fabric 鼠标动态绘制图形

import { fabric } from 'fabric';
import { Rect } from "./rect";

/**
 * 动态拖动鼠标绘制图形
 * 滚轮 重置绘图次数
 */
export class DynamicShape {
    count = 1;
    isDrawing = false;
    constructor(canvas) {
        // 绑定鼠标动态绘制图形
        this.bindDrawEvent(canvas);
        // 绑定鼠标滚轮点击，用于重置绘制次数
        this.bindMouseClick(canvas);
    }

    /**
     * 绑定鼠标动态绘制图形
     * @param canvas
     */
    bindDrawEvent(canvas) {
        let rect, mouseS, objs = [];
        let self = this;
        canvas.on('mouse:down', (e) => {
            if (self.count) {
                self.isDrawing = true;
                mouseS = {
                    mx: e.e.offsetX,
                    my: e.e.offsetY,
                };
                rect = new fabric.Rect(Object.assign(Rect.defaultRect(), { left: mouseS.mx, top: mouseS.my,  0, height: 0, id: Math.random() }));
                objs.push(rect);
                // 添加图形至画布
                canvas.add(rect);
                canvas.renderAll();
            }
        });
        $(document).on('mousemove', (e) => {
            if (self.isDrawing && self.count) {
                let mouseE = { mx: e.originalEvent.offsetX, my: e.originalEvent.offsetY };
                rect.set({  mouseE.mx - mouseS.mx, height: mouseE.my - mouseS.my });
                canvas.renderAll();
            }
        });
        canvas.on('mouse:up', (e) => {
            if (self.isDrawing) {
                canvas.discardActiveObject();
                // 清空所有选中，只选中绘制图形
                canvas.setActiveObject(rect);
                canvas.renderAll();
                // 重置
                self.count = 0;
                self.isDrawing = false;
                rect = mouseS = null;
                objs = [];
            }
        });
    }

    /**
     * 将执行方法绑定到鼠标右键，以供快速测试功能可用性
     */
    bindMouseClick(canvas) {
        $('.upper-canvas').on('mousedown', (e) => {
            let type = e.originalEvent.which;
            switch (type) {
                case 1:
                    // console.log('left');
                    break;
                case 2:
                    // 重置绘制次数
                    this.count = 1;
                    break;
                case 3:
                    // console.log('right');
                    break;
            }
        });
    }
}