Extend level line interaction

Support tracking the mouse cursor using a new `on_tracked_sources()`
callback method. Make hovered highlight a bit thicker and highlight when
click-dragged. Add a delete method for removing from the scene along
with label.

piker/ui/_graphics/_lines.py

@@ -33,8 +33,6 @@ from .._axes import YSticky
 
 class LevelLabel(YSticky):
 
-    line_pen = pg.mkPen(hcolor('bracket'))
-
     _w_margin = 4
     _h_margin = 3
     level: float = 0
@@ -43,13 +41,15 @@ class LevelLabel(YSticky):
         self,
         chart,
         *args,
+        color: str = 'bracket',
         orient_v: str = 'bottom',
         orient_h: str = 'left',
         **kwargs
     ) -> None:
         super().__init__(chart, *args, **kwargs)
 
-        self._pen = self.line_pen
+        # TODO: this is kinda cludgy
+        self._pen = self.pen = pg.mkPen(hcolor(color))
 
         # orientation around axis options
         self._orient_v = orient_v
@@ -77,7 +77,7 @@ class LevelLabel(YSticky):
         br = self.boundingRect()
         h, w = br.height(), br.width()
 
-        # this triggers ``.pain()`` implicitly?
+        # this triggers ``.paint()`` implicitly?
         self.setPos(QPointF(
             self._h_shift * w - offset,
             abs_pos.y() - (self._v_shift * h) - offset
@@ -118,11 +118,10 @@ class LevelLabel(YSticky):
         self.update()
 
     def unhighlight(self):
-        self._pen = self.line_pen
+        self._pen = self.pen
         self.update()
 
 
-
 class L1Label(LevelLabel):
 
     size: float = 0
@@ -192,52 +191,124 @@ class L1Labels:
 
 
 class LevelLine(pg.InfiniteLine):
+
+    # TODO: fill in these slots for orders
+    # .sigPositionChangeFinished.emit(self)
+
     def __init__(
         self,
+        chart: 'ChartPlotWidget',  # type: ignore # noqa
         label: LevelLabel,
+        highlight_color: str = 'default_light',
         **kwargs,
     ) -> None:
         self.label = label
         super().__init__(**kwargs)
+
         self.sigPositionChanged.connect(self.set_level)
 
+        self._chart = chart
+
         # use slightly thicker highlight
-        self.setHoverPen(
+        pen = pg.mkPen(hcolor(highlight_color))
-            color=(255, 0, 0),
+        pen.setWidth(2)
-            width=self.pen.width() + 1
+        self.setHoverPen(pen)
-        )
+        self._track_cursor: bool = False
 
     def set_level(self, value: float) -> None:
         self.label.update_from_data(0, self.value())
 
+    def on_tracked_source(
+        self,
+        x: int,
+        y: float
+    ) -> None:
+        self.movable = True
+        self.setPos(y)  # implictly calls ``.set_level()``
+        self.update()
+
     def setMouseHover(self, hover: bool) -> None:
         """Mouse hover callback.
 
         """
         if self.mouseHovering == hover:
             return
+
         self.mouseHovering = hover
 
+        chart = self._chart
+
         if hover:
 
             self.currentPen = self.hoverPen
             self.label.highlight(self.hoverPen)
 
+            # add us to cursor state
+            chart._cursor.add_hovered(self)
+
+            # # hide y-crosshair
+            # chart._cursor.graphics[chart]['hl'].hide()
+
         else:
             self.currentPen = self.pen
             self.label.unhighlight()
 
+            chart._cursor._hovered.remove(self)
+
         # highlight any attached label
 
         # self.setCursor(QtCore.Qt.OpenHandCursor)
         # self.setCursor(QtCore.Qt.DragMoveCursor)
         self.update()
 
+    def mouseDragEvent(self, ev):
+        chart = self._chart
+        # hide y-crosshair
+        chart._cursor.graphics[chart]['hl'].hide()
+
+        # highlight
+        self.currentPen = self.hoverPen
+        self.label.highlight(self.hoverPen)
+
+        # normal tracking behavior
+        super().mouseDragEvent(ev)
+
+        # This is the final position in the drag
+        if ev.isFinish():
+            # show y-crosshair again
+            chart = self._chart
+            chart._cursor.graphics[chart]['hl'].show()
+
+    def mouseDoubleClickEvent(
+        self,
+        ev: QtGui.QMouseEvent,
+    ) -> None:
+        print(f'double click {ev}')
+
+    # def mouseMoved(
+    #     self,
+    #     ev: Tuple[QtGui.QMouseEvent],
+    # ) -> None:
+    #     pos = evt[0]
+    #     print(pos)
+
+    def delete(self) -> None:
+        """Remove this line from containing chart/view/scene.
+
+        """
+        scene = self.scene()
+        if scene:
+            # self.label.parent.scene().removeItem(self.label)
+            scene.removeItem(self.label)
+
+        self._chart.plotItem.removeItem(self)
+
 
 def level_line(
     chart: 'ChartPlogWidget',  # noqa
     level: float,
     digits: int = 1,
+    color: str = 'default',
 
     # size 4 font on 4k screen scaled down, so small-ish.
     font_size_inches: float = _down_2_font_inches_we_like,
@@ -254,11 +325,13 @@ def level_line(
         parent=chart.getAxis('right'),
         # TODO: pass this from symbol data
         digits=digits,
-        opacity=1,
+        opacity=0.666,
         font_size_inches=font_size_inches,
+        color=color,
+
         # TODO: make this take the view's bg pen
         bg_color='papas_special',
-        fg_color='default',
+        fg_color=color,
         **linelabelkwargs
     )
     label.update_from_data(0, level)
@@ -267,12 +340,16 @@ def level_line(
     label._size_br_from_str(label.label_str)
 
     line = LevelLine(
+        chart,
         label,
+        # lookup "highlight" equivalent
+        highlight_color=color + '_light',
         movable=True,
         angle=0,
     )
     line.setValue(level)
-    line.setPen(pg.mkPen(hcolor('default')))
+    line.setPen(pg.mkPen(hcolor(color)))
+
     # activate/draw label
     line.setValue(level)