How to display LaTex in real time in a text box in Tkinter?

Python Matplotlib library is useful in applications where we need to visualize data points and draw graphs and plots to analyze the data. Let us suppose that we want to create a Tkinter application where we can process LaTeX syntax in real time.

LaTeX syntax is used for preparing scientific documentation such as formulae, scientific notations, mathematical characters, and punctuations. To prepare the application, we are required to use matplotlib and TkAgg (backend API for Matplotlib in Tkinter) modules.

Application Structure

The following steps are used to structure the application functions and widgets:

• Import the required libraries such as Matplotlib, Tkinter, Ttk (for styling the widgets), TkAgg, etc.
• Add a Frame and define a label and an Entry widget in it.
• Define the size of the Figure using the figure() method in Matplotlib. This figure can be used to plot the syntax in canvas.
• Create a Canvas widget where we will define our figure using TkAgg.
• Define a function to get the content of the Entry widget and convert the text in a figure using the predefined function in Matplotlib, i.e., text().
• Display the output on the canvas after binding the Return or Click event with the function.

Complete Example

Here's a complete implementation that displays LaTeX expressions in real time as you type ?

# Import required libraries
from tkinter import *
from tkinter import ttk
import matplotlib
import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg

# Use TkAgg in the backend of tkinter application
matplotlib.use('TkAgg')

# Create an instance of tkinter frame
win = Tk()

# Set the size of the window
win.geometry("700x350")

# Set the title of the window
win.title("LaTeX Viewer")

# Define a function to get the figure output
def graph(event=None):
    # Get the Entry Input
    tmptext = entry.get()
    if tmptext:  # Only process if there's text
        tmptext = "$" + tmptext + "$"
        # Clear any previous Syntax from the figure
        wx.clear()
        try:
            wx.text(0.2, 0.6, tmptext, fontsize=20)
        except:
            # If LaTeX rendering fails, show the raw text
            wx.text(0.2, 0.6, "Invalid LaTeX syntax", fontsize=16, color='red')
        canvas.draw()

# Create a Frame object
frame = Frame(win)
frame.pack()

# Create an Entry widget
var = StringVar()
entry = Entry(frame, width=70, textvariable=var)
entry.pack()

# Bind real-time update to the Entry widget
entry.bind('<KeyRelease>', graph)

# Add a label widget in the frame
label = Label(frame)
label.pack()

# Define the figure size and plot the figure
fig = matplotlib.figure.Figure(figsize=(7, 4), dpi=100)
wx = fig.add_subplot(111)
canvas = FigureCanvasTkAgg(fig, master=label)
canvas.get_tk_widget().pack(side=TOP, fill=BOTH, expand=1)
canvas._tkcanvas.pack(side=TOP, fill=BOTH, expand=1)

# Set the visibility of the Canvas figure
wx.get_xaxis().set_visible(False)
wx.get_yaxis().set_visible(False)

# Also bind Return key for Enter key support
win.bind('<Return>', graph)

win.mainloop()

How It Works

The application works by:

• Real-time binding: The <KeyRelease> event updates the display as you type
• LaTeX wrapping: Input text is wrapped with $ symbols for mathematical rendering
• Error handling: Invalid LaTeX syntax displays an error message instead of crashing
• Canvas clearing: Previous content is cleared before rendering new LaTeX

Example LaTeX Expressions

Try typing these LaTeX expressions in the text box:

• \frac{x^2 + y^2}{z} - Fractions with superscripts
• \alpha + \beta = \gamma - Greek letters
• \sum_{i=1}^{n} x_i - Summation notation
• \int_{0}^{\infty} e^{-x} dx - Integration

Output

Executing the above code will display a window with an Entry widget and a figure plot. Now, type some scientific expression to show the resultant output in LaTeX format ?

Conclusion

This LaTeX viewer provides real-time rendering of mathematical expressions using Matplotlib's text rendering capabilities. The <KeyRelease> event binding ensures immediate visual feedback as users type their LaTeX expressions.