Draw Half Infinite Lines?

I use pyqtgraph for data acquisition and I have to represent some thresholds on the graphics view. For example to represent a high voltage limit, etc. I used the class InfiniteLin

Solution 1:

Your approach looks good and is mostly what pyqtgraph.InfiniteLine is doing. I examined the source of InfiniteLine and extracted those parts which are absolutely necessary and added the change point and two level information, then drawing three lines (left border to change point at left level, change point to right border at right level, connection of both).

Here is the full code:

from pyqtgraph.Qt import QtGui
import numpy as np
import pyqtgraph as pg

classInfiniteLineWithBreak(pg.GraphicsObject):

    def__init__(self, changeX, levelsY, pen=None):
        pg.GraphicsObject.__init__(self)

        self.changeX = changeX
        self.levelsY = levelsY

        self.maxRange = [None, None]
        self.moving = False
        self.movable = False
        self.mouseHovering = False

        pen = (200, 200, 100)
        self.setPen(pen)
        self.setHoverPen(color=(255,0,0), width=self.pen.width())
        self.currentPen = self.pen


    defsetBounds(self, bounds):
        self.maxRange = bounds
        self.setValue(self.value())

    defsetPen(self, *args, **kwargs):
        self.pen = pg.fn.mkPen(*args, **kwargs)
        ifnot self.mouseHovering:
            self.currentPen = self.pen
            self.update()

    defsetHoverPen(self, *args, **kwargs):
        self.hoverPen = pg.fn.mkPen(*args, **kwargs)
        if self.mouseHovering:
            self.currentPen = self.hoverPen
            self.update()

    defboundingRect(self):
        br = self.viewRect()
        return br.normalized()

    defpaint(self, p, *args):
        br = self.boundingRect()
        p.setPen(self.currentPen)
        # three lines (left border to change point, change point vertical, change point to right)
        p.drawLine(pg.Point(br.left(), self.levelsY[0]), pg.Point(self.changeX, self.levelsY[0]))
        p.drawLine(pg.Point(self.changeX, self.levelsY[0]), pg.Point(self.changeX, self.levelsY[1]))
        p.drawLine(pg.Point(self.changeX, self.levelsY[1]), pg.Point(br.right(), self.levelsY[1]))

    defdataBounds(self, axis, frac=1.0, orthoRange=None):
        if axis == 0:
            returnNone## x axis should never be auto-scaledelse:
            return (0,0)

    defsetMouseHover(self, hover):
        pass

app = QtGui.QApplication([])
w = pg.GraphicsWindow()
w.resize(1000, 600)
v = w.addPlot(y=np.random.normal(size=100))
v.addItem(InfiniteLineWithBreak(changeX=50, levelsY=(-1, 1)))
app.exec_()

It looks like:

What one could add is reaction to hovering and changing the values with the mouse (change point as well as levels) or even rotate by 90 degree. InfiniteLine is a good example of how to do that.

Solution 2:

thanks you for you very complete answer ! Your code works very well. I made some modifications on your class InfiniteLineWithBreak in order to set multiple threshold transitions. I modified the init and the paint methods only:

def__init__(self, listOfcouplesOfThresholdAndItsDate, pen=None):
    pg.GraphicsObject.__init__(self)

    self.listOfcouplesOfThresholdAndItsDate=listOfcouplesOfThresholdAndItsDate
    self.maxRange = [None, None]
    self.moving = False
    self.movable = False
    self.mouseHovering = False

    pen = (200, 200, 100)
    self.setPen(pen)
    self.setHoverPen(color=(255,0,0), width=self.pen.width())
    self.currentPen = self.pen




 defpaint(self, p, *args):
    br = self.boundingRect()
    p.setPen(self.currentPen)
    iflen(self.listOfcouplesOfThresholdAndItsDate)==0:
        passeliflen(self.listOfcouplesOfThresholdAndItsDate)==1:
        threshold = self.listOfcouplesOfThresholdAndItsDate[0][1]
        date = self.listOfcouplesOfThresholdAndItsDate[0][0]
        p.drawLine(pg.Point(date, threshold), pg.Point(br.right(), threshold))

    else:

        threshold = self.listOfcouplesOfThresholdAndItsDate[0][1]
        date = self.listOfcouplesOfThresholdAndItsDate[0][0]
        i=0for i inrange(0, len(self.listOfcouplesOfThresholdAndItsDate)-2):
            threshold = self.listOfcouplesOfThresholdAndItsDate[i][1]
            date = self.listOfcouplesOfThresholdAndItsDate[i][0]
            nexteDate = self.listOfcouplesOfThresholdAndItsDate[i+1][0]
            nextThreshold = self.listOfcouplesOfThresholdAndItsDate[i+1][1]
            p.drawLine(pg.Point(date, threshold), pg.Point(nexteDate, threshold))
            p.drawLine(pg.Point(nexteDate, threshold), pg.Point(nexteDate, nextThreshold))


        threshold = self.listOfcouplesOfThresholdAndItsDate[-2][1]
        date = self.listOfcouplesOfThresholdAndItsDate[-2][0]
        nexteDate = self.listOfcouplesOfThresholdAndItsDate[-1][0]
        nextThreshold = self.listOfcouplesOfThresholdAndItsDate[-1][1]
        p.drawLine(pg.Point(date, threshold), pg.Point(nexteDate, threshold))
        p.drawLine(pg.Point(nexteDate, threshold), pg.Point(nexteDate, nextThreshold))

        p.drawLine(pg.Point(nexteDate, nextThreshold), pg.Point(br.right(), nextThreshold))

Moreover, I added a method to append a new threshold transition point to the listOfcouplesOfThersholdAndItsDate :

def addANewThreshold(self,date, threshold):
    self.listOfcouplesOfThresholdAndItsDate.append((date, threshold))

Here is an example of what it looks like : example of multiple thresholds

Does the code look okay to you ? Thank you,