linguist: Show remaining global&context translation counts in tooltips

Linguist shows the number of finished units and the number of editable
units in the lower right corner of the window (e.g.: 6714/6833).
It also shows this completion progress number per context.

With this change, it displays the difference between these numbers
in a tooltip (i.e. hovering the mouse on the count 6714/6833), for
both global progress count and per context progress count.

While this change may be arguable, the remaining count is the number
that a translator tracks and is constantly checking, other numbers
are less relevant. This small change improves User Experience since
the translator doesn't need to use a calculator or do a mental
calculation, which takes time and may also lead to miscalculations.

Change-Id: Icbb5e73bb4430d28f07eeff790b186579c48c8fb
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

src/linguist/linguist/mainwindow.cpp

@@ -2321,11 +2321,14 @@ void MainWindow::updateProgress()
 {
     int numEditable = m_dataModel->getNumEditable();
     int numFinished = m_dataModel->getNumFinished();
-    if (!m_dataModel->modelCount())
+    if (!m_dataModel->modelCount()) {
         m_progressLabel->setText(QString(QLatin1String("    ")));
-    else
-        m_progressLabel->setText(QString(QLatin1String(" %1/%2 "))
-                                 .arg(numFinished).arg(numEditable));
+        m_progressLabel->setToolTip(QString());
+    } else {
+        m_progressLabel->setText(QStringLiteral(" %1/%2 ").arg(numFinished).arg(numEditable));
+        m_progressLabel->setToolTip(tr("%n unfinished message(s) left.", 0,
+                                       numEditable - numFinished));
+    }
     bool enable = numFinished != numEditable;
     m_ui.actionPrevUnfinished->setEnabled(enable);
     m_ui.actionNextUnfinished->setEnabled(enable);

src/linguist/linguist/messagemodel.cpp

@@ -1351,7 +1351,7 @@ QVariant MessageModel::data(const QModelIndex &index, int role) const
 
         MultiContextItem *mci = m_data->multiContextItem(row);
 
-        if (role == Qt::DisplayRole || (role == Qt::ToolTipRole && column == numLangs)) {
+        if (role == Qt::DisplayRole || role == Qt::ToolTipRole) {
             switch (column - numLangs) {
             case 0: // Context
                 {
@@ -1361,6 +1361,10 @@ QVariant MessageModel::data(const QModelIndex &index, int role) const
                 }
             case 1:
                 {
+                    if (role == Qt::ToolTipRole) {
+                        return tr("%n unfinished message(s) left.", 0,
+                                  mci->getNumEditable() - mci->getNumFinished());
+                    }
                     QString s;
                     s.sprintf("%d/%d", mci->getNumFinished(), mci->getNumEditable());
                     return s;