In this post, I am showing how to use Squeak Small talk to draw a circle on the screen using a Pen object and math functions. Not only it shows you how to draw a circle, but it also shows how to create a basic window and set it up for drawing functionality.
Here is code to draw a circle using Pen.
"Create Window" window := SystemWindow new. window setLabel:'New Window'. pasteUpMorph := PasteUpMorph new. window addMorph: pasteUpMorph frame: (0@0 corner: 1@1). window openInWorld. "Create ImageMorph" myImageMorph := ImageMorph new. pasteUpMorph addMorph: myImageMorph. myImageMorph newForm: (Form extent: (pasteUpMorph extent) depth: 32). myImageMorph bounds: (pasteUpMorph bounds). "Create Pen and use it to draw on ImageMorph" myPen := Pen newOnForm: myImageMorph image. myPen squareNib: 3. myPen color: Color blue. x := 0.0. y := 0.0. th := 0.0. 1 to: 200 do: [:i | th := i * (3.14 / 100). x := th sin * 100 + 200. y := th cos * 100 + 200. myPen place: x@y. myPen go: 0@0. ].
And, here is the screenshot of code from Squeak.