Connect presentation screen selection to KConfigWidgets

This adds a class PreferredScreenSelector, which is a QComboBox that
holds items for each connected screen, and provides a preferredScreen
property which is accessed by KConfigDialogManager.
This class also allows to remember a disconnected screen by adding
a temporary item “Screen xy (disconnected)”.

part/dlgpresentation.cpp

@@ -12,10 +12,8 @@
 #include "ui_dlgpresentationbase.h"
 #include "widgetdrawingtools.h"
 
-#include <KConfigDialogManager>
-#include <KLocalizedString>
 #include <QApplication>
-#include <QDesktopWidget>
+#include <QScreen>
 
 #include "settings.h"
 
@@ -29,27 +27,7 @@ DlgPresentation::DlgPresentation(QWidget *parent)
     m_dlg->verticalLayout_4->addWidget(kcfg_DrawingTools);
     kcfg_DrawingTools->setObjectName(QStringLiteral("kcfg_DrawingTools"));
 
-    QStringList choices;
-    choices.append(i18nc("@label:listbox The current screen, for the presentation mode", "Current Screen"));
-    choices.append(i18nc("@label:listbox The default screen for the presentation mode", "Default Screen"));
-    const int screenCount = QGuiApplication::screens().count();
-    for (int i = 0; i < screenCount; ++i) {
-        choices.append(i18nc("@label:listbox %1 is the screen number (0, 1, ...)", "Screen %1", i));
-    }
-    m_dlg->screenCombo->addItems(choices);
-
-    const int screen = Okular::Settings::slidesScreen();
-    if (screen >= -2 && screen < screenCount) {
-        m_dlg->screenCombo->setCurrentIndex(screen + 2);
-    } else {
-        m_dlg->screenCombo->setCurrentIndex(0);
-        Okular::Settings::setSlidesScreen(-2);
-    }
-
     m_dlg->kcfg_SlidesAdvanceTime->setSuffix(ki18ncp("Advance every %1 seconds", " second", " seconds"));
-
-    connect(m_dlg->screenCombo, static_cast<void (QComboBox::*)(int)>(&QComboBox::activated), this, &DlgPresentation::screenComboChanged);
-    connect(m_dlg->kcfg_SlidesAdvance, &QAbstractButton::toggled, m_dlg->kcfg_SlidesAdvanceTime, &QWidget::setEnabled);
 }
 
 DlgPresentation::~DlgPresentation()
@@ -57,9 +35,57 @@ DlgPresentation::~DlgPresentation()
     delete m_dlg;
 }
 
-void DlgPresentation::screenComboChanged(int which)
+PreferredScreenSelector::PreferredScreenSelector(QWidget *parent)
+    : QComboBox(parent)
+    , m_disconnectedScreenNumber(k_noDisconnectedScreenNumber)
+{
+    // Populate list:
+    static_assert(k_specialScreenCount == 2, "Special screens unknown to PreferredScreenSelector constructor.");
+    addItem(i18nc("@item:inlistbox Config dialog, presentation page, preferred screen", "Current Screen"));
+    addItem(i18nc("@item:inlistbox Config dialog, presentation page, preferred screen", "Default Screen"));
+
+    const QList<QScreen *> screens = qApp->screens();
+    for (int screenNumber = 0; screenNumber < screens.count(); ++screenNumber) {
+        QScreen *screen = screens.at(screenNumber);
+        addItem(i18nc("@item:inlistbox Config dialog, presentation page, preferred screen. %1 is the screen number (0, 1, ...). %2 is the screen manufacturer name. %3 is the screen model name. %4 is the screen name like DVI-0",
+                      "Screen %1 (%2 %3 %4)",
+                      screenNumber,
+                      screen->manufacturer(),
+                      screen->model(),
+                      screen->name()));
+    }
+
+    // If a disconnected screen is configured, it will be appended last:
+    m_disconnectedScreenIndex = count();
+
+    // KConfigWidgets setup:
+    setProperty("kcfg_property", QByteArray("preferredScreen"));
+    connect(this, QOverload<int>::of(&QComboBox::currentIndexChanged), [this](int index) { emit preferredScreenChanged(index - k_specialScreenCount); });
+}
+
+void PreferredScreenSelector::setPreferredScreen(int newScreen)
 {
-    Okular::Settings::setSlidesScreen(which - 2);
+    // Check whether the new screen is not in the list of connected screens:
+    if (newScreen >= m_disconnectedScreenIndex - k_specialScreenCount) {
+        if (m_disconnectedScreenNumber == k_noDisconnectedScreenNumber) {
+            addItem(QString());
+        }
+        setItemText(m_disconnectedScreenIndex, i18nc("@item:inlistbox Config dialog, presentation page, preferred screen. %1 is the screen number (0, 1, ...), hopefully not 0.", "Screen %1 (disconnected)", newScreen));
+        setCurrentIndex(m_disconnectedScreenIndex);
+        m_disconnectedScreenNumber = newScreen;
+        return;
+    }
+
+    setCurrentIndex(newScreen + k_specialScreenCount);
+
+    // screenChanged() is emitted through currentIndexChanged().
 }
 
-#include "moc_dlgpresentation.cpp"
+int PreferredScreenSelector::preferredScreen() const
+{
+    if (currentIndex() == m_disconnectedScreenIndex) {
+        return m_disconnectedScreenNumber;
+    } else {
+        return currentIndex() - k_specialScreenCount;
+    }
+}

part/dlgpresentation.h

@@ -10,7 +10,8 @@
 #ifndef _DLGPRESENTATION_H
 #define _DLGPRESENTATION_H
 
-#include <qwidget.h>
+#include <QComboBox>
+#include <QWidget>
 
 class Ui_DlgPresentationBase;
 
@@ -22,11 +23,53 @@ public:
     explicit DlgPresentation(QWidget *parent = nullptr);
     ~DlgPresentation() override;
 
-protected Q_SLOTS:
-    void screenComboChanged(int which);
-
 protected:
     Ui_DlgPresentationBase *m_dlg;
 };
 
+/**
+ * We need this because there are some special screens,
+ * which are not represented by the typical currentIndex(),
+ * which would be used by KConfigWidgets.
+ *
+ * Additionally this class allows to remember a disconnected screen.
+ */
+class PreferredScreenSelector : public QComboBox
+{
+    Q_OBJECT
+
+    Q_PROPERTY(int preferredScreen READ preferredScreen WRITE setPreferredScreen NOTIFY preferredScreenChanged)
+
+public:
+    explicit PreferredScreenSelector(QWidget *parent);
+    int preferredScreen() const;
+
+Q_SIGNALS:
+    void preferredScreenChanged(int screen);
+
+public Q_SLOTS:
+    void setPreferredScreen(int newScreen);
+
+protected:
+    // These two variables protect the screen setting from changing
+    // when the configured screen is currently disconnected.
+
+    /**
+     * When setScreen() is called with a disconnected screen,
+     * a “disconnected” entry is created at this index:
+     */
+    int m_disconnectedScreenIndex;
+
+    /**
+     * Which screen is referred by @c m_disconnectedScreenIndex.
+     * Until @c m_disconnectedScreenIndex entry is created, this is @c k_noDisconnectedScreenNumber.
+     */
+    int m_disconnectedScreenNumber;
+};
+
+/** “Current” and “Default” */
+const int k_specialScreenCount = 2;
+/** Default value of m_disconnectedScreenNumber when no disconnected screen is remembered */
+const int k_noDisconnectedScreenNumber = -3;
+
 #endif

part/dlgpresentationbase.ui

@@ -348,7 +348,7 @@
        </widget>
       </item>
       <item row="0" column="1">
-       <widget class="QComboBox" name="screenCombo"/>
+       <widget class="PreferredScreenSelector" name="kcfg_SlidesScreen"/>
       </item>
      </layout>
     </widget>
@@ -374,6 +374,11 @@
    <extends>QSpinBox</extends>
    <header>KPluralHandlingSpinBox</header>
   </customwidget>
+  <customwidget>
+   <class>PreferredScreenSelector</class>
+   <extends>QComboBox</extends>
+   <header>part/dlgpresentation.h</header>
+  </customwidget>
  </customwidgets>
  <resources/>
 </ui>