Rewrite dialog code to use Quick Controls 2

app/gui/NavigableMessageDialog.qml

@@ -1,21 +1,53 @@
 import QtQuick 2.0
-import QtQuick.Dialogs 1.2
+import QtQuick.Controls 2.2
 
-MessageDialog {
-    property Item originalFocusItem
+import SystemProperties 1.0
 
-    onVisibleChanged: {
-        if (!isWindow) {
-            if (visible) {
-                originalFocusItem = window.activeFocusItem
+NavigableDialog {
+    id: dialog
+
+    property alias text: dialogTextControl.dialogText
+
+    property string helpText
+    property string helpUrl : "https://github.com/moonlight-stream/moonlight-docs/wiki/Troubleshooting"
+
+    Row {
+        spacing: 10
+
+        Image {
+            source: (standardButtons & Dialog.Yes) ?
+                        "qrc:/res/baseline-help_outline-24px.svg" :
+                        "qrc:/res/baseline-error_outline-24px.svg"
+            sourceSize {
+                // The icon should be square so use the height as the width too
+                width: 50
+                height: 50
             }
-            else {
-                // We must force focus back to the last item for platforms without
-                // support for more than one active window like Steam Link. If
-                // we don't, gamepad and keyboard navigation will break after a
-                // dialog appears.
-                originalFocusItem.forceActiveFocus()
+        }
+
+        Label {
+            property string dialogText
+
+            id: dialogTextControl
+            text: dialogText + (SystemProperties.hasBrowser ? (" " + helpText) : "")
+            wrapMode: Text.WordWrap
+            focus: true
+
+            anchors.verticalCenter: parent.verticalCenter
+
+            Keys.onReturnPressed: {
+                accept()
             }
         }
     }
+
+    footer: DialogButtonBox {
+        id: dialogButtonBox
+        standardButtons: dialog.standardButtons
+
+        onHelpRequested: {
+            Qt.openUrlExternally(helpUrl)
+            close()
+        }
+    }
 }