box(ctx) {
        ctx.lineWidth = 1;
        ctx.beginPath();
        ctx.strokeStyle = "#0b90dc";
        ctx.rect(this.model.rect.x, this.model.rect.y, this.model.rect.w, this.model.rect.h);
        ctx.stroke();
    }
Draw outline box for the text.
@param {CanvasRenderingContext2D} ctx
@private