When should I use a Canvas vs a Label?

Question

Taking a class that says I should use the Canvas object to display text. Why is this superior to using a Label? Seems like a more complicated way to just display a text box.

In example below, see the "# Create canvas" and "# Create labels" comments for relevant lines.

from tkinter import *

# Set globals, constants -------------------------------------------------------------
BG_COLOR = "#375362"
FG_COLOR = "white"
FONT = ("Arial", 20, "italic")
PADDING = 20
QBOX_HEIGHT = 250
QBOX_WIDTH = 300


# Create UI for Quizzler game --------------------------------------------------------
class QuizUI:
    def __init__(self):
        # Create window
        self.window = Tk()
        self.window.title("Quizzler")
        self.window.config(padx=PADDING, pady=PADDING, bg=BG_COLOR)

        # Create canvas
        self.qbox_canvas = Canvas(width=QBOX_WIDTH, height=QBOX_HEIGHT)
        self.qbox_canvas.grid(row=1, column=0, columnspan=2, padx=PADDING, pady=PADDING)

        # Create labels
        self.score_label = Label(text="Score: 0", bg=BG_COLOR, fg=FG_COLOR, font=FONT)
        self.score_label.grid(row=0, column=1, padx=PADDING, pady=PADDING)
        self.question_label = self.qbox_canvas.create_text(QBOX_WIDTH / 2, QBOX_HEIGHT / 2, text="PLACEHOLDER", font=FONT)

        # Run window loop
        self.window.mainloop()

Expected: just use Labels. Canvas seems unnecessary. Actual: instructor recommended Canvas.

Answer 1

Labels serve as convenient tools for displaying static text within a Tkinter application, but they do come with certain limitations. Customization options for labels are somewhat restricted, offering limited control over text attributes like font, color, and alignment. This can impede the creation of visually rich interfaces, particularly in scenarios where more intricate designs are desired, positioning labels within a layout can be challenging, as they rely on grid or pack geometry managers, making it difficult to achieve precise alignment or positioning compared to using a Canvas. Also, Labels lack inherent support for interactivity, such as responding to user actions like mouse clicks or hover events, as it has to be bind on the Label widget and Canvas You can bind events individually to the items, limiting their usefulness in creating dynamic user interfaces. Labels primarily focus on text display and lack integration with other graphical elements like shapes or images, which can constrain the creation of more complex and visually appealing interfaces. In some situations involving a large number of Labels or complex layouts, performance may be adversely affected, as Labels may not offer the same level of performance optimization as Canvas. So, while Labels are suitable for basic text display, their limitations in customization, positioning, interactivity, integration with graphics, and performance may make them less suitable for more advanced graphical user interfaces, but for small implementations Labels can be a positive alternative.

Answer 2

The answer is going to sound trite, but use a Canvas when you need the features that the Canvas provides. If you're only displaying text and/or a single image, there's no reason to use a Canvas. If you need to display multiple images, or need to draw geometric shapes then you should use the Canvas.

If you're displaying several text items and want to be able to scroll, then the Canvas will be more useful. Labels inside a frame aren't scrollable.