How to limit scrolling outside bounds in pyqtgraph? - pyqt5

Question

I've set up a chart for candlestick display using PyQtGraph.
I've made a simplified example below.
I'm trying to figure out how to limit the viewable/scrollable range on the chart for the y1 and y2 axis.
I want to limit them to equal the ymin and ymax settings in the boundingRect() function.
If I run the chart it starts off with the bounds set correctly but it allows you to manually scroll around the chart outside of the bounds that are set within the boundingRect()
I want to prevent the ability to scroll beyond what the boundingRect() allows.
I want to be able to scroll along the X axis without issue but I want the Y axis to dynamically limit the bounds to the Y axis of the candlesticks that are currently viewable.
For starters I can't figure out how to force limits on scrollable bounds in a way that is compatible with what I have written below.
QPainterPath or QRectF doesn't seem to have a function to limit the scrollable view that I can find. Or at the very least I can't figure out the proper syntax.
Then I need to figure out how to return the axis range of the currently viewable candles in order to dynamically set the scrollable/viewable limits. Haven't gotten that far yet.
Any help is appreciated.
import pyqtgraph as pg
from pyqtgraph import QtCore, QtGui, QtWidgets
import numpy as np
data = np.array([ ## fields are (time, open, close, min, max).
(1., 10, 13),
(2., 13, 17),
(3., 17, 14),
(4., 14, 15),
(5., 15, 9),
(6., 9, 15),
(7., 15, 5),
(8., 5, 7),
(9., 7, 3),
(10., 3, 10),
(11., 10, 15),
(12., 15, 25),
(13., 25, 20),
(14., 20, 17),
(15., 17, 30),
(16., 30, 32),
(17., 32, 35),
(18., 35, 28),
(19., 28, 27),
(20., 27, 25),
(21., 25, 29),
(22., 29, 35),
(23., 35, 40),
(24., 40, 45),
])
class CandlestickItem(pg.GraphicsObject):
global data
_boundingRect = QtCore.QRectF()
# ...
def __init__(self):
pg.GraphicsObject.__init__(self)
self.flagHasData = False
def set_data(self, data):
self.data = data
self.flagHasData = True
self.generatePicture()
self.informViewBoundsChanged()
def generatePicture(self):
self.picture = QtGui.QPicture()
path = QtGui.QPainterPath()
p = QtGui.QPainter(self.picture)
p.setPen(pg.mkPen('w'))
w = (self.data[1][0] - self.data[0][0]) / 3.
for (t, open, close) in self.data:
rect = QtCore.QRectF(t-w, open, w*2, close-open)
path.addRect(rect)
if open > close:
p.setBrush(pg.mkBrush('r'))
else:
p.setBrush(pg.mkBrush('g'))
p.drawRect(rect)
p.end()
self._boundingRect = path.boundingRect()
def paint(self, p, *args):
if self.flagHasData:
p.drawPicture(0, 0, self.picture)
def boundingRect(self):
# data =data
# xmin = np.nanmin(data[:,0])
xmax = np.nanmax(data[:,0])
xmin = xmax - 5
ymin = np.nanmin(data[:,2])
ymax = np.nanmax(data[:,2])
return QtCore.QRectF(xmin, ymin, xmax-xmin, ymax-ymin)
item = CandlestickItem()
plt = pg.plot()
plt.addItem(item)
plt.setWindowTitle('pyqtgraph example: customGraphicsItem')
item.set_data(data)
if __name__ == '__main__':
import sys
if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
QtWidgets.QApplication.instance().exec_()

Answer 1

If I understood you correctly, you want to prevent user to zoom or scroll outside boundictRect of your candlesitck plot. That can be achieved with setting limit to viewbox.
EDIT: y view is now limited to min and max value within current view specified by x_start and x_end.
Here is modified code, that does that:
import math
import numpy as np
import pyqtgraph as pg
from pyqtgraph import QtCore, QtGui, QtWidgets
data = np.array([ ## fields are (time, open, close, min, max).
(1., 10, 13),
(2., 13, 17),
(3., 17, 14),
(4., 14, 15),
(5., 15, 9),
(6., 9, 15),
(7., 15, 5),
(8., 5, 7),
(9., 7, 3),
(10., 3, 10),
(11., 10, 15),
(12., 15, 25),
(13., 25, 20),
(14., 20, 17),
(15., 17, 30),
(16., 30, 32),
(17., 32, 35),
(18., 35, 28),
(19., 28, 27),
(20., 27, 25),
(21., 25, 29),
(22., 29, 35),
(23., 35, 40),
(24., 40, 45),
])
class CandlestickItem(pg.GraphicsObject):
global data
_boundingRect = QtCore.QRectF()
# ...
def __init__(self):
pg.GraphicsObject.__init__(self)
self.picture = QtGui.QPicture()
self.flagHasData = False
def set_data(self, data):
self.data = data
self.flagHasData = True
self.generatePicture()
self.informViewBoundsChanged()
def generatePicture(self):
self.picture = QtGui.QPicture()
path = QtGui.QPainterPath()
p = QtGui.QPainter(self.picture)
p.setPen(pg.mkPen('w'))
w = (self.data[1][0] - self.data[0][0]) / 3.
for (t, open, close) in self.data:
rect = QtCore.QRectF(t - w, open, w * 2, close - open)
path.addRect(rect)
if open > close:
p.setBrush(pg.mkBrush('r'))
else:
p.setBrush(pg.mkBrush('g'))
p.drawRect(rect)
p.end()
self._boundingRect = path.boundingRect()
def paint(self, p, *args):
if self.flagHasData:
p.drawPicture(0, 0, self.picture)
def boundingRect(self):
return QtCore.QRectF(self.picture.boundingRect())
def viewTransformChanged(self):
super(CandlestickItem, self).viewTransformChanged()
br = self.boundingRect()
# Get coords of view mapped to data
mapped_view = self.mapRectToView(self.viewRect())
# Get start and end of x slice
x_slice_start = int(mapped_view.x()) - 1
x_slice_end = x_slice_start + (math.ceil(mapped_view.width()) + 1)
if x_slice_start < 0:
x_slice_start = 0
if x_slice_end > data.shape[0]:
x_slice_end = data.shape[0]
# Get data in x interval
y_slice = data[x_slice_start:x_slice_end]
try:
ymin = np.nanmin(y_slice[:, 2])
ymax = np.nanmax(y_slice[:, 2])
if ymin != ymax:
self.getViewBox().setLimits(xMin=br.x(), xMax=br.width(), yMin=ymin, yMax=ymax)
except ValueError:
pass
return br
item = CandlestickItem()
plt = pg.plot()
plt.addItem(item)
plt.setWindowTitle('pyqtgraph example: customGraphicsItem')
item.set_data(data)
if __name__ == '__main__':
import sys
if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
QtWidgets.QApplication.instance().exec_()