'JS/TS proper structuring: canvas drawing from class, without class "knowing" about the canvas
I have a parent class, that has a <canvas> and a tool property.
(written in Typescript):
class CanvasHandler {
canvas: HTMLCanvasElement;
tool: Tool;
constructor(canvas: HTMLCanvasElement, tool: Tool) {
this.canvas = canvas;
this.tool = tool;
}
}
The tool is going to be an instance of the class Pen, that extends Tool:
interface IPen {
size: number;
color: string;
}
class Pen extends Tool implements IPen {
size: number;
color: string;
constructor(size: number, color: string) {
super(ToolNames.PEN, ToolDescriptions.PEN);
this.size = size;
this.color = color;
}
override onMouseMove(event: Event) {
// DRAW CIRCLE TO CANVAS
}
}
I have implemented an Observer on the <canvas>-Element, so now every time the mouse moves over the canvas, the method onMouseMove of CanvasHandler.tool gets executed. Now, every time the onMouseMove function gets called, I want to draw a circle to the <canvas>. I could provide a reference to the <canvas>, so that the class Tool "knows" the <canvas>, and ´onMouseMove´ I could override the drawing behaviour in Pen. However I wonder, if theres not a better way, to relocate the drawing functionality, so that the class Pen and Tool dont directly "know" about the <canvas> element.
Sources
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