Dive pictures: don't repopulate DivePictureModel on deletion

On deletion of a single or multiple pictures, the whole DivePictureModel
was repopulated, which was clearly visible in the UI, owing to the
reconstructing of all images in the profile plot.

To avoid this vexing behavior, implement proper deletion routines in
DivePictureModel and ProfileWidget2. Since this needs sensible erase()
semantics the QList<PictureEntry> member of DivePictureModel was
replaced by a QVector. A QVector should be the default anyway, unless
there are very specific reasons to use a QList (which actually is
a deque, not a classical linked list).

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

profile-widget/profilewidget2.cpp

@@ -1118,7 +1118,7 @@ void ProfileWidget2::setProfileState()
 #ifndef SUBSURFACE_MOBILE
 	connect(DivePictureModel::instance(), &DivePictureModel::dataChanged, this, &ProfileWidget2::updatePictures);
 	connect(DivePictureModel::instance(), SIGNAL(rowsInserted(const QModelIndex &, int, int)), this, SLOT(plotPictures()));
-	connect(DivePictureModel::instance(), SIGNAL(rowsRemoved(const QModelIndex &, int, int)), this, SLOT(plotPictures()));
+	connect(DivePictureModel::instance(), &DivePictureModel::rowsRemoved, this, &ProfileWidget2::removePictures);
 	connect(DivePictureModel::instance(), &DivePictureModel::modelReset, this, &ProfileWidget2::plotPictures);
 #endif
 	/* show the same stuff that the profile shows. */
@@ -2089,6 +2089,19 @@ void ProfileWidget2::plotPictures()
 		item->setPos(x, y);
 	}
 }
+
+void ProfileWidget2::removePictures(const QModelIndex &, int first, int last)
+{
+	DivePictureModel *m = DivePictureModel::instance();
+	first = std::max(0, first - m->rowDDStart);
+	// Note that last points *to* the last item and not *past* the last item,
+	// therefore we add 1 to achieve conventional C++ semantics.
+	last = std::min((int)pictures.size(), last + 1 - m->rowDDStart);
+	if (first >= (int)pictures.size() || last <= first)
+		return;
+	pictures.erase(pictures.begin() + first, pictures.begin() + last);
+}
+
 #endif
 
 void ProfileWidget2::dropEvent(QDropEvent *event)

profile-widget/profilewidget2.h

@@ -110,6 +110,7 @@ slots: // Necessary to call from QAction's signals.
 	void replot(dive *d = 0);
 #ifndef SUBSURFACE_MOBILE
 	void plotPictures();
+	void removePictures(const QModelIndex &, int first, int last);
 	void setPlanState();
 	void setAddState();
 	void changeGas();

qt-models/divepicturemodel.cpp

@@ -149,7 +149,22 @@ void DivePictureModel::removePictures(const QVector<QString> &fileUrls)
 	copy_dive(current_dive, &displayed_dive);
 	mark_divelist_changed(true);
 
-	updateDivePictures();
+	for (int i = 0; i < pictures.size(); ++i) {
+		// Find range [i j) of pictures to remove
+		if (std::find(fileUrls.begin(), fileUrls.end(), pictures[i].filename) == fileUrls.end())
+			continue;
+		int j;
+		for (j = i + 1; j < pictures.size(); ++j) {
+			if (std::find(fileUrls.begin(), fileUrls.end(), pictures[j].filename) == fileUrls.end())
+				break;
+		}
+
+		// Qt's model-interface is surprisingly idiosyncratic: you don't pass [first last), but [first last] ranges.
+		// For example, an empty list would be [0 -1].
+		beginRemoveRows(QModelIndex(), i, j - 1);
+		pictures.erase(pictures.begin() + i, pictures.begin() + j);
+		endRemoveRows();
+	}
 }
 
 int DivePictureModel::rowCount(const QModelIndex &parent) const

qt-models/divepicturemodel.h

@@ -30,7 +30,7 @@ public slots:
 	void updateThumbnail(QString filename, QImage thumbnail);
 private:
 	DivePictureModel();
-	QList<PictureEntry> pictures;
+	QVector<PictureEntry> pictures;
 	int findPictureId(const QString &filename);	// Return -1 if not found
 	double zoomLevel;	// -1.0: minimum, 0.0: standard, 1.0: maximum
 	int size;