--- a/kcm/src/scalingconfig.cpp

+++ b/kcm/src/scalingconfig.cpp

@@ -30,9 +30,9 @@

 //slider can only handle ints so goes 10-30

 #define SLIDER_RATIO 10.0

-ScalingConfig::ScalingConfig(const KScreen::OutputList &outputList, QWidget* parent):

+ScalingConfig::ScalingConfig(const KScreen::OutputPtr &output, QWidget* parent):

     QDialog(parent),

-    m_outputList(outputList)

+    m_output(output)

 {

     ui.setupUi(this);

@@ -50,6 +50,8 @@ ScalingConfig::ScalingConfig(const KScre

     ui.previewWidget->setScale(1);

     ui.scaleLabel->setText(QString::number(1));

+

+    this->setWindowTitle(this->windowTitle() + QLatin1String(" : ") + m_output->name());

     load();

 }

@@ -61,35 +63,58 @@ ScalingConfig::~ScalingConfig()

 void ScalingConfig::load()

 {

     //we load UI from a config, as rdb value might not be updated yet

+    qreal screenDpi = 1.0;

+    QString screenFactor = QString::number(screenDpi);

     auto config = KSharedConfig::openConfig(QStringLiteral("kdeglobals"));

-    const qreal dpi = config->group("KScreen").readEntry("ScaleFactor", 1.0);

-    

-    m_initialScalingFactor = dpi;

-    ui.scaleSlider->setValue(dpi * SLIDER_RATIO);

+    QString readScreenFactors = config->group("KScreen").readEntry(

+                "ScreenScaleFactors", "");

+    QString searchName = m_output->name() + QLatin1Char('=');

+    if (readScreenFactors.contains(searchName)) {

+        foreach (const QString &str, readScreenFactors.split(QLatin1Char(';'), QString::SkipEmptyParts)) {

+            if (str.startsWith(searchName)) {

+                screenFactor = str.mid(str.indexOf(QLatin1Char('=')) + 1);

+                break;

+            }

+        }

+        bool convertionResult = false;

+        screenDpi = screenFactor.toDouble(&convertionResult);

+        if (!convertionResult) {

+            screenDpi = 1.0;

+        }

+    }

+    ui.scaleSlider->setValue(screenDpi * SLIDER_RATIO);

 }

 void ScalingConfig::accept()

 {

-    if (qFuzzyCompare(scaleFactor(), m_initialScalingFactor)) {

-        QDialog::accept();

-        return;

-    }

     const qreal scalingFactor = scaleFactor();

     //save to config

-    auto config = KSharedConfig::openConfig(QStringLiteral("kdeglobals"));

-    config->group("KScreen").writeEntry("ScaleFactor", scalingFactor);

     //write env var to be used by startkde.sh to populate the QT_SCREEN_SCALE_FACTORS env var

     //we use QT_SCREEN_SCALE_FACTORS as opposed to QT_SCALE_FACTOR as we need to use one that will *NOT* scale fonts according to the scale

     //scaling the fonts makes sense if you don't also set a font DPI, but we *need* to set a font DPI for both PlasmaShell which does it's own thing, and for KDE4/GTK2 applications

-

+    auto config = KSharedConfig::openConfig(QStringLiteral("kdeglobals"));

+    QString readScreenFactors = config->group("KScreen").readEntry("ScreenScaleFactors", "");

     QString screenFactors;

-    foreach (const KScreen::OutputPtr &output, m_outputList) {

-        screenFactors.append(output->name() + QLatin1Char('=') + QString::number(scalingFactor) + QLatin1Char(';'));

+    QString searchName = m_output->name() + QLatin1Char('=');

+    if (readScreenFactors.contains(searchName)) {

+        foreach (const QString &str, readScreenFactors.split(QLatin1Char(';'), QString::SkipEmptyParts)) {

+            if (!str.startsWith(searchName)) {

+                screenFactors += str + QLatin1Char(';');

+            }

+        }

+        screenFactors += searchName + QString::number(scalingFactor) + QLatin1Char(';');

+    } else {

+        screenFactors = readScreenFactors + searchName + QString::number(scalingFactor) + QLatin1Char(';');

     }

     config->group("KScreen").writeEntry("ScreenScaleFactors", screenFactors);

+    if (!m_output->isPrimary()) {

+        QDialog::accept();

+        return;

+    }

+    config->group("KScreen").writeEntry("ScaleFactor", scalingFactor);

     KConfig fontConfig(QStringLiteral("kcmfonts"));

     auto fontConfigGroup = fontConfig.group("General");

--- a/kcm/src/scalingconfig.h

+++ b/kcm/src/scalingconfig.h

@@ -30,7 +30,7 @@ class ScalingConfig : public QDialog

 {

     Q_OBJECT

 public:

-    explicit ScalingConfig(const KScreen::OutputList &outputList, QWidget* parent = nullptr);

+    explicit ScalingConfig(const KScreen::OutputPtr &output, QWidget* parent = nullptr);

     ~ScalingConfig() override;

 protected:

@@ -41,7 +41,7 @@ private:

     int scaleDPI() const;

     Ui::Scaling ui;

     qreal m_initialScalingFactor = 1.0;

-    KScreen::OutputList m_outputList;

+    KScreen::OutputPtr m_output;

 };

 #endif // SCALINGCONFIG_H

--- a/kcm/src/widget.cpp

+++ b/kcm/src/widget.cpp

@@ -73,9 +73,11 @@ Widget::Widget(QWidget *parent)

     connect(ui->scaleAllOutputsButton, &QPushButton::released,

             [this] {

-                QPointer<ScalingConfig> dialog = new ScalingConfig(mConfig->outputs(), this);

-                dialog->exec();

-                delete dialog;

+                if (mSelectedOutput) {

+                    QPointer<ScalingConfig> dialog = new ScalingConfig(mSelectedOutput, this);

+                    dialog->exec();

+                    delete dialog;

+                }

             });

     mOutputTimer = new QTimer(this);

@@ -216,6 +218,7 @@ void Widget::addOutputToPrimaryCombo(con

 void Widget::slotFocusedOutputChanged(QMLOutput *output)

 {

     mControlPanel->activateOutput(output->outputPtr());

+    mSelectedOutput = output->outputPtr();

 }

 void Widget::slotOutputEnabledChanged()

@@ -302,6 +305,7 @@ void Widget::slotUnifyOutputs()

         ui->primaryCombo->setEnabled(false);

         mControlPanel->setUnifiedOutput(base->outputPtr());

+        mSelectedOutput = base->outputPtr();

         ui->unifyButton->setText(i18n("Break Unified Outputs"));

     }

--- a/kcm/src/widget.h

+++ b/kcm/src/widget.h

@@ -93,6 +93,7 @@ class Widget : public QWidget

     QMLScreen *mScreen = nullptr;

     KScreen::ConfigPtr mConfig = nullptr;

     KScreen::ConfigPtr mPrevConfig = nullptr;

+    KScreen::OutputPtr mSelectedOutput = nullptr;

     ControlPanel *mControlPanel = nullptr;