Warn when no hardware decoding is available

app/gui/PcView.qml

@@ -6,6 +6,7 @@ import QtQuick.Layouts 1.3
 import ComputerModel 1.0
 
 import ComputerManager 1.0
+import StreamingPreferences 1.0
 
 GridView {
     property ComputerModel computerModel : createModel()
@@ -25,9 +26,17 @@ GridView {
     // routine to run, but only if we start as invisible
     visible: false
 
+    StreamingPreferences {
+        id: prefs
+    }
+
     Component.onCompleted: {
         // Setup signals on CM
         ComputerManager.computerAddCompleted.connect(addComplete)
+
+        if (!prefs.hasAnyHardwareAcceleration()) {
+            noHwDecoderDialog.open()
+        }
     }
 
     onVisibleChanged: {
@@ -184,6 +193,19 @@ GridView {
         standardButtons: StandardButton.Ok
     }
 
+    MessageDialog {
+        id: noHwDecoderDialog
+        modality:Qt.WindowModal
+        icon: StandardIcon.Warning
+        standardButtons: StandardButton.Ok | StandardButton.Help
+        text: "No functioning hardware accelerated H.264 video decoder was detected by Moonlight. " +
+              "Your streaming performance may be severely degraded in this configuration. " +
+              "Click the Help button for more information on solving this problem."
+        onHelp: {
+            Qt.openUrlExternally("https://github.com/moonlight-stream/moonlight-docs/wiki/Fixing-Hardware-Decoding-Problems");
+        }
+    }
+
     MessageDialog {
         id: pairDialog
         // don't allow edits to the rest of the window while open

app/settings/streamingpreferences.cpp

@@ -1,4 +1,5 @@
 #include "streamingpreferences.h"
+#include "streaming/session.hpp"
 
 #include <QSettings>
 
@@ -57,6 +58,15 @@ void StreamingPreferences::save()
     settings.setValue(SER_VIDEODEC, static_cast<int>(videoDecoderSelection));
 }
 
+bool StreamingPreferences::hasAnyHardwareAcceleration()
+{
+    // Always use VDS_AUTO to avoid spamming the user with warnings
+    // if they've forced software decoding.
+    return Session::isHardwareDecodeAvailable(VDS_AUTO,
+                                              VIDEO_FORMAT_H264,
+                                              1920, 1080, 60);
+}
+
 int StreamingPreferences::getDefaultBitrate(int width, int height, int fps)
 {
     if (width * height * fps <=  1280 * 720 * 30) {

app/settings/streamingpreferences.h

@@ -14,6 +14,8 @@ public:
 
     Q_INVOKABLE void save();
 
+    Q_INVOKABLE static bool hasAnyHardwareAcceleration();
+
     void reload();
 
     enum AudioConfig

app/streaming/session.hpp

@@ -21,6 +21,10 @@ public:
 
     Q_INVOKABLE void exec();
 
+    static
+    bool isHardwareDecodeAvailable(StreamingPreferences::VideoDecoderSelection vds,
+                                   int videoFormat, int width, int height, int frameRate);
+
 signals:
     void stageStarting(QString stage);
 
@@ -45,10 +49,6 @@ private:
 
     void toggleFullscreen();
 
-    static
-    bool isHardwareDecodeAvailable(StreamingPreferences::VideoDecoderSelection vds,
-                                   int videoFormat, int width, int height, int frameRate);
-
     static
     bool chooseDecoder(StreamingPreferences::VideoDecoderSelection vds,
                        SDL_Window* window, int videoFormat, int width, int height,