refactor: simplify the code

GPClient/standardloginwindow.cpp

@@ -0,0 +1,41 @@
+#include <QtGui/QCloseEvent>
+
+#include "standardloginwindow.h"
+#include "ui_standardloginwindow.h"
+
+StandardLoginWindow::StandardLoginWindow(const QString &portalAddress, const QString &labelUsername,
+                                         const QString &labelPassword, const QString &authMessage) :
+        QDialog(nullptr),
+        ui(new Ui::StandardLoginWindow) {
+    ui->setupUi(this);
+    ui->portalAddress->setText(portalAddress);
+    ui->username->setPlaceholderText(labelUsername);
+    ui->password->setPlaceholderText(labelPassword);
+    ui->authMessage->setText(authMessage);
+
+    setWindowTitle("GlobalProtect Login");
+    setFixedSize(width(), height());
+    setModal(true);
+}
+
+void StandardLoginWindow::setProcessing(bool isProcessing) {
+    ui->username->setReadOnly(isProcessing);
+    ui->password->setReadOnly(isProcessing);
+    ui->loginButton->setDisabled(isProcessing);
+}
+
+void StandardLoginWindow::on_loginButton_clicked() {
+    const QString username = ui->username->text().trimmed();
+    const QString password = ui->password->text().trimmed();
+
+    if (username.isEmpty() || password.isEmpty()) {
+        return;
+    }
+
+    emit performLogin(username, password);
+}
+
+void StandardLoginWindow::closeEvent(QCloseEvent *event) {
+    event->accept();
+    reject();
+}