Tkinter Canvas create_window: Parent, Events, Rendering

Set the widget’s parent to the Canvas when you use canvas.create_window so the Canvas truly owns the widget’s geometry, clipping, stacking and event delivery — that fixes the enter/leave ordering and keeps the widget inside the canvas coordinate system. If the widget is a sibling (parented to root), Tk treats it as an independent window: rendering won’t be clipped or scrolled by the canvas and Enter/Leave (tkinter events) arrive in the “jumping” order your examples show.

Contents

• Why set the widget’s parent to the Canvas (tkinter canvas create_window)
• Event propagation and tkinter events: Enter/Leave sequences
• Rendering, clipping and geometry when embedding frames in Canvas
• Best practices and working examples (tkinter bind events)
• Common pitfalls and troubleshooting
• Sources
• Conclusion

Why set the widget’s parent to the Canvas (tkinter canvas create_window)

A Canvas “window” item can hold a real widget, but for the Canvas to manage that widget as part of its own coordinate system the widget must be created as a child (or descendant) of the Canvas. When the widget is parented to the Canvas, Tk treats it as a canvas-owned window item: the Canvas controls its position, clipping and stacking, and the widget moves when the canvas scrolls or is resized. The tkdocs Canvas guide explains this clearly: if the widget is not a child of the canvas, the canvas is just a visual container and does not actually own the widget’s geometry or event ordering.

Some reference pages are looser in wording — the raw Tk docs mention that the widget must be in the same top-level window — but that permissive phrasing hides the practical differences. In short: create the widget with the Canvas as its master:

frame = tk.Frame(canvas, width=200, height=150, bg='red') # parent is canvas
window_id = canvas.create_window(100, 100, window=frame, anchor='center')

If you instead do frame = tk.Frame(root, ...) and pass that frame to create_window, Tk may display it, but the Canvas won’t own it properly; you’ll see odd event sequences and rendering/scrolling problems. See the Stack Overflow discussion that walks this through with examples: https://stackoverflow.com/questions/79860131/why-should-i-set-the-parent-of-a-widget-to-the-canvas-when-placing-it-as-window

Event propagation and tkinter events: Enter/Leave sequences

Why do your Enter/Leave traces differ so much? Because Tk’s pointer events are delivered relative to the widget window tree. When the Frame is a child of the Canvas the widget hierarchy is nested, so pointer entry/exit looks nested, too:

• Embedded (Frame parent = Canvas): Enter sequence: root → canvas → frame. Leave sequence: frame → canvas → root.
  That matches the output you posted for the “Canvas is parent” case.

When the Frame is parented to root instead, the Frame is a sibling of the Canvas, not a descendant. The pointer crosses widget rectangles that are not nested in the same window tree, so Enter/Leave events are delivered in a non-nested order — Canvas sees its own enter/leave, the Frame sees its enter/leave, and they interleave. That produces the “jumping” sequence in your second output.

Two practical points to read or test:

• root.bind_all will print whatever widget actually received the event (event.widget), so it’s a good diagnostic for which window got the event.
• The tkdocs tutorial and community answers show this exact enter/leave behavior and recommend parenting the widget to the canvas to get the natural nested ordering.

If you want a concise mental model: nested widgets => nested events; siblings/overlays => events can bounce between the two because the OS/tk layer sees different windows under the pointer.

(If you want a deeper OS-level explanation: X11/Win32 generate Enter/Leave notifications per window; whether those notifications look “nested” depends on the actual widget window nesting. But you rarely need that depth: parent the widget to the canvas and things behave as expected.)

Rendering, clipping and geometry when embedding frames in Canvas

The visual differences you saw when filling the frame (many Labels) come from whether the Canvas owns the frame in its coordinate system.

• If the frame is a child of the Canvas:

• The Canvas includes the frame in its coordinate system and in its scroll region.

• The Canvas will clip the frame to the Canvas viewport (anything outside the Canvas area is not drawn).

• Scrolling the Canvas moves the frame and its contents as a single canvas item.

• Anchors, width and height options on create_window affect how the Canvas reserves space (see the Tk docs: https://anzeljg.github.io/rin2/book2/2405/docs/tkinter/create_window.html).

• If the frame is parented to root:

• The Canvas only positioned the widget visually but did not take ownership of its geometry. The frame remains a normal child of the toplevel.

• The frame won’t be clipped by the Canvas; it may draw outside the Canvas bounds or overlap other canvas items unpredictably.

• Scrolling the Canvas does not reliably move that frame; the frame won’t be included in canvas scrollregion calculations unless you manually manage it (which is brittle).

That explains why the left and right versions of your populate() test render differently: one is truly embedded and clipped/scrollable, the other merely sits on top as a separate widget and can appear shifted or partially clipped by other windowing rules. The Stack Overflow thread about adding widgets to a frame placed on a canvas shows similar layout/visibility issues and the standard fix: make the interior frame a canvas child and update scrollregion on configure: https://stackoverflow.com/questions/50568854/i-want-to-add-entry-boxes-in-the-frame-f1b-which-in-turn-is-placed-on-a-canvas

Best practices and working examples (tkinter bind events)

Here’s a robust pattern for a scrollable frame that avoids event and rendering problems. Note the frame is created with canvas as its parent and the canvas owns the window item:

import tkinter as tk

root = tk.Tk()
canvas = tk.Canvas(root)
vsb = tk.Scrollbar(root, orient='vertical', command=canvas.yview)
canvas.configure(yscrollcommand=vsb.set)

canvas.pack(side='left', fill='both', expand=True)
vsb.pack(side='right', fill='y')

# create the interior frame as a child of the canvas
frame = tk.Frame(canvas)
window_id = canvas.create_window((0, 0), window=frame, anchor='nw')

# update scrollregion when the frame changes size
def on_frame_configure(event):
 canvas.configure(scrollregion=canvas.bbox('all'))

frame.bind('<Configure>', on_frame_configure)

# optional: make the frame match the canvas width when the canvas resizes
def on_canvas_configure(event):
 canvas.itemconfigure(window_id, width=event.width)

canvas.bind('<Configure>', on_canvas_configure)

# populate the frame (pack/grid inside the frame, not on the canvas)
for i in range(50):
 tk.Label(frame, text=f'Line {i}').pack(anchor='w')

root.mainloop()

Why this pattern works:

• The Canvas owns the frame, so clipping, scrolling and enter/leave order are consistent.
• frame.bind('<Configure>') updates the Canvas scrollregion dynamically.
• canvas.itemconfigure(window_id, width=...) keeps widths in sync so widgets inside the frame wrap/align predictably.

If you only need to place a few static widgets and don’t plan to scroll, embedding still works best if the widget is parented to the Canvas; it avoids the event oddities and stacking surprises that come from sibling widgets.

For more background and examples, read the Canvas tutorial here: https://tkdocs.com/tutorial/canvas.html and the Canvas reference: https://tkinter-docs.readthedocs.io/en/latest/widgets/canvas.html

Common pitfalls and troubleshooting

• Jumping Enter/Leave? Check the widget parent. If it’s not the Canvas, re-parent it and test again. For debugging, bind to the widget itself rather than root.bind_all to see the widget-local behavior.
• Content not scrolling or getting clipped incorrectly? Make sure the frame is a child of the Canvas and update canvas.configure(scrollregion=...) on the frame’s <Configure> event.
• Width/height mismatches after embedding? Use canvas.itemconfigure(window_id, width=...) on Canvas <Configure> so the embedded frame adapts to canvas resizing.
• Stacking order surprises? A widget not parented to the canvas is a separate window; its stacking relative to canvas items can be unpredictable. Parent it to the canvas and use canvas.tag_raise / canvas.tag_lower on the window item if needed.
• Performance: embedding many hundreds of native widgets is expensive. If you only need textual or simple graphical content, the Canvas drawing primitives are far lighter.

If you want a quick experiment to confirm behavior: create two frames (one parented to canvas, one parented to root), bind <Enter>/<Leave> to each widget and move the mouse — you’ll reproduce the exact sequences in your question. Community threads walk through these experiments step by step: https://stackoverflow.com/questions/79860131/why-should-i-set-the-parent-of-a-widget-to-the-canvas-when-placing-it-as-window

Sources

• TkDocs Tutorial - Canvas
• Why should I set the parent of a widget to the canvas when placing it as window item? (Stack Overflow)
• Canvas window objects (Tkinter reference)
• Canvas — tkinter-docs documentation (ReadTheDocs)
• Events and Binds in Tkinter (python-course.eu)
• How To Master Python Tkinter Events? (pythonguides.com)
• I want to add entry boxes in the frame f1b, which in turn is placed on a canvas (Stack Overflow)

Conclusion

Make the embedded widget a child of the Canvas when using canvas.create_window. That lets the Canvas own the widget’s coordinates, clipping, stacking and event flow — so Enter/Leave and other tkinter events behave in the natural nested order and the widget scrolls and clips predictably. If you see the “jumping” event sequence or odd clipping, re-parent the frame to the canvas and use the standard create_window + configure(scrollregion) pattern shown above.