[Qt] Support initializing SettingsWidget by reference to cvar

This prevents a situation where one developer changes the name of a cvar but doesn't update calls to Config::FindCvar*

src/xenia/ui/qt/settings/panes/general_pane.cc

@@ -8,7 +8,9 @@
 #include "xenia/ui/qt/widgets/groupbox.h"
 #include "xenia/ui/qt/widgets/scroll_area.h"
 
-DECLARE_bool(show_debug_tab)
+DECLARE_bool(show_debug_tab);
+DECLARE_bool(discord);
+DECLARE_bool(use_game_icon);
 
     namespace xe {
   namespace ui {
@@ -53,7 +55,7 @@ DECLARE_bool(show_debug_tab)
     groupbox_layout->setContentsMargins(16, 16, 16, 16);
     groupbox->setLayout(groupbox_layout);
 
-    auto discord_presence_checkbox = new SettingsCheckBox("discord");
+    auto discord_presence_checkbox = new SettingsCheckBox(cvars::discord);
     discord_presence_checkbox->setText("Discord Rich Presence");
     
     groupbox_layout->addWidget(discord_presence_checkbox);

src/xenia/ui/qt/settings/widgets/settings_checkbox.cc

@@ -0,0 +1,36 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "settings_checkbox.h"
+
+namespace xe {
+namespace ui {
+namespace qt {
+
+void SettingsCheckBox::Initialize() {
+  if (!cvar_) {
+    return;
+  }
+
+  setChecked(*cvar_->current_value());
+
+  connect(this, &SettingsCheckBox::stateChanged, [&](int state) {
+    if (state == Qt::Checked) {
+      UpdateValue(true);
+    } else if (state == Qt::Unchecked) {
+      UpdateValue(false);
+    } else {
+      XELOGW("PartiallyChecked state not supported for SettingsCheckBox");
+    }
+  });
+}
+
+}  // namespace qt
+}  // namespace ui
+}  // namespace xe

src/xenia/ui/qt/settings/widgets/settings_checkbox.h

@@ -18,27 +18,23 @@ namespace xe {
 namespace ui {
 namespace qt {
 
-class SettingsCheckBox : public SettingsWidget<bool, XCheckBox> {
+using SettingsType = bool;
+
+class SettingsCheckBox : public SettingsWidget<SettingsType, XCheckBox> {
  public:
   explicit SettingsCheckBox(const std::string& config_name,
                             QWidget* parent = nullptr)
       : SettingsWidget(config_name, parent) {
-    if (!cvar_) {
-      return;
-    }
-
-    setChecked(*cvar_->current_value());
-
-    connect(this, &SettingsCheckBox::stateChanged, [&](int state) {
-      if (state == Qt::Checked) {
-        UpdateValue(true);
-      } else if (state == Qt::Unchecked) {
-        UpdateValue(false);
-      } else {
-        XELOGW("PartiallyChecked state not supported for SettingsCheckBox");
-      }
-    });
+    Initialize();
   }
+
+  explicit SettingsCheckBox(const SettingsType& config_var,
+                            QWidget* parent = nullptr)
+      : SettingsWidget(config_var, parent) {
+    Initialize();
+  }
+
+  void Initialize();
 };
 
 }  // namespace qt

src/xenia/ui/qt/settings/widgets/settings_widget.h

@@ -25,7 +25,14 @@ class SettingsWidget : public Widget {
   SettingsWidget(const std::string& config_name, Args... args)
       : Widget(args...), cvar_(nullptr) {
     cvar_ = dynamic_cast<cvar::ConfigVar<T>*>(
-        Config::Instance().FindConfigVar(config_name));
+        Config::Instance().FindConfigVarByName(config_name));
+  }
+
+  template <typename... Args>
+  SettingsWidget(const T& config_ref, Args... args)
+      : Widget(args...), cvar_(nullptr) {
+    cvar_ = dynamic_cast<cvar::ConfigVar<T>*>(
+        Config::Instance().FindConfigVar(config_ref));
   }
 
   void UpdateValue(T val) {