Add arrowheads to labels

For labels that want it add nice arrow paths that point just over the
respective axis. Couple label text offset from the axis line based on
parent 'tickTextOffset' setting. Drop `YSticky` it was not enough
meat to bother with.

piker/ui/_axes.py

@@ -53,10 +53,10 @@ class Axis(pg.AxisItem):
 
         self.setTickFont(_font.font)
         self.setStyle(**{
-            'textFillLimits': [(0, 0.666)],
+            'textFillLimits': [(0, 0.616)],
             'tickFont': _font.font,
             # offset of text *away from* axis line in px
-            'tickTextOffset': 2,
+            'tickTextOffset': 6,
         })
 
         self.setTickFont(_font.font)
@@ -78,6 +78,10 @@ class PriceAxis(Axis):
         **kwargs,
     ) -> None:
         super().__init__(*args, orientation='right', **kwargs)
+        self.setStyle(**{
+            # offset of text *away from* axis line in px
+            'tickTextOffset': 9,
+        })
 
     def resize(self) -> None:
         self.setWidth(self.typical_br.width())
@@ -151,8 +155,8 @@ class DynamicDateAxis(Axis):
 
 class AxisLabel(pg.GraphicsObject):
 
-    _w_margin = 0
+    _x_margin = 0
-    _h_margin = 0
+    _y_margin = 0
 
     def __init__(
         self,
@@ -161,6 +165,7 @@ class AxisLabel(pg.GraphicsObject):
         bg_color: str = 'bracket',
         fg_color: str = 'black',
         opacity: int = 0,
+        use_arrow: bool = True,
         font_size_inches: Optional[float] = None,
     ) -> None:
 
@@ -183,6 +188,10 @@ class AxisLabel(pg.GraphicsObject):
         self.bg_color = pg.mkColor(hcolor(bg_color))
         self.fg_color = pg.mkColor(hcolor(fg_color))
 
+        self._use_arrow = use_arrow
+
+        # create triangle path
+        self.path = None
         self.rect = None
 
     def paint(
@@ -195,13 +204,12 @@ class AxisLabel(pg.GraphicsObject):
 
         if self.label_str:
 
-            if not self.rect:
+            # if not self.rect:
-                self._size_br_from_str(self.label_str)
+            self._size_br_from_str(self.label_str)
 
             p.setFont(self._dpifont.font)
             p.setPen(self.fg_color)
             p.setOpacity(self.opacity)
-            p.fillRect(self.rect, self.bg_color)
 
             # can be overrided in subtype
             self.draw(p, self.rect)
@@ -215,13 +223,33 @@ class AxisLabel(pg.GraphicsObject):
     ) -> None:
         # this adds a nice black outline around the label for some odd
         # reason; ok by us
-        p.setOpacity(self.opacity)
+        # p.setOpacity(self.opacity)
         p.drawRect(self.rect)
 
+        if self._use_arrow:
+
+            if not self.path:
+                self._draw_arrow_path()
+
+            p.drawPath(self.path)
+            p.fillPath(self.path, pg.mkBrush(self.bg_color))
+
+        p.fillRect(self.rect, self.bg_color)
+
+
     def boundingRect(self):  # noqa
         if self.label_str:
             self._size_br_from_str(self.label_str)
-            return self.rect
+
+            # if self.path:
+            #     self.tl = self.path.controlPointRect().topLeft()
+            if not self.path:
+                self.tl = self.rect.topLeft()
+
+            return QtCore.QRectF(
+                self.tl,
+                self.rect.bottomRight(),
+            )
 
         return QtCore.QRectF()
 
@@ -237,16 +265,20 @@ class AxisLabel(pg.GraphicsObject):
         #     # XXX: this can't be c
         #     self._txt_br = self._dpifont.boundingRect(value)
 
-        br = self._txt_br = self._dpifont.boundingRect(value)
+        txt_br = self._txt_br = self._dpifont.boundingRect(value)
-        txt_h, txt_w = br.height(), br.width()
+        txt_h, txt_w = txt_br.height(), txt_br.width()
         h, w = self.size_hint()
 
         self.rect = QtCore.QRectF(
             0, 0,
-            (w or txt_w) + self._w_margin,
+            (w or txt_w) + self._x_margin/2,
-            (h or txt_h) + self._h_margin,
+            (h or txt_h) + self._y_margin/2,
         )
+        # print(self.rect)
+        # hb = self.path.controlPointRect()
+        # hb_size = hb.size()
 
+        return self.rect
 
 # _common_text_flags = (
 #     QtCore.Qt.TextDontClip |
@@ -258,7 +290,7 @@ class AxisLabel(pg.GraphicsObject):
 
 
 class XAxisLabel(AxisLabel):
-    _w_margin = 4
+    _x_margin = 8
 
     text_flags = (
         QtCore.Qt.TextDontClip
@@ -273,7 +305,7 @@ class XAxisLabel(AxisLabel):
         self,
         abs_pos: QPointF,  # scene coords
         value: float,  # data for text
-        offset: int = 1  # if have margins, k?
+        offset: int = 0  # if have margins, k?
     ) -> None:
 
         timestrs = self.parent._indexes_to_timestrs([int(value)])
@@ -281,18 +313,39 @@ class XAxisLabel(AxisLabel):
         if not timestrs.any():
             return
 
-        self.label_str = timestrs[0]
+        pad = 1*' '
+        self.label_str = pad + timestrs[0] + pad
+
+        y_offset = self.parent.style['tickTextOffset'][1]
 
         w = self.boundingRect().width()
         self.setPos(QPointF(
-            abs_pos.x() - w / 2 - offset,
+            abs_pos.x() - w/2,
-            1,
+            y_offset/2,
         ))
         self.update()
 
+    def _draw_arrow_path(self):
+        y_offset = self.parent.style['tickTextOffset'][1]
+        path = QtGui.QPainterPath()
+        h, w = self.rect.height(), self.rect.width()
+        # middle = (w + self._y_margin)/2
+        # middle = (w + self._x_margin)/2
+        middle = w/2 - 0.5
+        # aw = (h + self._x_margin)/2
+        aw = h/2
+        left = middle - aw
+        right = middle + aw
+        path.moveTo(left, 0)
+        path.lineTo(middle, -y_offset)
+        path.lineTo(right, 0)
+        path.closeSubpath()
+        self.path = path
+        self.tl = QtCore.QPointF(0, -y_offset)
+
 
 class YAxisLabel(AxisLabel):
-    _h_margin = 2
+    _y_margin = 4
 
     text_flags = (
         QtCore.Qt.AlignLeft
@@ -301,33 +354,6 @@ class YAxisLabel(AxisLabel):
         | QtCore.Qt.TextDontClip
     )
 
-    def size_hint(self) -> Tuple[float, float]:
-        # size to parent axis width
-        return None, self.parent.width()
-
-    def update_label(
-        self,
-        abs_pos: QPointF,  # scene coords
-        value: float,  # data for text
-        offset: int = 1  # on odd dimension and/or adds nice black line
-    ) -> None:
-
-        # this is read inside ``.paint()``
-        self.label_str = ' {value:,.{digits}f}'.format(
-            digits=self.digits, value=value).replace(',', ' ')
-
-        br = self.boundingRect()
-        h = br.height()
-        self.setPos(QPointF(
-            1,
-            abs_pos.y() - h / 2 - offset
-        ))
-        self.update()
-
-
-class YSticky(YAxisLabel):
-    """Y-axis label that sticks to where it's placed despite chart resizing.
-    """
     def __init__(
         self,
         chart,
@@ -341,11 +367,41 @@ class YSticky(YAxisLabel):
         chart.sigRangeChanged.connect(self.update_on_resize)
         self._last_datum = (None, None)
 
-    def update_on_resize(self, vr, r):
+        # pull text offset from axis from parent axis
-        # TODO: add an `.index` to the array data-buffer layer
+        self.x_offset = self.parent.style['tickTextOffset'][0]
-        # and make this way less shitty...
 
-        # pretty sure we did that ^ ?
+    def size_hint(self) -> Tuple[float, float]:
+        # size to parent axis width
+        return None, self.parent.width()
+
+    def update_label(
+        self,
+        abs_pos: QPointF,  # scene coords
+        value: float,  # data for text
+
+        # on odd dimension and/or adds nice black line
+        x_offset: Optional[int] = None
+    ) -> None:
+
+        # this is read inside ``.paint()``
+        self.label_str = '{value:,.{digits}f}'.format(
+            digits=self.digits, value=value).replace(',', ' ')
+
+        # pull text offset from axis from parent axis
+        x_offset = x_offset or self.x_offset
+
+        br = self.boundingRect()
+        h = br.height()
+        self.setPos(QPointF(
+            x_offset,
+            abs_pos.y() - h / 2 - self._y_margin / 2
+        ))
+        self.update()
+
+    def update_on_resize(self, vr, r):
+        """Tiis is a ``.sigRangeChanged()`` handler.
+
+        """
         index, last = self._last_datum
         if index is not None:
             self.update_from_data(index, last)
@@ -360,3 +416,14 @@ class YSticky(YAxisLabel):
             self._chart.mapFromView(QPointF(index, value)),
             value
         )
+
+    def _draw_arrow_path(self):
+        x_offset = self.parent.style['tickTextOffset'][0]
+        path = QtGui.QPainterPath()
+        h = self.rect.height()
+        path.moveTo(0, 0)
+        path.lineTo(-x_offset - 2, h/2.)
+        path.lineTo(0, h)
+        path.closeSubpath()
+        self.path = path
+        self.tl = path.controlPointRect().topLeft()