PYGLET – On Layout Update Event for Incremental Text Layout

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In this article we will see how we can get the position on line in incremental text layout object in PYGLET module in python. Pyglet is easy to use but powerful library for developing visually rich GUI applications like games, multimedia etc. A window is a “heavyweight” object occupying operating system resources. Windows may appear as floating regions or can be set to fill an entire screen (fullscreen). Incremental text layout displays text which is suitable for interactive editing and/or scrolling large documents. Unlike TextLayout and ScrollableTextLayout, this class generates vertex lists only for lines of text that are visible. As the document is scrolled, vertex lists are deleted and created as appropriate to keep video memory usage to a minimum and improve rendering speed. It get triggered due to text reflow. Text reflow is caused by document edits or changes to the layout’s size. Changes to the layout’s position or active selection, and certain document edits such as text color, do not cause a reflow.
We can create a window and incremental text layout with the help of commands given below

# creating a window
window = pyglet.window.Window(width, height, title)

# creating a in
layout = pyglet.text.layout.IncrementalTextLayout(document, width, height)

Below is the syntax of the layout update event

# layout update event
@window.event
def on_layout_update():
    
    # printing text
    print("Layout update Event")

Below is the implementation

Python3

# importing pyglet module
import pyglet
import pyglet.window.key
  
# width of window
width = 500
  
# height of window
height = 500
  
# caption i.e title of the window
title = "Geeksforzambiatek"
  
# creating a window
window = pyglet.window.Window(width, height, title)
  
# text 
text = "zambiatek Learn and Grow, Portal for Geeks"
  
# batch object
batch = pyglet.graphics.Batch()
  
# creating a formatted document
# unlike unformatted document it is formatted
document = pyglet.text.document.FormattedDocument(text)
  
# setting style to the document
document.set_style(0, len(document.text), dict(font_name ='Arial', font_size = 16, color =(255, 255, 255, 255)))
  
# creating a incremental text layout
layout = pyglet.text.layout.IncrementalTextLayout(document, 400, 350, multiline = True, batch = batch)
  
# creating a caret
caret = pyglet.text.caret.Caret(layout, color =(150, 255, 150))
  
  
  
# caret to window push handlers
window.push_handlers(caret)
  
# setting caret style
caret.set_style(dict(font_name ="Arial"))
 
# layout update event
@window.event
def on_layout_update():
     
    # printing text
    print("Layout update Event")
  
# on draw event
@window.event
def on_draw():
      
    # clear the window
    window.clear()
      
    # draw the batch
    batch.draw()
      
    # caret to window push handlers
    window.push_handlers(caret)
  
      
# key press event    
@window.event
def on_key_press(symbol, modifier):
  
    # key "C" get press
    if symbol == pyglet.window.key.C:
          
        # closing the window
        # window.close()
        pass
     
# image for icon
img = pyglet.resource.image("gfg.png")
 
# setting image as icon
window.set_icon(img)
 
# start running the application
pyglet.app.run()