Q scale factor from preferences

src/main.cpp

@@ -1,11 +1,13 @@
 #include <QApplication>
 #include <QDir>
+#include <QSettings>
 #include <QString>
 #include <QStringList>
 #include <QTextCodec>
 #include <QThread>
 #include <QtDebug>
 
+#include "config.h"
 #include "coreservices.h"
 #include "errordialoghandler.h"
 #include "mixxxapplication.h"
@@ -22,6 +24,9 @@ namespace {
 constexpr int kFatalErrorOnStartupExitCode = 1;
 constexpr int kParseCmdlineArgsErrorExitCode = 2;
 
+constexpr char kScaleFactorEnvVar[] = "QT_SCALE_FACTOR";
+const QString kScaleFactorConfigKey = QStringLiteral("ScaleFactor");
+
 int runMixxx(MixxxApplication* pApp, const CmdlineArgs& args) {
     const auto pCoreServices = std::make_shared<mixxx::CoreServices>(args, pApp);
 
@@ -48,6 +53,41 @@ int runMixxx(MixxxApplication* pApp, const CmdlineArgs& args) {
     }
 }
 
+void adjustScaleFactor(CmdlineArgs* pArgs) {
+    if (qEnvironmentVariableIsSet(kScaleFactorEnvVar)) {
+        bool ok;
+        const double f = qgetenv(kScaleFactorEnvVar).toDouble(&ok);
+        if (ok && f > 0) {
+            // The environment variable overrides the preferences option
+            qDebug() << "Using" << kScaleFactorEnvVar << f;
+            pArgs->storeScaleFactor(f);
+            return;
+        }
+    }
+    // We cannot use ConfigObject, because it depends on MixxxApplication
+    // but the scale factor is read during it's constructor.
+    // QHighDpiScaling can not be used afterwards because it is private.
+    auto cfgFile = QFile(QDir(pArgs->getSettingsPath()).filePath(MIXXX_SETTINGS_FILE));
+    if (cfgFile.open(QFile::ReadOnly | QFile::Text)) {
+        QTextStream in(&cfgFile);
+        QString strScaleFactor;
+        QString line = in.readLine();
+        while (!line.isNull()) {
+            if (line.startsWith(kScaleFactorConfigKey)) {
+                strScaleFactor = line.mid(kScaleFactorConfigKey.size() + 1);
+                break;
+            }
+            line = in.readLine();
+        }
+        double scaleFactor = strScaleFactor.toDouble();
+        if (scaleFactor > 0) {
+            qDebug() << "Using preferences ScaleFactor" << scaleFactor;
+            qputenv(kScaleFactorEnvVar, strScaleFactor.toLocal8Bit());
+            pArgs->storeScaleFactor(scaleFactor);
+        }
+    }
+}
+
 } // anonymous namespace
 
 int main(int argc, char * argv[]) {
@@ -99,6 +139,8 @@ int main(int argc, char * argv[]) {
     Sandbox::checkSandboxed();
 #endif
 
+    adjustScaleFactor(&args);
+
     MixxxApplication app(argc, argv);
 
 #ifdef __APPLE__

src/preferences/dialog/dlgprefinterface.cpp

@@ -24,6 +24,19 @@
 using mixxx::skin::SkinManifest;
 using mixxx::skin::SkinPointer;
 
+namespace {
+
+const QString kConfigGroup = QStringLiteral("[Config]");
+const QString kControlsGroup = QStringLiteral("[Controls]");
+const QString kScaleFactorKey = QStringLiteral("ScaleFactor");
+const QString kStartInFullscreenKey = QStringLiteral("StartInFullscreen");
+const QString kSchemeKey = QStringLiteral("Scheme");
+const QString kResizableSkinKey = QStringLiteral("ResizableSkin");
+const QString kLocaleKey = QStringLiteral("Locale");
+const QString kTooltipsKey = QStringLiteral("Tooltips");
+
+} // namespace
+
 DlgPrefInterface::DlgPrefInterface(
         QWidget* parent,
         std::shared_ptr<mixxx::ScreensaverManager> pScreensaverManager,
@@ -34,9 +47,8 @@ DlgPrefInterface::DlgPrefInterface(
           m_pScreensaverManager(pScreensaverManager),
           m_pSkinLoader(pSkinLoader),
           m_pSkin(pSkinLoader->getConfiguredSkin()),
-          m_dScaleFactorAuto(1.0),
-          m_bUseAutoScaleFactor(false),
           m_dScaleFactor(1.0),
+          m_minScaleFactor(1.0),
           m_dDevicePixelRatio(1.0),
           m_bStartWithFullScreen(false),
           m_bRebootMixxxView(false) {
@@ -45,6 +57,16 @@ DlgPrefInterface::DlgPrefInterface(
     // get the pixel ratio to display a crisp skin preview when Mixxx is scaled
     m_dDevicePixelRatio = getDevicePixelRatioF(this);
 
+    // Calculate the minimum scale factor that leads to a device pixel ratio of 1.0
+    // m_dDevicePixelRatio must not drop below 1.0 because this creates an
+    // unusable GUI with visual artefacts
+    double initialScaleFactor = CmdlineArgs::Instance().getScaleFactor();
+    if (initialScaleFactor <= 0) {
+        initialScaleFactor = 1.0;
+    }
+    double unscaledDevicePixelRatio = m_dDevicePixelRatio / initialScaleFactor;
+    m_minScaleFactor = 1 / unscaledDevicePixelRatio;
+
     VERIFY_OR_DEBUG_ASSERT(m_pSkin != nullptr) {
         qWarning() << "Skipping creation of DlgPrefInterface because there is no skin available.";
         return;
@@ -149,13 +171,9 @@ DlgPrefInterface::DlgPrefInterface(
             this,
             &DlgPrefInterface::slotSetScheme);
 
-    checkBoxScaleFactorAuto->hide();
-    spinBoxScaleFactor->hide();
-    labelScaleFactor->hide();
-
     // Start in fullscreen mode
-    checkBoxStartFullScreen->setChecked(m_pConfig->getValueString(
-                    ConfigKey("[Config]", "StartInFullscreen")).toInt()==1);
+    checkBoxStartFullScreen->setChecked(
+            m_pConfig->getValue(ConfigKey(kConfigGroup, kStartInFullscreenKey), 0) == 1);
 
     // Screensaver mode
     comboBoxScreensaver->clear();
@@ -211,7 +229,7 @@ void DlgPrefInterface::slotUpdateSchemes() {
         m_colorScheme = QString();
     } else {
         ComboBoxSchemeconf->setEnabled(true);
-        QString configScheme = m_pConfig->getValueString(ConfigKey("[Config]", "Scheme"));
+        QString configScheme = m_pConfig->getValue(ConfigKey(kConfigGroup, kSchemeKey));
         bool foundConfigScheme = false;
         for (int i = 0; i < schlist.size(); i++) {
             ComboBoxSchemeconf->addItem(schlist[i]);
@@ -234,7 +252,7 @@ void DlgPrefInterface::slotUpdateSchemes() {
 
 void DlgPrefInterface::slotUpdate() {
     const QString skinNameOnUpdate =
-            m_pConfig->getValueString(ConfigKey("[Config]", "ResizableSkin"));
+            m_pConfig->getValue(ConfigKey(kConfigGroup, kResizableSkinKey));
     const SkinPointer pSkinOnUpdate = m_skins[skinNameOnUpdate];
     if (pSkinOnUpdate != nullptr && pSkinOnUpdate->isValid()) {
         m_skinNameOnUpdate = pSkinOnUpdate->name();
@@ -245,19 +263,18 @@ void DlgPrefInterface::slotUpdate() {
     slotUpdateSchemes();
     m_bRebootMixxxView = false;
 
-    m_localeOnUpdate = m_pConfig->getValueString(ConfigKey("[Config]", "Locale"));
+    m_localeOnUpdate = m_pConfig->getValue(ConfigKey(kConfigGroup, kLocaleKey));
     ComboBoxLocale->setCurrentIndex(ComboBoxLocale->findData(m_localeOnUpdate));
 
-    checkBoxScaleFactorAuto->setChecked(m_pConfig->getValue(
-            ConfigKey("[Config]", "ScaleFactorAuto"), m_bUseAutoScaleFactor));
-
     // The spinbox shows a percentage but Mixxx stores a multiplication factor
     // with 1.00 as no scaling, so multiply the stored value by 100.
-    spinBoxScaleFactor->setValue(m_pConfig->getValue(
-                    ConfigKey("[Config]", "ScaleFactor"), m_dScaleFactor) * 100);
+    double configScaleFactor = m_pConfig->getValue(
+            ConfigKey(kConfigGroup, kScaleFactorKey), m_dScaleFactor);
+    spinBoxScaleFactor->setValue(configScaleFactor * 100);
+    spinBoxScaleFactor->setMinimum(m_minScaleFactor * 100);
 
     checkBoxStartFullScreen->setChecked(m_pConfig->getValue(
-            ConfigKey("[Config]", "StartInFullscreen"), m_bStartWithFullScreen));
+            ConfigKey(kConfigGroup, kStartInFullscreenKey), m_bStartWithFullScreen));
 
     loadTooltipPreferenceFromConfig();
 
@@ -276,9 +293,6 @@ void DlgPrefInterface::slotResetToDefaults() {
     // Default to normal size widgets
     // The spinbox shows a percentage with 100% as no scaling.
     spinBoxScaleFactor->setValue(100);
-    if (m_dScaleFactorAuto > 0) {
-        checkBoxScaleFactorAuto->setChecked(true);
-    }
 
     // Don't start in full screen.
     checkBoxStartFullScreen->setChecked(false);
@@ -291,29 +305,6 @@ void DlgPrefInterface::slotResetToDefaults() {
     radioButtonTooltipsLibraryAndSkin->setChecked(true);
 }
 
-void DlgPrefInterface::slotSetScaleFactor(double newValue) {
-    // The spinbox shows a percentage, but Mixxx stores a multiplication factor
-    // with 1.00 as no change.
-    newValue /= 100.0;
-    if (m_dScaleFactor != newValue) {
-        m_dScaleFactor = newValue;
-        m_bRebootMixxxView = true;
-    }
-}
-
-void DlgPrefInterface::slotSetScaleFactorAuto(bool newValue) {
-    if (newValue) {
-        if (!m_bUseAutoScaleFactor) {
-            m_bRebootMixxxView = true;
-        }
-    } else {
-        slotSetScaleFactor(newValue);
-    }
-
-    m_bUseAutoScaleFactor = newValue;
-    spinBoxScaleFactor->setEnabled(!newValue);
-}
-
 void DlgPrefInterface::slotSetTooltips() {
     m_tooltipMode = mixxx::TooltipsPreference::TOOLTIPS_ON;
     if (radioButtonTooltipsOff->isChecked()) {
@@ -325,9 +316,10 @@ void DlgPrefInterface::slotSetTooltips() {
 
 void DlgPrefInterface::notifyRebootNecessary() {
     // make the fact that you have to restart mixxx more obvious
-    QMessageBox::information(
-        this, tr("Information"),
-        tr("Mixxx must be restarted before the new locale setting will take effect."));
+    QMessageBox::information(this,
+            tr("Information"),
+            tr("Mixxx must be restarted before the new locale or scaling "
+               "settings will take effect."));
 }
 
 void DlgPrefInterface::slotSetScheme(int) {
@@ -389,26 +381,20 @@ void DlgPrefInterface::slotSetSkin(int) {
 }
 
 void DlgPrefInterface::slotApply() {
-    m_pConfig->set(ConfigKey("[Config]", "ResizableSkin"), m_pSkin->name());
-    m_pConfig->set(ConfigKey("[Config]", "Scheme"), m_colorScheme);
+    m_pConfig->set(ConfigKey(kConfigGroup, kResizableSkinKey), m_pSkin->name());
+    m_pConfig->set(ConfigKey(kConfigGroup, kSchemeKey), m_colorScheme);
 
     QString locale = ComboBoxLocale->itemData(
             ComboBoxLocale->currentIndex()).toString();
-    m_pConfig->set(ConfigKey("[Config]", "Locale"), locale);
+    m_pConfig->set(ConfigKey(kConfigGroup, kLocaleKey), locale);
 
-    m_pConfig->setValue(
-            ConfigKey("[Config]", "ScaleFactorAuto"), m_bUseAutoScaleFactor);
-    if (m_bUseAutoScaleFactor) {
-        m_pConfig->setValue(
-                ConfigKey("[Config]", "ScaleFactor"), m_dScaleFactorAuto);
-    } else {
-        m_pConfig->setValue(ConfigKey("[Config]", "ScaleFactor"), m_dScaleFactor);
-    }
+    double scaleFactor = spinBoxScaleFactor->value() / 100;
+    m_pConfig->setValue(ConfigKey(kConfigGroup, kScaleFactorKey), scaleFactor);
 
-    m_pConfig->set(ConfigKey("[Config]", "StartInFullscreen"),
+    m_pConfig->set(ConfigKey(kConfigGroup, kStartInFullscreenKey),
             ConfigValue(checkBoxStartFullScreen->isChecked()));
 
-    m_pConfig->set(ConfigKey("[Controls]", "Tooltips"),
+    m_pConfig->set(ConfigKey(kControlsGroup, kTooltipsKey),
             ConfigValue(static_cast<int>(m_tooltipMode)));
     emit tooltipModeChanged(m_tooltipMode);
 
@@ -421,10 +407,11 @@ void DlgPrefInterface::slotApply() {
                 static_cast<mixxx::ScreenSaverPreference>(screensaverComboBoxState));
     }
 
-    if (locale != m_localeOnUpdate) {
+    if (locale != m_localeOnUpdate || scaleFactor != m_dScaleFactor) {
         notifyRebootNecessary();
         // hack to prevent showing the notification when pressing "Okay" after "Apply"
         m_localeOnUpdate = locale;
+        m_dScaleFactor = scaleFactor;
     }
 
     if (m_bRebootMixxxView) {
@@ -437,7 +424,7 @@ void DlgPrefInterface::slotApply() {
 
 void DlgPrefInterface::loadTooltipPreferenceFromConfig() {
     const auto tooltipMode = static_cast<mixxx::TooltipsPreference>(
-            m_pConfig->getValue(ConfigKey("[Controls]", "Tooltips"),
+            m_pConfig->getValue(ConfigKey(kControlsGroup, kTooltipsKey),
                     static_cast<int>(mixxx::TooltipsPreference::TOOLTIPS_ON)));
     switch (tooltipMode) {
     case mixxx::TooltipsPreference::TOOLTIPS_OFF:

src/preferences/dialog/dlgprefinterface.h

@@ -46,8 +46,6 @@ class DlgPrefInterface : public DlgPreferencePage, public Ui::DlgPrefControlsDlg
     void slotSetSkinDescription();
     void slotSetSkinPreview();
     void slotUpdateSchemes();
-    void slotSetScaleFactor(double newValue);
-    void slotSetScaleFactorAuto(bool checked);
 
   signals:
     void reloadUserInterface();
@@ -75,9 +73,8 @@ class DlgPrefInterface : public DlgPreferencePage, public Ui::DlgPrefControlsDlg
     QString m_colorScheme;
     QString m_localeOnUpdate;
     mixxx::TooltipsPreference m_tooltipMode;
-    double m_dScaleFactorAuto;
-    bool m_bUseAutoScaleFactor;
     double m_dScaleFactor;
+    double m_minScaleFactor;
     double m_dDevicePixelRatio;
     bool m_bStartWithFullScreen;
     mixxx::ScreenSaverPreference m_screensaverMode;