
-            self.current.highlightClear()
             if self.outOfPixmap(pos):
                 # Don't allow the user to draw outside the pixmap.
                 # Project the point to the pixmap's edges.
@@ -895,6 +894,8 @@ def paintEvent(self, a0: QtGui.QPaintEvent) -> None:
             "ai_points_to_shape",
         ]:
             p.end()
+            if self.current is not None:
+                self.current.highlightClear()
             return
 
         drawing_shape: Shape = self.current.copy()
@@ -923,6 +924,8 @@ def paintEvent(self, a0: QtGui.QPaintEvent) -> None:
         drawing_shape.selected = self.fillDrawing()
         drawing_shape.paint(p)
         p.end()
+        if self.current is not None:
+            self.current.highlightClear()
 
     def transformPos(self, point: QPointF) -> QPointF:
         """Convert from widget-logical coordinates to painter-logical ones."""