Cast to float from decimal for level line y-increment

Qt only accepts `float` to it's APIs obvs..

piker/ui/_cursor.py

@@ -363,7 +363,8 @@ class Cursor(pg.GraphicsObject):
 
         # value used for rounding y-axis discreet tick steps
         # computing once, up front, here cuz why not
-        self._y_incr_mult = float(1 / self.linked._symbol.tick_size)
+        mkt = self.linked._symbol
+        self._y_tick_mult = 1/float(mkt.price_tick)
 
         # line width in view coordinates
         self._lw = self.pixelWidth() * self.lines_pen.width()
@@ -571,9 +572,15 @@ class Cursor(pg.GraphicsObject):
         line_offset = self._lw / 2
 
         # round y value to nearest tick step
-        m = self._y_incr_mult
+        m = self._y_tick_mult
         iy = round(y * m) / m
         vl_y = iy - line_offset
+        # print(
+        #     f'tick: {self._y_tick}\n'
+        #     f'y: {y}\n'
+        #     f'iy: {iy}\n'
+        #     f'vl_y: {vl_y}\n'
+        # )
 
         # update y-range items
         if iy != last_iy:

piker/ui/_lines.py

@@ -126,7 +126,7 @@ class LevelLine(pg.InfiniteLine):
         self._on_drag_start = lambda l: None
         self._on_drag_end = lambda l: None
 
-        self._y_incr_mult = 1 / chart.linked.symbol.tick_size
+        self._y_incr_mult = float(1 / chart.linked.symbol.size_tick)
         self._right_end_sc: float = 0
 
         # use px caching