diff --git a/autotests/kpasswordlineedittest.cpp b/autotests/kpasswordlineedittest.cpp
--- a/autotests/kpasswordlineedittest.cpp
+++ b/autotests/kpasswordlineedittest.cpp
@@ -38,7 +38,7 @@
 
     QHBoxLayout *mainLayout = lineEdit.findChild<QHBoxLayout *>(QStringLiteral("mainlayout"));
     QVERIFY(mainLayout);
-    QCOMPARE(mainLayout->margin(), 0);
+    QCOMPARE(mainLayout->contentsMargins(), QMargins(0, 0, 0, 0));
 
     QLineEdit *edit = lineEdit.findChild<QLineEdit *>(QStringLiteral("passwordlineedit"));
     QVERIFY(edit);
diff --git a/autotests/ksqueezedtextlabelautotest.cpp b/autotests/ksqueezedtextlabelautotest.cpp
--- a/autotests/ksqueezedtextlabelautotest.cpp
+++ b/autotests/ksqueezedtextlabelautotest.cpp
@@ -155,7 +155,7 @@
     QCOMPARE(label->sizeHint().width(), 0);
 
     const QString text = QStringLiteral("Squeeze me");
-    const int labelWidth = label->fontMetrics().width(text);  // no chrome set
+    const int labelWidth = label->fontMetrics().boundingRect(text).width();  // no chrome set
     label->setText(text);
 
     QVERIFY(label->isSqueezed());
@@ -199,7 +199,7 @@
 void KSqueezedTextLabelAutotest::testChrome_data()
 {
     const QFontMetrics fm(KSqueezedTextLabel().fontMetrics());
-    const int xWidth = fm.width(QLatin1Char('x')) / 2;
+    const int xWidth = fm.horizontalAdvance(QLatin1Char('x')) / 2;
 
     QTest::addColumn<QString>("attribute");
     QTest::addColumn<int>("amount");
diff --git a/src/kassistantdialog.cpp b/src/kassistantdialog.cpp
--- a/src/kassistantdialog.cpp
+++ b/src/kassistantdialog.cpp
@@ -49,7 +49,7 @@
         QModelIndex currentIndex;
         do {
             currentIndex = nextIndex;
-            nextIndex = currentIndex.child(0, 0);
+            nextIndex = pageModel->index(0, 0, currentIndex);
             if (!nextIndex.isValid()) {
                 nextIndex = currentIndex.sibling(currentIndex.row() + 1, 0);
             }
diff --git a/src/kcapacitybar.cpp b/src/kcapacitybar.cpp
--- a/src/kcapacitybar.cpp
+++ b/src/kcapacitybar.cpp
@@ -350,9 +350,7 @@
 
 QSize KCapacityBar::minimumSizeHint() const
 {
-    int width = (d->drawTextMode == KCapacityBar::DrawTextInline) ?
-                fontMetrics().width(d->text) + ROUND_MARGIN * 2 :
-                fontMetrics().width(d->text);
+    int width = fontMetrics().boundingRect(d->text).width() + ((d->drawTextMode == KCapacityBar::DrawTextInline) ? ROUND_MARGIN * 2 : 0);
 
     int height = (d->drawTextMode == KCapacityBar::DrawTextInline) ?
                  qMax(fontMetrics().height(), d->barHeight) :
diff --git a/src/kcollapsiblegroupbox.cpp b/src/kcollapsiblegroupbox.cpp
--- a/src/kcollapsiblegroupbox.cpp
+++ b/src/kcollapsiblegroupbox.cpp
@@ -285,15 +285,13 @@
 
 void KCollapsibleGroupBox::resizeEvent(QResizeEvent *event)
 {
-    int top, left, right, bottom;
-    getContentsMargins(&left, &top, &right, &bottom);
+    const QMargins margins = contentsMargins();
 
     if (layout()) {
         //we don't want the layout trying to fit the current frame of the animation so always set it to the target height
-        layout()->setGeometry(QRect(left, top, width() - left - right, layout()->sizeHint().height()));
+        layout()->setGeometry(QRect(margins.left(), margins.top(), width() - margins.left() - margins.right(), layout()->sizeHint().height()));
     }
 
-    Q_UNUSED(bottom)
     QWidget::resizeEvent(event);
 }
 
diff --git a/src/kcolorbutton.cpp b/src/kcolorbutton.cpp
--- a/src/kcolorbutton.cpp
+++ b/src/kcolorbutton.cpp
@@ -294,7 +294,7 @@
 {
     if ((e->buttons() & Qt::LeftButton) &&
             (e->pos() - d->mPos).manhattanLength() > QApplication::startDragDistance()) {
-        _k_createDrag(color(), this)->start();
+        _k_createDrag(color(), this)->exec();
         setDown(false);
     }
 }
diff --git a/src/kdatecombobox.cpp b/src/kdatecombobox.cpp
--- a/src/kdatecombobox.cpp
+++ b/src/kdatecombobox.cpp
@@ -584,7 +584,7 @@
 void KDateComboBox::wheelEvent(QWheelEvent *event)
 {
     QDate temp;
-    if (event->delta() < 0) {
+    if (event->angleDelta().y() < 0) {
         temp = d->m_date.addDays(-1);
     } else {
         temp = d->m_date.addDays(1);
diff --git a/src/kdatepicker.cpp b/src/kdatepicker.cpp
--- a/src/kdatepicker.cpp
+++ b/src/kdatepicker.cpp
@@ -608,7 +608,7 @@
 
     // stolen from QToolButton
     QSize textSize = metrics.size(Qt::TextShowMnemonic, longestMonth);
-    textSize.setWidth(textSize.width() + metrics.width(QLatin1Char(' ')) * 2);
+    textSize.setWidth(textSize.width() + metrics.horizontalAdvance(QLatin1Char(' ')) * 2);
     int w = textSize.width();
     int h = textSize.height();
     opt.rect.setHeight(h);   // PM_MenuButtonIndicator depends on the height
diff --git a/src/kdatetable.cpp b/src/kdatetable.cpp
--- a/src/kdatetable.cpp
+++ b/src/kdatetable.cpp
@@ -524,7 +524,7 @@
 
 void KDateTable::wheelEvent(QWheelEvent *e)
 {
-    setDate(d->m_date.addMonths(-(int)(e->delta() / 120)));
+    setDate(d->m_date.addMonths(-(int)(e->angleDelta().y() / 120)));
     e->accept();
 }
 
diff --git a/src/kfontchooser.cpp b/src/kfontchooser.cpp
--- a/src/kfontchooser.cpp
+++ b/src/kfontchooser.cpp
@@ -46,7 +46,7 @@
     for (int i = 0; i < list->count(); i++) {
         int itemWidth = list->visualItemRect(list->item(i)).width();
         // ...and add a space on both sides for not too tight look.
-        itemWidth += list->fontMetrics().width(QLatin1Char(' ')) * 2;
+        itemWidth += list->fontMetrics().horizontalAdvance(QLatin1Char(' ')) * 2;
         w = qMax(w, itemWidth);
     }
     if (w == 0) {
diff --git a/src/kmessagebox.cpp b/src/kmessagebox.cpp
--- a/src/kmessagebox.cpp
+++ b/src/kmessagebox.cpp
@@ -279,7 +279,7 @@
         QFontMetrics fm(styleOption.font);
         int w = listWidget->width();
         for (const QString &str : strlist) {
-            w = qMax(w, fm.width(str));
+            w = qMax(w, fm.boundingRect(str).width());
         }
         const int borderWidth = listWidget->width() - listWidget->viewport()->width() + listWidget->verticalScrollBar()->height();
         w += borderWidth;
diff --git a/src/kpixmapregionselectordialog.cpp b/src/kpixmapregionselectordialog.cpp
--- a/src/kpixmapregionselectordialog.cpp
+++ b/src/kpixmapregionselectordialog.cpp
@@ -23,6 +23,7 @@
 #include <QDesktopWidget>
 #include <QImage>
 #include <QLabel>
+#include <QScreen>
 #include <QVBoxLayout>
 
 #include <kpixmapregionselectorwidget.h>
@@ -49,10 +50,9 @@
     {
         if (pixmapSelectorWidget) {
             //Set maximum size for picture
-            QDesktopWidget desktopWidget;
-            QRect screen = desktopWidget.availableGeometry();
+            const QRect screenGeometry = pixmapSelectorWidget->screen()->availableGeometry();
             pixmapSelectorWidget->setMaximumWidgetSize(
-                (int)(screen.width() * 4.0 / 5), (int)(screen.height() * 4.0 / 5));
+                (int)(screenGeometry.width() * 4.0 / 5), (int)(screenGeometry.height() * 4.0 / 5));
         }
     }
 };
diff --git a/src/kpopupframe.cpp b/src/kpopupframe.cpp
--- a/src/kpopupframe.cpp
+++ b/src/kpopupframe.cpp
@@ -21,10 +21,11 @@
 
 #include "kpopupframe.h"
 
-#include <QApplication>
 #include <QDesktopWidget>
 #include <QEventLoop>
+#include <QGuiApplication>
 #include <QKeyEvent>
+#include <QScreen>
 
 class Q_DECL_HIDDEN KPopupFrame::KPopupFramePrivate
 {
@@ -149,23 +150,26 @@
 void KPopupFrame::popup(const QPoint &pos)
 {
     // Make sure the whole popup is visible.
-    QRect desktopGeometry = QApplication::desktop()->screenGeometry(pos);
+    QScreen *screen = QGuiApplication::screenAt(pos);
 
     int x = pos.x();
     int y = pos.y();
     int w = width();
     int h = height();
-    if (x + w > desktopGeometry.x() + desktopGeometry.width()) {
-        x = desktopGeometry.width() - w;
-    }
-    if (y + h > desktopGeometry.y() + desktopGeometry.height()) {
-        y = desktopGeometry.height() - h;
-    }
-    if (x < desktopGeometry.x()) {
-        x = 0;
-    }
-    if (y < desktopGeometry.y()) {
-        y = 0;
+    if (screen) {
+        const QRect desktopGeometry = screen->geometry();
+        if (x + w > desktopGeometry.x() + desktopGeometry.width()) {
+            x = desktopGeometry.width() - w;
+        }
+        if (y + h > desktopGeometry.y() + desktopGeometry.height()) {
+            y = desktopGeometry.height() - h;
+        }
+        if (x < desktopGeometry.x()) {
+            x = 0;
+        }
+        if (y < desktopGeometry.y()) {
+            y = 0;
+        }
     }
 
     // Pop the thingy up.
diff --git a/src/kruler.cpp b/src/kruler.cpp
--- a/src/kruler.cpp
+++ b/src/kruler.cpp
@@ -396,7 +396,7 @@
         QFont font = this->font();
         font.setPointSize(LABEL_SIZE);
         QFontMetrics fm(font);
-        d->fontWidth = fm.width(d->endlabel);
+        d->fontWidth = fm.horizontalAdvance(d->endlabel);
     }
     update(contentsRect());
 }
@@ -686,7 +686,7 @@
 #endif
                 p.drawText(END_LABEL_X, END_LABEL_Y, d->endlabel);
             }
-            p.resetMatrix();
+            p.resetTransform();
         }
 
         // draw the tiny marks
diff --git a/src/kselector.cpp b/src/kselector.cpp
--- a/src/kselector.cpp
+++ b/src/kselector.cpp
@@ -168,7 +168,7 @@
 
 void KSelector::wheelEvent(QWheelEvent *e)
 {
-    int val = value() + e->delta() / 120;
+    int val = value() + e->angleDelta().y() / 120;
     setSliderDown(true);
     setValue(val);
     setSliderDown(false);
@@ -333,14 +333,14 @@
     if (orientation() == Qt::Vertical) {
         int yPos = contentsRect().top() + painter->fontMetrics().ascent() + 2;
         int xPos = contentsRect().left() + (contentsRect().width() -
-                                            painter->fontMetrics().width(d->text2)) / 2;
+                                            painter->fontMetrics().horizontalAdvance(d->text2)) / 2;
         QPen pen(qGray(firstColor().rgb()) > 180 ? Qt::black : Qt::white);
         painter->setPen(pen);
         painter->drawText(xPos, yPos, d->text2);
 
         yPos = contentsRect().bottom() - painter->fontMetrics().descent() - 2;
         xPos = contentsRect().left() + (contentsRect().width() -
-                                        painter->fontMetrics().width(d->text1)) / 2;
+                                        painter->fontMetrics().horizontalAdvance(d->text1)) / 2;
         pen.setColor(qGray(secondColor().rgb()) > 180 ? Qt::black : Qt::white);
         painter->setPen(pen);
         painter->drawText(xPos, yPos, d->text1);
@@ -354,7 +354,7 @@
         pen.setColor(qGray(secondColor().rgb()) > 180 ? Qt::black : Qt::white);
         painter->setPen(pen);
         painter->drawText(contentsRect().right() -
-                          painter->fontMetrics().width(d->text2) - 2, yPos, d->text2);
+                          painter->fontMetrics().horizontalAdvance(d->text2) - 2, yPos, d->text2);
     }
 }
 
diff --git a/src/ksqueezedtextlabel.cpp b/src/ksqueezedtextlabel.cpp
--- a/src/ksqueezedtextlabel.cpp
+++ b/src/ksqueezedtextlabel.cpp
@@ -77,7 +77,7 @@
 {
     int maxWidth = QApplication::desktop()->screenGeometry(this).width() * 3 / 4;
     QFontMetrics fm(fontMetrics());
-    int textWidth = fm.width(d->fullText);
+    int textWidth = fm.boundingRect(d->fullText).width();
     if (textWidth > maxWidth) {
         textWidth = maxWidth;
     }
@@ -118,7 +118,7 @@
     const auto textLines = d->fullText.split(QLatin1Char('\n'));
     squeezedLines.reserve(textLines.size());
     for (const QString &line : textLines) {
-        int lineWidth = fm.width(line);
+        int lineWidth = fm.boundingRect(line).width();
         if (lineWidth > labelWidth) {
             squeezed = true;
             squeezedLines << fm.elidedText(line, d->elideMode, labelWidth);
@@ -145,7 +145,7 @@
         if (frameWidth() == 0) {
             indent = 0;
         } else {
-            indent = fontMetrics().width(QLatin1Char('x')) / 2 - margin;
+            indent = fontMetrics().horizontalAdvance(QLatin1Char('x')) / 2 - margin;
         }
     }
 
diff --git a/src/ktitlewidget.cpp b/src/ktitlewidget.cpp
--- a/src/ktitlewidget.cpp
+++ b/src/ktitlewidget.cpp
@@ -134,7 +134,6 @@
     // default image / text part start
     d->headerLayout = new QGridLayout(titleFrame);
     d->headerLayout->setColumnStretch(0, 1);
-    d->headerLayout->setMargin(6);
     d->headerLayout->setContentsMargins(0, 0, 0, 0);
 
     d->textLabel = new QLabel(titleFrame);
diff --git a/src/kxyselector.cpp b/src/kxyselector.cpp
--- a/src/kxyselector.cpp
+++ b/src/kxyselector.cpp
@@ -194,12 +194,7 @@
 
 void KXYSelector::wheelEvent(QWheelEvent *e)
 {
-    if (e->orientation() == Qt::Horizontal) {
-        setValues(xValue() + e->delta() / 120, yValue());
-    } else {
-        setValues(xValue(), yValue() + e->delta() / 120);
-    }
-
+    setValues(xValue() + e->angleDelta().x() / 120, yValue() + e->angleDelta().y() / 120);
     emit valueChanged(d->xPos, d->yPos);
 }