From 2cca9ebfdc367aa8e4651cf063f0cdea8fccb798 Mon Sep 17 00:00:00 2001
From: Soeren Apel <soeren@apelpie.net>
Date: Tue, 7 Mar 2017 22:14:49 +0100
Subject: [PATCH] GlobalSettings: Implement undo function for the "cancel"
 button

---
 pv/dialogs/settings.cpp | 10 ++++++++++
 pv/globalsettings.cpp   | 28 ++++++++++++++++++++++++++++
 pv/globalsettings.hpp   | 21 +++++++++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/pv/dialogs/settings.cpp b/pv/dialogs/settings.cpp
index 8cb8d67d..d443935e 100644
--- a/pv/dialogs/settings.cpp
+++ b/pv/dialogs/settings.cpp
@@ -45,6 +45,10 @@ Settings::Settings(QWidget *parent) :
 
 	connect(button_box, SIGNAL(accepted()), this, SLOT(accept()));
 	connect(button_box, SIGNAL(rejected()), this, SLOT(reject()));
+
+	// Start to record changes
+	GlobalSettings settings;
+	settings.start_tracking();
 }
 
 QWidget *Settings::get_view_settings_form(QWidget *parent) const
@@ -76,11 +80,17 @@ QWidget *Settings::get_view_settings_form(QWidget *parent) const
 
 void Settings::accept()
 {
+	GlobalSettings settings;
+	settings.stop_tracking();
+
 	QDialog::accept();
 }
 
 void Settings::reject()
 {
+	GlobalSettings settings;
+	settings.undo_tracked_changes();
+
 	QDialog::reject();
 }
 
diff --git a/pv/globalsettings.cpp b/pv/globalsettings.cpp
index 5da89ceb..d2482241 100644
--- a/pv/globalsettings.cpp
+++ b/pv/globalsettings.cpp
@@ -25,6 +25,8 @@ const QString GlobalSettings::Key_View_AlwaysZoomToFit = "View_AlwaysZoomToFit";
 const QString GlobalSettings::Key_View_ColouredBG = "View_ColouredBG";
 
 std::multimap< QString, std::function<void(QVariant)> > GlobalSettings::callbacks_;
+bool GlobalSettings::tracking_ = false;
+std::map<QString, QVariant> GlobalSettings::tracked_changes_;
 
 GlobalSettings::GlobalSettings() :
 	QSettings()
@@ -40,6 +42,11 @@ void GlobalSettings::register_change_handler(const QString key,
 
 void GlobalSettings::setValue(const QString &key, const QVariant &value)
 {
+	// Save previous value if we're tracking changes,
+	// not altering an already-existing saved setting
+	if (tracking_)
+		tracked_changes_.emplace(key, QSettings::value(key));
+
 	QSettings::setValue(key, value);
 
 	// Call all registered callbacks for this key
@@ -49,5 +56,26 @@ void GlobalSettings::setValue(const QString &key, const QVariant &value)
 		it->second(value);
 }
 
+void GlobalSettings::start_tracking()
+{
+	tracking_ = true;
+	tracked_changes_.clear();
+}
+
+void GlobalSettings::stop_tracking()
+{
+	tracking_ = false;
+	tracked_changes_.clear();
+}
+
+void GlobalSettings::undo_tracked_changes()
+{
+	tracking_ = false;
+
+	for (auto entry : tracked_changes_)
+		setValue(entry.first, entry.second);
+
+	tracked_changes_.clear();
+}
 
 } // namespace pv
diff --git a/pv/globalsettings.hpp b/pv/globalsettings.hpp
index b7457963..9581e294 100644
--- a/pv/globalsettings.hpp
+++ b/pv/globalsettings.hpp
@@ -45,8 +45,29 @@ public:
 
 	void setValue(const QString& key, const QVariant& value);
 
+	/**
+	 * Begins the tracking of changes. All changes will
+	 * be recorded until stop_tracking() is called.
+	 * The change tracking is global and doesn't support nesting.
+	 */
+	void start_tracking();
+
+	/**
+	 * Ends the tracking of changes without any changes to the settings.
+	 */
+	void stop_tracking();
+
+	/**
+	 * Ends the tracking of changes, undoing the changes since the
+	 * change tracking began.
+	 */
+	void undo_tracked_changes();
+
 private:
 	static std::multimap< QString, std::function<void(QVariant)> > callbacks_;
+
+	static bool tracking_;
+	static std::map<QString, QVariant> tracked_changes_;
 };
 
 } // namespace pv
-- 
2.30.2