Dive pictures: automatically recalculate thumbnails

If a thumbnail and the original picture can be accessed and the
modification date of the thumbnail is before the modification date
of the picture, recalculate the thumbnail.

This causes more disk access and might give strange effects for
picture files with messed up file timestamps (i.e. lying in the
future) or messed up computer clocks (i.e. running in the past).
Therefore, add a preference option to disable the new behavior.
Default is set to enabled.

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

core/imagedownloader.cpp

@@ -151,8 +151,24 @@ static QImage getThumbnailFromCache(const QString &picture_filename)
 	QString filename = thumbnailFileName(picture_filename);
 	if (filename.isEmpty())
 		return QImage();
-
 	QFile file(filename);
+
+	if (prefs.auto_recalculate_thumbnails) {
+		// Check if thumbnails is older than the (local) image file
+		QString filenameLocal = localFilePath(qPrintable(picture_filename));
+		QFileInfo pictureInfo(filenameLocal);
+		QFileInfo thumbnailInfo(file);
+		if (pictureInfo.exists() && thumbnailInfo.exists()) {
+			QDateTime pictureTime = pictureInfo.lastModified();
+			QDateTime thumbnailTime = thumbnailInfo.lastModified();
+			if (pictureTime.isValid() && thumbnailTime.isValid() && thumbnailTime < pictureTime) {
+				// Both files exist, have valid timestamps and thumbnail was calculated before picture.
+				// Return an empty thumbnail to signal recalculation of the thumbnail
+				return QImage();
+			}
+		}
+	}
+
 	if (!file.open(QIODevice::ReadOnly))
 		return QImage();
 	QDataStream stream(&file);

core/pref.h

@@ -154,6 +154,7 @@ struct preferences {
 	int distance_threshold;
 	bool git_local_only;
 	short cloud_timeout;
+	bool auto_recalculate_thumbnails;
 	locale_prefs_t locale; //: TODO: move the rest of locale based info here.
 	update_manager_prefs_t update_manager;
 	dive_computer_prefs_t dive_computer;

core/subsurface-qt/SettingsObjectWrapper.cpp

@@ -1802,6 +1802,11 @@ int GeneralSettingsObjectWrapper::pscrRatio() const
 	return prefs.pscr_ratio;
 }
 
+bool GeneralSettingsObjectWrapper::autoRecalculateThumbnails() const
+{
+	return prefs.auto_recalculate_thumbnails;
+}
+
 void GeneralSettingsObjectWrapper::setDefaultFilename(const QString& value)
 {
 	if (value == prefs.default_filename)
@@ -1895,6 +1900,18 @@ void GeneralSettingsObjectWrapper::setPscrRatio(int value)
 	emit pscrRatioChanged(value);
 }
 
+void GeneralSettingsObjectWrapper::setAutoRecalculateThumbnails(bool value)
+{
+	if (value == prefs.auto_recalculate_thumbnails)
+		return;
+
+	QSettings s;
+	s.beginGroup(group);
+	s.setValue("auto_recalculate_thumbnails", value);
+	prefs.auto_recalculate_thumbnails = value;
+	emit autoRecalculateThumbnailsChanged(value);
+}
+
 DisplaySettingsObjectWrapper::DisplaySettingsObjectWrapper(QObject *parent) :
 	QObject(parent)
 {
@@ -2266,6 +2283,7 @@ void SettingsObjectWrapper::load()
 	GET_INT("defaultsetpoint", defaultsetpoint);
 	GET_INT("o2consumption", o2consumption);
 	GET_INT("pscr_ratio", pscr_ratio);
+	GET_BOOL("auto_recalculate_thumbnails", auto_recalculate_thumbnails);
 	s.endGroup();
 
 	s.beginGroup("Display");

core/subsurface-qt/SettingsObjectWrapper.h

@@ -559,6 +559,7 @@ class GeneralSettingsObjectWrapper : public QObject {
 	Q_PROPERTY(int defaultsetpoint              READ defaultSetPoint           WRITE setDefaultSetPoint           NOTIFY defaultSetPointChanged)
 	Q_PROPERTY(int o2consumption                READ o2Consumption             WRITE setO2Consumption             NOTIFY o2ConsumptionChanged)
 	Q_PROPERTY(int pscr_ratio                   READ pscrRatio                 WRITE setPscrRatio                 NOTIFY pscrRatioChanged)
+	Q_PROPERTY(bool auto_recalculate_thumbnails READ autoRecalculateThumbnails WRITE setAutoRecalculateThumbnails NOTIFY autoRecalculateThumbnailsChanged)
 
 public:
 	GeneralSettingsObjectWrapper(QObject *parent);
@@ -569,6 +570,7 @@ public:
 	int defaultSetPoint() const;
 	int o2Consumption() const;
 	int pscrRatio() const;
+	bool autoRecalculateThumbnails() const;
 
 public slots:
 	void setDefaultFilename           (const QString& value);
@@ -578,6 +580,7 @@ public slots:
 	void setDefaultSetPoint           (int value);
 	void setO2Consumption             (int value);
 	void setPscrRatio                 (int value);
+	void setAutoRecalculateThumbnails (bool value);
 
 signals:
 	void defaultFilenameChanged(const QString& value);
@@ -587,6 +590,7 @@ signals:
 	void defaultSetPointChanged(int value);
 	void o2ConsumptionChanged(int value);
 	void pscrRatioChanged(int value);
+	void autoRecalculateThumbnailsChanged(int value);
 private:
 	const QString group = QStringLiteral("GeneralSettings");
 };

core/subsurfacestartup.c

@@ -99,6 +99,7 @@ struct preferences default_prefs = {
 #else
 	.cloud_timeout = 5,
 #endif
+	.auto_recalculate_thumbnails = true,
 };
 
 int run_survey;

desktop-widgets/preferences/preferences_graph.cpp

@@ -47,6 +47,7 @@ void PreferencesGraph::refreshSettings()
 
 	ui->display_unused_tanks->setChecked(prefs.display_unused_tanks);
 	ui->show_average_depth->setChecked(prefs.show_average_depth);
+	ui->auto_recalculate_thumbnails->setChecked(prefs.auto_recalculate_thumbnails);
 	ui->show_icd->setChecked(prefs.show_icd);
 }
 
@@ -56,6 +57,7 @@ void PreferencesGraph::syncSettings()
 	general->setDefaultSetPoint(lrint(ui->defaultSetpoint->value() * 1000.0));
 	general->setO2Consumption(lrint(ui->psro2rate->value() *1000.0));
 	general->setPscrRatio(lrint(1000.0 / ui->pscrfactor->value()));
+	general->setAutoRecalculateThumbnails(ui->auto_recalculate_thumbnails->isChecked());
 
 	auto pp_gas = SettingsObjectWrapper::instance()->pp_gas;
 	pp_gas->setPheThreshold(ui->pheThreshold->value());

desktop-widgets/preferences/preferences_graph.ui

@@ -368,6 +368,13 @@
         </property>
        </widget>
       </item>
+      <item row="2" column="0" colspan="2">
+       <widget class="QCheckBox" name="auto_recalculate_thumbnails">
+        <property name="text">
+         <string>Recalculate thumbnails if older than image</string>
+        </property>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>