def onShortcutUnindentWithBackspace(self):
        """Backspace pressed, unindent
        """
        assert self._qpart.textBeforeCursor().endswith(self.text())

        charsToRemove = len(self._qpart.textBeforeCursor()) % len(self.text())
        if charsToRemove == 0:
            charsToRemove = len(self.text())

        cursor = self._qpart.textCursor()
        cursor.setPosition(cursor.position() - charsToRemove, QTextCursor.KeepAnchor)
        cursor.removeSelectedText()
def setRT(self, r, t):
        self.r = r
        self.t = t
        x = self.r * math.cos(self.t)
        y = self.r * math.sin(self.t)
        self.Tail.Eq(self.p1)
        self.Head.setPoint(self.Tail.x + x,self.Tail.y + y)