media: add small C++ helper describing a picture struct

By using a std::string instead of a C-string, memory management
becomes so much simpler! This class will be used for keeping track
of deleted/added pictures in the undo system.

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

core/CMakeLists.txt

@@ -127,6 +127,8 @@ set(SUBSURFACE_CORE_LIB_SRCS
 	parse.h
 	picture.c
 	picture.h
+	pictureobj.cpp
+	pictureobj.h
 	planner.c
 	planner.h
 	plannernotes.c

core/pictureobj.cpp

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "pictureobj.h"
+#include "qthelper.h"
+
+PictureObj::PictureObj() : offset({ 0 }), location({ 0 })
+{
+}
+
+PictureObj::PictureObj(const picture &pic) : filename(pic.filename), offset(pic.offset), location(pic.location)
+{
+}
+
+picture PictureObj::toCore() const
+{
+	return picture {
+		strdup(filename.c_str()),
+		offset,
+		location
+	};
+}
+
+bool PictureObj::operator<(const PictureObj &p2) const
+{
+	if (offset.seconds != p2.offset.seconds)
+		return offset.seconds < p2.offset.seconds;
+	return strcmp(filename.c_str(), p2.filename.c_str()) < 0;
+}

core/pictureobj.h

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef PICTUREOBJ_H
+#define PICTUREOBJ_H
+
+// A tiny helper class that represents a struct picture of the core
+// It does, however, keep the filename as a std::string so that C++ code
+// doesn't have do its own memory-management.
+
+#include "core/units.h"
+#include "core/picture.h"
+#include <string>
+
+struct PictureObj {
+	std::string filename;
+	offset_t offset;
+	location_t location;
+
+	PictureObj();			// Initialize to empty picture.
+	PictureObj(const picture &pic); // Create from core struct picture.
+	picture toCore() const;		// Turn into core structure. Caller responsible for freeing.
+	bool operator<(const PictureObj &p2) const;
+};
+
+#endif // PICTUREOBJ_H

packaging/ios/Subsurface-mobile.pro

@@ -64,6 +64,7 @@ SOURCES += ../../subsurface-mobile-main.cpp \
 	../../core/parse-xml.c \
 	../../core/parse.c \
 	../../core/picture.c \
+	../../core/pictureobj.cpp \
 	../../core/import-suunto.c \
 	../../core/import-shearwater.c \
 	../../core/import-cobalt.c \
@@ -205,6 +206,7 @@ HEADERS += \
 	../../core/units.h \
 	../../core/version.h \
 	../../core/picture.h \
+	../../core/pictureobj.h \
 	../../core/planner.h \
 	../../core/divesite.h \
 	../../core/checkcloudconnection.h \