undo: implement undo of setting a picture time by drag&drop

Even though the functionality is seemingly trivial, this is a bit
invasive, as the code has to be split into two distinct parts:
1) Post undo command
2) React to changes to the divelist

Don't compile that code on mobile.

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

commands/CMakeLists.txt

@@ -16,6 +16,8 @@ set(SUBSURFACE_GENERIC_COMMANDS_SRCS
 	command_edit_trip.h
 	command_event.cpp
 	command_event.h
+	command_pictures.cpp
+	command_pictures.h
 )
 add_library(subsurface_commands STATIC ${SUBSURFACE_GENERIC_COMMANDS_SRCS})
 target_link_libraries(subsurface_commands ${QT_LIBRARIES})

commands/command.cpp

@@ -6,6 +6,7 @@
 #include "command_edit.h"
 #include "command_edit_trip.h"
 #include "command_event.h"
+#include "command_pictures.h"
 
 namespace Command {
 
@@ -359,4 +360,11 @@ void addGasSwitch(struct dive *d, int dcNr, int seconds, int tank)
 	execute(new AddGasSwitch(d, dcNr, seconds, tank));
 }
 
+// Picture (media) commands
+
+void setPictureOffset(dive *d, const QString &filename, offset_t offset)
+{
+	execute(new SetPictureOffset(d, filename, offset));
+}
+
 } // namespace Command

commands/command.h

@@ -118,6 +118,10 @@ void renameEvent(struct dive *d, int dcNr, struct event *ev, const char *name);
 void removeEvent(struct dive *d, int dcNr, struct event *ev);
 void addGasSwitch(struct dive *d, int dcNr, int seconds, int tank);
 
+// 7) Picture (media) commands
+
+void setPictureOffset(dive *d, const QString &filename, offset_t offset);
+
 } // namespace Command
 
 #endif // COMMAND_H

commands/command_pictures.cpp

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "command_pictures.h"
+#include "core/subsurface-qt/divelistnotifier.h"
+
+namespace Command {
+
+static picture *dive_get_picture(const dive *d, const QString &fn)
+{
+	int idx = get_picture_idx(&d->pictures, qPrintable(fn));
+	return idx < 0 ? nullptr : &d->pictures.pictures[idx];
+}
+
+SetPictureOffset::SetPictureOffset(dive *dIn, const QString &filenameIn, offset_t offsetIn) :
+	d(dIn), filename(filenameIn), offset(offsetIn)
+{
+	if (!dive_get_picture(d, filename))
+		d = nullptr;
+	setText(Command::Base::tr("Change media time"));
+}
+
+void SetPictureOffset::redo()
+{
+	picture *pic = dive_get_picture(d, filename);
+	if (!pic) {
+		fprintf(stderr, "SetPictureOffset::redo(): picture disappeared!");
+		return;
+	}
+	std::swap(pic->offset, offset);
+	offset_t newOffset = pic->offset;
+
+	// Instead of trying to be smart, let's simply resort the picture table.
+	// If someone complains about speed, do our usual "smart" thing.
+	sort_picture_table(&d->pictures);
+	emit diveListNotifier.pictureOffsetChanged(d, filename, newOffset);
+	invalidate_dive_cache(d);
+}
+
+// Undo and redo do the same thing
+void SetPictureOffset::undo()
+{
+	redo();
+}
+
+bool SetPictureOffset::workToBeDone()
+{
+	return !!d;
+}
+
+} // namespace Command

commands/command_pictures.h

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+// Note: this header file is used by the undo-machinery and should not be included elsewhere.
+
+#ifndef COMMAND_PICTURES_H
+#define COMMAND_PICTURES_H
+
+#include "command_base.h"
+
+// We put everything in a namespace, so that we can shorten names without polluting the global namespace
+namespace Command {
+
+class SetPictureOffset final : public Base {
+public:
+	SetPictureOffset(dive *d, const QString &filename, offset_t offset); // Pictures are identified by the unique (dive,filename) pair
+private:
+	dive *d; // null means no work to be done
+	QString filename;
+	offset_t offset;
+
+	void undo() override;
+	void redo() override;
+	bool workToBeDone() override;
+};
+
+} // namespace Command
+#endif