diff --git a/.arcconfig b/.arcconfig
new file mode 100644
--- /dev/null
+++ b/.arcconfig
@@ -0,0 +1,3 @@
+{
+  "phabricator.uri" : "https://phabricator.kde.org/"
+}
diff --git a/.gitignore b/.gitignore
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,6 @@
 Makefile
 avail
 random_seed
-/build*/
+/*build*/
 CMakeLists.txt.user*
 *.unc-backup*
diff --git a/app/formatdialog.cpp b/app/formatdialog.cpp
--- a/app/formatdialog.cpp
+++ b/app/formatdialog.cpp
@@ -227,7 +227,7 @@
     { nullptr, nullptr, 0, 0 }
 };
 
-static QString sLastFormat = QString::null;		// format last used, whether
+static QString sLastFormat = QString();		// format last used, whether
 							// remembered or not
 
 FormatDialog::FormatDialog(QWidget *parent, ImageMetaInfo::ImageType type,
diff --git a/app/galleryhistory.cpp b/app/galleryhistory.cpp
--- a/app/galleryhistory.cpp
+++ b/app/galleryhistory.cpp
@@ -51,7 +51,7 @@
 // Data for display - what the user sees
 static QString entryName(const FileTreeBranch *branch, const QString &relPath)
 {
-    QString name = QString::null;
+    QString name = QString();
 
     FileTreeView *view = static_cast<FileTreeView *>(branch->root()->treeWidget());
     if (view == nullptr) {
@@ -110,7 +110,7 @@
 
 void GalleryHistory::slotActivated(int idx)
 {
-    QString branchName = QString::null;
+    QString branchName = QString();
 
     QString relPath = itemData(idx).toString();
     int ix = relPath.indexOf(GALLERY_PATH_SEP);     // is the separator present?
diff --git a/app/imgprintdialog.cpp b/app/imgprintdialog.cpp
--- a/app/imgprintdialog.cpp
+++ b/app/imgprintdialog.cpp
@@ -318,7 +318,7 @@
         return (i18n("A valid size must be specified for custom scaling. One or both of the specified dimensions is zero."));
     }
 
-    return (QString::null);				// no problems
+    return QString();				// no problems
 }
 
 
diff --git a/app/imgsaver.h b/app/imgsaver.h
--- a/app/imgsaver.h
+++ b/app/imgsaver.h
@@ -101,7 +101,7 @@
     ImgSaver::ImageSaveStatus saveImage(const QImage *image,
                                         const QUrl &url,
                                         const ImageFormat &format,
-                                        const QString &subformat = QString::null);
+                                        const QString &subformat = QString());
 
     /**
      * Save an image.
@@ -200,7 +200,7 @@
      * this must be either 1, 8, 24 or 32.  The default is for no colour
      * conversion.
      *
-     * @return The file name as saved, or @c QString::null if there was
+     * @return The file name as saved, or @c QString() if there was
      *         an error.
      **/
     static QString tempSaveImage(const KookaImage *img, const ImageFormat &format, int colors = -1);
diff --git a/app/imgsaver.cpp b/app/imgsaver.cpp
--- a/app/imgsaver.cpp
+++ b/app/imgsaver.cpp
@@ -244,7 +244,7 @@
  **/
 QString ImgSaver::createFilename()
 {
-    if (!m_saveDirectory.isLocalFile()) return (QString::null);
+    if (!m_saveDirectory.isLocalFile()) return QString();
     // TODO: allow non-local files
     QDir files(m_saveDirectory.path(), "kscan_[0-9][0-9][0-9][0-9].*");
     QStringList l(files.entryList());
@@ -360,7 +360,7 @@
 QString ImgSaver::findSubFormat(const ImageFormat &format)
 {
     //qDebug() << "for" << format;
-    return (QString::null);             // no subformats currently used
+    return QString();             // no subformats currently used
 }
 
 QString ImgSaver::errorString(ImgSaver::ImageSaveStatus status) const
@@ -396,7 +396,7 @@
 
 bool copyRenameImage(bool isCopying, const QUrl &fromUrl, const QUrl &toUrl, bool askExt, QWidget *overWidget)
 {
-    QString errorString = QString::null;
+    QString errorString = QString();
 
     /* Check if the provided filename has a extension */
     QString extFrom = extension(fromUrl);
diff --git a/app/kookaimage.cpp b/app/kookaimage.cpp
--- a/app/kookaimage.cpp
+++ b/app/kookaimage.cpp
@@ -126,7 +126,7 @@
             const QString fileName = url.adjusted(QUrl::RemoveFragment).toLocalFile();
             qDebug() << "subimage" << subno << "from" << fileName;
             loadTiffDir(fileName, subno);		// load TIFF subimage
-            return (QString::null);
+            return QString();
         }
 
     }
@@ -179,7 +179,7 @@
 
     m_url = url;					// record image source
     m_fileBound = true;					// note loaded from file
-    return (QString::null);				// loaded OK
+    return QString();				// loaded OK
 }
 
 
@@ -258,7 +258,7 @@
 #else
     return (i18n("TIFF not supported"));
 #endif							// HAVE_TIFF
-    return (QString::null);				// TIFF read succeeded
+    return QString();				// TIFF read succeeded
 }
 
 
diff --git a/app/kookapref.cpp b/app/kookapref.cpp
--- a/app/kookapref.cpp
+++ b/app/kookapref.cpp
@@ -137,7 +137,7 @@
 
 // Support for the gallery location - moved here from Previewer class in libkscan
 
-QString KookaPref::sGalleryRoot = QString::null;    // global resolved location
+QString KookaPref::sGalleryRoot = QString();    // global resolved location
 
 // The static variable above ensures that the user is only asked
 // at most once in an application run.
@@ -211,7 +211,7 @@
     if (galleryName.isEmpty())
     {
         qWarning() << "Gallery name not configured";
-        return (QString::null);
+        return QString();
     }
 
     QString oldpath = QStandardPaths::locate(QStandardPaths::AppDataLocation, "ScanImages", QStandardPaths::LocateDirectory);
@@ -257,7 +257,7 @@
                                                 "<nl/>then you may do so by simply copying or moving the files.",
                                                 newpath, oldpath),
                                          i18n("New Gallery Created"),
-                                         QString::null,
+                                         QString(),
                                          KMessageBox::Notify | KMessageBox::AllowLink);
             }
         } else {					// no, don't create
diff --git a/app/kookaview.cpp b/app/kookaview.cpp
--- a/app/kookaview.cpp
+++ b/app/kookaview.cpp
@@ -489,7 +489,7 @@
                                      KScanDevice::statusMessage(stat),
                                      selDevice.constData());
 
-                int tryAgain = KMessageBox::warningContinueCancel(mMainWindow, msg, QString::null,
+                int tryAgain = KMessageBox::warningContinueCancel(mMainWindow, msg, QString(),
                                KGuiItem("Retry"));
                 if (tryAgain == KMessageBox::Cancel) {
                     break;
@@ -563,7 +563,7 @@
                                                       "you need to specify the device to use. "
                                                       "Use the <interface>Add Scan Device</interface> option to enter the backend name and parameters, "
                                                       "or see that dialog for more information."),
-                                               QString::null,
+                                               QString(),
                                                KGuiItem(i18n("Add Scan Device..."))) != KMessageBox::Continue)
         {
             return ("");
diff --git a/app/scangallery.h b/app/scangallery.h
--- a/app/scangallery.h
+++ b/app/scangallery.h
@@ -127,7 +127,7 @@
 
 private:
     void loadImageForItem(FileTreeViewItem *item);
-    FileTreeBranch *openRoot(const QUrl &root, const QString &title = QString::null);
+    FileTreeBranch *openRoot(const QUrl &root, const QString &title = QString());
 
     FileTreeViewItem *findItemByUrl(const QUrl &url, FileTreeBranch *branch = nullptr);
     QUrl itemDirectory(const FileTreeViewItem *item) const;
diff --git a/app/scangallery.cpp b/app/scangallery.cpp
--- a/app/scangallery.cpp
+++ b/app/scangallery.cpp
@@ -472,7 +472,7 @@
                 if (isSubImage)				// subimages don't show size
                 {
                     item->setIcon(0, QIcon::fromTheme("edit-copy"));
-                    item->setText(1, QString::null);
+                    item->setText(1, QString());
                 }
                 else
                 {
@@ -699,7 +699,7 @@
 #ifdef DEBUG_LOADING
     qDebug() << "loading" << item->url();
 #endif // DEBUG_LOADING
-    QString ret = QString::null;			// no error so far
+    QString ret = QString();			// no error so far
 
     ImageFormat format = getImgFormat(item);		// check for valid image format
     if (!format.isValid())
@@ -833,11 +833,11 @@
     QString result = "";
 
     const FileTreeViewItem *curr = highlightedFileTreeViewItem();
-    if (curr==nullptr) return (QString::null);
+    if (curr==nullptr) return QString();
 
     bool isLocal = false;
     const QUrl u = curr->fileItem()->mostLocalUrl(isLocal);
-    if (!isLocal) return (QString::null);
+    if (!isLocal) return QString();
     return (u.toLocalFile());
 }
 
diff --git a/app/scanparamsdialog.cpp b/app/scanparamsdialog.cpp
--- a/app/scanparamsdialog.cpp
+++ b/app/scanparamsdialog.cpp
@@ -179,12 +179,12 @@
 
 void ScanParamsDialog::slotSave()
 {
-    QString name = QString::null;
+    QString name = QString();
     QListWidgetItem *item = paramsList->currentItem();
     if (item != nullptr) name = item->text();
     //qDebug() << "selected set" << name;
 
-    QString newdesc = QString::null;
+    QString newdesc = QString();
     if (sets.contains(name)) {
         newdesc = sets[name];
     } else {
diff --git a/app/statusbarmanager.cpp b/app/statusbarmanager.cpp
--- a/app/statusbarmanager.cpp
+++ b/app/statusbarmanager.cpp
@@ -120,7 +120,7 @@
 
 void StatusBarManager::clearStatus(StatusBarManager::Item item)
 {
-    setStatus(QString::null, item);
+    setStatus(QString(), item);
 }
 
 
diff --git a/libdialogutil/recentsaver.h b/libdialogutil/recentsaver.h
--- a/libdialogutil/recentsaver.h
+++ b/libdialogutil/recentsaver.h
@@ -92,7 +92,7 @@
      * @return The resolved URL, or a null URL if there is no saved
      * history.
      **/
-    QUrl recentUrl(const QString &suggestedName = QString::null);
+    QUrl recentUrl(const QString &suggestedName = QString());
 
     /**
      * Resolve the saved recent location (if there is one) and a suggested
@@ -104,7 +104,7 @@
      * @return The resolved file path, or a null string if there is no
      * saved history.
      **/
-    QString recentPath(const QString &suggestedName = QString::null);
+    QString recentPath(const QString &suggestedName = QString());
 
     /**
      * Save the location selected by the file dialogue as a new recent location.
diff --git a/libfiletree/filetreebranch.cpp b/libfiletree/filetreebranch.cpp
--- a/libfiletree/filetreebranch.cpp
+++ b/libfiletree/filetreebranch.cpp
@@ -307,7 +307,7 @@
 //
 //    QUrl url = fi.url();
 //    //qDebug() << "for" << url;
-//    url.setFileName(QString::null);
+//    url.setFileName(QString());
 //    return (findItemByUrl(url));
 //}
 
diff --git a/libkookascan/autoselectbar.cpp b/libkookascan/autoselectbar.cpp
--- a/libkookascan/autoselectbar.cpp
+++ b/libkookascan/autoselectbar.cpp
@@ -67,7 +67,7 @@
 
     // Threshold setting slider/spinbox
     int maxThresh = item->maxValue().toInt();
-    mThresholdSlider = new KScanSlider(nullptr, QString::null, 0, maxThresh);
+    mThresholdSlider = new KScanSlider(nullptr, QString(), 0, maxThresh);
     mThresholdSlider->setValue(initialValue);
     mThresholdSlider->setToolTip(item->toolTip());
     l->setBuddy(mThresholdSlider);
diff --git a/libkookascan/autoselectdialog.cpp b/libkookascan/autoselectdialog.cpp
--- a/libkookascan/autoselectdialog.cpp
+++ b/libkookascan/autoselectdialog.cpp
@@ -68,7 +68,7 @@
     int maxVal = item->maxValue().toInt();
     int minVal = item->minValue().toInt();
 
-    mMarginSlider = new KScanSlider(nullptr, QString::null, minVal, maxVal, true, defaultVal);
+    mMarginSlider = new KScanSlider(nullptr, QString(), minVal, maxVal, true, defaultVal);
     mMarginSlider->setValue(defaultVal);
     mMarginSlider->setToolTip(item->toolTip());
     connect(mMarginSlider, SIGNAL(settingChanged(int)), SLOT(slotControlChanged()));
@@ -93,7 +93,7 @@
     maxVal = item->maxValue().toInt();
     minVal = item->minValue().toInt();
 
-    mDustsizeSlider = new KScanSlider(nullptr, QString::null, minVal, maxVal, true, defaultVal);
+    mDustsizeSlider = new KScanSlider(nullptr, QString(), minVal, maxVal, true, defaultVal);
     mDustsizeSlider->setValue(defaultVal);
     mDustsizeSlider->setToolTip(item->toolTip());
     connect(mDustsizeSlider, SIGNAL(settingChanged(int)), SLOT(slotControlChanged()));
diff --git a/libkookascan/kscancontrols.h b/libkookascan/kscancontrols.h
--- a/libkookascan/kscancontrols.h
+++ b/libkookascan/kscancontrols.h
@@ -94,7 +94,7 @@
     /**
      * Get the control's current text value.
      *
-     * @return the text value, or @c QString::null for a @c Number
+     * @return the text value, or @c QString() for a @c Number
      * or @c Group control.
      */
     virtual QString text() const;
diff --git a/libkookascan/kscancontrols.cpp b/libkookascan/kscancontrols.cpp
--- a/libkookascan/kscancontrols.cpp
+++ b/libkookascan/kscancontrols.cpp
@@ -71,7 +71,7 @@
 
 QString KScanControl::text() const
 {
-    return (QString::null);
+    return QString();
 }
 void KScanControl::setText(const QString &text)     {}
 
@@ -257,7 +257,7 @@
 
 QString KScanCheckbox::label() const
 {
-    return (QString::null);
+    return QString();
 }
 
 //  KScanCombo - combo box with list of options
@@ -332,7 +332,7 @@
 
 QString KScanCombo::textAt(int i) const
 {
-    return (i == -1 ? QString::null : mCombo->itemData(i).toString());
+    return (i == -1 ? QString() : mCombo->itemData(i).toString());
 }
 
 int KScanCombo::count() const
@@ -392,7 +392,7 @@
 
 QString KScanGroup::label() const
 {
-    return (QString::null);
+    return QString();
 }
 
 //  KScanPushButton - action button
@@ -409,5 +409,5 @@
 
 QString KScanPushButton::label() const
 {
-    return (QString::null);
+    return QString();
 }
diff --git a/libkookascan/kscandevice.h b/libkookascan/kscandevice.h
--- a/libkookascan/kscandevice.h
+++ b/libkookascan/kscandevice.h
@@ -175,7 +175,7 @@
      * If this is a null or empty string, a real scan is performed.
      * @return The status of the operation
      **/
-    KScanDevice::Status acquireScan(const QString &filename = QString::null);
+    KScanDevice::Status acquireScan(const QString &filename = QString());
 
     /**
      * Get the standard file name for saving the preview image for the
diff --git a/libkookascan/kscanoptset.h b/libkookascan/kscanoptset.h
--- a/libkookascan/kscanoptset.h
+++ b/libkookascan/kscanoptset.h
@@ -120,7 +120,7 @@
      * optSet.saveConfig(saneDevice->scannerBackendName(), setDesc);
      * @endcode
      **/
-    void saveConfig(const QByteArray &scannerName, const QString &desc = QString::null) const;
+    void saveConfig(const QByteArray &scannerName, const QString &desc = QString()) const;
 
     /**
      * Load an option set from the global scanner configuration file.
diff --git a/libkookascan/kscanoptset.cpp b/libkookascan/kscanoptset.cpp
--- a/libkookascan/kscanoptset.cpp
+++ b/libkookascan/kscanoptset.cpp
@@ -57,7 +57,7 @@
 static QString setNameFromGroup(const QString &grpName)
 {
     QString prefix = ScanSettings::self()->saveSetDescItem()->group();
-    if (!grpName.startsWith(prefix)) return (QString::null);
+    if (!grpName.startsWith(prefix)) return QString();
     return (grpName.mid(prefix.length()+1));
 }
 
diff --git a/libkookascan/scanparams.cpp b/libkookascan/scanparams.cpp
--- a/libkookascan/scanparams.cpp
+++ b/libkookascan/scanparams.cpp
@@ -157,7 +157,7 @@
 {
     addGroup(nullptr);                 // hide last if present
 
-    mLayout->addWidget(new QLabel(QString::null, this), mNextRow, 0, 1, -1, Qt::AlignTop);
+    mLayout->addWidget(new QLabel(QString(), this), mNextRow, 0, 1, -1, Qt::AlignTop);
     mLayout->setRowStretch(mNextRow, 9);
 
     return (mNextRow > 0);
@@ -269,7 +269,7 @@
     lay->addWidget(pb, 5, 1, Qt::AlignRight);
 
     /* Initialise the progress dialog */
-    mProgressDialog = new QProgressDialog(QString::null, i18n("Stop"), 0, 100, nullptr);
+    mProgressDialog = new QProgressDialog(QString(), i18n("Stop"), 0, 100, nullptr);
     mProgressDialog->setModal(true);
     mProgressDialog->setAutoClose(true);
     mProgressDialog->setAutoReset(true);
@@ -279,7 +279,7 @@
     // appears to show itself after the default 'minimumDuration' (= 4 seconds),
     // even despite the previous and no 'value' being set.
     mProgressDialog->reset();
-    setScanDestination(QString::null);			// reset destination display
+    setScanDestination(QString());			// reset destination display
 
     connect(mProgressDialog, &QProgressDialog::canceled, mSaneDevice, &KScanDevice::slotStopScanning);
     connect(mSaneDevice, &KScanDevice::sigScanProgress, this, &ScanParams::slotScanProgress);
@@ -362,7 +362,7 @@
 
         // Separator line after these.  Using a KScanGroup with a null text,
         // so that it looks the same as any real group separators following.
-        frame->addGroup(new KScanGroup(frame, QString::null));
+        frame->addGroup(new KScanGroup(frame, QString()));
     }
 
     // Mode setting
@@ -449,7 +449,7 @@
     frame->addRow(l, mAreaSelect, nullptr, Qt::AlignTop);
 
     // Insert another beautification line
-    frame->addGroup(new KScanGroup(frame, QString::null));
+    frame->addGroup(new KScanGroup(frame, QString()));
 
     // Source selection
     mSourceSelect = mSaneDevice->getGuiElement(SANE_NAME_SCAN_SOURCE, frame);
@@ -712,7 +712,7 @@
 {
     //qDebug() << "scan mode=" << mScanMode;
 
-    setScanDestination(QString::null);          // reset progress display
+    setScanDestination(QString());          // reset progress display
 
     // Check compatibility of scan settings
     int format;
diff --git a/libkookascan/scansourcedialog.cpp b/libkookascan/scansourcedialog.cpp
--- a/libkookascan/scansourcedialog.cpp
+++ b/libkookascan/scansourcedialog.cpp
@@ -77,7 +77,7 @@
                            "Note that you may see more sources than actually exist"), vbox);
 
     /* Combo Box for sources */
-    d->sources = new KScanCombo(vbox, QString::null);
+    d->sources = new KScanCombo(vbox, QString());
     d->sources->setList(list);
     connect(d->sources, SIGNAL(activated(int)), SLOT(slotChangeSource(int)));
 
diff --git a/plugins/ocr/abstractocrdialogue.h b/plugins/ocr/abstractocrdialogue.h
--- a/plugins/ocr/abstractocrdialogue.h
+++ b/plugins/ocr/abstractocrdialogue.h
@@ -92,7 +92,7 @@
 
     QProgressBar *progressBar() const;
 
-    void ocrShowInfo(const QString &binary, const QString &version = QString::null);
+    void ocrShowInfo(const QString &binary, const QString &version = QString());
     void ocrShowVersion(const QString &version);
 
     QWidget *addExtraSetupWidget(QWidget *wid = nullptr, bool stretchBefore = false);
diff --git a/plugins/ocr/abstractocrdialogue.cpp b/plugins/ocr/abstractocrdialogue.cpp
--- a/plugins/ocr/abstractocrdialogue.cpp
+++ b/plugins/ocr/abstractocrdialogue.cpp
@@ -445,7 +445,7 @@
 {
     //qDebug() << "pixmap" << newPix.size();
     if (m_previewPix != nullptr) {
-        m_previewPix->setText(QString::null);
+        m_previewPix->setText(QString());
         m_previewPix->setPixmap(newPix);
     }
 }
diff --git a/plugins/ocr/abstractocrengine.h b/plugins/ocr/abstractocrengine.h
--- a/plugins/ocr/abstractocrengine.h
+++ b/plugins/ocr/abstractocrengine.h
@@ -124,16 +124,16 @@
      * this must be either 1, 8, 24 or 32.  The default is for no colour
      * conversion.
      *
-     * @return The file name as saved, or @c QString::null if there was
+     * @return The file name as saved, or @c QString() if there was
      *         an error.
      **/
     QString tempSaveImage(const KookaImage *img, const ImageFormat &format, int colors = -1);
 
     /**
      * Get a name to use for a temporary file.
      *
      * @param suffix File name suffix, no leading '.' is required
-     * @return The temporary file name, or @c QString::null if the file could not be created
+     * @return The temporary file name, or @c QString() if the file could not be created
      *
      * @note The temporary file is created and is left in place under the returned name,
      * but is not opened.  Its name should be saved and eventually returned in the
diff --git a/plugins/ocr/abstractocrengine.cpp b/plugins/ocr/abstractocrengine.cpp
--- a/plugins/ocr/abstractocrengine.cpp
+++ b/plugins/ocr/abstractocrengine.cpp
@@ -250,7 +250,7 @@
                                        i18n("OCR Temporary Files"),
                                        KStandardGuiItem::del(),
                                        KStandardGuiItem::close(),
-                                       QString::null,
+                                       QString(),
                                        KMessageBox::AllowLink)==KMessageBox::Yes) retain = false;
     }
 
@@ -411,7 +411,7 @@
     {
         qDebug() << "error creating temporary file" << protoName;
         setErrorText(xi18nc("@info", "Cannot create temporary file <filename>%1</filename>", protoName));
-        return (QString::null);
+        return QString();
     }
 
     QString tmpName = QFile::encodeName(tmpFile.fileName());
@@ -422,7 +422,7 @@
 
 QString AbstractOcrEngine::tempSaveImage(const KookaImage *img, const ImageFormat &format, int colors)
 {
-    if (img==nullptr) return (QString::null);		// no image to save
+    if (img==nullptr) return QString();		// no image to save
 
     QString tmpName = tempFileName(format.extension(), "imagetemp");
     const KookaImage *tmpImg = nullptr;
@@ -445,7 +445,7 @@
             break;
 
 default:    qWarning() << "bad colour depth" << colors;
-            return (QString::null);
+            return QString();
         }
 
         tmpImg = new KookaImage(img->convertToFormat(newfmt));
diff --git a/plugins/ocr/gocr/ocrgocrdialog.cpp b/plugins/ocr/gocr/ocrgocrdialog.cpp
--- a/plugins/ocr/gocr/ocrgocrdialog.cpp
+++ b/plugins/ocr/gocr/ocrgocrdialog.cpp
@@ -51,7 +51,7 @@
 
 OcrGocrDialog::OcrGocrDialog(AbstractOcrEngine *plugin, QWidget *pnt)
     : AbstractOcrDialogue(plugin, pnt),
-      m_ocrCmd(QString::null)
+      m_ocrCmd(QString())
 {
 }
 
@@ -68,7 +68,7 @@
     QLabel *l = new QLabel(ski->label(), w);
     gl->addWidget(l, 0, 0);
 
-    sliderGrayLevel = new KScanSlider(w, QString::null, 0, 254, true, 160);
+    sliderGrayLevel = new KScanSlider(w, QString(), 0, 254, true, 160);
     int numdefault = KookaSettings::ocrGocrGrayLevel();
     sliderGrayLevel->setValue(numdefault);
     sliderGrayLevel->setToolTip(ski->toolTip());
@@ -79,7 +79,7 @@
     Q_ASSERT(ski!=nullptr);
     l = new QLabel(ski->label(), w);
     gl->addWidget(l, 1, 0);
-    sliderDustSize = new KScanSlider(w, QString::null, 0, 60, true, 10);
+    sliderDustSize = new KScanSlider(w, QString(), 0, 60, true, 10);
     numdefault = KookaSettings::ocrGocrDustSize();
     sliderDustSize->setValue(numdefault);
     sliderDustSize->setToolTip(ski->toolTip());
@@ -90,7 +90,7 @@
     Q_ASSERT(ski!=nullptr);
     l = new QLabel(ski->label(), w);
     gl->addWidget(l, 2, 0);
-    sliderSpace = new KScanSlider(w, QString::null, 0, 60, true, 0);
+    sliderSpace = new KScanSlider(w, QString(), 0, 60, true, 0);
     numdefault = KookaSettings::ocrGocrSpaceWidth();
     sliderSpace->setValue(numdefault);
     sliderSpace->setToolTip(ski->toolTip());
diff --git a/plugins/ocr/gocr/ocrgocrengine.cpp b/plugins/ocr/gocr/ocrgocrengine.cpp
--- a/plugins/ocr/gocr/ocrgocrengine.cpp
+++ b/plugins/ocr/gocr/ocrgocrengine.cpp
@@ -69,8 +69,8 @@
     : AbstractOcrEngine(pnt, "OcrGocrEngine")
 {
     m_tempDir = nullptr;
-    m_inputFile = QString::null;			// input image file
-    m_resultFile = QString::null;			// OCR result text file
+    m_inputFile = QString();			// input image file
+    m_resultFile = QString();			// OCR result text file
 }
 
 
diff --git a/plugins/ocr/kadmos/ocrkadmosdialog.cpp b/plugins/ocr/kadmos/ocrkadmosdialog.cpp
--- a/plugins/ocr/kadmos/ocrkadmosdialog.cpp
+++ b/plugins/ocr/kadmos/ocrkadmosdialog.cpp
@@ -288,7 +288,7 @@
         slotFontChanged(0);    // Load machine print font language list
     }
 
-    ocrShowInfo(QString::null);
+    ocrShowInfo(QString());
     return err;
 }
 
diff --git a/plugins/ocr/kadmos/ocrkadmosengine.cpp b/plugins/ocr/kadmos/ocrkadmosengine.cpp
--- a/plugins/ocr/kadmos/ocrkadmosengine.cpp
+++ b/plugins/ocr/kadmos/ocrkadmosengine.cpp
@@ -47,7 +47,7 @@
 OcrKadmosEngine::OcrKadmosEngine(QWidget *parent)
     : OcrEngine(parent)
 {
-    m_tmpFile = QString::null;
+    m_tmpFile = QString();
 }
 
 OcrKadmosEngine::~OcrKadmosEngine()
@@ -211,7 +211,7 @@
 #ifdef USE_KADMOS_FILEOP
     if (!m_tmpFile.isNull()) {
         result << m_tmpFile;
-        m_tmpFile = QString::null;
+        m_tmpFile = QString();
     }
 #endif
 
diff --git a/plugins/ocr/ocrad/ocrocraddialog.cpp b/plugins/ocr/ocrad/ocrocraddialog.cpp
--- a/plugins/ocr/ocrad/ocrocraddialog.cpp
+++ b/plugins/ocr/ocrad/ocrocraddialog.cpp
@@ -58,9 +58,9 @@
       m_setupWidget(nullptr),
       m_orfUrlRequester(nullptr),
       m_layoutMode(0),
-      m_ocrCmd(QString::null),
+      m_ocrCmd(QString()),
       m_versionNum(0),
-      m_versionStr(QString::null)
+      m_versionStr(QString())
 {
 }
 
@@ -223,15 +223,15 @@
     KookaSettings::setOcrOcradLayoutDetection(m_layoutMode->currentIndex());
 
     int ix = m_characterSet->currentIndex();
-    QString value = (m_characterSet->itemData(ix).toBool() ? m_characterSet->currentText() : QString::null);
+    QString value = (m_characterSet->itemData(ix).toBool() ? m_characterSet->currentText() : QString());
     KookaSettings::setOcrOcradCharset(value);
 
     ix = m_filter->currentIndex();
-    value = (m_filter->itemData(ix).toBool() ? m_filter->currentText() : QString::null);
+    value = (m_filter->itemData(ix).toBool() ? m_filter->currentText() : QString());
     KookaSettings::setOcrOcradFilter(value);
 
     ix = m_transform->currentIndex();
-    value = (m_transform->itemData(ix).toBool() ? m_transform->currentText() : QString::null);
+    value = (m_transform->itemData(ix).toBool() ? m_transform->currentText() : QString());
     KookaSettings::setOcrOcradTransform(value);
 
     KookaSettings::setOcrOcradInvert(m_invert->isChecked());
@@ -252,7 +252,7 @@
     if (m_orfUrlRequester != nullptr) {
         return (m_orfUrlRequester->url().url());
     } else {
-        return (QString::null);
+        return QString();
     }
 }
 
diff --git a/plugins/ocr/ocrad/ocrocradengine.cpp b/plugins/ocr/ocrad/ocrocradengine.cpp
--- a/plugins/ocr/ocrad/ocrocradengine.cpp
+++ b/plugins/ocr/ocrad/ocrocradengine.cpp
@@ -58,8 +58,8 @@
 OcrOcradEngine::OcrOcradEngine(QObject *pnt, const QVariantList &args)
     : AbstractOcrEngine(pnt, "OcrOcradEngine")
 {
-    m_ocrImagePBM = QString::null;
-    m_tempOrfName = QString::null;
+    m_ocrImagePBM = QString();
+    m_tempOrfName = QString();
     ocradVersion = 0;
 }
 
@@ -383,7 +383,7 @@
                     wd.setProperty(OcrWordData::Rectangle, wordRect);
                     addWord(word, wd);
 
-                    word = QString::null;       // reset for next time
+                    word = QString();       // reset for next time
                     wordRect = QRect();
                 } else {
                     word.append(detectedChar);    // append char to word
@@ -400,7 +400,7 @@
                 wd.setProperty(OcrWordData::Rectangle, wordRect);
                 addWord(word, wd);
 
-                word = QString::null;           // reset for next time
+                word = QString();           // reset for next time
                 wordRect = QRect();
             }
 
@@ -414,7 +414,7 @@
     finishResultDocument();
     qDebug() << "Finished analysing ORF";
 
-    return (QString::null);             // no error detected
+    return QString();             // no error detected
 }