Migrate to C++ 20 & switch to websocketpp develop branch (#4252)

* feat: c++ 20

* fix: c++ 20 deprecations

* fix(msvc): warnings

* chore: add changelog entry

* fix: formatting

* Update websocketpp to the `develop` branch

* Specify other template type in FlagsEnum != operator

* Remove the user of simple template ids in our websocketpp template class

Also standardizes the file a bit by using nested namespaces, using
pragma once

* fix: turn `MAGIC_MESSAGE_SUFFIX` into a `QString`

* hacky unhacky hacky const char hack

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/widgets/dialogs/BadgePickerDialog.cpp

@@ -42,7 +42,7 @@ BadgePickerDialog::BadgePickerDialog(QList<DisplayBadge> badges,
         this->dropdown_->addItem(item.displayName(), item.badgeName());
     }
 
-    const auto updateBadge = [=](int index) {
+    const auto updateBadge = [=, this](int index) {
         BadgeOpt badge;
         if (index >= 0 && index < badges.size())
         {

src/widgets/dialogs/ColorPickerDialog.cpp

@@ -94,13 +94,14 @@ ColorPickerDialog::ColorPickerDialog(const QColor &initial, QWidget *parent)
         layout.emplace<QHBoxLayout>().emplace<QDialogButtonBox>(this);
     {
         auto *button_ok = buttons->addButton(QDialogButtonBox::Ok);
-        QObject::connect(button_ok, &QPushButton::clicked, [=](bool) {
+        QObject::connect(button_ok, &QPushButton::clicked, [this](bool) {
             this->ok();
         });
         auto *button_cancel = buttons->addButton(QDialogButtonBox::Cancel);
-        QObject::connect(button_cancel, &QAbstractButton::clicked, [=](bool) {
-            this->close();
-        });
+        QObject::connect(button_cancel, &QAbstractButton::clicked,
+                         [this](bool) {
+                             this->close();
+                         });
     }
 
     this->themeChangedEvent();
@@ -226,7 +227,7 @@ void ColorPickerDialog::initRecentColors(LayoutCreator<QWidget> &creator)
 
         grid->addWidget(button, rowInd, columnInd);
 
-        QObject::connect(button, &QPushButton::clicked, [=] {
+        QObject::connect(button, &QPushButton::clicked, [=, this] {
             this->selectColor(button->color(), false);
         });
 
@@ -260,7 +261,7 @@ void ColorPickerDialog::initDefaultColors(LayoutCreator<QWidget> &creator)
 
         grid->addWidget(button, rowInd, columnInd);
 
-        QObject::connect(button, &QPushButton::clicked, [=] {
+        QObject::connect(button, &QPushButton::clicked, [=, this] {
             this->selectColor(button->color(), false);
         });
 
@@ -299,7 +300,7 @@ void ColorPickerDialog::initColorPicker(LayoutCreator<QWidget> &creator)
 
     QObject::connect(
         luminancePicker, &QColorLuminancePicker::newHsv,
-        [=](int h, int s, int v) {
+        [this](int h, int s, int v) {
             int alpha = this->ui_.picker.spinBoxes[SpinBox::ALPHA]->value();
             this->selectColor(QColor::fromHsv(h, s, v, alpha), true);
         });
@@ -344,7 +345,7 @@ void ColorPickerDialog::initSpinBoxes(LayoutCreator<QWidget> &creator)
     {
         QObject::connect(
             this->ui_.picker.spinBoxes[i],
-            QOverload<int>::of(&QSpinBox::valueChanged), [=](int value) {
+            QOverload<int>::of(&QSpinBox::valueChanged), [=, this](int value) {
                 this->selectColor(QColor(red->value(), green->value(),
                                          blue->value(), alpha->value()),
                                   false);

src/widgets/dialogs/LoginDialog.cpp

@@ -177,16 +177,16 @@ AdvancedLoginWidget::AdvancedLoginWidget()
 
     this->ui_.oauthTokenInput.setEchoMode(QLineEdit::Password);
 
-    connect(&this->ui_.userIDInput, &QLineEdit::textChanged, [=]() {
+    connect(&this->ui_.userIDInput, &QLineEdit::textChanged, [this]() {
         this->refreshButtons();
     });
-    connect(&this->ui_.usernameInput, &QLineEdit::textChanged, [=]() {
+    connect(&this->ui_.usernameInput, &QLineEdit::textChanged, [this]() {
         this->refreshButtons();
     });
-    connect(&this->ui_.clientIDInput, &QLineEdit::textChanged, [=]() {
+    connect(&this->ui_.clientIDInput, &QLineEdit::textChanged, [this]() {
         this->refreshButtons();
     });
-    connect(&this->ui_.oauthTokenInput, &QLineEdit::textChanged, [=]() {
+    connect(&this->ui_.oauthTokenInput, &QLineEdit::textChanged, [this]() {
         this->refreshButtons();
     });
 
@@ -201,22 +201,23 @@ AdvancedLoginWidget::AdvancedLoginWidget()
         &this->ui_.buttonUpperRow.clearFieldsButton);
 
     connect(&this->ui_.buttonUpperRow.clearFieldsButton, &QPushButton::clicked,
-            [=]() {
+            [this]() {
                 this->ui_.userIDInput.clear();
                 this->ui_.usernameInput.clear();
                 this->ui_.clientIDInput.clear();
                 this->ui_.oauthTokenInput.clear();
             });
 
-    connect(
-        &this->ui_.buttonUpperRow.addUserButton, &QPushButton::clicked, [=]() {
-            QString userID = this->ui_.userIDInput.text();
-            QString username = this->ui_.usernameInput.text();
-            QString clientID = this->ui_.clientIDInput.text();
-            QString oauthToken = this->ui_.oauthTokenInput.text();
+    connect(&this->ui_.buttonUpperRow.addUserButton, &QPushButton::clicked,
+            [this]() {
+                QString userID = this->ui_.userIDInput.text();
+                QString username = this->ui_.usernameInput.text();
+                QString clientID = this->ui_.clientIDInput.text();
+                QString oauthToken = this->ui_.oauthTokenInput.text();
 
-            logInWithCredentials(this, userID, username, clientID, oauthToken);
-        });
+                logInWithCredentials(this, userID, username, clientID,
+                                     oauthToken);
+            });
 }
 
 void AdvancedLoginWidget::refreshButtons()

src/widgets/dialogs/SelectChannelDialog.cpp

@@ -223,13 +223,14 @@ SelectChannelDialog::SelectChannelDialog(QWidget *parent)
         layout.emplace<QHBoxLayout>().emplace<QDialogButtonBox>(this);
     {
         auto *button_ok = buttons->addButton(QDialogButtonBox::Ok);
-        QObject::connect(button_ok, &QPushButton::clicked, [=](bool) {
+        QObject::connect(button_ok, &QPushButton::clicked, [this](bool) {
             this->ok();
         });
         auto *button_cancel = buttons->addButton(QDialogButtonBox::Cancel);
-        QObject::connect(button_cancel, &QAbstractButton::clicked, [=](bool) {
-            this->close();
-        });
+        QObject::connect(button_cancel, &QAbstractButton::clicked,
+                         [this](bool) {
+                             this->close();
+                         });
     }
 
     this->setMinimumSize(300, 310);

src/widgets/dialogs/UserInfoPopup.cpp

@@ -919,7 +919,7 @@ void UserInfoPopup::loadAvatar(const QUrl &url)
     static auto manager = new QNetworkAccessManager();
     auto *reply = manager->get(req);
 
-    QObject::connect(reply, &QNetworkReply::finished, this, [=] {
+    QObject::connect(reply, &QNetworkReply::finished, this, [=, this] {
         if (reply->error() == QNetworkReply::NoError)
         {
             const auto data = reply->readAll();