Start "interaction" module

piker/ui/_interaction.py

@@ -0,0 +1,77 @@
+"""
+UX interaction customs.
+"""
+import pyqtgraph as pg
+from pyqtgraph import functions as fn
+
+from ..log import get_logger
+from ._style import _min_points_to_show
+
+
+log = get_logger(__name__)
+
+
+class ChartView(pg.ViewBox):
+    """Price chart view box with interaction behaviors you'd expect from
+    any interactive platform:
+
+        - zoom on mouse scroll that auto fits y-axis
+        - no vertical scrolling
+        - zoom to a "fixed point" on the y-axis
+    """
+    def __init__(
+        self,
+        parent=None,
+        **kwargs,
+    ):
+        super().__init__(parent=parent, **kwargs)
+        # disable vertical scrolling
+        self.setMouseEnabled(x=True, y=False)
+        self.linked_charts = None
+
+    def wheelEvent(self, ev, axis=None):
+        """Override "center-point" location for scrolling.
+
+        This is an override of the ``ViewBox`` method simply changing
+        the center of the zoom to be the y-axis.
+
+        TODO: PR a method into ``pyqtgraph`` to make this configurable
+        """
+
+        if axis in (0, 1):
+            mask = [False, False]
+            mask[axis] = self.state['mouseEnabled'][axis]
+        else:
+            mask = self.state['mouseEnabled'][:]
+
+        # don't zoom more then the min points setting
+        l, lbar, rbar, r = self.linked_charts.chart.bars_range()
+        vl = r - l
+
+        if ev.delta() > 0 and vl <= _min_points_to_show:
+            log.trace("Max zoom bruh...")
+            return
+        if ev.delta() < 0 and vl >= len(self.linked_charts._array):
+            log.trace("Min zoom bruh...")
+            return
+
+        # actual scaling factor
+        s = 1.015 ** (ev.delta() * -1 / 20)  # self.state['wheelScaleFactor'])
+        s = [(None if m is False else s) for m in mask]
+
+        # center = pg.Point(
+        #     fn.invertQTransform(self.childGroup.transform()).map(ev.pos())
+        # )
+
+        # XXX: scroll "around" the right most element in the view
+        furthest_right_coord = self.boundingRect().topRight()
+        center = pg.Point(
+            fn.invertQTransform(
+                self.childGroup.transform()
+            ).map(furthest_right_coord)
+        )
+
+        self._resetTarget()
+        self.scaleBy(s, center)
+        ev.accept()
+        self.sigRangeChangedManually.emit(mask)