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>

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.

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);

desktop-widgets/divelogexportdialog.cpp

@@ -254,7 +254,7 @@ void DiveLogExportDialog::exportProfile(const QString filename, const bool selec
 void DiveLogExportDialog::saveProfile(const struct dive *dive, const QString filename)
 {
 	ProfileWidget2 *profile = MainWindow::instance()->graphics;
-	profile->plotDive(dive, true);
+	profile->plotDive(dive, true, false, true);
 	profile->setToolTipVisibile(false);
 	QPixmap pix = profile->grab();
 	profile->setToolTipVisibile(true);

profile-widget/profilewidget2.cpp

@@ -165,7 +165,7 @@ ProfileWidget2::ProfileWidget2(QWidget *parent) : QGraphicsView(parent),
 	addActionShortcut(Qt::Key_Right, &ProfileWidget2::keyRightAction);
 
 	connect(Thumbnailer::instance(), &Thumbnailer::thumbnailChanged, this, &ProfileWidget2::updateThumbnail, Qt::QueuedConnection);
-	connect(DivePictureModel::instance(), SIGNAL(rowsInserted(const QModelIndex &, int, int)), this, SLOT(plotPictures()));
+	connect(DivePictureModel::instance(), &DivePictureModel::rowsInserted, this, &ProfileWidget2::plotPictures);
 	connect(DivePictureModel::instance(), &DivePictureModel::picturesRemoved, this, &ProfileWidget2::removePictures);
 	connect(DivePictureModel::instance(), &DivePictureModel::modelReset, this, &ProfileWidget2::plotPictures);
 #endif // SUBSURFACE_MOBILE
@@ -548,7 +548,7 @@ void ProfileWidget2::resetZoom()
 }
 
 // Currently just one dive, but the plan is to enable All of the selected dives.
-void ProfileWidget2::plotDive(const struct dive *d, bool force, bool doClearPictures)
+void ProfileWidget2::plotDive(const struct dive *d, bool force, bool doClearPictures, bool plotPicturesSynchronously)
 {
 	static bool firstCall = true;
 #ifndef SUBSURFACE_MOBILE
@@ -827,7 +827,7 @@ void ProfileWidget2::plotDive(const struct dive *d, bool force, bool doClearPict
 	if (doClearPictures)
 		clearPictures();
 	else
-		plotPictures();
+		plotPicturesInternal(plotPicturesSynchronously);
 
 	toolTipItem->refresh(mapToScene(mapFromGlobal(QCursor::pos())));
 #endif
@@ -2153,7 +2153,7 @@ void ProfileWidget2::updateThumbnail(QString filename, QImage thumbnail, duratio
 }
 
 // Create a PictureEntry object and add its thumbnail to the scene if profile pictures are shown.
-ProfileWidget2::PictureEntry::PictureEntry(offset_t offsetIn, const QString &filenameIn, QGraphicsScene *scene) : offset(offsetIn),
+ProfileWidget2::PictureEntry::PictureEntry(offset_t offsetIn, const QString &filenameIn, QGraphicsScene *scene, bool synchronous) : offset(offsetIn),
 	duration(duration_t {0}),
 	filename(filenameIn),
 	thumbnail(new DivePictureItem)
@@ -2161,7 +2161,7 @@ ProfileWidget2::PictureEntry::PictureEntry(offset_t offsetIn, const QString &fil
 	int size = Thumbnailer::defaultThumbnailSize();
 	scene->addItem(thumbnail.get());
 	thumbnail->setVisible(prefs.show_pictures_in_profile);
-	QImage img = Thumbnailer::instance()->fetchThumbnail(filename).scaled(size, size, Qt::KeepAspectRatio);
+	QImage img = Thumbnailer::instance()->fetchThumbnail(filename, synchronous).scaled(size, size, Qt::KeepAspectRatio);
 	thumbnail->setPixmap(QPixmap::fromImage(img));
 	thumbnail->setFileUrl(filename);
 }
@@ -2227,6 +2227,11 @@ void ProfileWidget2::updateThumbnailXPos(PictureEntry &e)
 
 // This function resets the picture thumbnails of the current dive.
 void ProfileWidget2::plotPictures()
+{
+	plotPicturesInternal(false);
+}
+
+void ProfileWidget2::plotPicturesInternal(bool synchronous)
 {
 	pictures.clear();
 	if (currentState == ADD || currentState == PLAN)
@@ -2238,7 +2243,7 @@ void ProfileWidget2::plotPictures()
 	// Note that FOR_EACH_PICTURE handles current_dive being null gracefully.
 	FOR_EACH_PICTURE(current_dive) {
 		if (picture->offset.seconds > 0 && picture->offset.seconds <= current_dive->duration.seconds)
-			pictures.emplace_back(picture->offset, QString(picture->filename), scene());
+			pictures.emplace_back(picture->offset, QString(picture->filename), scene(), synchronous);
 	}
 	if (pictures.empty())
 		return;
@@ -2346,7 +2351,7 @@ void ProfileWidget2::dropEvent(QDropEvent *event)
 				// The parameters are passed directly to the contructor.
 				// The call returns an iterator to the new element (which might differ from
 				// the old iterator, since the buffer might have been reallocated).
-				newPos = pictures.emplace(newPos, offset, filename, scene());
+				newPos = pictures.emplace(newPos, offset, filename, scene(), false);
 				updateThumbnailXPos(*newPos);
 				calculatePictureYPositions();
 			}

profile-widget/profilewidget2.h

@@ -75,7 +75,7 @@ public:
 	ProfileWidget2(QWidget *parent = 0);
 	void resetZoom();
 	void scale(qreal sx, qreal sy);
-	void plotDive(const struct dive *d = 0, bool force = false, bool clearPictures = false);
+	void plotDive(const struct dive *d = 0, bool force = false, bool clearPictures = false, bool plotPicturesSynchronously = false);
 	void setupItem(AbstractProfilePolygonItem *item, DiveCartesianAxis *vAxis, int vData, int hData, int zValue);
 	void setPrintMode(bool mode, bool grayscale = false);
 	bool getPrintMode();
@@ -173,6 +173,7 @@ private: /*methods*/
 	void createPPGas(PartialPressureGasItem *item, int verticalColumn, color_index_t color, color_index_t colorAlert,
 			 const double *thresholdSettingsMin, const double *thresholdSettingsMax);
 	void clearPictures();
+	void plotPicturesInternal(bool synchronous);
 private:
 	DivePlotDataModel *dataModel;
 	int zoomLevel;
@@ -240,7 +241,7 @@ private:
 		std::unique_ptr<DivePictureItem> thumbnail;
 		// For videos with known duration, we represent the duration of the video by a line
 		std::unique_ptr<QGraphicsRectItem> durationLine;
-		PictureEntry (offset_t offsetIn, const QString &filenameIn, QGraphicsScene *scene);
+		PictureEntry (offset_t offsetIn, const QString &filenameIn, QGraphicsScene *scene, bool synchronous);
 		bool operator< (const PictureEntry &e) const;
 	};
 	void updateThumbnailXPos(PictureEntry &e);

qt-models/divepicturemodel.cpp

@@ -42,7 +42,7 @@ void DivePictureModel::updateThumbnails()
 {
 	updateZoom();
 	for (PictureEntry &entry: pictures)
-		entry.image = Thumbnailer::instance()->fetchThumbnail(entry.filename);
+		entry.image = Thumbnailer::instance()->fetchThumbnail(entry.filename, false);
 }
 
 void DivePictureModel::updateDivePictures()