Fullscreen: show popup with with fullscreen and menu hotkeys

This modal popup is displayed every time when going fullscreen as long as the
"Remind me again" checkbox is ticked when Okay is clicked.
It can be styled to match the skin.

src/mixxxmainwindow.cpp

@@ -1,5 +1,6 @@
 #include "mixxxmainwindow.h"
 
+#include <QCheckBox>
 #include <QDesktopServices>
 #include <QFileDialog>
 #include <QGLFormat>
@@ -97,6 +98,7 @@ MixxxMainWindow::MixxxMainWindow(std::shared_ptr<mixxx::CoreServices> pCoreServi
         : m_pCoreServices(pCoreServices),
           m_pCentralWidget(nullptr),
           m_pLaunchImage(nullptr),
+          m_pFullScreenHint(nullptr),
           m_pGuiTick(nullptr),
 #ifdef __LINUX__
           m_supportsGlobalMenuBar(supportsGlobalMenu()),
@@ -338,6 +340,13 @@ void MixxxMainWindow::initialize() {
     // otherwise it would shift the launch image shortly before the skin is visible.
     m_pMenuBar->show();
 
+    // Show the fullscreen hotkey hint if we went fullscreen earlier.
+    // This should make users aware of the new feature (press Alt to show/hide menu bar)
+    // if they upgraded Mixxx with 'Start in fullscreen mode'.
+    // Show the hint now so it doesn't interfere with other popups, e.g. the
+    // sound device warnings.
+    showFullScreenHotkeyHint();
+
     // The launch image widget is automatically disposed, but we still have a
     // pointer to it.
     m_pLaunchImage = nullptr;
@@ -363,6 +372,14 @@ void MixxxMainWindow::initialize() {
             &PlayerInfo::currentPlayingTrackChanged,
             this,
             &MixxxMainWindow::slotUpdateWindowTitle);
+
+    if (m_pCoreServices->getSettings()->getValueString(
+                ConfigKey("[Config]", "hide_fullscreen_hint")) != "1") {
+        connect(this,
+                &MixxxMainWindow::fullScreenChanged,
+                this,
+                &MixxxMainWindow::showFullScreenHotkeyHint);
+    }
 }
 
 MixxxMainWindow::~MixxxMainWindow() {
@@ -1233,3 +1250,127 @@ void MixxxMainWindow::initializationProgressUpdate(int progress, const QString&
     }
     qApp->processEvents();
 }
+
+void MixxxMainWindow::showFullScreenHotkeyHint() {
+    if (!isFullScreen()) {
+        return;
+    }
+    if (m_pCoreServices->getSettings()->getValueString(
+                ConfigKey("[Config]", "hide_fullscreen_hint")) == "1") {
+        return;
+    }
+    // don't show fullscreen hotkey hint during startup
+    if (centralWidget() == m_pLaunchImage) {
+        return;
+    }
+
+    if (!m_pFullScreenHint) {
+        m_pFullScreenHint = new WFullScreenHint(this, m_pCoreServices->getSettings());
+    }
+    if (m_pFullScreenHint->isVisible()) {
+        return;
+    }
+    // apply skin stylesheet
+    m_pFullScreenHint->setStyleSheet(m_pCentralWidget->styleSheet());
+    m_pFullScreenHint->popup();
+}
+
+WFullScreenHint::WFullScreenHint(QWidget* parent, UserSettingsPointer pConfig)
+        : QWidget(parent),
+          m_pConfig(pConfig) {
+    QWidget::hide();
+    // stay on top, remove OS window frame
+    setWindowFlags(Qt::Dialog | Qt::FramelessWindowHint);
+    // block the GUI as long as it is open
+    setWindowModality(Qt::ApplicationModal);
+    // allow custom styles? at least the custom border is not applied without this
+    setAttribute(Qt::WA_StyledBackground);
+    // name it like the class so /tools/qsscheck.py can pick it up
+    setObjectName("WFullScreenHint");
+
+    QVBoxLayout* pLabelLayout = new QVBoxLayout();
+    pLabelLayout->addStretch();
+
+    auto* fullScreenTitle = new QLabel(tr("<b>Mixxx is now fullscreen</b>"), this);
+    fullScreenTitle->setObjectName("FullScreenTitle");
+    pLabelLayout->addWidget(fullScreenTitle);
+
+    // list all fullscreen keyboard shortcuts
+    const QList<QKeySequence> fsshortcuts = WMainMenuBar::s_fullScreenShortcuts;
+    if (!fsshortcuts.isEmpty()) {
+        QString fssString;
+        int i = 1;
+        for (const auto& shortcut : fsshortcuts) {
+            if (i > 1) { // separate multiple shortcuts
+                fssString.append(" / ");
+            }
+            fssString.append(QStringLiteral("<b>%1</b>").arg(shortcut.toString()));
+            i++;
+        }
+        QLabel* fullScreenHotkeys = new QLabel(this);
+        fullScreenHotkeys->setObjectName("FullScreenHotkeyLabel");
+        fullScreenHotkeys->setText(tr("Press %1 to toggle fullscreen").arg(fssString));
+        pLabelLayout->addWidget(fullScreenHotkeys);
+    }
+
+#ifndef __APPLE__
+    auto* menuHotkey = new QLabel(tr("Press <b>Alt</b> to toggle the menu bar"), this);
+    menuHotkey->setObjectName("MenuHotkeyLabel");
+    pLabelLayout->addWidget(menuHotkey);
+#endif
+
+    pLabelLayout->addStretch();
+
+    m_pRemindCheckBox = new QCheckBox(tr("&Remind me again"), this);
+    m_pRemindCheckBox->setObjectName("RemindAgainCheckBox");
+    m_pRemindCheckBox->setChecked(true);
+    pLabelLayout->addWidget(m_pRemindCheckBox);
+
+    pLabelLayout->addStretch();
+
+    m_pOkayBtn = new QPushButton(tr("&Okay"), this);
+    connect(m_pOkayBtn,
+            &QPushButton::clicked,
+            this,
+            &WFullScreenHint::close);
+    pLabelLayout->addWidget(m_pOkayBtn);
+
+    QHBoxLayout* pMainLayout = new QHBoxLayout();
+    // center the labels horizontally
+    pMainLayout->addStretch();
+    pMainLayout->addLayout(pLabelLayout);
+    pMainLayout->addStretch();
+    setLayout(pMainLayout);
+
+    // we need to update the the layout here since the size is used to
+    // calculate the positioning later
+    layout()->update();
+    layout()->activate();
+}
+
+void WFullScreenHint::popup() {
+    const QWidget* pParentWidget = parentWidget();
+    VERIFY_OR_DEBUG_ASSERT(pParentWidget) {
+        qWarning() << "WFullScreenHint: no parent widget!";
+    }
+    const QScreen* const pScreen = mixxx::widgethelper::getScreen(*pParentWidget);
+    int dlgWidth = 400;
+    VERIFY_OR_DEBUG_ASSERT(pScreen) {
+        qWarning() << "No screen detectable, assuming screen size of 800x600px.";
+    }
+    else {
+        dlgWidth = pScreen->geometry().width() / 2;
+    }
+    setFixedWidth(dlgWidth);
+    setFixedHeight(static_cast<int>(sizeHint().height() * 1.2));
+    // Show the hint centered in the upper part of the window.
+    move(dlgWidth / 2, 100);
+    QWidget::show();
+    m_pOkayBtn->setFocus();
+}
+
+void WFullScreenHint::closeEvent(QCloseEvent* event) {
+    int remind = m_pRemindCheckBox->isChecked() ? 0 : 1;
+    m_pConfig->set(ConfigKey("[Config]", "hide_fullscreen_hint"), ConfigValue(remind));
+    QWidget::closeEvent(event);
+}

src/mixxxmainwindow.h

@@ -17,7 +17,9 @@ class DlgKeywheel;
 class GuiTick;
 class LaunchImage;
 class VisualsManager;
+class WFullScreenHint;
 class WMainMenuBar;
+class QCheckBox;
 
 namespace mixxx {
 
@@ -100,6 +102,9 @@ class MixxxMainWindow : public QMainWindow {
     bool loadConfiguredSkin();
 
     bool confirmExit();
+
+    void showFullScreenHotkeyHint();
+
     QDialog::DialogCode soundDeviceErrorDlg(
             const QString &title, const QString &text, bool* retryClicked);
     QDialog::DialogCode soundDeviceBusyDlg(bool* retryClicked);
@@ -111,6 +116,7 @@ class MixxxMainWindow : public QMainWindow {
 
     QWidget* m_pCentralWidget;
     LaunchImage* m_pLaunchImage;
+    WFullScreenHint* m_pFullScreenHint;
 
     std::shared_ptr<mixxx::skin::SkinLoader> m_pSkinLoader;
     GuiTick* m_pGuiTick;
@@ -137,3 +143,19 @@ class MixxxMainWindow : public QMainWindow {
 
     QSet<ControlObject*> m_skinCreatedControls;
 };
+
+class WFullScreenHint : public QWidget {
+    Q_OBJECT
+  public:
+    WFullScreenHint(QWidget* parent, UserSettingsPointer pConfig);
+
+    void popup();
+
+  protected:
+    void closeEvent(QCloseEvent* event) override;
+
+  private:
+    QCheckBox* m_pRemindCheckBox;
+    QPushButton* m_pOkayBtn;
+    UserSettingsPointer m_pConfig;
+};

src/widget/wmainmenubar.cpp

@@ -70,6 +70,8 @@ QUrl documentationUrl(
 }
 }  // namespace
 
+QList<QKeySequence> WMainMenuBar::s_fullScreenShortcuts = {};
+
 WMainMenuBar::WMainMenuBar(QWidget* pParent, UserSettingsPointer pConfig,
                            ConfigObject<ConfigValueKbd>* pKbdConfig)
         : QMenuBar(pParent),
@@ -313,7 +315,7 @@ void WMainMenuBar::initialize() {
     if (!osShortcut.isEmpty() && !shortcuts.contains(osShortcut)) {
         shortcuts << osShortcut;
     }
-
+    s_fullScreenShortcuts = shortcuts;
     pViewFullScreen->setShortcuts(shortcuts);
     pViewFullScreen->setShortcutContext(Qt::ApplicationShortcut);
     pViewFullScreen->setCheckable(true);

src/widget/wmainmenubar.h

@@ -36,6 +36,8 @@ class WMainMenuBar : public QMenuBar {
     WMainMenuBar(QWidget* pParent, UserSettingsPointer pConfig,
                  ConfigObject<ConfigValueKbd>* pKbdConfig);
 
+    static QList<QKeySequence> s_fullScreenShortcuts;
+
   public slots:
     void onLibraryScanStarted();
     void onLibraryScanFinished();