Add UI scale factor setting for high DPI screens

app/main.cpp

@@ -22,6 +22,7 @@
 #include <QStyleFactory>
 #include <QFontDatabase>
 #include <QSysInfo>
+#include <QSettings>
 #ifdef __APPLE__
 #include <QGLFormat>
 #include <QSurfaceFormat>
@@ -56,6 +57,16 @@ static int runQtApplication(int argc, char* argv[], qtwebapp::LoggerWithFile *lo
      QApplication::setAttribute(Qt::AA_DontUseNativeDialogs); // Don't use on Android, otherwise we can't access files on internal storage
 #endif
 
+    // Set UI scale factor for High DPI displays
+    QSettings settings;
+    QString uiScaleFactor = "graphics.ui_scale_factor";
+    if (settings.contains(uiScaleFactor))
+    {
+        QString scaleFactor = settings.value(uiScaleFactor).toString();
+        qDebug() << "Setting QT_SCALE_FACTOR to" << scaleFactor;
+        qputenv("QT_SCALE_FACTOR", scaleFactor.toLatin1());
+    }
+
 	QApplication a(argc, argv);
 
 #if 1

sdrgui/gui/graphicsdialog.cpp

@@ -16,6 +16,8 @@
 ///////////////////////////////////////////////////////////////////////////////////
 
 #include <QFileDialog>
+#include <QSettings>
+#include <QMessageBox>
 
 #include "graphicsdialog.h"
 #include "ui_graphicsdialog.h"
@@ -39,6 +41,10 @@ GraphicsDialog::GraphicsDialog(MainSettings& mainSettings, QWidget* parent) :
         ui->mapMultisampling->setCurrentText(QString::number(samples));
     }
     ui->mapSmoothing->setChecked(m_mainSettings.getMapSmoothing());
+
+    QSettings settings;
+    m_initScaleFactor = settings.value("graphics.ui_scale_factor", "1").toFloat();
+    ui->uiScaleFactor->setValue((int)(m_initScaleFactor * 100.0f));
 }
 
 GraphicsDialog::~GraphicsDialog()
@@ -51,5 +57,30 @@ void GraphicsDialog::accept()
     m_mainSettings.setMultisampling(ui->multisampling->currentText().toInt());
     m_mainSettings.setMapMultisampling(ui->mapMultisampling->currentText().toInt());
     m_mainSettings.setMapSmoothing(ui->mapSmoothing->isChecked());
+
+    // We use QSetting rather than MainSettings, as we need to set QT_SCALE_FACTOR
+    // before MainSettings are currently read
+    QSettings settings;
+    bool showRestart = false;
+
+    float scaleFactor = ui->uiScaleFactor->value() / 100.0f;
+    if (m_initScaleFactor != scaleFactor)
+    {
+        QString newScaleFactor = QString("%1").arg(scaleFactor);
+        settings.setValue("graphics.ui_scale_factor", newScaleFactor);
+        showRestart = true;
+    }
+
+    if (showRestart)
+    {
+        QMessageBox msgBox;
+        msgBox.setText("Please restart SDRangel to use the new UI settings.");
+        msgBox.exec();
+    }
     QDialog::accept();
 }
+
+void GraphicsDialog::on_uiScaleFactor_valueChanged(int value)
+{
+    ui->uiScaleFactorText->setText(QString("%1%").arg(value));
+}

sdrgui/gui/graphicsdialog.h

@@ -35,9 +35,11 @@ public:
 private:
     Ui::GraphicsDialog* ui;
     MainSettings& m_mainSettings;
+    float m_initScaleFactor;
 
 private slots:
     void accept();
+    void on_uiScaleFactor_valueChanged(int value);
 };
 
 #endif /* SDRGUI_GUI_GRAPHICS_H_ */

sdrgui/gui/graphicsdialog.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>282</width>
-    <height>155</height>
+    <height>218</height>
    </rect>
   </property>
   <property name="font">
@@ -20,6 +20,45 @@
    <string>Graphics settings</string>
   </property>
   <layout class="QVBoxLayout" name="verticalLayout">
+   <item>
+    <widget class="QGroupBox" name="groupBox">
+     <property name="title">
+      <string>UI</string>
+     </property>
+     <layout class="QGridLayout" name="gridLayout">
+      <item row="0" column="2">
+       <widget class="QLabel" name="uiScaleFactorText">
+        <property name="text">
+         <string>100.0%</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="0">
+       <widget class="QLabel" name="uiScaleFactorLabel">
+        <property name="text">
+         <string>UI Scale Factor</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="1">
+       <widget class="QSlider" name="uiScaleFactor">
+        <property name="toolTip">
+         <string>UI scale factor. Set &gt;100% for high DPI displays. Requires restarting SDRangel to apply</string>
+        </property>
+        <property name="minimum">
+         <number>100</number>
+        </property>
+        <property name="maximum">
+         <number>300</number>
+        </property>
+        <property name="orientation">
+         <enum>Qt::Horizontal</enum>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </widget>
+   </item>
    <item>
     <layout class="QFormLayout" name="formLayout">
      <item row="0" column="0">
@@ -165,7 +204,10 @@ Requires windows to be reopened to take effect</string>
   </layout>
  </widget>
  <tabstops>
-  <tabstop>buttonBox</tabstop>
+  <tabstop>uiScaleFactor</tabstop>
+  <tabstop>multisampling</tabstop>
+  <tabstop>mapMultisampling</tabstop>
+  <tabstop>mapSmoothing</tabstop>
  </tabstops>
  <resources>
   <include location="../resources/res.qrc"/>