Profile: add "synchronous" mode for picture plotting

The thumbnails were fetched in the background to achieve a
snappier UI. The problem with that is that on LaTeX etc.
export only placeholder thumbnails were shown.

Therefore, implement a synchronous mode. This only tries
to fetch cached thumbnails or calculate thumbnails for
images. Videos and remote files are not supported.

Fixes #1963

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

2 files changed, 23 insertions, 4 deletions

diff --git a/core/imagedownloader.cpp b/core/imagedownloader.cpp
index d78409a3c..1559b129b 100644
--- a/core/imagedownloader.cpp
+++ b/core/imagedownloader.cpp
@@ -456,8 +456,23 @@ void Thumbnailer::imageDownloadFailed(QString filename)
 	workingOn.remove(filename);
 }
 
-QImage Thumbnailer::fetchThumbnail(const QString &filename)
+QImage Thumbnailer::fetchThumbnail(const QString &filename, bool synchronous)
 {
+	if (synchronous) {
+		// In synchronous mode, first try the thumbnail cache.
+		Thumbnail thumbnail = getThumbnailFromCache(filename);
+		if (!thumbnail.img.isNull())
+			return thumbnail.img;
+
+		// If that didn't work, try to thumbnail the image.
+		thumbnail = getHashedImage(filename, false);
+		if (thumbnail.type == MEDIATYPE_STILL_LOADING || thumbnail.img.isNull())
+			return failImage; // No support for delayed thumbnails (web).
+
+		int size = maxThumbnailSize();
+		return thumbnail.img.scaled(size, size, Qt::KeepAspectRatio);
+	}
+
 	QMutexLocker l(&lock);
 
 	// We are not currently fetching this thumbnail - add it to the list.
diff --git a/core/imagedownloader.h b/core/imagedownloader.h
index e0d70f59f..280383250 100644
--- a/core/imagedownloader.h
+++ b/core/imagedownloader.h
@@ -31,9 +31,13 @@ public:
 	static Thumbnailer *instance();
 
 	// Schedule a thumbnail for fetching or calculation.
-	// Returns a placeholder thumbnail. The actual thumbnail will be sent
-	// via a signal later.
-	QImage fetchThumbnail(const QString &filename);
+	// If synchronous is false, returns a placeholder thumbnail.
+	// The actual thumbnail will be sent via a signal later.
+	// If synchronous is true, try to fetch the actual thumbnail.
+	// In this mode only precalculated thumbnails or thumbnails
+	// from pictures are returned. Video extraction and remote
+	// images are not supported.
+	QImage fetchThumbnail(const QString &filename, bool synchronous);
 
 	// Schedule multiple thumbnails for forced recalculation
 	void calculateThumbnails(const QVector<QString> &filenames);