Draw square for C++

ofApp.cpp

#include "ofApp.h"
#include <math.h>

#define WIDTH 200
#define HEIGHT 200

void ofApp::setup()
{
    ofSetFrameRate(60);
    
    ofSetWindowShape(WIDTH, HEIGHT);

    ofSetBackgroundColor(0, 0, 0);
    
    _currentFrame = 0;
    
    _square = new Square();
}

void ofApp::update()
{
}

void ofApp::draw()
{
    ofSetColor(0, 0, 0);
    ofRect(0, 0, ofGetWindowWidth(), ofGetWindowHeight());

    _currentFrame += 1;
    
    _square->draw(ofGetWindowWidth() / 2, ofGetWindowHeight() / 2, 50, 50);    
    
    if (_currentFrame > ofGetFrameRate()) {
        _currentFrame = 0;
    }
}

ofApp.h

#pragma once

#include "ofMain.h"
#include "Square.h"

class ofApp : public ofBaseApp
{
public:
    void setup();
    void update();
    void draw();
    
private:
    Square *_square;
    
    int _currentFrame;
};

Square.cpp

#include "Square.h"

Square::Square()
: _linearType(LinearTypeTop)
, _lineLength(0)
, _alpha(0)
{
}

Square::~Square()
{
}

void Square::draw(float centerX, float centerY, float width, float height)
{
    this->drawSquare(centerX, centerY, width, height);

    _lineLength += 1.0;

    switch (_linearType) {
        case LinearTypeTop:
        case LinearTypeBottom:
        {
            if (_lineLength > width) {
                _lineLength = 0;
                _alpha = 0;
                
                this->nextLinearType();
            } else {
                _alpha = _lineLength / width;
            }
        }
        break;
        case LinearTypeRight:
        case LinearTypeLeft:
        {
            if (_lineLength > height) {
                _lineLength = 0;
                _alpha = 0;
                
                this->nextLinearType();
            } else {
                _alpha = _lineLength / height;
            }
        }
        break;
    }
}

void Square::drawSquare(float centerX, float centerY, float width, float height)
{
    ofPath line = ofPath();
    line.setStrokeColor(ofColor(255, 255, 255, 255 * _alpha));
    line.setFilled(false);
    line.setStrokeWidth(3.0 * _alpha);
    
    switch (_linearType) {
        case LinearTypeTop:
        {
            line.moveTo((centerX - width / 2), (centerY - height / 2), 0);
            line.lineTo((centerX - width / 2) + _lineLength, (centerY - height / 2), 0);
        }
        break;
        case LinearTypeRight:
        {
            line.moveTo((centerX + width / 2), (centerY - height / 2), 0);
            line.lineTo((centerX + width / 2), (centerY - height / 2) + _lineLength, 0);
        }
        break;
        case LinearTypeBottom:
        {
            line.moveTo((centerX + width / 2), (centerY + height / 2), 0);
            line.lineTo((centerX + width / 2) - _lineLength, (centerY + height / 2), 0);
        }
        break;
        case LinearTypeLeft:
        {
            line.moveTo((centerX - width / 2), (centerY + height / 2), 0);
            line.lineTo((centerX - width / 2), (centerY + height / 2) - _lineLength, 0);
        }
        break;
        default:
        {
        }
        break;
    }
    
    line.draw();
    line.close();
}

void Square::nextLinearType()
{
    switch (_linearType) {
        case LinearTypeTop:
        {
            _linearType = LinearTypeRight;
        }
        break;
        case LinearTypeRight:
        {
            _linearType = LinearTypeBottom;
        }
        break;
        case LinearTypeBottom:
        {
            _linearType = LinearTypeLeft;
        }
        break;
        case LinearTypeLeft:
        {
            _linearType = LinearTypeTop;
        }
        break;
        default:
        {
            _linearType = LinearTypeTop;
        }
        break;
    }    
}

Square.h

#pragma once

#include "ofMain.h"

class Square
{
public:
    Square();
    ~Square();
    void draw(float centerX, float centerY, float width, float height);

private:
    enum LinearType {
        LinearTypeTop,
        LinearTypeRight,
        LinearTypeBottom,
        LinearTypeLeft
    };
    
private:
    LinearType _linearType;
    float _lineLength;
    float _alpha;
    
private:
    /**
     *  @brief 四角を描画する
     */
    void drawSquare(float centerX, float centerY, float width, float height);
    
    /**
     *  @brief 次の線形のタイプへ
     */
    void nextLinearType();
};