Undo: isolate undo-commands

This refactors the undo-commands (which are now only "commands").

- Move everything in namespace Command. This allows shortening of
  names without polluting the global namespace. Moreover, the prefix
  Command:: will immediately signal that the undo-machinery is
  invoked. This is more terse than UndoCommands::instance()->...
- Remove the Undo in front of the class-names. Creating an "UndoX"
  object to do "X" is paradoxical.
- Create a base class for all commands that defines the Qt-translation
  functions. Thus all translations end up in the "Command" context.
- Add a workToBeDone() function, which signals whether this should be
  added to the UndoStack. Thus the caller doesn't have to check itself
  whether this any work will be done. Note: Qt5.9 introduces "setObsolete"
  which does the same.
- Split into public and internal header files. In the public header
  file only export the function calls, thus hiding all implementation
  details from the caller.
- Split in different translation units: One for the stubs, one for
  the base classes and one for groups of commands. Currently, there
  is only one class of commands: divelist-commands.
- Move the undoStack from the MainWindow class into commands_base.cpp.
  If we want to implement MDI, this can easily be moved into an
  appropriate Document class.

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

16 files changed, 471 insertions, 1176 deletions

diff --git a/desktop-widgets/CMakeLists.txt b/desktop-widgets/CMakeLists.txt
index f5da2ae84..519061ac0 100644
--- a/desktop-widgets/CMakeLists.txt
+++ b/desktop-widgets/CMakeLists.txt
@@ -85,7 +85,9 @@ set(SUBSURFACE_INTERFACE
 	divepicturewidget.cpp
 	usersurvey.cpp
 	configuredivecomputerdialog.cpp
-	undocommands.cpp
+	command.cpp
+	command_base.cpp
+	command_divelist.cpp
 	locationinformation.cpp
 	qtwaitingspinner.cpp
 	tab-widgets/TabDiveStatistics.cpp
diff --git a/desktop-widgets/command.cpp b/desktop-widgets/command.cpp
new file mode 100644
index 000000000..a86b1fe76
--- /dev/null
+++ b/desktop-widgets/command.cpp
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "command.h"
+#include "command_divelist.h"
+
+namespace Command {
+
+// Dive-list related commands
+void addDive(dive *d)
+{
+	execute(new AddDive(d));
+}
+
+void deleteDive(const QVector<struct dive*> &divesToDelete)
+{
+	execute(new DeleteDive(divesToDelete));
+}
+
+void shiftTime(const QVector<dive *> &changedDives, int amount)
+{
+	execute(new ShiftTime(changedDives, amount));
+}
+
+void renumberDives(const QVector<QPair<int, int>> &divesToRenumber)
+{
+	execute(new RenumberDives(divesToRenumber));
+}
+
+void removeDivesFromTrip(const QVector<dive *> &divesToRemove)
+{
+	execute(new RemoveDivesFromTrip(divesToRemove));
+}
+
+void removeAutogenTrips()
+{
+	execute(new RemoveAutogenTrips);
+}
+
+void addDivesToTrip(const QVector<dive *> &divesToAddIn, dive_trip *trip)
+{
+	execute(new AddDivesToTrip(divesToAddIn, trip));
+}
+
+void createTrip(const QVector<dive *> &divesToAddIn)
+{
+	execute(new CreateTrip(divesToAddIn));
+}
+
+void autogroupDives()
+{
+	execute(new AutogroupDives);
+}
+
+void mergeTrips(dive_trip *trip1, dive_trip *trip2)
+{
+	execute(new MergeTrips(trip1, trip2));
+}
+
+void splitDives(dive *d, duration_t time)
+{
+	execute(new SplitDives(d, time));
+}
+
+void mergeDives(const QVector <dive *> &dives)
+{
+	execute(new MergeDives(dives));
+}
+
+} // namespace Command
diff --git a/desktop-widgets/command.h b/desktop-widgets/command.h
new file mode 100644
index 000000000..213d8bcda
--- /dev/null
+++ b/desktop-widgets/command.h
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef COMMAND_H
+#define COMMAND_H
+
+#include "core/dive.h"
+#include <QVector>
+#include <QAction>
+
+// We put everything in a namespace, so that we can shorten names without polluting the global namespace
+namespace Command {
+
+// General commands
+void clear();				// Reset the undo stack. Delete all commands.
+QAction *undoAction(QObject *parent);	// Create an undo action.
+QAction *redoAction(QObject *parent);	// Create an redo action.
+
+// Dive-list related commands
+void addDive(dive *d);
+void deleteDive(const QVector<struct dive*> &divesToDelete);
+void shiftTime(const QVector<dive *> &changedDives, int amount);
+void renumberDives(const QVector<QPair<int, int>> &divesToRenumber);
+void removeDivesFromTrip(const QVector<dive *> &divesToRemove);
+void removeAutogenTrips();
+void addDivesToTrip(const QVector<dive *> &divesToAddIn, dive_trip *trip);
+void createTrip(const QVector<dive *> &divesToAddIn);
+void autogroupDives();
+void mergeTrips(dive_trip *trip1, dive_trip *trip2);
+void splitDives(dive *d, duration_t time);
+void mergeDives(const QVector <dive *> &dives);
+
+} // namespace Command
+
+#endif // COMMAND_H
diff --git a/desktop-widgets/command_base.cpp b/desktop-widgets/command_base.cpp
new file mode 100644
index 000000000..24ce81225
--- /dev/null
+++ b/desktop-widgets/command_base.cpp
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "command_base.h"
+
+namespace Command {
+
+static QUndoStack undoStack;
+
+// General commands
+void clear()
+{
+	undoStack.clear();
+}
+
+QAction *undoAction(QObject *parent)
+{
+	return undoStack.createUndoAction(parent, QCoreApplication::translate("Command", "&Undo"));
+}
+
+QAction *redoAction(QObject *parent)
+{
+	return undoStack.createRedoAction(parent, QCoreApplication::translate("Command", "&Redo"));
+}
+
+void execute(Base *cmd)
+{
+	if (cmd->workToBeDone())
+		undoStack.push(cmd);
+	else
+		delete cmd;
+}
+
+} // namespace Command
+
+
diff --git a/desktop-widgets/undocommands.h b/desktop-widgets/command_base.h
index 11c35bb40..f965b8689 100644
--- a/desktop-widgets/undocommands.h
+++ b/desktop-widgets/command_base.h
@@ -1,15 +1,16 @@
 // SPDX-License-Identifier: GPL-2.0
-#ifndef UNDOCOMMANDS_H
-#define UNDOCOMMANDS_H
+// Note: this header file is used by the undo-machinery and should not be included elsewhere.
+
+#ifndef COMMAND_BASE_H
+#define COMMAND_BASE_H
 
 #include "core/dive.h"
 
 #include <QUndoCommand>
-#include <QCoreApplication> // For Q_DECLARE_TR_FUNCTIONS
-#include <QVector>
+#include <QCoreApplication>	// For Q_DECLARE_TR_FUNCTIONS
 #include <memory>
 
-// The classes declared in this file represent units-of-work, which can be exectuted / undone
+// The classes derived from Command::Base represent units-of-work, which can be exectuted / undone
 // repeatedly. The command objects are collected in a linear list implemented in the QUndoStack class.
 // They contain the information that is necessary to either perform or undo the unit-of-work.
 // The usage is:
@@ -136,6 +137,9 @@
 //	v.clear(v);				// Reset the vector to zero length. If the elements weren't release()d,
 //						// the pointed-to dives are freed with free_dive()
 
+// We put everything in a namespace, so that we can shorten names without polluting the global namespace
+namespace Command {
+
 // Classes used to automatically call free_dive()/free_trip for owning pointers that go out of scope.
 struct DiveDeleter {
 	void operator()(dive *d) { free_dive(d); }
@@ -148,157 +152,22 @@ struct TripDeleter {
 typedef std::unique_ptr<dive, DiveDeleter> OwningDivePtr;
 typedef std::unique_ptr<dive_trip, TripDeleter> OwningTripPtr;
 
-// This helper structure describes a dive that we want to add.
-// Potentially it also adds a trip (if deletion of the dive resulted in deletion of the trip)
-struct DiveToAdd {
-	OwningDivePtr	 dive;		// Dive to add
-	OwningTripPtr	 tripToAdd;	// Not-null if we also have to add a dive
-	dive_trip	*trip;		// Trip the dive belongs to, may be null
-	int		 idx;		// Position in divelist
-};
-
-// This helper structure describes a dive that should be moved to / removed from
-// a trip. If the "trip" member is null, the dive is removed from its trip (if
-// it is in a trip, that is)
-struct DiveToTrip
-{
-	struct dive	*dive;
-	dive_trip	*trip;
-};
-
-// This helper structure describes a number of dives to add to /remove from /
-// move between trips.
-// It has ownership of the trips (if any) that have to be added before hand.
-struct DivesToTrip
-{
-	std::vector<DiveToTrip> divesToMove;		// If dive_trip is null, remove from trip
-	std::vector<OwningTripPtr> tripsToAdd;
-};
-
-class UndoAddDive : public QUndoCommand {
-public:
-	UndoAddDive(dive *dive);
-private:
-	void undo() override;
-	void redo() override;
-
-	// For redo
-	DiveToAdd	diveToAdd;
-
-	// For undo
-	dive		*diveToRemove;
-};
-
-class UndoDeleteDive : public QUndoCommand {
+// This is the base class of all commands.
+// It defines the Qt-translation functions
+class Base : public QUndoCommand {
 	Q_DECLARE_TR_FUNCTIONS(Command)
 public:
-	UndoDeleteDive(const QVector<dive *> &divesToDelete);
-private:
-	void undo() override;
-	void redo() override;
-
-	// For redo
-	std::vector<struct dive*> divesToDelete;
-
-	std::vector<OwningTripPtr> tripsToAdd;
-	std::vector<DiveToAdd> divesToAdd;
+	// Check whether work is to be done.
+	// TODO: replace by setObsolete (>Qt5.9)
+	virtual bool workToBeDone() = 0;
 };
 
-class UndoShiftTime : public QUndoCommand {
-	Q_DECLARE_TR_FUNCTIONS(Command)
-public:
-	UndoShiftTime(const QVector<dive *> &changedDives, int amount);
-private:
-	void undo() override;
-	void redo() override;
+// Put a command on the undoStack, but test whether there is something to be done
+// beforehand by calling the workToBeDone() function. If nothing is to be done,
+// the command will be deleted.
+void execute(Base *cmd);
 
-	// For redo and undo
-	QVector<dive *> diveList;
-	int timeChanged;
-};
+} // namespace Command
 
-class UndoRenumberDives : public QUndoCommand {
-	Q_DECLARE_TR_FUNCTIONS(Command)
-public:
-	UndoRenumberDives(const QVector<QPair<int, int>> &divesToRenumber);
-private:
-	void undo() override;
-	void redo() override;
-
-	// For redo and undo: pairs of dive-id / new number
-	QVector<QPair<int, int>> divesToRenumber;
-};
-
-// The classes UndoRemoveDivesFromTrip, UndoRemoveAutogenTrips, UndoCreateTrip,
-// UndoAutogroupDives and UndoMergeTrips all do the same thing, just the intialization
-// differs. Therefore, define a base class with the proper data-structures, redo()
-// and undo() functions and derive to specialize the initialization.
-class UndoTripBase : public QUndoCommand {
-	Q_DECLARE_TR_FUNCTIONS(Command)
-protected:
-	void undo() override;
-	void redo() override;
-
-	// For redo and undo
-	DivesToTrip divesToMove;
-};
-struct UndoRemoveDivesFromTrip : public UndoTripBase {
-	UndoRemoveDivesFromTrip(const QVector<dive *> &divesToRemove);
-};
-struct UndoRemoveAutogenTrips : public UndoTripBase {
-	UndoRemoveAutogenTrips();
-};
-struct UndoAddDivesToTrip : public UndoTripBase {
-	UndoAddDivesToTrip(const QVector<dive *> &divesToAdd, dive_trip *trip);
-};
-struct UndoCreateTrip : public UndoTripBase {
-	UndoCreateTrip(const QVector<dive *> &divesToAdd);
-};
-struct UndoAutogroupDives : public UndoTripBase {
-	UndoAutogroupDives();
-};
-struct UndoMergeTrips : public UndoTripBase {
-	UndoMergeTrips(dive_trip *trip1, dive_trip *trip2);
-};
-
-class UndoSplitDives : public QUndoCommand {
-public:
-	// If time is < 0, split at first surface interval
-	UndoSplitDives(dive *d, duration_t time);
-private:
-	void undo() override;
-	void redo() override;
-
-	// For redo
-	// For each dive to split, we remove one from and put two dives into the backend
-	dive		*diveToSplit;
-	DiveToAdd	 splitDives[2];
-
-	// For undo
-	// For each dive to unsplit, we remove two dives from and add one into the backend
-	DiveToAdd	 unsplitDive;
-	dive		*divesToUnsplit[2];
-};
-
-class UndoMergeDives : public QUndoCommand {
-public:
-	UndoMergeDives(const QVector<dive *> &dives);
-private:
-	void undo() override;
-	void redo() override;
-
-	// For redo
-	// Add one and remove a batch of dives
-	DiveToAdd		 mergedDive;
-	std::vector<dive *>	 divesToMerge;
-
-	// For undo
-	// Remove one and add a batch of dives
-	dive			*diveToUnmerge;
-	std::vector<DiveToAdd>	 unmergedDives;
-
-	// For undo and redo
-	QVector<QPair<int, int>> divesToRenumber;
-};
+#endif // COMMAND_BASE_H
 
-#endif // UNDOCOMMANDS_H
diff --git a/desktop-widgets/command_divelist.cpp b/desktop-widgets/command_divelist.cpp
index 6f638b2a6..d12aebfc2 100644
--- a/desktop-widgets/command_divelist.cpp
+++ b/desktop-widgets/command_divelist.cpp
@@ -4,60 +4,14 @@
 #include "desktop-widgets/mainwindow.h"
 #include "desktop-widgets/divelistview.h"
 #include "core/divelist.h"
-#include "core/display.h" // for amount_selected
-#include "core/subsurface-qt/DiveListNotifier.h"
-#include "qt-models/filtermodels.h"
 
 namespace Command {
 
-// Generally, signals are sent in batches per trip. To avoid writing the same loop
-// again and again, this template takes a vector of trip / dive pairs, sorts it
-// by trip and then calls a function-object with trip and a QVector of dives in that trip.
-// Input parameters:
-//	- dives: a vector of trip,dive pairs, which will be sorted and processed in batches by trip.
-//	- action: a function object, taking a trip-pointer and a QVector of dives, which will be called for each batch.
-template<typename Function>
-void processByTrip(std::vector<std::pair<dive_trip *, dive *>> &dives, Function action)
-{
-	// Use std::tie for lexicographical sorting of trip, then start-time
-	std::sort(dives.begin(), dives.end(),
-		  [](const std::pair<dive_trip *, dive *> &e1, const std::pair<dive_trip *, dive *> &e2)
-		  { return std::tie(e1.first, e1.second->when) < std::tie(e2.first, e2.second->when); });
-
-	// Then, process the dives in batches by trip
-	size_t i, j; // Begin and end of batch
-	for (i = 0; i < dives.size(); i = j) {
-		dive_trip *trip = dives[i].first;
-		for (j = i + 1; j < dives.size() && dives[j].first == trip; ++j)
-			; // pass
-		// Copy dives into a QVector. Some sort of "range_view" would be ideal, but Qt doesn't work this way.
-		QVector<dive *> divesInTrip(j - i);
-		for (size_t k = i; k < j; ++k)
-			divesInTrip[k - i] = dives[k].second;
-
-		// Finally, emit the signal
-		action(trip, divesInTrip);
-	}
-}
-
-
 // This helper function removes a dive, takes ownership of the dive and adds it to a DiveToAdd structure.
 // It is crucial that dives are added in reverse order of deletion, so the the indices are correctly
 // set and that the trips are added before they are used!
-DiveToAdd DiveListBase::removeDive(struct dive *d)
-{
-	// If the dive to be removed is selected, we will inform the frontend
-	// later via a signal that the dive changed.
-	if (d->selected)
-		selectionChanged = true;
-
-	// If the dive was the current dive, reset the current dive. The calling
-	// command is responsible of finding a new dive.
-	if (d == current_dive) {
-		selectionChanged = true; // Should have been set above, as current dive is always selected.
-		current_dive = nullptr;
-	}
-
+static DiveToAdd removeDive(struct dive *d)
+{
 	DiveToAdd res;
 	res.idx = get_divenr(d);
 	if (res.idx < 0)
@@ -72,68 +26,37 @@ DiveToAdd DiveListBase::removeDive(struct dive *d)
 	}
 
 	res.dive.reset(unregister_dive(res.idx));	// Remove dive from backend
-
 	return res;
 }
 
 // This helper function adds a dive and returns ownership to the backend. It may also add a dive trip.
 // It is crucial that dives are added in reverse order of deletion (see comment above)!
 // Returns pointer to added dive (which is owned by the backend!)
-dive *DiveListBase::addDive(DiveToAdd &d)
+static dive *addDive(DiveToAdd &d)
 {
-	if (d.tripToAdd)
-		insert_trip_dont_merge(d.tripToAdd.release()); // Return ownership to backend
+	if (d.tripToAdd) {
+		dive_trip *t = d.tripToAdd.release();	// Give up ownership of trip
+		insert_trip(&t);			// Return ownership to backend
+	}
 	if (d.trip)
 		add_dive_to_trip(d.dive.get(), d.trip);
-	dive *res = d.dive.release();		// Give up ownership of dive
-
-	// Set the filter flag according to current filter settings
-	bool show = MultiFilterSortModel::instance()->showDive(res);
-	res->hidden_by_filter = !show;
-
-	add_single_dive(d.idx, res);		// Return ownership to backend
-
-	// If the dive to be removed is selected, we will inform the frontend
-	// later via a signal that the dive changed.
-	if (res->selected)
-		selectionChanged = true;
-
+	dive *res = d.dive.release();			// Give up ownership of dive
+	add_single_dive(d.idx, res);			// Return ownership to backend
 	return res;
 }
 
 // This helper function calls removeDive() on a list of dives to be removed and
 // returns a vector of corresponding DiveToAdd objects, which can later be readded.
 // The passed in vector is cleared.
-std::vector<DiveToAdd> DiveListBase::removeDives(std::vector<dive *> &divesToDelete)
+static std::vector<DiveToAdd> removeDives(std::vector<dive *> &divesToDelete)
 {
 	std::vector<DiveToAdd> res;
 	res.reserve(divesToDelete.size());
 
-	// First, tell the filters that dives are removed. This could
-	// be done later using the emitted signals, but we do this here
-	// for symmetry with addDives()
-	MultiFilterSortModel::instance()->divesDeleted(QVector<dive *>::fromStdVector(divesToDelete));
-
 	for (dive *d: divesToDelete)
 		res.push_back(removeDive(d));
 	divesToDelete.clear();
 
-	// We send one dives-deleted signal per trip (see comments in DiveListNotifier.h).
-	// Therefore, collect all dives in an array and sort by trip.
-	std::vector<std::pair<dive_trip *, dive *>> dives;
-	dives.reserve(res.size());
-	for (const DiveToAdd &entry: res)
-		dives.push_back({ entry.trip, entry.dive.get() });
-
-	// Send signals.
-	processByTrip(dives, [&](dive_trip *trip, const QVector<dive *> &divesInTrip) {
-		// Now, let's check if this trip is supposed to be deleted, by checking if it was marked
-		// as "add it". We could be smarter here, but let's just check the whole array for brevity.
-		bool deleteTrip = trip &&
-				  std::find_if(res.begin(), res.end(), [trip](const DiveToAdd &entry)
-					       { return entry.tripToAdd.get() == trip; }) != res.end();
-		emit diveListNotifier.divesDeleted(trip, deleteTrip, divesInTrip);
-	});
 	return res;
 }
 
@@ -141,79 +64,29 @@ std::vector<DiveToAdd> DiveListBase::removeDives(std::vector<dive *> &divesToDel
 // of dives to be (re)added and returns a vector of the added dives. It does this in reverse
 // order, so that trips are created appropriately and indexing is correct.
 // The passed in vector is cleared.
-std::vector<dive *> DiveListBase::addDives(std::vector<DiveToAdd> &divesToAdd)
+static std::vector<dive *> addDives(std::vector<DiveToAdd> &divesToAdd)
 {
 	std::vector<dive *> res;
-	res.resize(divesToAdd.size());
-
-	// First, tell the filters that new dives are added. We do this here
-	// instead of later by signals, so that the filter can set the
-	// checkboxes of the new rows to its liking. The added dives will
-	// then appear in the correct shown/hidden state.
-	QVector<dive *> divesForFilter;
-	for (const DiveToAdd &entry: divesToAdd)
-		divesForFilter.push_back(entry.dive.get());
-	MultiFilterSortModel::instance()->divesAdded(divesForFilter);
-
-	// At the end of the function, to send the proper dives-added signals,
-	// we the the list of added trips. Create this list now.
-	std::vector<dive_trip *> addedTrips;
-	for (const DiveToAdd &entry: divesToAdd) {
-		if (entry.tripToAdd)
-			addedTrips.push_back(entry.tripToAdd.get());
-	}
+	res.reserve(divesToAdd.size());
 
-	// Now, add the dives
-	// Note: the idiomatic STL-way would be std::transform, but let's use a loop since
-	// that is closer to classical C-style.
-	auto it2 = res.rbegin();
-	for (auto it = divesToAdd.rbegin(); it != divesToAdd.rend(); ++it, ++it2)
-		*it2 = addDive(*it);
+	for (auto it = divesToAdd.rbegin(); it != divesToAdd.rend(); ++it)
+		res.push_back(addDive(*it));
 	divesToAdd.clear();
 
-	// We send one dives-deleted signal per trip (see comments in DiveListNotifier.h).
-	// Therefore, collect all dives in a array and sort by trip.
-	std::vector<std::pair<dive_trip *, dive *>> dives;
-	dives.reserve(res.size());
-	for (dive *d: res)
-		dives.push_back({ d->divetrip, d });
-
-	// Send signals.
-	processByTrip(dives, [&](dive_trip *trip, const QVector<dive *> &divesInTrip) {
-		// Now, let's check if this trip is supposed to be created, by checking if it was marked
-		// as "add it". We could be smarter here, but let's just check the whole array for brevity.
-		bool createTrip = trip && std::find(addedTrips.begin(), addedTrips.end(), trip) != addedTrips.end();
-		// Finally, emit the signal
-		emit diveListNotifier.divesAdded(trip, createTrip, divesInTrip);
-	});
 	return res;
 }
 
 // This helper function renumbers dives according to an array of id/number pairs.
 // The old numbers are stored in the array, thus calling this function twice has no effect.
 // TODO: switch from uniq-id to indexes once all divelist-actions are controlled by undo-able commands
-static void renumberDives(QVector<QPair<dive *, int>> &divesToRenumber)
+static void renumberDives(QVector<QPair<int, int>> &divesToRenumber)
 {
 	for (auto &pair: divesToRenumber) {
-		dive *d = pair.first;
+		dive *d = get_dive_by_uniq_id(pair.first);
 		if (!d)
 			continue;
 		std::swap(d->number, pair.second);
 	}
-
-	// Emit changed signals per trip.
-	// First, collect all dives and sort by trip
-	std::vector<std::pair<dive_trip *, dive *>> dives;
-	dives.reserve(divesToRenumber.size());
-	for (const auto &pair: divesToRenumber) {
-		dive *d = pair.first;
-		dives.push_back({ d->divetrip, d });
-	}
-
-	// Send signals.
-	processByTrip(dives, [&](dive_trip *trip, const QVector<dive *> &divesInTrip) {
-		emit diveListNotifier.divesChanged(trip, divesInTrip);
-	});
 }
 
 // This helper function moves a dive to a trip. The old trip is recorded in the
@@ -250,16 +123,10 @@ static OwningTripPtr moveDiveToTrip(DiveToTrip &diveToTrip)
 // a no-op.
 static void moveDivesBetweenTrips(DivesToTrip &dives)
 {
-	// We collect an array of created trips so that we can instruct
-	// the model to create a new entry
-	std::vector<dive_trip *> createdTrips;
-	createdTrips.reserve(dives.tripsToAdd.size());
-
-	// First, bring back the trip(s)
+	// first bring back the trip(s)
 	for (OwningTripPtr &trip: dives.tripsToAdd) {
 		dive_trip *t = trip.release();	// Give up ownership
-		createdTrips.push_back(t);
-		insert_trip_dont_merge(t);	// Return ownership to backend
+		insert_trip(&t);		// Return ownership to backend
 	}
 	dives.tripsToAdd.clear();
 
@@ -270,247 +137,22 @@ static void moveDivesBetweenTrips(DivesToTrip &dives)
 			dives.tripsToAdd.push_back(std::move(tripToAdd));
 	}
 
-	// We send one signal per from-trip/to-trip pair.
-	// First, collect all dives in a struct and sort by from-trip/to-trip.
-	struct DiveMoved {
-		dive_trip *from;
-		dive_trip *to;
-		dive *d;
-	};
-	std::vector<DiveMoved> divesMoved;
-	divesMoved.reserve(dives.divesToMove.size());
-	for (const DiveToTrip &entry: dives.divesToMove)
-		divesMoved.push_back({ entry.trip, entry.dive->divetrip, entry.dive });
-
-	// Sort lexicographically by from-trip, to-trip and by start-time.
-	// Use std::tie() for lexicographical sorting.
-	std::sort(divesMoved.begin(), divesMoved.end(), [] ( const DiveMoved &d1, const DiveMoved &d2)
-		  { return std::tie(d1.from, d1.to, d1.d->when) < std::tie(d2.from, d2.to, d2.d->when); });
-
-	// Now, process the dives in batches by trip
-	// TODO: this is a bit different from the cases above, so we don't use the processByTrip template,
-	// but repeat the loop here. We might think about generalizing the template, if more of such
-	// "special cases" appear.
-	size_t i, j; // Begin and end of batch
-	for (i = 0; i < divesMoved.size(); i = j) {
-		dive_trip *from = divesMoved[i].from;
-		dive_trip *to = divesMoved[i].to;
-		for (j = i + 1; j < divesMoved.size() && divesMoved[j].from == from && divesMoved[j].to == to; ++j)
-			; // pass
-		// Copy dives into a QVector. Some sort of "range_view" would be ideal, but Qt doesn't work this way.
-		QVector<dive *> divesInTrip(j - i);
-		for (size_t k = i; k < j; ++k)
-			divesInTrip[k - i] = divesMoved[k].d;
-
-		// Check if the from-trip was deleted: If yes, it was recorded in the tripsToAdd structure
-		bool deleteFrom = from &&
-				  std::find_if(dives.tripsToAdd.begin(), dives.tripsToAdd.end(),
-					       [from](const OwningTripPtr &trip) { return trip.get() == from; }) != dives.tripsToAdd.end();
-		// Check if the to-trip has to be created. For this purpose, we saved an array of trips to be created.
-		bool createTo = false;
-		if (to) {
-			// Check if the element is there...
-			auto it = std::find(createdTrips.begin(), createdTrips.end(), to);
-
-			// ...if it is - remove it as we don't want the model to create the trip twice!
-			if (it != createdTrips.end()) {
-				createTo = true;
-				// erase/remove would be more performant, but this is irrelevant in the big scheme of things.
-				createdTrips.erase(it);
-			}
-		}
-
-		// Finally, emit the signal
-		emit diveListNotifier.divesMovedBetweenTrips(from, to, deleteFrom, createTo, divesInTrip);
-	}
-
 	// Reverse the tripsToAdd and the divesToAdd, so that on undo/redo the operations
 	// will be performed in reverse order.
 	std::reverse(dives.tripsToAdd.begin(), dives.tripsToAdd.end());
 	std::reverse(dives.divesToMove.begin(), dives.divesToMove.end());
 }
 
-// When we initialize the command we don't have to roll-back any selection change
-DiveListBase::DiveListBase() : firstExecution(true)
-{
-}
-
-// Turn current selection into a vector.
-// TODO: This could be made much more efficient if we kept a sorted list of selected dives!
-static std::vector<dive *> getDiveSelection()
-{
-	std::vector<dive *> res;
-	res.reserve(amount_selected);
-
-	int i;
-	dive *d;
-	for_each_dive(i, d) {
-		if (d->selected)
-			res.push_back(d);
-	}
-	return res;
-}
-
-void DiveListBase::initWork()
-{
-	selectionChanged = false;
-}
-
-void DiveListBase::finishWork()
-{
-	if (selectionChanged) // If the selection changed -> tell the frontend
-		emit diveListNotifier.selectionChanged();
-}
-
-// Set the current dive either from a list of selected dives,
-// or a newly selected dive. In both cases, try to select the
-// dive that is newer that is newer than the given date.
-// This mimics the old behavior when the current dive changed.
-static void setClosestCurrentDive(timestamp_t when, const std::vector<dive *> &selection)
-{
-	// Start from back until we get the first dive that is before
-	// the supposed-to-be selected dive. (Note: this mimics the
-	// old behavior when the current dive changed).
-	for (auto it = selection.rbegin(); it < selection.rend(); ++it) {
-		if ((*it)->when > when && !(*it)->hidden_by_filter) {
-			current_dive = *it;
-			return;
-		}
-	}
-
-	// We didn't find a more recent selected dive -> try to
-	// find *any* visible selected dive.
-	for (dive *d: selection) {
-		if (!d->hidden_by_filter) {
-			current_dive = d;
-			return;
-		}
-	}
-
-	// No selected dive is visible! Take the closest dive. Note, this might
-	// return null, but that just means unsetting the current dive (as no
-	// dive is visible anyway).
-	current_dive = find_next_visible_dive(when);
-}
-
-// Rese the selection to the dives of the "selection" vector and send the appropriate signals.
-// Set the current dive to "currentDive". "currentDive" must be an element of "selection" (or
-// null if "seletion" is empty).
-void DiveListBase::restoreSelection(const std::vector<dive *> &selection, dive *currentDive)
-{
-	// To do so, generate vectors of dives to be selected and deselected.
-	// We send signals batched by trip, so keep track of trip/dive pairs.
-	std::vector<std::pair<dive_trip *, dive *>> divesToSelect;
-	std::vector<std::pair<dive_trip *, dive *>> divesToDeselect;
-
-	// TODO: We might want to keep track of selected dives in a more efficient way!
-	int i;
-	dive *d;
-	amount_selected = 0; // We recalculate amount_selected
-	for_each_dive(i, d) {
-		// We only modify dives that are currently visible.
-		if (d->hidden_by_filter) {
-			d->selected = false; // Note, not necessary, just to be sure
-					     // that we get amount_selected right
-			continue;
-		}
-
-		// Search the dive in the list of selected dives.
-		// TODO: By sorting the list in the same way as the backend, this could be made more efficient.
-		bool newState = std::find(selection.begin(), selection.end(), d) != selection.end();
-
-		// TODO: Instead of using select_dive() and deselect_dive(), we set selected directly.
-		// The reason is that deselect() automatically sets a new current dive, which we
-		// don't want, as we set it later anyway.
-		// There is other parts of the C++ code that touches the innards directly, but
-		// ultimately this should be pushed down to C.
-		if (newState && !d->selected) {
-			d->selected = true;
-			++amount_selected;
-			divesToSelect.push_back({ d->divetrip, d });
-		} else if (!newState && d->selected) {
-			d->selected = false;
-			divesToDeselect.push_back({ d->divetrip, d });
-		}
-	}
-
-	// Send the select and deselect signals
-	processByTrip(divesToSelect, [&](dive_trip *trip, const QVector<dive *> &divesInTrip) {
-		emit diveListNotifier.divesSelected(trip, divesInTrip);
-	});
-	processByTrip(divesToDeselect, [&](dive_trip *trip, const QVector<dive *> &divesInTrip) {
-		emit diveListNotifier.divesDeselected(trip, divesInTrip);
-	});
-
-	bool currentDiveChanged = false;
-	if (current_dive != currentDive) {
-		currentDiveChanged = true;
-
-		// We cannot simply change the currentd dive to the given dive.
-		// It might be hidden by a filter and thus not be selected.
-		if (currentDive->selected)
-			// Current dive is visible and selected. Excellent.
-			current_dive = currentDive;
-		else
-			// Current not visible -> find a different dive.
-			setClosestCurrentDive(currentDive->when, selection);
-		emit diveListNotifier.currentDiveChanged();
-	}
-
-	// If anything changed (selection or current dive), send a final signal.
-	if (!divesToSelect.empty() || !divesToDeselect.empty() || currentDiveChanged)
-		selectionChanged = true;
-}
-
-void DiveListBase::undo()
-{
-	auto marker = diveListNotifier.enterCommand();
-	initWork();
-	undoit();
-	finishWork();
-}
-
-void DiveListBase::redo()
-{
-	auto marker = diveListNotifier.enterCommand();
-	initWork();
-	redoit();
-	finishWork();
-}
-
-AddDive::AddDive(dive *d, bool autogroup, bool newNumber)
+AddDive::AddDive(dive *d)
 {
 	setText(tr("add dive"));
-	// By convention, d is "displayed dive" and can be overwritten.
 	d->maxdepth.mm = 0;
-	d->dc.maxdepth.mm = 0;
 	fixup_dive(d);
-
-	// Get an owning pointer to a copied or moved dive
-	// Note: if move is true, this destroys the old dive!
-	OwningDivePtr divePtr(clone_dive(d));
-	divePtr->selected = false; // If we clone a planned dive, it might have been selected.
-				   // We have to clear the flag, as selections will be managed
-				   // on dive-addition.
-
-	// If we alloc a new-trip for autogrouping, get an owning pointer to it.
-	OwningTripPtr allocTrip;
-	dive_trip *trip = divePtr->divetrip;
-	// We have to delete the pointer-to-trip, because this would prevent the core from adding to the trip
-	// and we would get the count-of-dives in the trip wrong. Yes, that's all horribly subtle!
-	divePtr->divetrip = nullptr;
-	if (!trip && autogroup) {
-		bool alloc;
-		trip = get_trip_for_new_dive(divePtr.get(), &alloc);
-		if (alloc)
-			allocTrip.reset(trip);
-	}
-
-	int idx = dive_get_insertion_index(divePtr.get());
-	if (newNumber)
-		divePtr->number = get_dive_nr_at_idx(idx);
-
-	divesToAdd.push_back({ std::move(divePtr), std::move(allocTrip), trip, idx });
+	diveToAdd.trip = d->divetrip;
+	d->divetrip = nullptr;
+	diveToAdd.idx = dive_get_insertion_index(d);
+	d->number = get_dive_nr_at_idx(diveToAdd.idx);
+	diveToAdd.dive.reset(clone_dive(d));
 }
 
 bool AddDive::workToBeDone()
@@ -518,34 +160,24 @@ bool AddDive::workToBeDone()
 	return true;
 }
 
-void AddDive::redoit()
+void AddDive::redo()
 {
-	// Remember selection so that we can undo it
-	selection = getDiveSelection();
-	currentDive = current_dive;
-
-	divesToRemove = addDives(divesToAdd);
+	diveToRemove = addDive(diveToAdd);
 	mark_divelist_changed(true);
 
-	// Select the newly added dive
-	restoreSelection(divesToRemove, divesToRemove[0]);
-
-	// Exit from edit mode, but don't recalculate dive list
-	// TODO: Remove edit mode
-	MainWindow::instance()->refreshDisplay(false);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->dive_list()->unselectDives();
+	MainWindow::instance()->dive_list()->selectDive(diveToAdd.idx, true);
+	MainWindow::instance()->refreshDisplay();
 }
 
-void AddDive::undoit()
+void AddDive::undo()
 {
-	// Simply remove the dive that was previously added...
-	divesToAdd = removeDives(divesToRemove);
-
-	// ...and restore the selection
-	restoreSelection(selection, currentDive);
+	// Simply remove the dive that was previously added
+	diveToAdd = removeDive(diveToRemove);
 
-	// Exit from edit mode, but don't recalculate dive list
-	// TODO: Remove edit mode
-	MainWindow::instance()->refreshDisplay(false);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
 }
 
 DeleteDive::DeleteDive(const QVector<struct dive*> &divesToDeleteIn) : divesToDelete(divesToDeleteIn.toStdVector())
@@ -558,31 +190,23 @@ bool DeleteDive::workToBeDone()
 	return !divesToDelete.empty();
 }
 
-void DeleteDive::undoit()
+void DeleteDive::undo()
 {
 	divesToDelete = addDives(divesToAdd);
+
 	mark_divelist_changed(true);
 
-	// Select all re-added dives and make the first one current
-	dive *currentDive = !divesToDelete.empty() ? divesToDelete[0] : nullptr;
-	restoreSelection(divesToDelete, currentDive);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
 }
 
-void DeleteDive::redoit()
+void DeleteDive::redo()
 {
 	divesToAdd = removeDives(divesToDelete);
 	mark_divelist_changed(true);
 
-	// Deselect all dives and select dive that was close to the first deleted dive
-	dive *newCurrent = nullptr;
-	if (!divesToAdd.empty()) {
-		timestamp_t when = divesToAdd[0].dive->when;
-		newCurrent = find_next_visible_dive(when);
-	}
-	if (newCurrent)
-		restoreSelection(std::vector<dive *>{ newCurrent }, newCurrent);
-	else
-		restoreSelection(std::vector<dive *>(), nullptr);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
 }
 
 
@@ -592,30 +216,20 @@ ShiftTime::ShiftTime(const QVector<dive *> &changedDives, int amount)
 	setText(tr("shift time of %n dives", "", changedDives.count()));
 }
 
-void ShiftTime::redoit()
+void ShiftTime::undo()
 {
 	for (dive *d: diveList)
 		d->when -= timeChanged;
 
 	// Changing times may have unsorted the dive table
 	sort_table(&dive_table);
-
-	// We send one dives-deleted signal per trip (see comments in DiveListNotifier.h).
-	// Therefore, collect all dives in a array and sort by trip.
-	std::vector<std::pair<dive_trip *, dive *>> dives;
-	dives.reserve(diveList.size());
-	for (dive *d: diveList)
-		dives.push_back({ d->divetrip, d });
-
-	// Send signals.
-	processByTrip(dives, [&](dive_trip *trip, const QVector<dive *> &divesInTrip) {
-		emit diveListNotifier.divesTimeChanged(trip, timeChanged, divesInTrip);
-	});
+	mark_divelist_changed(true);
 
 	// Negate the time-shift so that the next call does the reverse
 	timeChanged = -timeChanged;
 
-	mark_divelist_changed(true);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
 }
 
 bool ShiftTime::workToBeDone()
@@ -623,22 +237,25 @@ bool ShiftTime::workToBeDone()
 	return !diveList.isEmpty();
 }
 
-void ShiftTime::undoit()
+void ShiftTime::redo()
 {
-	// Same as redoit(), since after redoit() we reversed the timeOffset
-	redoit();
+	// Same as undo(), since after undo() we reversed the timeOffset
+	undo();
 }
 
 
-RenumberDives::RenumberDives(const QVector<QPair<dive *, int>> &divesToRenumberIn) : divesToRenumber(divesToRenumberIn)
+RenumberDives::RenumberDives(const QVector<QPair<int, int>> &divesToRenumberIn) : divesToRenumber(divesToRenumberIn)
 {
 	setText(tr("renumber %n dive(s)", "", divesToRenumber.count()));
 }
 
-void RenumberDives::undoit()
+void RenumberDives::undo()
 {
 	renumberDives(divesToRenumber);
 	mark_divelist_changed(true);
+
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
 }
 
 bool RenumberDives::workToBeDone()
@@ -646,10 +263,10 @@ bool RenumberDives::workToBeDone()
 	return !divesToRenumber.isEmpty();
 }
 
-void RenumberDives::redoit()
+void RenumberDives::redo()
 {
 	// Redo and undo do the same thing!
-	undoit();
+	undo();
 }
 
 bool TripBase::workToBeDone()
@@ -657,17 +274,20 @@ bool TripBase::workToBeDone()
 	return !divesToMove.divesToMove.empty();
 }
 
-void TripBase::redoit()
+void TripBase::redo()
 {
 	moveDivesBetweenTrips(divesToMove);
 
 	mark_divelist_changed(true);
+
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
 }
 
-void TripBase::undoit()
+void TripBase::undo()
 {
 	// Redo and undo do the same thing!
-	redoit();
+	redo();
 }
 
 RemoveDivesFromTrip::RemoveDivesFromTrip(const QVector<dive *> &divesToRemove)
@@ -748,18 +368,14 @@ SplitDives::SplitDives(dive *d, duration_t time)
 		split_dive_dont_insert(d, &new1, &new2) :
 		split_dive_at_time_dont_insert(d, time, &new1, &new2);
 
-	// If this didn't work, simply return. Empty arrays indicate that nothing is to be done.
-	if (idx < 0)
+	// If this didn't work, reset pointers so that redo() and undo() do nothing
+	if (idx < 0) {
+		diveToSplit = nullptr;
+		divesToUnsplit[0] = divesToUnsplit[1];
 		return;
+	}
 
-	// Currently, the core code selects the dive -> this is not what we want, as
-	// we manually manage the selection post-command.
-	// TODO: Reset selection in core.
-	new1->selected = false;
-	new2->selected = false;
-
-	diveToSplit.push_back(d);
-	splitDives.resize(2);
+	diveToSplit = d;
 	splitDives[0].dive.reset(new1);
 	splitDives[0].trip = d->divetrip;
 	splitDives[0].idx = idx;
@@ -770,34 +386,45 @@ SplitDives::SplitDives(dive *d, duration_t time)
 
 bool SplitDives::workToBeDone()
 {
-	return !diveToSplit.empty();
+	return !!diveToSplit;
 }
 
-void SplitDives::redoit()
+void SplitDives::redo()
 {
-	divesToUnsplit = addDives(splitDives);
-	unsplitDive = removeDives(diveToSplit);
+	if (!diveToSplit)
+		return;
+	divesToUnsplit[0] = addDive(splitDives[0]);
+	divesToUnsplit[1] = addDive(splitDives[1]);
+	unsplitDive = removeDive(diveToSplit);
 	mark_divelist_changed(true);
 
-	// Select split dives and make first dive current
-	restoreSelection(divesToUnsplit, divesToUnsplit[0]);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
+	MainWindow::instance()->refreshProfile();
 }
 
-void SplitDives::undoit()
+void SplitDives::undo()
 {
-	// Note: reverse order with respect to redoit()
-	diveToSplit = addDives(unsplitDive);
-	splitDives = removeDives(divesToUnsplit);
+	if (!unsplitDive.dive)
+		return;
+	// Note: reverse order with respect to redo()
+	diveToSplit = addDive(unsplitDive);
+	splitDives[1] = removeDive(divesToUnsplit[1]);
+	splitDives[0] = removeDive(divesToUnsplit[0]);
 	mark_divelist_changed(true);
 
-	// Select unsplit dive and make it current
-	restoreSelection(diveToSplit, diveToSplit[0] );
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
+	MainWindow::instance()->refreshProfile();
 }
 
 MergeDives::MergeDives(const QVector <dive *> &dives)
 {
 	setText(tr("merge dive"));
 
+	// We start in redo mode
+	diveToUnmerge = nullptr;
+
 	// Just a safety check - if there's not two or more dives - do nothing
 	// The caller should have made sure that this doesn't happen.
 	if (dives.count() < 2) {
@@ -808,11 +435,6 @@ MergeDives::MergeDives(const QVector <dive *> &dives)
 	dive_trip *preferred_trip;
 	OwningDivePtr d(merge_dives(dives[0], dives[1], dives[1]->when - dives[0]->when, false, &preferred_trip));
 
-	// Currently, the core code selects the dive -> this is not what we want, as
-	// we manually manage the selection post-command.
-	// TODO: Remove selection code from core.
-	d->selected = false;
-
 	// Set the preferred dive trip, so that for subsequent merges the better trip can be selected
 	d->divetrip = preferred_trip;
 	for (int i = 2; i < dives.count(); ++i) {
@@ -864,41 +486,42 @@ MergeDives::MergeDives(const QVector <dive *> &dives)
 			// Stop renumbering if stuff isn't in order (see also core/divelist.c)
 			if (newnr <= previousnr)
 				break;
-			divesToRenumber.append(QPair<dive *,int>(dive_table.dives[i], newnr));
+			divesToRenumber.append(QPair<int,int>(dive_table.dives[i]->id, newnr));
 			previousnr = newnr;
 		}
 	}
 
-	mergedDive.resize(1);
-	mergedDive[0].dive = std::move(d);
-	mergedDive[0].idx = get_divenr(dives[0]);
-	mergedDive[0].trip = preferred_trip;
+	mergedDive.dive = std::move(d);
+	mergedDive.idx = get_divenr(dives[0]);
+	mergedDive.trip = preferred_trip;
 	divesToMerge = dives.toStdVector();
 }
 
 bool MergeDives::workToBeDone()
 {
-	return !mergedDive.empty();
+	return !!mergedDive.dive;
 }
 
-void MergeDives::redoit()
+void MergeDives::redo()
 {
 	renumberDives(divesToRenumber);
-	diveToUnmerge = addDives(mergedDive);
+	diveToUnmerge = addDive(mergedDive);
 	unmergedDives = removeDives(divesToMerge);
 
-	// Select merged dive and make it current
-	restoreSelection(diveToUnmerge, diveToUnmerge[0]);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
+	MainWindow::instance()->refreshProfile();
 }
 
-void MergeDives::undoit()
+void MergeDives::undo()
 {
 	divesToMerge = addDives(unmergedDives);
-	mergedDive = removeDives(diveToUnmerge);
+	mergedDive = removeDive(diveToUnmerge);
 	renumberDives(divesToRenumber);
 
-	// Select unmerged dives and make first one current
-	restoreSelection(divesToMerge, divesToMerge[0]);
+	// Finally, do the UI stuff:
+	MainWindow::instance()->refreshDisplay();
+	MainWindow::instance()->refreshProfile();
 }
 
 } // namespace Command
diff --git a/desktop-widgets/command_divelist.h b/desktop-widgets/command_divelist.h
new file mode 100644
index 000000000..8cff4f1ef
--- /dev/null
+++ b/desktop-widgets/command_divelist.h
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0
+// Note: this header file is used by the undo-machinery and should not be included elsewhere.
+
+#ifndef COMMAND_DIVELIST_H
+#define COMMAND_DIVELIST_H
+
+#include "command_base.h"
+
+#include <QVector>
+
+// We put everything in a namespace, so that we can shorten names without polluting the global namespace
+namespace Command {
+
+// This helper structure describes a dive that we want to add.
+// Potentially it also adds a trip (if deletion of the dive resulted in deletion of the trip)
+struct DiveToAdd {
+	OwningDivePtr	 dive;		// Dive to add
+	OwningTripPtr	 tripToAdd;	// Not-null if we also have to add a dive
+	dive_trip	*trip;		// Trip the dive belongs to, may be null
+	int		 idx;		// Position in divelist
+};
+
+// This helper structure describes a dive that should be moved to / removed from
+// a trip. If the "trip" member is null, the dive is removed from its trip (if
+// it is in a trip, that is)
+struct DiveToTrip
+{
+	struct dive	*dive;
+	dive_trip	*trip;
+};
+
+// This helper structure describes a number of dives to add to /remove from /
+// move between trips.
+// It has ownership of the trips (if any) that have to be added before hand.
+struct DivesToTrip
+{
+	std::vector<DiveToTrip> divesToMove;		// If dive_trip is null, remove from trip
+	std::vector<OwningTripPtr> tripsToAdd;
+};
+
+class AddDive : public Base {
+public:
+	AddDive(dive *dive);
+private:
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+
+	// For redo
+	DiveToAdd	diveToAdd;
+
+	// For undo
+	dive		*diveToRemove;
+};
+
+class DeleteDive : public Base {
+public:
+	DeleteDive(const QVector<dive *> &divesToDelete);
+private:
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+
+	// For redo
+	std::vector<struct dive*> divesToDelete;
+
+	std::vector<OwningTripPtr> tripsToAdd;
+	std::vector<DiveToAdd> divesToAdd;
+};
+
+class ShiftTime : public Base {
+public:
+	ShiftTime(const QVector<dive *> &changedDives, int amount);
+private:
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+
+	// For redo and undo
+	QVector<dive *> diveList;
+	int timeChanged;
+};
+
+class RenumberDives : public Base {
+public:
+	RenumberDives(const QVector<QPair<int, int>> &divesToRenumber);
+private:
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+
+	// For redo and undo: pairs of dive-id / new number
+	QVector<QPair<int, int>> divesToRenumber;
+};
+
+// The classes RemoveDivesFromTrip, RemoveAutogenTrips, CreateTrip, AutogroupDives
+// and MergeTrips all do the same thing, just the intialization differs.
+// Therefore, define a base class with the proper data-structures, redo()
+// and undo() functions and derive to specialize the initialization.
+class TripBase : public Base {
+protected:
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+
+	// For redo and undo
+	DivesToTrip divesToMove;
+};
+struct RemoveDivesFromTrip : public TripBase {
+	RemoveDivesFromTrip(const QVector<dive *> &divesToRemove);
+};
+struct RemoveAutogenTrips : public TripBase {
+	RemoveAutogenTrips();
+};
+struct AddDivesToTrip : public TripBase {
+	AddDivesToTrip(const QVector<dive *> &divesToAdd, dive_trip *trip);
+};
+struct CreateTrip : public TripBase {
+	CreateTrip(const QVector<dive *> &divesToAdd);
+};
+struct AutogroupDives : public TripBase {
+	AutogroupDives();
+};
+struct MergeTrips : public TripBase {
+	MergeTrips(dive_trip *trip1, dive_trip *trip2);
+};
+
+class SplitDives : public Base {
+public:
+	// If time is < 0, split at first surface interval
+	SplitDives(dive *d, duration_t time);
+private:
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+
+	// For redo
+	// For each dive to split, we remove one from and put two dives into the backend
+	dive		*diveToSplit;
+	DiveToAdd	 splitDives[2];
+
+	// For undo
+	// For each dive to unsplit, we remove two dives from and add one into the backend
+	DiveToAdd	 unsplitDive;
+	dive		*divesToUnsplit[2];
+};
+
+class MergeDives : public Base {
+public:
+	MergeDives(const QVector<dive *> &dives);
+private:
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+
+	// For redo
+	// Add one and remove a batch of dives
+	DiveToAdd		 mergedDive;
+	std::vector<dive *>	 divesToMerge;
+
+	// For undo
+	// Remove one and add a batch of dives
+	dive			*diveToUnmerge;
+	std::vector<DiveToAdd>	 unmergedDives;
+
+	// For undo and redo
+	QVector<QPair<int, int>> divesToRenumber;
+};
+
+} // namespace Command
+
+#endif // COMMAND_DIVELIST_H
diff --git a/desktop-widgets/divelistview.cpp b/desktop-widgets/divelistview.cpp
index 27b7e3ed9..4d68baca2 100644
--- a/desktop-widgets/divelistview.cpp
+++ b/desktop-widgets/divelistview.cpp
@@ -20,7 +20,7 @@
 #include <QMessageBox>
 #include <QHeaderView>
 #include "core/qthelper.h"
-#include "desktop-widgets/undocommands.h"
+#include "desktop-widgets/command.h"
 #include "desktop-widgets/divelistview.h"
 #include "qt-models/divepicturemodel.h"
 #include "core/metrics.h"
@@ -633,10 +633,8 @@ void DiveListView::mergeDives()
 	if (current_batch.count() > 1)
 		merge_batches.append(current_batch);
 
-	for (const QVector<dive *> &batch: merge_batches) {
-		UndoMergeDives *undoCommand = new UndoMergeDives(batch);
-		MainWindow::instance()->undoStack->push(undoCommand);
-	}
+	for (const QVector<dive *> &batch: merge_batches)
+		Command::mergeDives(batch);
 }
 
 void DiveListView::splitDives()
@@ -650,10 +648,8 @@ void DiveListView::splitDives()
 		if (dive->selected)
 			dives.append(dive);
 	}
-	for (struct dive *d: dives) {
-		UndoSplitDives *undoCommand = new UndoSplitDives(d, duration_t{-1});
-		MainWindow::instance()->undoStack->push(undoCommand);
-	}
+	for (struct dive *d: dives)
+		Command::splitDives(d, duration_t{-1});
 }
 
 void DiveListView::renumberDives()
@@ -671,8 +667,7 @@ void DiveListView::merge_trip(const QModelIndex &a, int offset)
 	dive_trip_t *trip_b = (dive_trip_t *)b.data(DiveTripModel::TRIP_ROLE).value<void *>();
 	if (trip_a == trip_b || !trip_a || !trip_b)
 		return;
-	UndoMergeTrips *undoCommand = new UndoMergeTrips(trip_a, trip_b);
-	MainWindow::instance()->undoStack->push(undoCommand);
+	Command::mergeTrips(trip_a, trip_b);
 	rememberSelection();
 	reload(currentLayout, false);
 	restoreSelection();
@@ -700,11 +695,7 @@ void DiveListView::removeFromTrip()
 		if (d->selected && d->divetrip)
 			divesToRemove.append(d);
 	}
-	if (divesToRemove.isEmpty())
-		return;
-
-	UndoRemoveDivesFromTrip *undoCommand = new UndoRemoveDivesFromTrip(divesToRemove);
-	MainWindow::instance()->undoStack->push(undoCommand);
+	Command::removeDivesFromTrip(divesToRemove);
 
 	rememberSelection();
 	reload(currentLayout, false);
@@ -725,8 +716,7 @@ void DiveListView::newTripAbove()
 		if (d->selected)
 			dives.append(d);
 	}
-	UndoCreateTrip *undoCommand = new UndoCreateTrip(dives);
-	MainWindow::instance()->undoStack->push(undoCommand);
+	Command::createTrip(dives);
 
 	reload(currentLayout, false);
 	mark_divelist_changed(true);
@@ -774,8 +764,7 @@ void DiveListView::addToTrip(int delta)
 				dives.append(d);
 		}
 	}
-	UndoAddDivesToTrip *undoEntry = new UndoAddDivesToTrip(dives, trip);
-	MainWindow::instance()->undoStack->push(undoEntry);
+	Command::addDivesToTrip(dives, trip);
 
 	reload(currentLayout, false);
 	restoreSelection();
@@ -814,7 +803,7 @@ void DiveListView::deleteDive()
 
 	int i;
 	int lastDiveNr = -1;
-	QVector<struct dive*> deletedDives; //a list of all deleted dives to be stored in the undo command
+	QVector<struct dive*> deletedDives;
 	for_each_dive (i, d) {
 		if (!d->selected)
 			continue;
@@ -822,8 +811,7 @@ void DiveListView::deleteDive()
 		lastDiveNr = i;
 	}
 	// the actual dive deletion is happening in the redo command that is implicitly triggered
-	UndoDeleteDive *undoEntry = new UndoDeleteDive(deletedDives);
-	MainWindow::instance()->undoStack->push(undoEntry);
+	Command::deleteDive(deletedDives);
 	if (amount_selected == 0) {
 		MainWindow::instance()->cleanUpEmpty();
 	}
diff --git a/desktop-widgets/divelogimportdialog.cpp b/desktop-widgets/divelogimportdialog.cpp
index 151488c0b..668b230a8 100644
--- a/desktop-widgets/divelogimportdialog.cpp
+++ b/desktop-widgets/divelogimportdialog.cpp
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "desktop-widgets/divelogimportdialog.h"
 #include "desktop-widgets/mainwindow.h"
+#include "desktop-widgets/command.h"
 #include "core/color.h"
 #include "ui_divelogimportdialog.h"
 #include <QShortcut>
@@ -1010,7 +1011,7 @@ void DiveLogImportDialog::on_buttonBox_accepted()
 
 	process_imported_dives(&table, false, false);
 	autogroup_dives();
-	MainWindow::instance()->undoStack->clear();
+	Command::clear();
 	MainWindow::instance()->refreshDisplay();
 }
 
diff --git a/desktop-widgets/downloadfromdivecomputer.cpp b/desktop-widgets/downloadfromdivecomputer.cpp
index e63de8f56..de0dd0626 100644
--- a/desktop-widgets/downloadfromdivecomputer.cpp
+++ b/desktop-widgets/downloadfromdivecomputer.cpp
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "desktop-widgets/downloadfromdivecomputer.h"
+#include "desktop-widgets/command.h"
 #include "core/display.h"
 #include "core/qthelper.h"
 #include "core/settings/qPrefDiveComputer.h"
@@ -508,7 +509,8 @@ void DownloadFromDCWidget::on_ok_clicked()
 		// first new dive) and select it again after processing all the dives
 		int uniqId = downloadTable.dives[downloadTable.nr - 1]->id;
 		process_imported_dives(&downloadTable, preferDownloaded(), true);
-		MainWindow::instance()->undoStack->clear();
+		autogroup_dives();
+		Command::clear();
 		// after process_imported_dives does any merging or resorting needed, we need
 		// to recreate the model for the dive list so we can select the newest dive
 		MainWindow::instance()->recreateDiveList();
diff --git a/desktop-widgets/mainwindow.cpp b/desktop-widgets/mainwindow.cpp
index 06f6b8968..d55913e25 100644
--- a/desktop-widgets/mainwindow.cpp
+++ b/desktop-widgets/mainwindow.cpp
@@ -37,6 +37,7 @@
 #include "core/settings/qPrefTechnicalDetails.h"
 
 #include "desktop-widgets/about.h"
+#include "desktop-widgets/command.h"
 #include "desktop-widgets/divecomputermanagementdialog.h"
 #include "desktop-widgets/divelistview.h"
 #include "desktop-widgets/divelogexportdialog.h"
@@ -48,7 +49,6 @@
 #include "desktop-widgets/mapwidget.h"
 #include "desktop-widgets/subsurfacewebservices.h"
 #include "desktop-widgets/tab-widgets/maintab.h"
-#include "desktop-widgets/undocommands.h"
 #include "desktop-widgets/updatemanager.h"
 #include "desktop-widgets/usersurvey.h"
 
@@ -258,9 +258,8 @@ MainWindow::MainWindow() : QMainWindow(),
 	memset(&what, 0, sizeof(what));
 
 	updateManager = new UpdateManager(this);
-	undoStack = new QUndoStack(this);
-	QAction *undoAction = undoStack->createUndoAction(this, tr("&Undo"));
-	QAction *redoAction = undoStack->createRedoAction(this, tr("&Redo"));
+	QAction *undoAction = Command::undoAction(this);
+	QAction *redoAction = Command::redoAction(this);
 	undoAction->setShortcut(QKeySequence(Qt::CTRL + Qt::Key_Z));
 	redoAction->setShortcut(QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_Z));
 	QList<QAction*>undoRedoActions;
@@ -620,7 +619,7 @@ void MainWindow::on_actionCloudstorageopen_triggered()
 	process_loaded_dives();
 	if (autogroup)
 		autogroup_dives();
-	undoStack->clear();
+	Command::clear();
 	hideProgressBar();
 	refreshDisplay();
 }
@@ -1075,9 +1074,9 @@ void MainWindow::on_actionAutoGroup_triggered()
 {
 	set_autogroup(ui.actionAutoGroup->isChecked());
 	if (autogroup)
-		undoStack->push(new UndoAutogroupDives);
+		Command::autogroupDives();
 	else
-		undoStack->push(new UndoRemoveAutogenTrips);
+		Command::removeAutogenTrips();
 	refreshDisplay();
 	mark_divelist_changed(true);
 }
@@ -1745,7 +1744,7 @@ void MainWindow::importFiles(const QStringList fileNames)
 	process_imported_dives(&table, false, false);
 	if (autogroup)
 		autogroup_dives();
-	undoStack->clear();
+	Command::clear();
 	refreshDisplay();
 }
 
@@ -1770,7 +1769,7 @@ void MainWindow::loadFiles(const QStringList fileNames)
 	process_loaded_dives();
 	if (autogroup)
 		autogroup_dives();
-	undoStack->clear();
+	Command::clear();
 
 	refreshDisplay();
 
diff --git a/desktop-widgets/mainwindow.h b/desktop-widgets/mainwindow.h
index 05f6ade68..113f0699c 100644
--- a/desktop-widgets/mainwindow.h
+++ b/desktop-widgets/mainwindow.h
@@ -34,7 +34,6 @@ class DivePlannerWidget;
 class ProfileWidget2;
 class PlannerDetails;
 class PlannerSettingsWidget;
-class QUndoStack;
 class LocationInformationWidget;
 
 typedef std::pair<QByteArray, QVariant> WidgetProperty;
@@ -82,7 +81,6 @@ public:
 	void setApplicationState(const QByteArray& state);
 	void setStateProperties(const QByteArray& state, const PropertyList& tl, const PropertyList& tr, const PropertyList& bl,const PropertyList& br);
 	bool inPlanner();
-	QUndoStack *undoStack;
 	NotificationWidget *getNotificationWidget();
 	void enableDisableCloudActions();
 	void setCheckedActionFilterTags(bool checked);
diff --git a/desktop-widgets/simplewidgets.cpp b/desktop-widgets/simplewidgets.cpp
index b7f985bc9..72a81d873 100644
--- a/desktop-widgets/simplewidgets.cpp
+++ b/desktop-widgets/simplewidgets.cpp
@@ -18,7 +18,7 @@
 #include "desktop-widgets/divelistview.h"
 #include "core/display.h"
 #include "profile-widget/profilewidget2.h"
-#include "desktop-widgets/undocommands.h"
+#include "desktop-widgets/command.h"
 #include "core/metadata.h"
 
 class MinMaxAvgWidgetPrivate {
@@ -171,8 +171,7 @@ void RenumberDialog::buttonClicked(QAbstractButton *button)
 				renumberedDives.append(QPair<int, int>(dive->id, newNr++));
 			}
 		}
-		UndoRenumberDives *undoCommand = new UndoRenumberDives(renumberedDives);
-		MainWindow::instance()->undoStack->push(undoCommand);
+		Command::renumberDives(renumberedDives);
 
 		mark_divelist_changed(true);
 		MainWindow::instance()->dive_list()->restoreSelection();
@@ -246,7 +245,7 @@ void ShiftTimesDialog::buttonClicked(QAbstractButton *button)
 				if (d->selected)
 					affectedDives.append(d);
 			}
-			MainWindow::instance()->undoStack->push(new UndoShiftTime(affectedDives, amount));
+			Command::shiftTime(affectedDives, amount);
 		}
 	}
 }
diff --git a/desktop-widgets/tab-widgets/maintab.cpp b/desktop-widgets/tab-widgets/maintab.cpp
index 7f1e6cbc2..46217af54 100644
--- a/desktop-widgets/tab-widgets/maintab.cpp
+++ b/desktop-widgets/tab-widgets/maintab.cpp
@@ -26,7 +26,7 @@
 #include "core/subsurface-string.h"
 #include "core/gettextfromc.h"
 #include "desktop-widgets/locationinformation.h"
-#include "desktop-widgets/undocommands.h"
+#include "desktop-widgets/command.h"
 
 #include "TabDiveExtraInfo.h"
 #include "TabDiveInformation.h"
@@ -799,8 +799,7 @@ void MainTab::acceptChanges()
 		updateDiveSite(ui.location->currDiveSiteUuid(), &displayed_dive);
 		copyTagsToDisplayedDive();
 
-		UndoAddDive *undoCommand = new UndoAddDive(&displayed_dive);
-		MainWindow::instance()->undoStack->push(undoCommand);
+		Command::addDive(&displayed_dive);
 
 		editMode = NONE;
 		MainWindow::instance()->exitEditState();
@@ -969,7 +968,7 @@ void MainTab::acceptChanges()
 		if (displayed_dive.when != cd->when) {
 			timestamp_t offset = cd->when - displayed_dive.when;
 			if (offset)
-				MainWindow::instance()->undoStack->push(new UndoShiftTime(selectedDives, (int)offset));
+				Command::shiftTime(selectedDives, (int)offset);
 		}
 	}
 	if (editMode != TRIP && current_dive->divetrip) {
diff --git a/desktop-widgets/undocommands.cpp b/desktop-widgets/undocommands.cpp
deleted file mode 100644
index 8470e4f2d..000000000
--- a/desktop-widgets/undocommands.cpp
+++ /dev/null
@@ -1,493 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#include "desktop-widgets/undocommands.h"
-#include "desktop-widgets/mainwindow.h"
-#include "desktop-widgets/divelistview.h"
-#include "core/divelist.h"
-#include "core/subsurface-string.h"
-#include "core/gettextfromc.h"
-
-// This helper function removes a dive, takes ownership of the dive and adds it to a DiveToAdd structure.
-// It is crucial that dives are added in reverse order of deletion, so the the indices are correctly
-// set and that the trips are added before they are used!
-static DiveToAdd removeDive(struct dive *d)
-{
-	DiveToAdd res;
-	res.idx = get_divenr(d);
-	if (res.idx < 0)
-		qWarning() << "Deletion of unknown dive!";
-
-	// remove dive from trip - if this is the last dive in the trip
-	// remove the whole trip.
-	res.trip = unregister_dive_from_trip(d, false);
-	if (res.trip && res.trip->nrdives == 0) {
-		unregister_trip(res.trip);		// Remove trip from backend
-		res.tripToAdd.reset(res.trip);		// Take ownership of trip
-	}
-
-	res.dive.reset(unregister_dive(res.idx));	// Remove dive from backend
-	return res;
-}
-
-// This helper function adds a dive and returns ownership to the backend. It may also add a dive trip.
-// It is crucial that dives are added in reverse order of deletion (see comment above)!
-// Returns pointer to added dive (which is owned by the backend!)
-static dive *addDive(DiveToAdd &d)
-{
-	if (d.tripToAdd) {
-		dive_trip *t = d.tripToAdd.release();	// Give up ownership of trip
-		insert_trip(&t);			// Return ownership to backend
-	}
-	if (d.trip)
-		add_dive_to_trip(d.dive.get(), d.trip);
-	dive *res = d.dive.release();			// Give up ownership of dive
-	add_single_dive(d.idx, res);			// Return ownership to backend
-	return res;
-}
-
-// This helper function calls removeDive() on a list of dives to be removed and
-// returns a vector of corresponding DiveToAdd objects, which can later be readded.
-// The passed in vector is cleared.
-static std::vector<DiveToAdd> removeDives(std::vector<dive *> &divesToDelete)
-{
-	std::vector<DiveToAdd> res;
-	res.reserve(divesToDelete.size());
-
-	for (dive *d: divesToDelete)
-		res.push_back(removeDive(d));
-	divesToDelete.clear();
-
-	return res;
-}
-
-// This helper function is the counterpart fo removeDives(): it calls addDive() on a list
-// of dives to be (re)added and returns a vector of the added dives. It does this in reverse
-// order, so that trips are created appropriately and indexing is correct.
-// The passed in vector is cleared.
-static std::vector<dive *> addDives(std::vector<DiveToAdd> &divesToAdd)
-{
-	std::vector<dive *> res;
-	res.reserve(divesToAdd.size());
-
-	for (auto it = divesToAdd.rbegin(); it != divesToAdd.rend(); ++it)
-		res.push_back(addDive(*it));
-	divesToAdd.clear();
-
-	return res;
-}
-
-// This helper function renumbers dives according to an array of id/number pairs.
-// The old numbers are stored in the array, thus calling this function twice has no effect.
-// TODO: switch from uniq-id to indexes once all divelist-actions are controlled by "UndoCommands".
-static void renumberDives(QVector<QPair<int, int>> &divesToRenumber)
-{
-	for (auto &pair: divesToRenumber) {
-		dive *d = get_dive_by_uniq_id(pair.first);
-		if (!d)
-			continue;
-		std::swap(d->number, pair.second);
-	}
-}
-
-// This helper function moves a dive to a trip. The old trip is recorded in the
-// passed-in structure. This means that calling the function twice on the same
-// object is a no-op concerning the dive. If the old trip was deleted from the
-// core, an owning pointer to the removed trip is returned, otherwise a null pointer.
-static OwningTripPtr moveDiveToTrip(DiveToTrip &diveToTrip)
-{
-	// Firstly, check if we move to the same trip and bail if this is a no-op.
-	if (diveToTrip.trip == diveToTrip.dive->divetrip)
-		return {};
-
-	// Remove from old trip
-	OwningTripPtr res;
-
-	// Remove dive from trip - if this is the last dive in the trip, remove the whole trip.
-	dive_trip *trip = unregister_dive_from_trip(diveToTrip.dive, false);
-	if (trip && trip->nrdives == 0) {
-		unregister_trip(trip);		// Remove trip from backend
-		res.reset(trip);
-	}
-
-	// Store old trip and get new trip we should associate this dive with
-	std::swap(trip, diveToTrip.trip);
-	add_dive_to_trip(diveToTrip.dive, trip);
-	return res;
-}
-
-// This helper function moves a set of dives between trips using the
-// moveDiveToTrip function. Before doing so, it adds the necessary trips to
-// the core. Trips that are removed from the core because they are empty
-// are recorded in the passed in struct. The vectors of trips and dives
-// are reversed. Thus, calling the function twice on the same object is
-// a no-op.
-static void moveDivesBetweenTrips(DivesToTrip &dives)
-{
-	// first bring back the trip(s)
-	for (OwningTripPtr &trip: dives.tripsToAdd) {
-		dive_trip *t = trip.release();	// Give up ownership
-		insert_trip(&t);		// Return ownership to backend
-	}
-	dives.tripsToAdd.clear();
-
-	for (DiveToTrip &dive: dives.divesToMove) {
-		OwningTripPtr tripToAdd = moveDiveToTrip(dive);
-		// register trips that we'll have to readd
-		if (tripToAdd)
-			dives.tripsToAdd.push_back(std::move(tripToAdd));
-	}
-
-	// Reverse the tripsToAdd and the divesToAdd, so that on undo/redo the operations
-	// will be performed in reverse order.
-	std::reverse(dives.tripsToAdd.begin(), dives.tripsToAdd.end());
-	std::reverse(dives.divesToMove.begin(), dives.divesToMove.end());
-}
-
-UndoAddDive::UndoAddDive(dive *d)
-{
-	setText(gettextFromC::tr("add dive"));
-	// TODO: handle tags
-	//saveTags();
-	d->maxdepth.mm = 0;
-	fixup_dive(d);
-	diveToAdd.trip = d->divetrip;
-	d->divetrip = nullptr;
-	diveToAdd.idx = dive_get_insertion_index(d);
-	d->number = get_dive_nr_at_idx(diveToAdd.idx);
-	diveToAdd.dive.reset(clone_dive(d));
-}
-
-void UndoAddDive::redo()
-{
-	diveToRemove = addDive(diveToAdd);
-	mark_divelist_changed(true);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->dive_list()->unselectDives();
-	MainWindow::instance()->dive_list()->selectDive(diveToAdd.idx, true);
-	MainWindow::instance()->refreshDisplay();
-}
-
-void UndoAddDive::undo()
-{
-	// Simply remove the dive that was previously added
-	diveToAdd = removeDive(diveToRemove);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-}
-
-UndoDeleteDive::UndoDeleteDive(const QVector<struct dive*> &divesToDeleteIn) : divesToDelete(divesToDeleteIn.toStdVector())
-{
-	setText(tr("delete %n dive(s)", "", divesToDelete.size()));
-}
-
-void UndoDeleteDive::undo()
-{
-	divesToDelete = addDives(divesToAdd);
-
-	mark_divelist_changed(true);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-}
-
-void UndoDeleteDive::redo()
-{
-	divesToAdd = removeDives(divesToDelete);
-	mark_divelist_changed(true);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-}
-
-
-UndoShiftTime::UndoShiftTime(const QVector<dive *> &changedDives, int amount)
-	: diveList(changedDives), timeChanged(amount)
-{
-	setText(tr("delete %n dive(s)", "", changedDives.size()));
-}
-
-void UndoShiftTime::undo()
-{
-	for (dive *d: diveList)
-		d->when -= timeChanged;
-
-	// Changing times may have unsorted the dive table
-	sort_table(&dive_table);
-	mark_divelist_changed(true);
-
-	// Negate the time-shift so that the next call does the reverse
-	timeChanged = -timeChanged;
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-}
-
-void UndoShiftTime::redo()
-{
-	// Same as undo(), since after undo() we reversed the timeOffset
-	undo();
-}
-
-
-UndoRenumberDives::UndoRenumberDives(const QVector<QPair<int, int>> &divesToRenumberIn) : divesToRenumber(divesToRenumberIn)
-{
-	setText(tr("renumber %n dive(s)", "", divesToRenumber.count()));
-}
-
-void UndoRenumberDives::undo()
-{
-	renumberDives(divesToRenumber);
-	mark_divelist_changed(true);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-}
-
-void UndoRenumberDives::redo()
-{
-	// Redo and undo do the same thing!
-	undo();
-}
-
-void UndoTripBase::redo()
-{
-	moveDivesBetweenTrips(divesToMove);
-
-	mark_divelist_changed(true);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-}
-
-void UndoTripBase::undo()
-{
-	// Redo and undo do the same thing!
-	redo();
-}
-
-UndoRemoveDivesFromTrip::UndoRemoveDivesFromTrip(const QVector<dive *> &divesToRemove)
-{
-	setText(divesToRemove.size() == 1 ? gettextFromC::tr("remove dive from trip")
-					  : gettextFromC::tr("remove %1 dives from trip").arg(divesToRemove.size()));
-	divesToMove.divesToMove.reserve(divesToRemove.size());
-	for (dive *d: divesToRemove)
-		divesToMove.divesToMove.push_back( {d, nullptr} );
-}
-
-UndoRemoveAutogenTrips::UndoRemoveAutogenTrips()
-{
-	setText(gettextFromC::tr("remove autogenerated trips"));
-	// TODO: don't touch core-innards directly
-	int i;
-	struct dive *dive;
-	for_each_dive(i, dive) {
-		if (dive->divetrip && dive->divetrip->autogen)
-			divesToMove.divesToMove.push_back( {dive, nullptr} );
-	}
-}
-
-UndoAddDivesToTrip::UndoAddDivesToTrip(const QVector<dive *> &divesToAddIn, dive_trip *trip)
-{
-	setText(divesToAddIn.size() == 1 ? gettextFromC::tr("add dives to trip")
-					 : gettextFromC::tr("add %1 dives to trip").arg(divesToAddIn.size()));
-	for (dive *d: divesToAddIn)
-		divesToMove.divesToMove.push_back( {d, trip} );
-}
-
-UndoCreateTrip::UndoCreateTrip(const QVector<dive *> &divesToAddIn)
-{
-	setText(gettextFromC::tr("create trip"));
-
-	if (divesToAddIn.isEmpty())
-		return;
-
-	dive_trip *trip = create_trip_from_dive(divesToAddIn[0]);
-	divesToMove.tripsToAdd.emplace_back(trip);
-	for (dive *d: divesToAddIn)
-		divesToMove.divesToMove.push_back( {d, trip} );
-}
-
-UndoAutogroupDives::UndoAutogroupDives()
-{
-	setText(gettextFromC::tr("autogroup dives"));
-
-	dive_trip *trip;
-	bool alloc;
-	int from, to;
-	for(int i = 0; (trip = get_dives_to_autogroup(i, &from, &to, &alloc)) != NULL; i = to) {
-		// If this is an allocated trip, take ownership
-		if (alloc)
-			divesToMove.tripsToAdd.emplace_back(trip);
-		for (int j = from; j < to; ++j)
-			divesToMove.divesToMove.push_back( { get_dive(j), trip } );
-	}
-}
-
-UndoMergeTrips::UndoMergeTrips(dive_trip *trip1, dive_trip *trip2)
-{
-	if (trip1 == trip2)
-		return;
-	dive_trip *newTrip = combine_trips_create(trip1, trip2);
-	divesToMove.tripsToAdd.emplace_back(newTrip);
-	for (dive *d = trip1->dives; d; d = d->next)
-		divesToMove.divesToMove.push_back( { d, newTrip } );
-	for (dive *d = trip2->dives; d; d = d->next)
-		divesToMove.divesToMove.push_back( { d, newTrip } );
-}
-
-UndoSplitDives::UndoSplitDives(dive *d, duration_t time)
-{
-	setText(gettextFromC::tr("split dive"));
-
-	// Split the dive
-	dive *new1, *new2;
-	int idx = time.seconds < 0 ?
-		split_dive_dont_insert(d, &new1, &new2) :
-		split_dive_at_time_dont_insert(d, time, &new1, &new2);
-
-	// If this didn't work, reset pointers so that redo() and undo() do nothing
-	if (idx < 0) {
-		diveToSplit = nullptr;
-		divesToUnsplit[0] = divesToUnsplit[1];
-		return;
-	}
-
-	diveToSplit = d;
-	splitDives[0].dive.reset(new1);
-	splitDives[0].trip = d->divetrip;
-	splitDives[0].idx = idx;
-	splitDives[1].dive.reset(new2);
-	splitDives[1].trip = d->divetrip;
-	splitDives[1].idx = idx + 1;
-}
-
-void UndoSplitDives::redo()
-{
-	if (!diveToSplit)
-		return;
-	divesToUnsplit[0] = addDive(splitDives[0]);
-	divesToUnsplit[1] = addDive(splitDives[1]);
-	unsplitDive = removeDive(diveToSplit);
-	mark_divelist_changed(true);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-	MainWindow::instance()->refreshProfile();
-}
-
-void UndoSplitDives::undo()
-{
-	if (!unsplitDive.dive)
-		return;
-	// Note: reverse order with respect to redo()
-	diveToSplit = addDive(unsplitDive);
-	splitDives[1] = removeDive(divesToUnsplit[1]);
-	splitDives[0] = removeDive(divesToUnsplit[0]);
-	mark_divelist_changed(true);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-	MainWindow::instance()->refreshProfile();
-}
-
-UndoMergeDives::UndoMergeDives(const QVector <dive *> &dives)
-{
-	setText(gettextFromC::tr("merge dive"));
-
-	// We start in redo mode
-	diveToUnmerge = nullptr;
-
-	// Just a safety check - if there's not two or more dives - do nothing
-	// The caller should have made sure that this doesn't happen.
-	if (dives.count() < 2) {
-		qWarning() << "Merging less than two dives";
-		return;
-	}
-
-	dive_trip *preferred_trip;
-	OwningDivePtr d(merge_dives(dives[0], dives[1], dives[1]->when - dives[0]->when, false, &preferred_trip));
-
-	// Set the preferred dive trip, so that for subsequent merges the better trip can be selected
-	d->divetrip = preferred_trip;
-	for (int i = 2; i < dives.count(); ++i) {
-		d.reset(merge_dives(d.get(), dives[i], dives[i]->when - d->when, false, &preferred_trip));
-		// Set the preferred dive trip, so that for subsequent merges the better trip can be selected
-		d->divetrip = preferred_trip;
-	}
-
-	// We got our preferred trip, so now the reference can be deleted from the newly generated dive
-	d->divetrip = nullptr;
-
-	// The merged dive gets the number of the first dive
-	d->number = dives[0]->number;
-
-	// We will only renumber the remaining dives if the joined dives are consecutive.
-	// Otherwise all bets are off concerning what the user wanted and doing nothing seems
-	// like the best option.
-	int idx = get_divenr(dives[0]);
-	int num = dives.count();
-	if (idx < 0 || idx + num > dive_table.nr) {
-		// It was the callers responsibility to pass only known dives.
-		// Something is seriously wrong - give up.
-		qWarning() << "Merging unknown dives";
-		return;
-	}
-	// std::equal compares two ranges. The parameters are (begin_range1, end_range1, begin_range2).
-	// Here, we can compare C-arrays, because QVector guarantees contiguous storage.
-	if (std::equal(&dives[0], &dives[0] + num, &dive_table.dives[idx]) &&
-	    dives[0]->number && dives.last()->number && dives[0]->number < dives.last()->number) {
-		// We have a consecutive set of dives. Rename all following dives according to the
-		// number of erased dives. This considers that there might be missing numbers.
-		// Comment copied from core/divelist.c:
-		// So if you had a dive list  1 3 6 7 8, and you
-		// merge 1 and 3, the resulting numbered list will
-		// be 1 4 5 6, because we assume that there were
-		// some missing dives (originally dives 4 and 5),
-		// that now will still be missing (dives 2 and 3
-		// in the renumbered world).
-		//
-		// Obviously the normal case is that everything is
-		// consecutive, and the difference will be 1, so the
-		// above example is not supposed to be normal.
-		int diff = dives.last()->number - dives[0]->number;
-		divesToRenumber.reserve(dive_table.nr - idx - num);
-		int previousnr = dives[0]->number;
-		for (int i = idx + num; i < dive_table.nr; ++i) {
-			int newnr = dive_table.dives[i]->number - diff;
-
-			// Stop renumbering if stuff isn't in order (see also core/divelist.c)
-			if (newnr <= previousnr)
-				break;
-			divesToRenumber.append(QPair<int,int>(dive_table.dives[i]->id, newnr));
-			previousnr = newnr;
-		}
-	}
-
-	mergedDive.dive = std::move(d);
-	mergedDive.idx = get_divenr(dives[0]);
-	mergedDive.trip = preferred_trip;
-	divesToMerge = dives.toStdVector();
-}
-
-void UndoMergeDives::redo()
-{
-	renumberDives(divesToRenumber);
-	diveToUnmerge = addDive(mergedDive);
-	unmergedDives = removeDives(divesToMerge);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-	MainWindow::instance()->refreshProfile();
-}
-
-void UndoMergeDives::undo()
-{
-	divesToMerge = addDives(unmergedDives);
-	mergedDive = removeDive(diveToUnmerge);
-	renumberDives(divesToRenumber);
-
-	// Finally, do the UI stuff:
-	MainWindow::instance()->refreshDisplay();
-	MainWindow::instance()->refreshProfile();
-}
diff --git a/profile-widget/profilewidget2.cpp b/profile-widget/profilewidget2.cpp
index 79b70d719..9221ff293 100644
--- a/profile-widget/profilewidget2.cpp
+++ b/profile-widget/profilewidget2.cpp
@@ -23,7 +23,7 @@
 #include "desktop-widgets/diveplanner.h"
 #include "desktop-widgets/simplewidgets.h"
 #include "desktop-widgets/divepicturewidget.h"
-#include "desktop-widgets/undocommands.h"
+#include "desktop-widgets/command.h"
 #include "desktop-widgets/mainwindow.h"
 #include "core/qthelper.h"
 #include "core/gettextfromc.h"
@@ -1685,8 +1685,7 @@ void ProfileWidget2::splitDive()
 	QPointF scenePos = mapToScene(mapFromGlobal(action->data().toPoint()));
 	duration_t time;
 	time.seconds = lrint(timeAxis->valueAt(scenePos));
-	UndoSplitDives *undoCommand = new UndoSplitDives(d, time);
-	MainWindow::instance()->undoStack->push(undoCommand);
+	Command::splitDives(d, time);
 	emit updateDiveInfo(false);
 #endif
 }