from PyQt5 import QtCore
from PyQt5 import QtWidgets
from PyQt5 import QtGui

# This class has to be defined to obtain a labeled slider used in the group
# assigned dialog. The predefined slider of pyqt has no labels. This solution
# was copied from stackoverflow.com
class LabeledSlider(QtWidgets.QWidget):
    def __init__(self, minimum, maximum, interval=1, orientation=QtCore.Qt.Horizontal,
            labels=None, parent=None):
        # Initialize the labeled slider 

        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==QtCore.Qt.Horizontal:
            self.layout=QtWidgets.QVBoxLayout(self)
        elif orientation==QtCore.Qt.Vertical:
            self.layout=QtWidgets.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=QtWidgets.QSlider(orientation, self)
        self.sl.setMinimum(minimum)
        self.sl.setMaximum(maximum)
        self.sl.setValue(minimum)
        if orientation==QtCore.Qt.Horizontal:
            self.sl.setTickPosition(QtWidgets.QSlider.TicksBelow)
            self.sl.setMinimumWidth(300) # just to make it easier to read
        else:
            self.sl.setTickPosition(QtWidgets.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 setValue(self, nb):
        # From the python code set a new value

        self.sl.setValue(nb)

    def valueChanged(self, function):
        # Overload the value changed function of the predefined slider

        self.sl.valueChanged.connect(function)

    def value(self):
        # Overload the value function of the predefined slider

        return self.sl.value()

    def paintEvent(self, e):
        # Paint the numbers below the slider

        super(LabeledSlider,self).paintEvent(e)

        style=self.sl.style()
        painter=QtGui.QPainter(self)
        st_slider=QtWidgets.QStyleOptionSlider()
        st_slider.initFrom(self.sl)
        st_slider.orientation=self.sl.orientation()

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

        for v, v_str in self.levels:

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

            if self.sl.orientation()==QtCore.Qt.Horizontal:
                # I assume the offset is half the length of slider, therefore
                # + length//2
                x_loc=QtWidgets.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=QtWidgets.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=QtCore.QPoint(left, bottom)
            painter.drawText(pos, v_str)

        return
