Is it possible to delete text element on canvas without clear/draw new canvas?

Comments

• lvanderlinden

  October 2022 edited October 2022

  Hi @Lars ,

  
  

  Just a quick response to your question as formulated in the title of this post: Yes, you can delete elements from a canvas object, but (I think) only if you named them:

  • https://osdoc.cogsci.nl/3.3/manual/python/canvas/#naming-accessing-and-modifying-elements

  
  

  And then:

  del my_canvas["my_named_element"]
  

  
  

  Whether this helps your script getting faster I cannot tell from a first glance. If you want a more detailed response, could you please copy-paste the code here? Or even better, upload the experiment?

  
  

  Cheers,

  
  

  Lotje

  Did you like my answer? Feel free to
• Lars

  October 2022

  Hi @lvanderlinden,

  Thank you very much! It is much faster!

  
  

  For some reasons the text gets bigger as if it is still overdrawn. By using the clear function, the text keeps the shape, but is clearing the canvas. However, Iam satisfied with the solution. To replicate my function, use the codeblock below and run the function with some (random) text.

  
  

  Thank you again!

  Cheers,

  Lars

  
  

  Here is my function. It prints character for character on the canvas and is now very fast, even with a background picture.

  
  

  def print_text(text, sleep=0, image_path=None, scale=None, x=None, y=None, imagex=None):
    blah = text + '\n'
    text_part = ''
    base = canvas(font_size = 30)
    if image_path != None:
      if imagex == None:
         base.image(image_path, scale = scale)
      else:
         base.image(image_path, scale = scale, x=imagex)
    for l in blah:
      base["text"]=Text(text_part+l, center=False, y=y, x=x)
      base.show()
      del base["text"]
      text_part = text_part+l
      clock.sleep(sleep)
    return base;
  
• Lars

  October 2022

  Sorry to spam you again. The Text gets bigger, indeed, because the text element is not deleted. Can you help me solving this standalone example below?

  1. draw a red line
  2. make the line green
  3. make the line disappear (delete)

  my_canvas = Canvas()
  my_canvas['my_line'] = Line(-100, -100, 100, 100, color='red')
  my_canvas.show()
  clock.sleep(1000)
  my_canvas['my_line'].color = 'green'
  my_canvas.show()
  clock.sleep(1000)
  del my_canvas['my_line']
  my_canvas.show()
  clock.sleep(1000)
  

  
  

  Thank you,

  Lars
• lvanderlinden

  October 2022

  Hi Lars,

  
  

  I think the above script (and hopefully the other one too) works fine if you change the backend from Legacy to PsychoPy or Expyriment.

  
  

  Could you try that?

  
  

  Cheers,

  
  

  Lotje

  Did you like my answer? Feel free to
• Lars

  January 2023

  Sorry for the late response! It works!

  Thank you