QR Code generator app for GTK/GNOME

qrgen.py

#!/usr/bin/env -S uv run -s
# This script generates a QR code from a string input and displays it in a GTK window.

# /// script
# requires-python = ">=3.13"
# dependencies = [
#     "pillow>=11.2.1",
#     "pygobject==3.50.0",
#     "qrcode>=8.2",
# ]
# ///

# Run from command line with: `python3 qrgen.py <data>` or just `python3 qrgen.py`
# If no data is provided, a GUI window will open for input.

# To use directly from GNOME Shell or equivalent start menus, you can
# create a .desktop file with the following content:
#
# ```ini
# [Desktop Entry]
# Name=QR Gen
# Exec=/usr/local/bin/qrgen
# Type=Application
# Keywords=qr;qrgen
# Icon=/home/<youruser>/.local/share/icons/qrgen.png
# ```
# Make sure to replace `/usr/local/bin/qrgen` with the actual path to
# your script, and point the icon to (any) PNG file.

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk, GdkPixbuf, Gdk

import qrcode
from PIL import Image as PILImage # Rename to avoid conflict with Gtk.Image
import io
import sys

def generate_qr_pil_image(data_string, box_size=10, border=4):
    """
    Generates a QR code and returns it as a PIL Image object.
    """
    qr = qrcode.QRCode(
        version=None,  # Let the library choose the version based on data
        error_correction=qrcode.constants.ERROR_CORRECT_L,
        box_size=box_size,
        border=border,
    )
    qr.add_data(data_string)
    qr.make(fit=True)

    # Create an image from the QR Code instance
    # Ensure it's RGB for easier conversion to GdkPixbuf
    img = qr.make_image(fill_color="black", back_color="white").convert('RGB')
    return img

def display_qr_in_gtk(pil_image, title_text="QR Code", existing_window=None):
    """
    Displays a PIL Image in a GTK3 window.
    If existing_window is provided, it clears and reuses that window.
    """
    # Convert PIL Image to GdkPixbuf
    # Method 1: Using io.BytesIO (more robust for various PIL formats)
    byte_io = io.BytesIO()
    pil_image.save(byte_io, format='PNG') # Save as PNG to the in-memory buffer
    byte_io.seek(0) # Rewind the buffer to the beginning

    # Create a GdkPixbufLoader for PNG
    loader = GdkPixbuf.PixbufLoader.new_with_type('png')
    try:
        loader.write(byte_io.read())
    except gi.repository.GLib.Error as e:
        print(f"Error loading Pixbuf: {e}")
        return
    finally:
        loader.close()

    pixbuf = loader.get_pixbuf()

    if not pixbuf:
        print("Failed to create GdkPixbuf.")
        return

    # Handler for keyboard shortcuts
    def on_key_press(widget, event):
        # Check for ESC key
        if event.keyval == Gdk.KEY_Escape:
            Gtk.main_quit()
            return True

        # Check for Ctrl+W and Ctrl+Q
        if (event.state & Gdk.ModifierType.CONTROL_MASK) != 0:
            if event.keyval == Gdk.KEY_q or event.keyval == Gdk.KEY_w:
                Gtk.main_quit()
                return True

        return False

    if existing_window:
        # Clear the existing window content
        for child in existing_window.get_children():
            existing_window.remove(child)

        window = existing_window
        window.set_title(title_text)
    else:
        # Create a new GTK window
        window = Gtk.Window(title=title_text)
        window.set_position(Gtk.WindowPosition.CENTER)
        window.connect("destroy", Gtk.main_quit)
        window.connect("key-press-event", on_key_press)

    window.set_border_width(10)

    # Create a GTK Image widget
    gtk_image = Gtk.Image()
    gtk_image.set_from_pixbuf(pixbuf)

    # Add the image to the window
    window.add(gtk_image)
    window.show_all()

    if not existing_window:
        Gtk.main()

    return window

def create_input_window():
    """
    Creates a GTK window with a text input field.
    When the user enters text and presses Enter, it generates and displays the QR code.
    """
    window = Gtk.Window(title="Enter text for QR code")
    window.set_position(Gtk.WindowPosition.CENTER)
    window.connect("destroy", Gtk.main_quit)
    window.set_border_width(10)
    window.set_default_size(400, -1)  # Set width, let height adjust automatically

    # Handler for keyboard shortcuts
    def on_key_press(widget, event):
        # Check for ESC key
        if event.keyval == Gdk.KEY_Escape:
            Gtk.main_quit()
            return True

        # Check for Ctrl+W and Ctrl+Q
        if (event.state & Gdk.ModifierType.CONTROL_MASK) != 0:
            if event.keyval == Gdk.KEY_q or event.keyval == Gdk.KEY_w:
                Gtk.main_quit()
                return True

        return False

    window.connect("key-press-event", on_key_press)

    # Create a vertical box to hold our widgets
    vbox = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=8)
    window.add(vbox)

    # Add a label
    label = Gtk.Label(label="Enter text or URL to encode as QR code:")
    vbox.pack_start(label, False, False, 0)

    # Add a text entry
    entry = Gtk.Entry()
    entry.set_placeholder_text("Type or paste here and press Enter")
    vbox.pack_start(entry, False, False, 0)

    # Function to generate QR code from entry text
    def generate_qr_from_entry(widget):
        data_to_encode = entry.get_text().strip()
        if not data_to_encode:
            return

        print(f"Generating QR code for: \"{data_to_encode}\"")

        try:
            pil_qr_image = generate_qr_pil_image(data_to_encode)
        except Exception as e:
            # Show error in the window
            for child in vbox.get_children():
                vbox.remove(child)

            error_label = Gtk.Label(label=f"Error generating QR code: {e}")
            vbox.pack_start(error_label, True, True, 0)
            vbox.show_all()
            return

        window_title = f"QR Code: {data_to_encode[:50]}"
        if len(data_to_encode) > 50:
            window_title += "..."

        # Display QR code in the same window
        display_qr_in_gtk(pil_qr_image, window_title, window)

    # Connect the entry's activate signal (Enter key press)
    entry.connect("activate", generate_qr_from_entry)

    window.show_all()
    # Focus the entry automatically
    entry.grab_focus()

    Gtk.main()

def main():
    if len(sys.argv) < 2:
        # Show input window if no arguments provided
        create_input_window()
    else:
        # Join all arguments after the script name to form the data string
        data_to_encode = " ".join(sys.argv[1:])

        print(f"Generating QR code for: \"{data_to_encode}\"")

        try:
            pil_qr_image = generate_qr_pil_image(data_to_encode)
        except Exception as e:
            print(f"Error generating QR code: {e}")
            sys.exit(1)

        window_title = f"QR Code: {data_to_encode[:50]}"
        if len(data_to_encode) > 50:
            window_title += "..."

        display_qr_in_gtk(pil_qr_image, window_title)

if __name__ == "__main__":
    main()