Improved error handling for media items

- Display a meaningful error message to the user when adding or trying
to play a video
- Make sure the video placeholder is visible even after switching pages

src/domain/UBGraphicsMediaItem.cpp

@@ -71,6 +71,8 @@ UBGraphicsMediaItem::UBGraphicsMediaItem(const QUrl& pMediaFileUrl, QGraphicsIte
         , mInitialPos(0)
 {
 
+    mErrorString = "";
+
     mMediaObject = new QMediaPlayer(this);
     mMediaObject->setMedia(pMediaFileUrl);
 
@@ -141,6 +143,9 @@ UBGraphicsVideoItem::UBGraphicsVideoItem(const QUrl &pMediaFileUrl, QGraphicsIte
     connect(mMediaObject, SIGNAL(stateChanged(QMediaPlayer::State)),
             this, SLOT(mediaStateChanged(QMediaPlayer::State)));
 
+    connect(mMediaObject, static_cast<void(QMediaPlayer::*)(QMediaPlayer::Error)>(&QMediaPlayer::error),
+            this, &UBGraphicsVideoItem::mediaError);
+
     setAcceptHoverEvents(true);
 
     update();
@@ -346,6 +351,11 @@ void UBGraphicsMediaItem::stop()
 
 void UBGraphicsMediaItem::togglePlayPause()
 {
+    if (!mErrorString.isEmpty()) {
+        UBApplication::showMessage("Can't play media: " + mErrorString);
+        return;
+    }
+
     if (mMediaObject->state() == QMediaPlayer::StoppedState)
         mMediaObject->play();
 
@@ -378,8 +388,29 @@ void UBGraphicsMediaItem::togglePlayPause()
 
 void UBGraphicsMediaItem::mediaError(QMediaPlayer::Error errorCode)
 {
-    if (errorCode != QMediaPlayer::NoError)
-        UBApplication::showMessage(mMediaObject->errorString());
+    // QMediaPlayer::errorString() isn't very descriptive, so we generate our own message
+
+    switch (errorCode) {
+        case QMediaPlayer::NoError:
+            mErrorString = "";
+            break;
+        case QMediaPlayer::ResourceError:
+            mErrorString = tr("Media resource couldn't be resolved");
+            break;
+        case QMediaPlayer::FormatError:
+            mErrorString = tr("Unsupported media format");
+            break;
+        case QMediaPlayer::ServiceMissingError:
+            mErrorString = tr("Media playback service not found");
+            break;
+        default:
+            mErrorString = tr("Media error: ") + QString(errorCode) + " (" + mMediaObject->errorString() + ")";
+    }
+
+    if (!mErrorString.isEmpty() ) {
+        UBApplication::showMessage(mErrorString);
+        qDebug() << mErrorString;
+    }
 }
 
 void UBGraphicsMediaItem::copyItemParameters(UBItem *copy) const
@@ -569,6 +600,19 @@ void UBGraphicsVideoItem::mediaStateChanged(QMediaPlayer::State state)
 
 }
 
+void UBGraphicsVideoItem::activeSceneChanged()
+{
+    // Update the visibility of the placeholder, to prevent it being hidden when switching pages
+    setPlaceholderVisible(!mErrorString.isEmpty());
+
+    UBGraphicsMediaItem::activeSceneChanged();
+}
+
+void UBGraphicsVideoItem::mediaError(QMediaPlayer::Error errorCode)
+{
+    setPlaceholderVisible(errorCode != QMediaPlayer::NoError);
+}
+
 /**
  * @brief Set the brush and fill to display a black rectangle
  * @param visible If true, a black rectangle is displayed in place of the video

src/domain/UBGraphicsMediaItem.h

@@ -149,6 +149,8 @@ protected:
     QGraphicsPixmapItem *mLinkedImage;
 
     qint64 mInitialPos;
+
+    QString mErrorString;
 };
 
 class UBGraphicsAudioItem: public UBGraphicsMediaItem
@@ -183,6 +185,10 @@ public slots:
     void videoSizeChanged(QSizeF newSize);
     void hasVideoChanged(bool hasVideo);
     void mediaStateChanged(QMediaPlayer::State state);
+    void activeSceneChanged();
+
+protected slots:
+    void mediaError(QMediaPlayer::Error errorCode);
 
 protected: