[label_slider]Pyqt5 Label slider. This create text ticks alongside qt slider #python #qt

label_slider.py

from PyQt5.QtGui import QPainter, QPen, QFont
from PyQt5.QtWidgets import QAbstractButton, QSlider, QWidget, QVBoxLayout, QHBoxLayout,\
    QStyleOptionSlider, QStyle
from PyQt5.QtCore import Qt, QRect, QPoint
import numpy as np

class LabeledSlider(QWidget):
    def __init__(self, minimum, maximum, interval=1, orientation=Qt.Horizontal,
            labels=None, p0=0, parent=None):
        super(LabeledSlider, self).__init__(parent=parent)

        levels=range(minimum, maximum + interval, interval)

        if labels is not None:
            if not isinstance(labels, (tuple, list)):
                raise Exception("<labels> is a list or tuple.")
            if len(labels) != len(levels):
                raise Exception("Size of <labels> doesn't match levels.")
            self.levels=list(zip(levels,labels))
        else:
            self.levels=list(zip(levels,map(str,levels)))

        if orientation==Qt.Horizontal:
            self.layout=QVBoxLayout(self)
        elif orientation==Qt.Vertical:
            self.layout=QHBoxLayout(self)
        else:
            raise Exception("<orientation> wrong.")

        # gives some space to print labels
        self.left_margin=10
        self.top_margin=10
        self.right_margin=10
        self.bottom_margin=10

        self.layout.setContentsMargins(self.left_margin,self.top_margin,
                self.right_margin,self.bottom_margin)

        self.sl=QSlider(orientation, self)
        self.sl.setMinimum(minimum)
        self.sl.setMaximum(maximum)
        self.sl.setValue(minimum)
        self.sl.setSliderPosition(p0)
        if orientation==Qt.Horizontal:
            self.sl.setTickPosition(QSlider.TicksBelow)
            self.sl.setMinimumWidth(300) # just to make it easier to read
        else:
            self.sl.setTickPosition(QSlider.TicksLeft)
            self.sl.setMinimumHeight(300) # just to make it easier to read
        self.sl.setTickInterval(interval)
        self.sl.setSingleStep(1)

        self.layout.addWidget(self.sl)

    def paintEvent(self, e):

        super(LabeledSlider,self).paintEvent(e)
        style=self.sl.style()
        painter=QPainter(self)
        st_slider=QStyleOptionSlider()
        st_slider.initFrom(self.sl)
        st_slider.orientation=self.sl.orientation()

        length=style.pixelMetric(QStyle.PM_SliderLength, st_slider, self.sl)
        available=style.pixelMetric(QStyle.PM_SliderSpaceAvailable, st_slider, self.sl)

        for v, v_str in self.levels:

            # get the size of the label
            rect=painter.drawText(QRect(), Qt.TextDontPrint, v_str)

            if self.sl.orientation()==Qt.Horizontal:
                # I assume the offset is half the length of slider, therefore
                # + length//2
                x_loc=QStyle.sliderPositionFromValue(self.sl.minimum(),
                        self.sl.maximum(), v, available)+length//2

                # left bound of the text = center - half of text width + L_margin
                left=x_loc-rect.width()//2+self.left_margin
                bottom=self.rect().bottom()

                # enlarge margins if clipping
                if v==self.sl.minimum():
                    if left<=0:
                        self.left_margin=rect.width()//2-x_loc
                    if self.bottom_margin<=rect.height():
                        self.bottom_margin=rect.height()

                    self.layout.setContentsMargins(self.left_margin,
                            self.top_margin, self.right_margin,
                            self.bottom_margin)

                if v==self.sl.maximum() and rect.width()//2>=self.right_margin:
                    self.right_margin=rect.width()//2
                    self.layout.setContentsMargins(self.left_margin,
                            self.top_margin, self.right_margin,
                            self.bottom_margin)

            else:
                y_loc=QStyle.sliderPositionFromValue(self.sl.minimum(),
                        self.sl.maximum(), v, available, upsideDown=True)

                bottom=y_loc+length//2+rect.height()//2+self.top_margin-3
                # there is a 3 px offset that I can't attribute to any metric

                left=self.left_margin-rect.width()
                if left<=0:
                    self.left_margin=rect.width()+2
                    self.layout.setContentsMargins(self.left_margin,
                            self.top_margin, self.right_margin,
                            self.bottom_margin)

            pos=QPoint(left, bottom)
            painter.drawText(pos, v_str)

        return