Launcher: fixes for lingering previews

Also better fix for some ‘assign Qurl from undefined’ warnings

src/GUI/PreviewImageItem.cxx

@@ -78,6 +78,17 @@ float PreviewImageItem::aspectRatio() const
     return static_cast<float>(m_image.width()) / m_image.height();
 }
 
+void PreviewImageItem::clear()
+{
+    m_imageUrl.clear();
+    m_image = QImage{};
+    m_imageDirty = true;
+    m_requestActive = false;
+    update();
+    emit imageUrlChanged();
+    emit isLoadingChanged();
+}
+
 void PreviewImageItem::setImageUrl( QUrl url)
 {
     if (m_imageUrl == url)
@@ -117,6 +128,11 @@ void PreviewImageItem::setImage(QImage image)
 void PreviewImageItem::onFinished()
 {
     QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
+    if (reply->url() != m_imageUrl) {
+        // if replies arrive out of order, don't trample the correct one
+        return;
+    }
+
     QImage img;
     if (!img.load(reply, nullptr)) {
         qWarning() << Q_FUNC_INFO << "failed to read image data from" << reply->url();
@@ -137,8 +153,8 @@ void PreviewImageItem::onDownloadError(QNetworkReply::NetworkError errorCode)
         }
     }
 
-    qWarning() << "failed to download:" << reply->url();
-    qWarning() << reply->errorString();
+    qWarning() << Q_FUNC_INFO << "failed to download:" << reply->url();
+    qWarning() << "\t" << reply->errorString();
     m_requestActive = false;
     emit isLoadingChanged();
 }

src/GUI/PreviewImageItem.hxx

@@ -37,6 +37,11 @@ public:
 
     float aspectRatio() const;
 
+    /**
+      @brief clear the image immediately, so we don't see a stale / expired
+      one while attemtping to load the next one
+      */
+    Q_INVOKABLE void clear();
 signals:
     void imageUrlChanged();
     void sourceSizeChanged();

src/GUI/qml/AircraftPreviewPanel.qml

@@ -9,6 +9,7 @@ Rectangle {
     readonly property bool __havePreviews: (previews.length > 0)
     onPreviewsChanged: {
         activePreview = 0
+        preview.clear()
     }
 
     height: width / preview.aspectRatio
@@ -25,7 +26,15 @@ Rectangle {
         id: preview
         width: parent.width
         height: parent.height
-        imageUrl: __havePreviews ? root.previews[root.activePreview] : ""
+
+        function activePreviewUrl()
+        {
+            if (!__havePreviews) return "";
+            if (root.previews.length <= root.activePreview) return "";
+            return root.previews[root.activePreview];
+        }
+
+        imageUrl: activePreviewUrl();
 
         Rectangle {
             anchors.fill: parent

src/GUI/qml/Summary.qml

@@ -29,9 +29,14 @@ Item {
         width: height * aspectRatio
         height: scale * sourceSize.height
 
-        property var urlsList: []
+        property var urlsList: _launcher.defaultSplashUrls()
         property int __currentUrl: 0
 
+        Binding on urlsList {
+            when: _launcher.selectedAircraftInfo.previews.length > 0
+            value: _launcher.selectedAircraftInfo.previews
+        }
+
         onUrlsListChanged: {
             __currentUrl = 0;
         }
@@ -46,29 +51,14 @@ Item {
             }
         }
 
-        function currentPreviewUrl()
+        function currentUrl()
         {
-            if (__currentUrl >= urlsList.length) return "";
+            if (urlsList.length <= __currentUrl) return "";
             return urlsList[__currentUrl];
         }
 
         visible: imageUrl != ""
-        imageUrl: currentPreviewUrl()
-
-// conditional binding when we have valid previews
-        Binding {
-            when: (_launcher.selectedAircraftInfo.previews.length > 0)
-            target: preview
-            property: "urlsList"
-            value: _launcher.selectedAircraftInfo.previews
-        }
-
-        Binding {
-            when: _launcher.selectedAircraftInfo.previews.length === 0
-            target: preview
-            property: "urlsList"
-            value: _launcher.defaultSplashUrls()
-        }
+        imageUrl: currentUrl()
     }
 
     Text {