diff --git a/commands/command_divelist.cpp b/commands/command_divelist.cpp
index 261e492c1..b6901c523 100644
--- a/commands/command_divelist.cpp
+++ b/commands/command_divelist.cpp
@@ -514,7 +514,7 @@ ImportDives::ImportDives(struct divelog *log, int flags, const QString &source)
 	// When encountering filter presets with equal names, check whether they are
 	// the same. If they are, ignore them.
 	for (const filter_preset &preset: *log->filter_presets) {
-		QString name = preset.name;
+		std::string name = preset.name;
 		auto it = std::find_if(divelog.filter_presets->begin(), divelog.filter_presets->end(),
 				       [&name](const filter_preset &preset) { return preset.name == name; });
 		if (it != divelog.filter_presets->end() && it->data == preset.data)
@@ -580,7 +580,7 @@ void ImportDives::undoit()
 	// Remove filter presets. Do this in reverse order.
 	for (auto it = filterPresetsToRemove.rbegin(); it != filterPresetsToRemove.rend(); ++it) {
 		int index = *it;
-		QString oldName = filter_preset_name_qstring(index);
+		std::string oldName = filter_preset_name(index);
 		FilterData oldData = filter_preset_get(index);
 		filter_preset_delete(index);
 		emit diveListNotifier.filterPresetRemoved(index);
diff --git a/commands/command_divelist.h b/commands/command_divelist.h
index 2d333a171..43713fd58 100644
--- a/commands/command_divelist.h
+++ b/commands/command_divelist.h
@@ -112,7 +112,7 @@ private:
 
 	// For redo
 	std::vector<OwningDiveSitePtr>	sitesToAdd;
-	std::vector<std::pair<QString,FilterData>>
+	std::vector<std::pair<std::string,FilterData>>
 					filterPresetsToAdd;
 
 	// For undo
diff --git a/commands/command_filter.cpp b/commands/command_filter.cpp
index c79d4eff6..4c60eb947 100644
--- a/commands/command_filter.cpp
+++ b/commands/command_filter.cpp
@@ -6,16 +6,16 @@
 
 namespace Command {
 
-static int createFilterPreset(const QString &name, const FilterData &data)
+static int createFilterPreset(const std::string &name, const FilterData &data)
 {
 	int index = filter_preset_add(name, data);
 	emit diveListNotifier.filterPresetAdded(index);
 	return index;
 }
 
-static std::pair<QString, FilterData> removeFilterPreset(int index)
+static std::pair<std::string, FilterData> removeFilterPreset(int index)
 {
-	QString oldName = filter_preset_name_qstring(index);
+	std::string oldName = filter_preset_name(index);
 	FilterData oldData = filter_preset_get(index);
 	filter_preset_delete(index);
 	emit diveListNotifier.filterPresetRemoved(index);
@@ -23,7 +23,7 @@ static std::pair<QString, FilterData> removeFilterPreset(int index)
 }
 
 CreateFilterPreset::CreateFilterPreset(const QString &nameIn, const FilterData &dataIn) :
-	name(nameIn), data(dataIn), index(0)
+	name(nameIn.toStdString()), data(dataIn), index(0)
 {
 	setText(Command::Base::tr("Create filter preset %1").arg(nameIn));
 }
@@ -46,7 +46,7 @@ void CreateFilterPreset::undo()
 
 RemoveFilterPreset::RemoveFilterPreset(int indexIn) : index(indexIn)
 {
-	setText(Command::Base::tr("Delete filter preset %1").arg(filter_preset_name_qstring(index)));
+	setText(Command::Base::tr("Delete filter preset %1").arg(QString(filter_preset_name(index).c_str())));
 }
 
 bool RemoveFilterPreset::workToBeDone()
@@ -68,7 +68,7 @@ void RemoveFilterPreset::undo()
 EditFilterPreset::EditFilterPreset(int indexIn, const FilterData &dataIn) :
 	index(indexIn), data(dataIn)
 {
-	setText(Command::Base::tr("Edit filter preset %1").arg(filter_preset_name_qstring(index)));
+	setText(Command::Base::tr("Edit filter preset %1").arg(QString(filter_preset_name(index).c_str())));
 }
 
 bool EditFilterPreset::workToBeDone()
diff --git a/commands/command_filter.h b/commands/command_filter.h
index e09753edf..38e83bf46 100644
--- a/commands/command_filter.h
+++ b/commands/command_filter.h
@@ -17,7 +17,7 @@ public:
 	CreateFilterPreset(const QString &name, const FilterData &data);
 private:
 	// for redo
-	QString name;
+	std::string name;
 	FilterData data;
 
 	// for undo
@@ -33,7 +33,7 @@ public:
 	RemoveFilterPreset(int index);
 private:
 	// for undo
-	QString name;
+	std::string name;
 	FilterData data;
 
 	// for redo
diff --git a/core/filterpreset.cpp b/core/filterpreset.cpp
index 6969f9c68..40bd72cfa 100644
--- a/core/filterpreset.cpp
+++ b/core/filterpreset.cpp
@@ -14,14 +14,9 @@ extern "C" int filter_presets_count(void)
 	return (int)global_table().size();
 }
 
-extern "C" char *filter_preset_name(int preset)
+extern std::string filter_preset_fulltext_query(int preset)
 {
-	return copy_qstring(filter_preset_name_qstring(preset));
-}
-
-extern "C" char *filter_preset_fulltext_query(int preset)
-{
-	return copy_qstring(global_table()[preset].data.fullText.originalQuery);
+	return global_table()[preset].data.fullText.originalQuery.toStdString();
 }
 
 extern "C" const char *filter_preset_fulltext_mode(int preset)
@@ -73,7 +68,7 @@ extern "C" void filter_preset_set_name(struct filter_preset *preset, const char
 	preset->name = name;
 }
 
-static int filter_preset_add_to_table(const QString &name, const FilterData &d, struct filter_preset_table &table)
+static int filter_preset_add_to_table(const std::string name, const FilterData &d, struct filter_preset_table &table)
 {
 	// std::lower_bound does a binary search - the vector must be sorted.
 	filter_preset newEntry { name, d };
@@ -85,14 +80,14 @@ static int filter_preset_add_to_table(const QString &name, const FilterData &d,
 }
 
 // Take care that the name doesn't already exist by adding numbers
-static QString get_unique_preset_name(const QString &orig, const struct filter_preset_table &table)
+static std::string get_unique_preset_name(const std::string &orig, const struct filter_preset_table &table)
 {
-	QString res = orig;
+	std::string res = orig;
 	int count = 2;
 	while (std::find_if(table.begin(), table.end(),
 			    [&res](const filter_preset &preset)
 			    { return preset.name == res; }) != table.end()) {
-		res = orig + "#" + QString::number(count);
+		res = orig + "#" + std::to_string(count);
 		++count;
 	}
 	return res;
@@ -100,7 +95,7 @@ static QString get_unique_preset_name(const QString &orig, const struct filter_p
 
 extern "C" void add_filter_preset_to_table(const struct filter_preset *preset, struct filter_preset_table *table)
 {
-	QString name = get_unique_preset_name(preset->name, *table);
+	std::string name = get_unique_preset_name(preset->name, *table);
 	filter_preset_add_to_table(name, preset->data, *table);
 }
 
@@ -110,14 +105,14 @@ extern "C" void filter_preset_add_constraint(struct filter_preset *preset, const
 	preset->data.constraints.emplace_back(type, string_mode, range_mode, negate, data);
 }
 
-int filter_preset_id(const QString &name)
+int filter_preset_id(const std::string &name)
 {
 	auto it = std::find_if(global_table().begin(), global_table().end(),
 			       [&name] (filter_preset &p) { return p.name == name; });
 	return it != global_table().end() ? it - global_table().begin() : -1;
 }
 
-QString filter_preset_name_qstring(int preset)
+std::string filter_preset_name(int preset)
 {
 	return global_table()[preset].name;
 }
@@ -132,9 +127,9 @@ FilterData filter_preset_get(int preset)
 	return global_table()[preset].data;
 }
 
-int filter_preset_add(const QString &nameIn, const FilterData &d)
+int filter_preset_add(const std::string &nameIn, const FilterData &d)
 {
-	QString name = get_unique_preset_name(nameIn, global_table());
+	std::string name = get_unique_preset_name(nameIn, global_table());
 	return filter_preset_add_to_table(name, d, global_table());
 }
 
diff --git a/core/filterpreset.h b/core/filterpreset.h
index 77fef88b1..059934b88 100644
--- a/core/filterpreset.h
+++ b/core/filterpreset.h
@@ -18,9 +18,9 @@ struct filter_constraint;
 #ifdef __cplusplus
 #include "divefilter.h"
 #include <vector>
-#include <QStringList>
+#include <string>
 struct filter_preset {
-	QString name;
+	std::string name;
 	FilterData data;
 };
 
@@ -44,8 +44,6 @@ extern "C" {
 
 // The C IO code accesses the filter presets via integer indices.
 extern int filter_presets_count(void);
-extern char *filter_preset_name(int preset); // name of filter preset - caller must free the result.
-extern char *filter_preset_fulltext_query(int preset); // fulltext query of filter preset - caller must free the result.
 extern const char *filter_preset_fulltext_mode(int preset); // string mode of fulltext query. ownership is *not* passed to caller.
 extern int filter_preset_constraint_count(int preset); // number of constraints in the filter preset.
 extern const struct filter_constraint *filter_preset_constraint(int preset, int constraint); // get constraint. ownership is *not* passed to caller.
@@ -66,12 +64,13 @@ extern void filter_preset_add_constraint(struct filter_preset *preset, const cha
 
 struct FilterData;
 
-int filter_preset_id(const QString &s); // for now, we assume that names are unique. returns -1 if no preset with that name.
-QString filter_preset_name_qstring(int preset);
+int filter_preset_id(const std::string &s); // for now, we assume that names are unique. returns -1 if no preset with that name.
 void filter_preset_set(int preset, const FilterData &d); // this will override a preset if the name already exists.
 FilterData filter_preset_get(int preset);
-int filter_preset_add(const QString &name, const FilterData &d); // returns point of insertion
+int filter_preset_add(const std::string &name, const FilterData &d); // returns point of insertion
 void filter_preset_delete(int preset);
+std::string filter_preset_name(int preset); // name of filter preset - caller must free the result.
+std::string filter_preset_fulltext_query(int preset); // fulltext query of filter preset - caller must free the result.
 
 #endif
 
diff --git a/core/save-git.cpp b/core/save-git.cpp
index e836c9f30..9964ad9aa 100644
--- a/core/save-git.cpp
+++ b/core/save-git.cpp
@@ -984,18 +984,14 @@ static void format_one_filter_constraint(int preset_id, int constraint_id, struc
  */
 static void format_one_filter_preset(int preset_id, struct membuffer *b)
 {
-	char *name, *fulltext;
+	std::string name = filter_preset_name(preset_id);
+	show_utf8(b, "name ", name.c_str(), "\n");
 
-	name = filter_preset_name(preset_id);
-	show_utf8(b, "name ", name, "\n");
-	free(name);
-
-	fulltext = filter_preset_fulltext_query(preset_id);
-	if (!empty_string(fulltext)) {
+	std::string fulltext = filter_preset_fulltext_query(preset_id);
+	if (!fulltext.empty()) {
 		show_utf8(b, "fulltext mode=", filter_preset_fulltext_mode(preset_id), "");
-		show_utf8(b, " query=", fulltext, "\n");
+		show_utf8(b, " query=", fulltext.c_str(), "\n");
 	}
-	free(fulltext);
 
 	for (int i = 0; i < filter_preset_constraint_count(preset_id); i++)
 		format_one_filter_constraint(preset_id, i, b);
diff --git a/core/save-xml.cpp b/core/save-xml.cpp
index 78cc8d043..d789d64fd 100644
--- a/core/save-xml.cpp
+++ b/core/save-xml.cpp
@@ -641,20 +641,17 @@ static void save_filter_presets(struct membuffer *b)
 		return;
 	put_format(b, "<filterpresets>\n");
 	for (i = 0; i < filter_presets_count(); i++) {
-		char *name, *fulltext;
-		name = filter_preset_name(i);
+		std::string name = filter_preset_name(i);
 		put_format(b, " <filterpreset");
-		show_utf8(b, name, " name='", "'", 1);
+		show_utf8(b, name.c_str(), " name='", "'", 1);
 		put_format(b, ">\n");
-		free(name);
 
-		fulltext = filter_preset_fulltext_query(i);
-		if (!empty_string(fulltext)) {
+		std::string fulltext = filter_preset_fulltext_query(i);
+		if (!fulltext.empty()) {
 			const char *fulltext_mode = filter_preset_fulltext_mode(i);
 			show_utf8(b, fulltext_mode, "  <fulltext mode='", "'>", 1);
-			show_utf8(b, fulltext, "", "</fulltext>\n", 0);
+			show_utf8(b, fulltext.c_str(), "", "</fulltext>\n", 0);
 		}
-		free(fulltext);
 
 		for (int j = 0; j < filter_preset_constraint_count(i); j++) {
 			const struct filter_constraint *constraint = filter_preset_constraint(i, j);
diff --git a/desktop-widgets/filterwidget.cpp b/desktop-widgets/filterwidget.cpp
index 5c910ea72..b4d3188cf 100644
--- a/desktop-widgets/filterwidget.cpp
+++ b/desktop-widgets/filterwidget.cpp
@@ -227,7 +227,7 @@ void FilterWidget::updatePresetLabel()
 	int presetId = selectedPreset();
 	QString text;
 	if (presetId >= 0) {
-		text = filter_preset_name_qstring(presetId);
+		text = QString(filter_preset_name(presetId).c_str());
 		if (presetModified)
 			text += " (" + tr("modified") + ")";
 	}
@@ -240,13 +240,13 @@ void FilterWidget::on_addSetButton_clicked()
 	// Thus, if the user selects an item and modify the filter,
 	// they can simply overwrite the preset.
 	int presetId = selectedPreset();
-	QString selectedPreset = presetId >= 0 ? filter_preset_name_qstring(presetId) : QString();
+	QString selectedPreset = presetId >= 0 ? QString(filter_preset_name(presetId).c_str()) : QString();
 
 	AddFilterPresetDialog dialog(selectedPreset, this);
 	QString name = dialog.doit();
 	if (name.isEmpty())
 		return;
-	int idx = filter_preset_id(name);
+	int idx = filter_preset_id(name.toStdString());
 	if (idx >= 0)
 		Command::editFilterPreset(idx, createFilterData());
 	else
diff --git a/desktop-widgets/simplewidgets.cpp b/desktop-widgets/simplewidgets.cpp
index 07edfb5b7..90657b282 100644
--- a/desktop-widgets/simplewidgets.cpp
+++ b/desktop-widgets/simplewidgets.cpp
@@ -385,7 +385,7 @@ AddFilterPresetDialog::AddFilterPresetDialog(const QString &defaultName, QWidget
 	int count = filter_presets_count();
 	presets.reserve(count);
 	for (int i = 0; i < count; ++i)
-		presets.push_back(filter_preset_name_qstring(i));
+		presets.push_back(QString(filter_preset_name(i).c_str()));
 	QCompleter *completer = new QCompleter(presets, this);
 	completer->setCaseSensitivity(Qt::CaseInsensitive);
 	ui.name->setCompleter(completer);
@@ -395,7 +395,7 @@ void AddFilterPresetDialog::nameChanged(const QString &text)
 {
 	QString trimmed = text.trimmed();
 	bool isEmpty = trimmed.isEmpty();
-	bool exists = !isEmpty && filter_preset_id(trimmed) >= 0;
+	bool exists = !isEmpty && filter_preset_id(trimmed.toStdString()) >= 0;
 	ui.duplicateWarning->setVisible(exists);
 	ui.buttonBox->button(QDialogButtonBox::Ok)->setEnabled(!isEmpty);
 }
diff --git a/qt-models/filterpresetmodel.cpp b/qt-models/filterpresetmodel.cpp
index 3853b4c34..52276315e 100644
--- a/qt-models/filterpresetmodel.cpp
+++ b/qt-models/filterpresetmodel.cpp
@@ -32,7 +32,7 @@ QVariant FilterPresetModel::data(const QModelIndex &index, int role) const
 	switch (role) {
 	case Qt::DisplayRole:
 		if (index.column() == NAME)
-			return filter_preset_name_qstring(index.row());
+			return QString(filter_preset_name(index.row()).c_str());
 		break;
 	case Qt::DecorationRole:
 		if (index.column() == REMOVE)