How is a text area created in a programming language [on hold]

How is a textarea designed or made at a very basic level.

Let's for example say JTextArea or JEditorPane (I know only Java and Javascript). How are they made from the very basic level. Looking at the source code of the mentioned components is very hallucinating. I wish to know the basic thought process or major steps involved in creating a textArea using a programming language.

Just guessing if it involves usage of 2d graphics to show the rectangle, the border, the scrollbar and showing the text over the rectangle, etc. The reason I am thinking that way is because, some text editors have indentation guidelines, collapsible areas, etc.

Can anyone please throw some light on this question as to how can I build my own text area. I can't think of any simpler way of putting this.

Kindly refrain from mentioning different plugins. I know there are many. But I want to know the approach to create one from scratch.

via Chebli Mohamed