Tk - Widgets Overview

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The basic component of a Tk-based application is called a widget. A component is also sometimes called a window, since, in Tk, "window" and "widget" are often used interchangeably. Tk is a package that provides a rich set of graphical components for creating graphical applications with Tcl.

Tk provides a range of widgets ranging from basic GUI widgets like buttons and menus to data display widgets. The widgets are very configurable as they have default configurations making them easy to use.

Tk applications follow a widget hierarchy where any number of widgets may be placed within another widget, and those widgets within another widget. The main widget in a Tk program is referred to as the root widget and can be created by making a new instance of the TkRoot class.

Creating a Widget

The syntax for creating a widget is given below.

type variableName arguments options

The type here refers to the widget type like button, label, and so on. Arguments can be optional and required based on individual syntax of each widget. The options range from size to formatting of each component.

Widget Naming Convention

Widget uses a structure similar to naming packages. In Tk, the root window is named with a period (.) and an element in window, for example button is named .myButton1. The variable name should start with a lowercase letter, digit, or punctuation mark (except a period). After the first character, other characters may be uppercase or lowercase letters, numbers, or punctuation marks (except periods). It is recommended to use a lowercase letter to start the label.

Color Naming Convention

The colors can be declared using name like red, green, and so on. It can also use hexadecimal representing with #. The number of hexadecimal digits can be 3, 6, 9, or 12.

Dimension Convention

The default unit is pixels and it is used when we specify no dimension. The other dimensions are i for inches, m for millimeters, c for centimeters and p for points.

Common Options

There are so many common options available to all widgets and they are listed below in the following table −

A simple example for options is shown below.

#!/usr/bin/wish

grid [label .myLabel -background red -text "Hello World" -relief ridge -borderwidth 3]
   -padx 100 -pady 100

When we run the above program, we will get the following output.

The list of available widgets are categorized below −

Basic widgets

Layout Widgets

Selection Widgets

Mega Widgets

Other Widgets

We will cover each of these widgets in the upcoming chapters.