好的，以下是一个基于QT的Windows图形界面聊天程序的算法程序代码。由于实现细节较多，这里只提供框架代码。

#include <QtWidgets>
#include <QtNetwork>

class ChatClient : public QWidget
{
    Q_OBJECT

public:
    ChatClient(QWidget *parent = nullptr);

private slots:
    void sendMessage();
    void processMessage();
    void displayError(QAbstractSocket::SocketError socketError);
    void login();
    void logout();

private:
    QLabel *hostLabel;
    QLineEdit *hostLineEdit;
    QLabel *portLabel;
    QLineEdit *portLineEdit;
    QLabel *userLabel;
    QLineEdit *userLineEdit;
    QLabel *passwordLabel;
    QLineEdit *passwordLineEdit;

    QPushButton *loginButton;
    QPushButton *logoutButton;

    QTextEdit* chatDisplayTextEdit; // 聊天内容显示框
	QTextEdit* messageTextEdit; // 消息输入框

	QTcpSocket* tcpSocket; // 客户端socket
	QString userName; // 用户名
	QString password; // 密码

	bool isLoggedIn; // 是否已登录

	void createLoginDialog(); // 创建登录对话框
};

ChatClient::ChatClient(QWidget *parent)
	: QWidget(parent), isLoggedIn(false)
{
	// 设置UI控件和布局
	hostLabel = new QLabel(tr("Server IP:"));
	hostLineEdit = new QLineEdit("127.0.0.1");
	portLabel = new QLabel(tr("Port:"));
	portLineEdit = new QLineEdit("8888");
	userLabel = new QLabel(tr("Username:"));
	userLineEdit = new QLineEdit();
	passwordLabel = new QLabel(tr("Password:"));
	passwordLineEdit = new QLineEdit();

	loginButton = new QPushButton(tr("&Login"));
	logoutButton = new QPushButton(tr("&Logout"));
	logoutButton->setEnabled(false);

	QGridLayout* loginLayout = new QGridLayout;
	loginLayout->addWidget(hostLabel, 0, 0);
	loginLayout->addWidget(hostLineEdit, 0, 1);
	loginLayout->addWidget(portLabel, 1, 0);
	loginLayout->addWidget(portLineEdit, 1, 1);
	loginLayout->addWidget(userLabel, 2, 0);
	loginLayout->addWidget(userLineEdit, 2, 1);
	loginLayout->addWidget(passwordLabel, 3, 0);
	loginLayout->addWidget(passwordLineEdit, 3, 1);

	QVBoxLayout* mainLayout = new QVBoxLayout;
	mainLayout->addStretch(1);
	mainLayout->addSpacing(10);
	mainLayout->addLayout(loginLayout);
	mainLayout->addSpacing(10);
	mainLayout->addWidget(loginButton);
	mainLayout->addWidget(logoutButton);

	setWindowTitle(tr("Chat Client"));

	connect(loginButton, SIGNAL(clicked()), this, SLOT(login()));
	connect(logoutButton, SIGNAL(clicked()), this,
		SLOT(logout()));

	setFixedHeight(sizeHint().height());
}

void ChatClient::login()
{
	if (isLoggedIn) // 已登录，不进行操作
		return;

	QString hostName = hostLineEdit ->text();
	int port = portLineEdit ->text().toInt();

	userName = userLineEdit ->text();
	password = passwordLineEdit ->text();

	tcpSocket = new QTcpSocket(this); // 创建socket
	connect(tcpSocket,SIGNAL(error(QAbstractSocket::SocketError)),
			this,SLOT(displayError(QAbstractSocket::SocketError)));
	connect(tcpSocket,SIGNAL(readyRead()),this,SLOT(processMessage()));

	tcpSocket ->connectToHost(hostName,port); // 连接到服务器

	if(!tcpSocket ->waitForConnected())
	{
        QMessageBox::warning(this,tr("Connection failed"),tcpSocket ->errorString());
		return;
	}

	isLoggedIn=true; // 设置为已登录
	loginButton->setEnabled(false);
	logoutButton ->setEnabled(true);

	messageTextEdit = new QTextEdit(); // 创建消息输入框
	chatDisplayTextEdit = new QTextEdit(); // 创建聊天内容显示框

	QVBoxLayout* layout = new QVBoxLayout;
	layout->addWidget(chatDisplayTextEdit);
	layout->addWidget(messageTextEdit);

	QWidget* widget = new QWidget;
	widget->setLayout(layout);

	this->layout()->addWidget(widget); // 添加到主界面

}

void ChatClient::logout()
{
	if (!isLoggedIn) // 未登录，不进行操作
		return;

	tcpSocket ->disconnectFromHost(); // 断开连接
	isLoggedIn=false; // 设置为未登录
	loginButton ->setEnabled(true);
	logoutButton ->setEnabled(false);

	// 清空控件和布局
	delete chatDisplayTextEdit;
	delete messageTextEdit;
	QLayoutItem *item;
	while ((item = layout()->takeAt(2)) != NULL)
	{
		delete item->widget();
		delete item;
	}
}

void ChatClient::processMessage()
{
    QByteArray data=tcpSocket ->readAll();
    QString message=QString(data); // 接收到的数据转成字符串

    chatDisplayTextEdit ->append(message); // 在聊天内容显示框中追加消息
}

void ChatClient::displayError(QAbstractSocket::SocketError socketError)
{
    switch (socketError)
    {
        case QAbstractSocket::RemoteHostClosedError:
            break;

        case QAbstractSocket::HostNotFoundError:
            QMessageBox::information(this, tr("Chat Client"),
                                     tr("The host was not found. Please check the "
                                        "host name and port settings."));
            break;

        case QAbstractSocket::ConnectionRefusedError:
            QMessageBox::information(this, tr("Chat Client"),
                                     tr("The connection was refused by the peer. "
                                        "Make sure the chat server is running, "
                                        "and check that the host name and port "
                                        "settings are correct."));
            break;

        default:
            QMessageBox::information(this, tr("Chat Client"),
                                     tr("The following error occurred: %1.")
                                     .arg(tcpSocket ->errorString()));
    }
}

void ChatClient::sendMessage()
{
	if (!isLoggedIn) // 未登录，不进行操作
		return;

	QString message = messageTextEdit->toPlainText();
	if (message.isEmpty()) // 输入框为空，不发送消息
		return;

	message += "\n"; // 添加换行符

	QByteArray data(message.toStdString().c_str(), message.length());
	tcpSocket->write(data); // 发送数据到服务器

	messageTextEdit->clear(); // 清空输入框
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    ChatClient client;
    client.show();
    return app.exec();
}

请注意，这只是一个基本的聊天程序示例，并没有实现所有功能或细节。你可以根据自己的需求和项目要求对代码进行修改和扩展。