Fix GitHub Issue #99: Program doesn't remember grid size

CHANGELOG

@@ -12,6 +12,8 @@ Bug fixes:
 
 Other:
 
+* Fix GitHub Issue #99: Program doesn't remember grid size
+
 1.18.0
 ======
 

src/main_window.cpp

@@ -229,7 +229,11 @@ QWidgetAction * MainWindow::createGridSizeAction()
 
     // The ugly cast is needed because there are QSpinBox::valueChanged(int) and QSpinBox::valueChanged(QString)
     // In Qt > 5.10 one can use QOverload<double>::of(...)
-    connect(m_gridSizeSpinBox, static_cast<void (QSpinBox::*)(int)>(&QSpinBox::valueChanged), this, &MainWindow::gridSizeChanged);
+    const auto signal = static_cast<void (QSpinBox::*)(int)>(&QSpinBox::valueChanged);
+    connect(m_gridSizeSpinBox, signal, this, &MainWindow::gridSizeChanged);
+    connect(m_gridSizeSpinBox, signal, Settings::saveGridSize);
+
+    m_gridSizeSpinBox->setValue(Settings::loadGridSize());
 
     return action;
 }

src/settings.cpp

@@ -17,15 +17,50 @@
 
 #include <QSettings>
 #include <QStandardPaths>
+#include <QTimer>
+
+#include <memory>
 
 namespace {
 const auto settingsGroupApplication = "Application";
 const auto settingsGroupMainWindow = "MainWindow";
 const auto recentImagePathKey = "recentImagePath";
+const auto gridSizeKey = "gridSize";
 const auto recentPathKey = "recentPath";
 const auto windowSizeKey = "size";
 } // namespace
 
+int Settings::loadGridSize()
+{
+    QSettings settings;
+    settings.beginGroup(settingsGroupMainWindow);
+    const auto gridSize = settings.value(gridSizeKey, 0).toInt();
+    settings.endGroup();
+    return gridSize;
+}
+
+void Settings::saveGridSize(int value)
+{
+    static std::unique_ptr<QTimer> gridSizeTimer;
+    static int sGridSizeValue;
+    sGridSizeValue = value;
+    if (!gridSizeTimer) {
+        gridSizeTimer = std::make_unique<QTimer>();
+        gridSizeTimer->setSingleShot(true);
+        gridSizeTimer->setInterval(500);
+        gridSizeTimer->connect(gridSizeTimer.get(), &QTimer::timeout, [&]() {
+            QSettings settings;
+            settings.beginGroup(settingsGroupMainWindow);
+            settings.setValue(gridSizeKey, sGridSizeValue);
+            settings.endGroup();
+        });
+    }
+    if (gridSizeTimer->isActive()) {
+        gridSizeTimer->stop();
+    }
+    gridSizeTimer->start();
+}
+
 QString Settings::loadRecentPath()
 {
     QSettings settings;

src/settings.hpp

@@ -20,6 +20,10 @@
 
 namespace Settings {
 
+int loadGridSize();
+
+void saveGridSize(int value);
+
 QString loadRecentPath();
 
 void saveRecentPath(QString path);