class_docstr:   This is an interactive example of how to display text on app.Canvas.
    The text rendering will respond to standard C escape sequences.
  
    - Scroll for changing text font size
    - Press left and right arrows for changing text anchor positions
    - Press up and down arrows for changing text content
  
    Standard C escape sequences:
        -     ->  alert (beep, bell)
        -     ->  Backspace
        -     ->  Formfeed
        -   
  ->  Newline
        -   
    ->  Carriage Return
        -         ->  Horizontal Tab
        -     ->  Vertical Tab
        -   \  ->  Backslash
        -   '  ->  Single quotation mark
        -   "  ->  Double quotation mark
    
code: def update_text(self):
      pre_text = "%s pt, " % round(self.font_size, 1)
      post_text = (
          "\n(anchor_x = " + self.anchor_variants[self.anchor_ind][1]
      )
      post_text += ", anchor_y = "
      post_text += self.anchor_variants[self.anchor_ind][0] + ")"
      new_txt = (
          pre_text + self.string_alternatives[self.str_ind] + post_text
      )
      self.text.text = new_txt
  
      anchor_x = self.anchor_variants[self.anchor_ind][1]
      anchor_y = self.anchor_variants[self.anchor_ind][0]
      self.text.anchors = (anchor_x, anchor_y)
  
      self.text.font_size = self.font_size
      self.text.pos = self.size[0] // 2, self.size[1] // 2
  
      self.update()
  
file_path: vispy/examples/basics/visuals/text_visual.py
imports: from vispy import app, gloo, visuals
  import numpy
label_desc: Use image node_id 6 for calling the Canvas obj's underlying member method code with example usage: obj.update_text() without return types