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Geometry & Layout

Layout in Tk is controlled by geometry managers. Understanding how geometry works is essential for building interfaces that resize, align, and behave predictably in bootstack applications.

This page explains how Tk layout works at a conceptual level and how bootstack expects you to structure layouts.

Geometry managers

Tk provides three geometry managers:

  • pack — simple, flow-based layout
  • grid — table-based, two-dimensional layout
  • place — absolute or relative positioning

Only one geometry manager may be used per container. Mixing geometry managers within the same container leads to undefined behavior.

bootstack does not change this rule.

How layout is resolved

Layout resolution is not immediate.

When geometry is assigned:

  • widgets request a size
  • containers negotiate available space
  • final sizes and positions are computed by Tk

Actual widget dimensions are only reliable after the event loop has run.

This is why size-dependent logic should not run in constructors.

Container responsibility

Layout responsibility belongs to the container, not the child widget.

Containers:

  • control spacing and alignment
  • determine how children expand or contract
  • define scroll behavior

bootstack encourages designing layouts by composing containers, rather than fine-tuning individual widgets. See Guides → Layout for the recommended layout approach using PackFrame and GridFrame.

Resizing behavior

Resizing is governed by:

  • geometry manager options (expand, fill, sticky)
  • weight configuration (for grid)
  • container size constraints

Predictable resizing requires explicitly defining how extra space is distributed.

bootstack favors explicit layout intent over implicit defaults.

Layout and scrolling

Scrollable layouts introduce additional constraints:

  • content size may exceed viewport size
  • geometry must adapt dynamically
  • scrollbars must stay synchronized

bootstack provides standardized scroll container patterns to avoid re-implementing these behaviors repeatedly.

bootstack layout conventions

While Tk allows many layout styles, bootstack promotes a few conventions:

  • prefer grid for structured layouts
  • use containers to manage spacing consistently
  • avoid deep nesting where possible
  • centralize scrolling behavior in dedicated containers

These conventions reduce layout complexity and improve maintainability:

Common pitfalls

  • querying widget size before layout resolution
  • mixing geometry managers in a single container
  • relying on implicit expansion behavior
  • implementing scrolling manually for each widget

Understanding layout mechanics helps avoid these problems.

Next steps