Move marker label anchor to anchors mod

piker/ui/_anchors.py

@@ -21,6 +21,7 @@ Anchor funtions for UI placement of annotions.
 from typing import Callable
 
 from PyQt5.QtCore import QPointF
+from PyQt5.QtGui import QGraphicsPathItem
 
 from ._label import Label
 
@@ -155,3 +156,18 @@ def update_pp_nav(
 
     # re-anchor label (i.e. trigger call of ``arrow_tr()`` from above
     label.update()
+
+
+def path_topright(
+    gpath: QGraphicsPathItem,
+    label: Label,  # noqa
+
+) -> QPointF:
+    # get actual arrow graphics path
+    path_br = gpath.mapToScene(
+        gpath.path()
+    ).boundingRect()
+
+    # vb.locate(arrow_path)  #, children=True)
+
+    return path_br.topRight() - QPointF(0, label.h / 3)

piker/ui/_lines.py

@@ -26,6 +26,7 @@ import pyqtgraph as pg
 from pyqtgraph import Point, functions as fn
 from PyQt5 import QtCore, QtGui, QtWidgets
 from PyQt5.QtCore import QPointF
+from PyQt5.QtGui import QGraphicsPathItem
 
 from ._annotate import mk_marker, qgo_draw_markers
 from ._anchors import (
@@ -33,6 +34,7 @@ from ._anchors import (
     vbr_left,
     right_axis,
     update_pp_nav,
+    path_topright,
 )
 from ._label import Label
 from ._style import hcolor, _font
@@ -767,17 +769,11 @@ def position_line(
     )
     arrow_path.label = marker_label
 
-    def arrow_tr():
+    marker_label.scene_anchor = partial(
-        # get actual arrow graphics path
+        path_topright,
-        path_br = arrow_path.mapToScene(
+        gpath=arrow_path,
-            arrow_path.path()
+        label=marker_label,
-        ).boundingRect()
+    )
-
-        # vb.locate(arrow_path)  #, children=True)
-
-        return path_br.topRight() - QPointF(0, marker_label.h / 3)
-
-    marker_label.scene_anchor = arrow_tr
 
     line._labels.append(marker_label)